Glossary of Terms Used in Atomic Spectroscopy

In all my years of working in the field of plasma spectrochemistry, I had never come across any written material that included a basic dictionary of terms, primarily aimed at someone new to the technique. When I first became involved in the ICP-MS technique, most of the literature I read tended to give complicated descriptions of instrument components and explanations of fundamental principles that more often than not sailed over my head. It was not until I became more familiar with the technique that I began to get a better understanding of the complex jargon used in technical journals and presentations at scientific conferences. So, when I wrote my second ICP-MS textbook, I knew that a glossary of terms was an absolute necessity and it has been in every subsequent book I’ve written since. In this book, the glossary has been expanded to also include all the atomic spectroscopy techniques described including ICP-OES, AA, AF, XRF, XRD. LIBS, LALI-TOFMS, and MIP-AES terms. Even though the glossary is not exhaustive, it contains explanations and definitions of the most common AS words, expressions, and terms used in this book. It should mainly be used as a quick reference guide. If you want more detailed information about the subject matter, you should use the index to find a more detailed explanation of the topic in the appropriate book chapter. Many of the same terms are used in different chapters, so to save duplication and where appropriate, those definitions have only been used once. (Note: the glossary does not include commercial names used by any of the instrument, accessories, or consumable vendors.)

Inductively Coupled Plasma Mass Spectrometry (ICP-MS) Glossary

A

AA: An abbreviation for atomic absorption.

abundance sensitivity: A way of assessing the ability of a mass separation device, such as a quadrupole, to identify and measure a small analyte peak adjacent to a much larger interfering peak. An abundance sensitivity specification is a combination of two measurements. The first is expressed as the ratio of the intensity of the peak at 1 amu (atomic mass unit) below the analyte peak to the intensity of the analyte peak, and the second is the ratio of the peak intensity 1 amu above the analyte mass to the intensity of the analyte peak. Because of the motion of the ion through the mass filter, the abundance sensitivity specification of a mass-filtering device is always worse on the low-mass side compared to the high-mass side.

active film multipliers: Another name for discrete dynode multipliers, which are used to detect, measure, and convert ions into electrical pulses in ICP-MS. Also refers to channel electron multiplier (CEM) and discrete dynode detector (DDD).

addition calibration: A method of calibration in ICP-MS using standard additions. All samples are assumed to have a similar matrix, so spiking is only carried out on one representative sample and not the entire batch of samples, as per conventional standard additions used in graphite furnace AA analysis.

AE: An abbreviation for atomic emission.

aerosol: The result of breaking up a liquid sample into small droplets by the nebulization process in the sample introduction system. Also refers to nebulizer and sample introduction system.

aerosol dilution: A way of introducing a flow of argon gas between the nebulizer and the torch, which has the effect of reducing the sample’s solvent loading on the plasma, so it can tolerate much higher total dissolved solids.

AF4: Refers to asymmetrical flow field flow fractionation.

alkylated metals: A metal complex containing an alkyl group. Typically detected by coupling liquid chromatography with ICP-MS. Also refers to speciation analysis, alpha-counting spectrometry: A particle-counting technique that uses the measurement of the radioactive decay of alpha particles. Also refers to particle-counting techniques, alternative sample introduction accessories: Alternative ways of introducing samples into an ICP mass spectrometer other than conventional nebulization. Also known as alternative sample introduction devices. Often used to describe desolvation techniques or laser ablation, analog counting: A way of measuring high signals by changing the gain or voltage of the detector.

Also refers to pulse counting, argon: The gas used to generate the plasma in an ICP.

argon-based interferences: A polyatomic spectral interference generated by argon ions combining with ions from the matrix, solvent, or any elements present in the sample, array detectors: An ion detector based on solid-state, direct charge arrays, similar to CID/CCD technology used in ICP optical emission. By projecting all the separated ions from a mass separation device onto a two-dimensional array, these detectors can view the entire mass spectrum simultaneously. Used with the Mattauch-Herzog sector technology, ashing: A sample preparation technique that involves heating the sample (typically in a muffle furnace) until the volatile material is driven off and an ash-like substance is left. Asymmetrical flow field flow fractionation (AF4): Field flow fractionation (FFF) is a single-phase chromatographic separation technique, where separation is achieved within a very thin channel, against which a perpendicular force field is applied. One of the most common forms of FFF is asymmetrical flow FFF (AF4), where the field is generated by a cross-flow applied perpendicular to the channel. Coupled with ICP-MS for the characterization of nanoparticles.

atom: A unit of matter. The smallest part of an element having all the characteristics of that element and consisting of a dense, central, positively charged nucleus surrounded by orbiting electrons. The entire structure has an approximate diameter of К)-8 cm and characteristically remains undivided in chemical reactions except for limited removal, transfer, or exchange of certain electrons.

atom-counting techniques: A generic name given to techniques that use atom or ion counting to carry out elemental quantitation. Some common ones, besides ICP-MS, include secondary ionization mass spectrometry (SIMS), thermal ionization mass spectrometry (TIMS), accelerator mass spectrometry (AMS), and fission track analysis (FTA). Also refers to ionizing radiation counting techniques.

atomic absorption (AA): An analytical technique for the measurement of trace elements that uses the principle of generating free atoms (of the element of interest) in a flame or electrothermal atomizer (ETA) and measuring the amount of light absorbed from a wavelength- specific light source, such as a hollow cathode lamp (HCL) or electrode discharge lamp (EDL).

atomic emission (AE): A trace element analytical technique that uses the principle of exciting atoms in a high-temperature source such as a plasma discharge and measuring the amount of light the atoms emit when electrons fall back down to a ground (stable) state, atomic mass or weight: The average mass or weight of an atom of an element, usually expressed relative to the mass of carbon 12, which is assigned 12 atomic mass units, atomic number: The number of protons in an atomic nucleus.

atomic structure: Describes the structural makeup of an atom. Also refers to neutron, proton, and electron.

attenuation (of the detector): Reduces the amplitude of the electrical signal generated by the detector, with little or no distortion. Usually carried out by applying a control voltage to extend the dynamic range of the detector. Also refers to extended dynamic range, autocalibration: A way of carrying out calibration with an automated in-line sample delivery system.

autodilution: A way of carrying out automatic in-line dilution of large numbers of samples with no manual intervention by the operator.

autosampler: A device to automatically introduce large numbers of samples into the ICP-MS system with no manual intervention by the operator, axial view: An ICP-OES system in which the plasma torch is positioned horizontally (end-on) to the optical system as opposed to the conventional vertical (radial) configuration. It is generally accepted that viewing the end of the plasma improves emission intensity by a factor of approximately 5- to 10-fold.

В

background equivalent concentration (ВЕС): Defined as the apparent concentration of the background signal based on the sensitivity of the element at a specified mass. The lower the ВЕС value, the more easily a signal generated by an element can be discerned from the background. Many analysts believe ВЕС is a more accurate indicator of the performance of an ICP-MS system than detection limit, especially when making comparisons of background reduction techniques, such as cool plasma or collision/reaction cell and interface technology.

background noise: The square root of the intensity of the blank in counts per second (cps) anywhere of analytical interest on the mass range. Detection limit (DL) is a ratio of the analyte signal to the background noise at the analyte mass. Background noise as an instrumental specification is usually measured at mass 220amu (where there are no spectral features), while aspirating deionized water. Also refers to background signal, instrument background noise, and detection limit.

background signal: The signal intensity of the blank in counts per second (cps) anywhere of analytical interest on the mass range. Detection limit (DL) is a ratio of the analyte signal to the noise of the background at the analyte mass. Background as an instrumental specification is usually measured at mass 220amu (where there are no spectral features), while aspirating deionized water. Also refers to background noise, instrument background signal, and detection limit.

bandpass tuning/filtering: A mechanism used in a dynamic reaction cell (DRC) to reject the by-products generated through secondary reactions utilizing the principle of mass discrimination. Achieved by optimizing the electrical fields of the reaction cell multipole (typically a quadrupole) to allow transmission of the analyte ion, while rejecting the polyatomic interfering ion.

ВЕС: An abbreviation for background equivalent concentration.

by-product ions: Ionic species formed as a result of secondary reactions that take place in a reaction/ collision cell. Also refers to secondary (side) reactions.

с

calibration: A plot, function, or equation generated using calibration standards and a blank, which describes the relationship between the concentration of an element and the signal intensity produced at the analyte mass of interest. Once determined, this relationship can be used to determine the analyte concentration in an unknown sample, calibration standard: A reference solution containing accurate and known concentrations of analytes for the purpose of generating a calibration curve or plot, capacitive coupling: An undesired electrostatic (or capacitive) coupling between the voltage on the load coil and the plasma discharge, which produces a potential difference of a few hundred volts. This creates an electrical discharge or arcing between the plasma and sampler cone of the interface, commonly known as a “secondary discharge” or “pinch effect.” capillary electrophoresis (CE): Refers to capillary-zone electrophoresis (CZE). capillary zone electrophoresis (CZE or CE): A chromatographic separation technique used to separate ionic species according to their charge and frictional forces. In traditional electrophoresis, electrically charged analytes move in a conductive liquid medium under the influence of an electric field. In capillary (zone) electrophoresis, species are separated based on their size-to-charge ratio inside a small capillary filled with an electrolyte. Its applicability to ICP-MS is mainly in the field of separation and detection of large biomolecules.

CCD: Charge-coupled device detector.

CE: Refers to capillary-zone electrophoresis.

cell: In ICP-MS terminology, a cell usually refers to a collision or reaction cell, ceramic torch: A plasma torch where either (or all) the sample injector, inner tube, or outer tube is made of a ceramic material. Typically has longer lifetime than a traditional quartz torch, certified reference material (CRM): Well-established reference matrix that comes with certified values and associated statistical data that have been analyzed by other complementary techniques. Its purpose is to check the validity of an analytical method, including sample preparation, instrument methodology, and calibration routines to achieve sample results that are as accurate and precise as possible and can be defended when subjected to intense scrutiny.

channel electron multiplier (CEM): A detector used in ICP-MS to convert ions into electrical pulses using the principle of multiplication of electrons via a potential gradient inside a sealed tube.

Channeltron©: Another name for a channel electron multiplier detector.

charge transfer reaction: Sometimes referred to as “charge exchange.” This is one of the ion- molecule reaction mechanisms that take place in a collision/reaction cell. Involves the transfer of a positive charge from the interfering ion to the reaction gas molecule, forming a neutral atom that is not seen by the mass analyzer. An example of this kind of reaction:

Charge-coupled device detector (CCD): A type of solid state detector technology for converting photons into an electrical signal. Typically applied to ICP-OES. charge injection device detector (CID): A type of solid-state detector technology for converting photons into an electrical signal. Typically applied to ICP-OES. chemical modification: The process of chemically modifying the sample in electrothermal vaporization (ETV) ICP-MS work to separate the analyte from the matrix. Also refers to chemical modifier and electrothermal vaporization, chemical modifier: A chemical or substance that is added to the sample in an electrothermal vaporizer to change the volatility of the analyte or matrix. Typically added at the ashing stage of the heating program to separate the vaporization of the analyte away from the potential interferences of the matrix components. Also refers to electrothermal vaporization, chromatographic separation device: Any device that separates analyte species according to their retention times or mobility through a stationary phase. When coupled with an ICP-MS system, it is used for the separation, detection, and quantitation of speciated forms of trace elements. Examples include liquid, ion, gas, size exclusion, and capillary electrophoresis chromatography. Also refers to speciation analysis, chromatography terminology (as applied to trace element speciation): The following are some of the most important terms used in the chapter on trace element speciation. For easy access, they are contained in one section and not distributed throughout the glossary, buffer: A mobile-phase solution that is resistant to extreme pH changes, even with additions of small amounts of acids or bases, chromatogram: The graphical output of the chromatographic separation. It is usually a plot of peak intensity of the separated species over time, column: The main component of the chromatographic separation. It is typically a tube containing the stationary-phase material that separates the species and an eluent that elutes the species off the column.

counter-ions: The mobile phase contains a large number of ions that have a charge opposite to that of the surface-bound ions. These are known as counterions, which establish equilibrium with the stationary phase, dead volume: Usually refers to the volume of the mobile phase between the point of injection and the detector that is accessible to the sample species, minus the volume of mobile phase that is contained in any union or connecting tubing, gradient elution: Involves variation of the mobile-phase composition over time through a number of steps such as changing the organic content, altering the pH, changing the concentration of the buffer, or using a completely different buffer, ion exchange: A technique in which separation is based on the exchange of ions (anions or cations) between the mobile phase and the ionic sites on a stationary phase bound to a support material in the column.

ion pairing: A type of separation that typically uses a reversed-phase column in conjunction with a special type of chemical in the mobile phase called an “ion-pairing reagent.” Also refers to reverse phase.

isochratic elution: An elution of the analytes or species using the same solvent throughout the analysis.

mobile phase: A combination of the sample or species being separated or analyzed and the solvent that moves the sample through the column, retention time: The time taken for a particular analyte or species to be separated and pass through the column to the detector.

reverse phase: A type of separation that is typically combined with ion pairing, and essentially means that the column’s stationary phase is less polar and more organic than the mobile-phase solvents.

stationary phase: A solid material, such as silica or a polymer, that is set in place and packed into the column for the chromatographic separation to take place, clean room: The general description given to a dedicated room for the sample preparation and analysis of ultrapure materials. Usually associated with a number that describes the number of particulates per cubic foot of air (e.g., a class 100 clean room will contain 100 particles/ft3 of air). It is commonly accepted that the semiconductor industry has the most stringent demands, which necessitates the use of class 10 and sometimes class 1 clean rooms.

cluster ions: Ions that are formed by two or more molecular ions combining together in a collision/ reaction cell to form molecular clusters.

CMOS: Complementary metal oxide semiconductor technology used in the direct charge array detector, which is utilized in the Mattauch-Herzog simultaneous sector instrument, cold plasma technology: Cool or cold plasma technology uses low-temperature plasma to minimize the formation of certain argon-based polyatomic species. Under normal plasma conditions (approximately 1,000 W RF power and 1.0 L/min nebulizer gas flow), argon ions combine with matrix and solvent components to generate problematic spectral interferences, such as 38ArH+, 40Ar+, and 40Arl6O+, which impact the detection limits of a small number of elements including K, Ca, and Fe. By using cool plasma conditions (approximately 600 W RF power and 1.6 L/min nebulizer gas flow), the ionization conditions in the plasma are changed so that many of these interferences are dramatically reduced and detection limits are improved.

cold vapor atomic absorption (CVAA): An analytical approach to determine low levels of mercury by generating mercuric vapor in a quartz cell and measuring the number of mercury atoms produced, using the principle of atomic absorption. Also refers to hydride generation atomic absorption.

collision cell: Specifically, a cell that predominantly uses the principle of collisional fragmentation to break apart polyatomic interfering ions generated in the plasma discharge. Collision cells typically utilize higher-order multipoles (such as hexapoles or octopoles) with inert or low- reactive gases (such as helium and hydrogen) to first stimulate ion-molecule collisions, and then kinetic energy discrimination to reject any undesirable by-product ionic species formed, collision-induced dissociation (CID): A basic principle, first used for the study of organic molecules using tandem mass spectrometry, that relies on using a nonreactive gas in a collision cell to stimulate ion-molecule collisions. The more collision-induced daughter species that are generated, the better the chance of identifying the structure of the parent molecule, collision/reaction cell (CRC) technology: A generic term applied to collision and reaction cells that use the principle of ion-molecule collisions and reactions to cleanse the ion beam of problematic polyatomic spectral interferences before they enter the mass analyzer. Both collision and reaction cells are positioned in the mass spectrometer vacuum chamber after the ion optics but prior to the mass analyzer. Also refers to collision cell and reaction cell, collision/reaction interface (CRI) technology: A collision/reaction mechanism approach, which instead of using a pressurized cell injects a gas directly into the interface between the sampler and skimmer cones. The injection of the collision/reaction gas into this region of the ion beam produces high collision frequency between the argon gas and the injected gas molecules. This has the effect of removing argon-based polyatomic interferences before they are extracted into the ion optics.

collisional damping: A mechanism that describes the temporal broadening of ion packets in a quadrupole-based dynamic reaction cell to dampen out fluctuations in ion energy. By optimizing cell conditions such as gas pressure, RF stability boundary (q parameter), entrance/ exit lens potentials, and cell rod offsets, it has been shown that fluctuation in ion energies can be dampened sufficiently to carry out isotope ratio precision measurements near their statistical limit.

collisional focusing: The mechanism of focusing ions towards the center of the ion beam in a collision/reaction cell. By using a neutral collision gas of lower molecular weight than the analyte, the analyte ions will lose kinetic energy and migrate towards the axis as a result of the collisions with the gaseous molecules. Therefore, the number of ions exiting the cell and reaching the detector will increase. Also refers to collision cell and reaction cell, collisional fragmentation: The mechanism of breaking apart (fragmenting) a polyatomic interfering ion in a collision/reaction cell using collisions with a gaseous molecule. The predominant mechanism used in a collision cell, as opposed to a reaction cell. Also refers to collision cell and reaction cell.

collisional mechanisms: The mechanisms by which the interfering ion is reduced or minimized to allow the determination of the analyte ion. The most common collisional mechanisms seen in collision/reaction cells include collisional focusing, dissociation, and fragmentation, whereas the major reaction mechanisms include exothermic/endothermic associations, charge transfer, molecular associations, and proton transfer, collisional retardation: A mechanism in a collision/reaction cell w'here the gas atoms/molecules undergo multiple collisions with the polyatomic interfering ion, retarding or lowering its kinetic energy. Because the interfering ion has a larger cross-sectional area than the analyte ion, it undergoes more collisions and, as a result, can be separated or discriminated from the analyte ion based on their kinetic energy differences, concentric nebulizer: A nebulizer that uses two narrow concentric capillary tubes (one inside the other) to aspirate a liquid into the ICP-MS spray chamber. Argon gas is usually passed through the outer tube, which creates a Venturi effect, and as a result, the liquid is sucked up through the inner capillary tube, cones: Refers to interface cones.

cool plasma technology: Refers to cold plasma technology.

cooled spray chamber: A spray chamber that is cooled in order to reduce the amount of solvent entering the plasma discharge. Used for a variety of reasons, including reducing oxide species, minimizing solvent-based spectral interferences, and allowing the trouble-free aspiration of organic solvents.

correction equation: A mathematical approach used to compensate for isobaric and polyatomic spectral overlaps. It works on the principle of measuring the intensity of the interfering species at another mass, which is ideally free of any interference. A correction is then applied by knowing the ratio of the intensity of the interfering species at the analyte mass to its intensity at the alternate mass.

counts per second (cps): Units of signal intensity used in ICP-MS. Number of detector electronic pulses counted per second, cps: An abbreviation for counts per second.

CRC: An abbreviation for collision/reaction cell technology.

CRI: An abbreviation for collision/reaction interface technology.

CRM: An abbreviation for certified reference materials.

cross-calibration: A calibration method that is used to correlate both pulse (low levels) and analog (high levels) signals in a dual-mode detector. This is possible because the analog and pulse outputs can be defined in identical terms (of incoming pulse counts per second) based on knowing the voltage at the first analog stage, the output current, and a conversion factor defined by the detection circuitry electronics. By carrying out a cross-calibration across the mass range, a dual-mode detector is capable of achieving approximately eight to nine orders of dynamic range in one simultaneous scan, cross-flow nebulizer: A nebulizer that is designed for samples that contain a heavier matrix or small amounts of undissolved solids. In this design, the argon gas flow is directed at right angles to the tip of a capillary tube through which the sample is drawn up with a peristaltic pump.

CVAA: An abbreviation for cold vapor atomic absorption.

cyclonic spray chamber: A spray chamber that operates using the principle of centrifugal force. Droplets are discriminated according to their size by means of a vortex produced by the tangential flow of the sample aerosol and argon gas inside the spray chamber. Smaller droplets are carried with the gas stream into the ICP-MS, while the larger droplets impinge on the walls and fall out through the drain, cylinder lens: A type of lens component used in the ion optics.

CZE: An abbreviation for capillary-zone electrophoresis.

D

data-quality objectives: A term used to describe the quality goals of the analytical result. Typically achieved by optimizing the measurement protocol to achieve the desired accuracy/ precision/sample throughput required for the analysis.

DCD: Refers to direct charge detector.

dead time correction: Sometimes ions hit the detector too fast for the measurement circuitry to handle in an efficient manner. This is caused by ions arriving at the detector during the output pulse of the preceding ion and not being detected by the counting system. This “dead time,” as it is known, is a fundamental limitation of the multiplier detector and is typically 30-50 ns, depending on the detection system. A compensation or “dead time correction” has to be made in the measurement circuitry in order to count the maximum number of ions hitting the detector. Debye length: The distance over which ions exert an electrostatic influence over one another as they move from the interface region into the ion optics. In the ion-sampling process, this distance is small compared to the orifice diameter of the sampler or skimmer cone. As a result, there is little electrical interaction between the ion beam and the cones, and relatively little interaction between the individual ions within the ion beam. In this way, the compositional integrity of the ion beam is maintained throughout the interface region, desolvating microconcentric nebulizer: A microconcentric nebulizer that uses some type of desolvation system to remove the sample solvent. Also refers to desolvation device and membrane desolvation.

desolvating spray chamber: A general name given to a spray chamber that removes or reduces the amount of solvent from a sample using the principle of desolvation. Some of the approaches that are typically used include conventional water cooling, heating with cooling condensers, Peltier (thermoelectric) cooling, or membrane-based desolvation techniques, desolvation device: A general name given to a device that removes or reduces the amount of solvent from a sample using the principle of desolvation. Some of the approaches that are typically used include conventional water cooling, heating/condensing units, Peltier (thermoelectric) cooling, or membrane-based desolvation techniques, detection capability: A generic term used to assess the overall detection performance of an ICP mass spectrometer. There are a number of different ways of evaluating detection capability, including instrument detection limit (IDL), method detection limit (MDL), element sensitivity, and background equivalent concentration (ВЕС), detection limit: Most often refers to the instrument detection limit (IDL) and is typically defined as a ratio of the analyte signal to the noise of the background at a particular mass. For a 99% confidence level, it is usually calculated as 3x standard deviation (SD) of ten replicates (measurements) of the sample blank expressed as concentration units, detector: A generic name used for a device that converts ions into electrical pulses in ICP-MS. detector dead time: Refers to dead time correction.

devitrification: Crystalline breakdown of glass or quartz by a combination of chemical attack and elevated temperatures, typically associated with the plasma torch, digital counting: Refers to the process of counting the number of pulses generated by the conversion of ions into an electrical signal by the detector measurement circuitry.

DIHEN: An abbreviation for direct injection high-efficiency nebulizer.

DIN: An abbreviation for direct injection nebulizer.

Direct charge detector (DCD): A detector technology used to convert photons into an electric current. A type of CMOS array ion detector used in the Mattauch-Herzog simultaneous sector instrument.

direct injection high-efficiency nebulizer (DIHEN): A more recent refinement of the direct injection nebulizer (DIN), which appears to have overcome many of the limitations of the original design.

direct injection nebulizer (DIN): A nebulizer that injects a liquid sample under high pressure directly into the base of the plasma torch. The benefit of this approach is that no spray chamber is required, which means that an extremely small volume of sample can be introduced directly into the ICP-MS with virtually no carryover or memory effects from the previous sample.

discrete dynode detector (DDD): The most common type of detector used in ICP-MS. As ions emerge from the quadrupole rods onto the detector, they strike the first dynode, liberating secondary electrons. The electron-optic design of the dynode produces acceleration of these secondary electrons to the next dynode, where they generate more electrons. This process is repeated at each dynode, generating a pulse of electrons that are finally captured by the multiplier anode. Also refers to active film multipliers.

double-focusing magnetic sector mass spectrometer (analyzer): A mass spectrometer that uses a very powerful magnet combined with an electrostatic analyzer (ESA) to produce a system with very high resolving power. This approach, known as “double focusing,” samples the ions from the plasma. The ions are accelerated in the plasma to a few kilovolts into the ion-optic region before they enter the mass analyzer. The magnetic field, which is dispersive with respect to ion energy and mass, then focuses all the ions w'ith diverging angles of motion from the entrance slit. The ESA, which is only dispersive with respect to ion energy, then focuses all the ions onto the exit slit, where the detector is positioned. If the energy dispersions of the magnet and ESA are equal in magnitude but opposite in direction, they will focus both ion angles (first focusing) and ion energies (second focusing) when combined together. Also refers to electrostatic analyzer.

double-pass spray chamber: A spray chamber that comprises an inner (central) tube inside the main body of the spray chamber. The smaller droplets are selected by directing the aerosol from the nebulizer into the central tube. The aerosol emerges from the tube, where the larger droplets fall out (because of gravity) through a drain tube at the rear of the spray chamber. The smaller droplets then travel back between the outer wall and the central tube into the sample injector of the plasma torch. The most common type of double-pass spray chamber is the Scott design.

doubly charged ion: A species that is formed when an ion is generated with a double-positive charge as opposed to a normal single charge and produces an isotopic peak at half its mass. For example, the major isotope of barium at mass 138 amu also exhibits a doubly charged ion at mass 69 amu, which can potentially interfere with gallium at mass 69. Some elements such as the rare earths readily form doubly charged species, whereas others do not. Formation of doubly charged ions is also impacted by the ionization conditions (RF power, nebulizer gas flow, etc.) in the plasma discharge.

DRC: An abbreviation for dynamic reaction cell.

droplet: Refers to individual particles (either small or large) that make up an aerosol generated by the nebulizer.

dry plasma: When a sample is introduced into the plasma that does not contain any liquid or solvent, such as laser ablation, ETV, or desolvation sample introduction systems.

duty cycle (%): Also known as the “measurement duty cycle.” It refers to the actual peak measurement time and is expressed as a percentage of the overall integration time. It is calculated by dividing the total peak quantitation time (dwell time x number of sweeps x replicates x elements) by the total integration time ([dwell time+settling/scanning time] x number of sweeps x replicates x elements).

dwell time: The time spent sitting (dwelling) on top of the analytical peak (mass) and taking measurements.

dynamic reaction cell (DRC): A type of collision/reaction cell. Unlike a simple collision cell, a quadrupole is used instead of a hexapole or octapole. A highly reactive gas such as ammonia or methane is bled into the cell, which is a catalyst for ion-molecule chemistry to take place. By a number of different reaction mechanisms, the gaseous molecules react with the interfering ions to convert them either into an innocuous species different from the analyte mass or a harmless neutral species. The analyte mass then emerges from the dynamic reaction cell, free of its interference, and is steered into the analyzer quadrupole for conventional mass separation. Through careful optimization of the quadrupole electrical fields, unwanted reactions between the gas and the sample matrix or solvent, which could potentially lead to new interferences, are prevented. Therefore, every time an analyte and interfering ions enter the dynamic reaction cell, the bandpass of the quadrupole can be optimized for that specific problem and then changed on the fly for the next one. dynamically scanned ion lens: A commercial ion optic approach to focus the maximum number of ions into the mass analyzer. In this design, the voltage is dynamically ramped on the fly in concert with the mass scan of the analyzer. The benefit is that the optimum lens voltage is placed on every mass in a multielement run to allow the maximum number of analyte ions through, while keeping the matrix ions down to an absolute minimum. This is typically used in conjunction with a grounded stop acting as a physical barrier to reduce particulates, neutral species, and photons from reaching the mass analyzer and detector.

E

EDR: An abbreviation for the term “extended dynamic range,” used in detector technology, electrodynamic forces: Flow of the ion beam through the interface region, where the positively charged ions of varying mass-to-charge exert no electrical influence on each other, electron: A negatively charged fundamental particle orbiting the nucleus of an atom. It has a mass equal to 1/1,836 of a proton’s mass. Removal of an electron by excitation in the plasma discharge generates a positively charged ion.

electrostatic analyzer (ESA): An ion-focusing device (utilizing a series of electrostatic lens components) that varies the electric field to allow the passage of ions of certain energy. In ICP-MS, it is typically used in combination with a conventional electromagnet to focus ions based on their angular motion and their kinetic energy to produce very high resolving power. Also refers to double-focusing magnetic sector mass spectrometer (analyzer), electrothermal atomization (ETA): An atomic absorption (AA) analytical technique that uses a heated metal filament or graphite tube (in place of the normal flame) to generate ground- state analyte atoms. The sample is first injected into the filament or tube, which is heated up slowly to remove the matrix components. Further heating then generates ground-state atoms of the analyte, which absorb light of a particular wavelength from an element- specific, hollow cathode lamp source. The amount of light absorbed is measured by a monochromator (optical system) and detected by a photomultiplier or solid-state detector, which converts the photons into an electrical pulse. This absorbance signal is used to determine the concentration of that element in the sample. Typically used for ppb-level determinations.

electrothermal vaporization (ETV): A sample pretreatment technique used in ICP-MS. Based on the principle of electrothermal atomization (ETA) used in atomic absorption (AA), ETV is not used to generate ground-state atoms but instead uses a carbon furnace (tube) or metal filament to thermally separate the analytes from the matrix components and then sweep them into the ICP mass spectrometer for analysis. This is achieved by injecting a small amount of the sample into a graphite tube or onto a metal filament. After the sample is introduced, drying, charring, and vaporization are achieved by slowly heating the graphite tube or metal filament. The sample material is vaporized into a flowing stream of carrier gas, which passes through the furnace or over the filament during the heating cycle. The analyte vapor recondenses in the carrier gas and is then swept into the plasma for ionization.

elemental fractionation: A term used in laser ablation. It is typically defined as the variation in intensity of a particular element over time compared to the total amount of dry aerosol generated by the sample. It is generally sample and element specific, but there is evidence to suggest that the shorter-wavelength excimer lasers exhibit better elemental fractionation characteristics than the longer-wavelength Nd:YAG design because they produce smaller particles that are easier to volatilize.

endothermic reaction: In thermodynamics, this describes a chemical reaction that absorbs energy in the form of heat. In ICP-MS, it generally refers to an ion-molecule reaction in a collision/ reaction cell that is not allowed to proceed because the ionization potential of the analyte ion is significantly less than that of the reaction gas molecule. Also refers to exothermic reaction.

engineered nanomaterials (ENMs): These are man-made materials made of particles with <100 nm diameter that can be made to exhibit: greater physical strength, enhanced magnetic properties, conduction of heat or electricity, greater chemical reactivity, or size-dependent optical properties. An example of an engineered nanomaterial is silver nanoparticles, which are added to detergents as a bactericide.

ENM: Refers to engineered nanomaterials.

ESA: An abbreviation for electrostatic analyzer.

ETA: An abbreviation for electrothermal atomization.

ETV: An abbreviation for electrothermal vaporization.

excimer laser: A gas-filled laser in which a very short electrical pulse excites a mixture containing a halogen such as fluorine and a rare gas such as argon or krypton. It produces a brief, intense pulse of UV light. The output of an excimer laser is used for writing patterns on semiconductor chips because the short wavelength can write very fine lines. In ICP-MS, the most common excimer laser used is ArF at 193 nm and is typically used to ablate material with a very small size, such as inclusions on the surface of a geological sample.

exothermic reaction: In thermodynamics, this describes a chemical reaction that releases energy in the form of heat. In ICP-MS, it generally refers to an ion-molecule reaction in a collision/ reaction cell that is spontaneous because the ionization potential of the interfering ion is much greater than the reaction gas molecule. Also refers to endothermic reaction.

extended dynamic range (EDR): An approach used in ICP-MS to extend the linear dynamic range of the detector from 5 orders of magnitude up to eight or 9 orders of magnitude. Also refers to discrete dynode detector and Faraday cup detector.

external standardization: The normal mode of calibration used in ICP-MS by comparing the analyte intensity of unknown samples to the intensity of known calibration or reference standards.

extraction lens: An ion lens used to electrostatically extract the ions out of the interface region.

F

FAA: An abbreviation for flame atomic absorption.

Faraday collector: Another name for a Faraday cup detector.

Faraday cup detector: A simple metal electrode detector used to measure high ion counts. When the ion beam hits the metal electrode, it will be charged, whereas the ions are neutralized. The electrode is then discharged to measure a small current equivalent to the number of discharged ions. By measuring the ion current on the metal part of the circuit, the number of ions in the circuit can be determined. Unfortunately, with this approach, there is no control over the applied voltage (gain). So, it can only be used for high ion counts and therefore is not suitable for ultratrace determinations.

field flow fractionation (FFF): Field flow fractionation (FFF) is a single-phase chromatographic separation technique, where separation is achieved within a very thin channel, against which a perpendicular force field is applied. One of the most common forms of FFF is asymmetrical flow FFF (AF4), where the field is generated by a cross-flow applied perpendicular to the channel. Coupled with ICP-MS for the characterization of nanoparticles.

FFF: Refers to field flow fractionation.

FGDW: Refers to flue gas desulfurization wastewaters.

FIA: An abbreviation for flow injection analysis.

flame atomic absorption (FAA): A n atomic absorption analytical technique that uses a flame (usually air-acetylene or nitrous oxide-acetylene) to generate ground-state atoms. The sample solution is aspirated into the flame via a nebulizer and a spray chamber. The ground-state atoms of the sample absorb light of a particular wavelength from an element-specific, hollow cathode lamp source. The amount of light absorbed is measured by a monochromator (optical system) and detected by a photomultiplier or solid-state detector, which converts the photons into an electrical pulse. This absorbance signal is used to determine the concentration of the element in the sample. Typically used for ppm-level determinations.

flatapole: A quadrupole with rods that have flat corners. Used in a particular commercial design of collision/reaction cell.

flight tube: A generic name given to the housing that contains a series of optical components which focus ions onto the detector of a time-of-flight (TOF) mass analyzer. There are basically two different kinds of flight tubes that are used in commercial TOF mass analyzers. One is the orthogonal design, where the flight tube is positioned at right angles to the sampled ion beam, and the other the axial design, where the flight tube is in the same axis as the ion beam. In both designs, all ions are sampled through the interface region, but instead of being focused into the mass filter in the conventional sequential way, packets (groups) of ions are electrostatically injected into the flight tube at exactly the same time.

flow injection analysis (FIA): A powerful front-end sampling accessory for ICP-MS that can be used for preparation, pretreatment, and delivery of the sample. It involves the introduction of a discrete sample aliquot into a flowing carrier stream. Using a series of automated pumps and valves, procedures can be carried out online to physically or chemically change the sample or analyte before introduction into the mass spectrometer for detection.

flue gas desulfurization wastewaters (FGDW): This is one of the most widely used technologies for removing pollutants such as sulfur dioxide, from flue gas emissions produced by coal- fired power plants. Sometimes called the limestone forced oxidation scrubbing system, but more commonly known as flue gas desulfurization (FGD), this process employs gas scrubbers to spray limestone slurry over the flue gas to convert gaseous sulfur dioxide to calcium sulfate.

fractogram: The separated particles that exit the outlet port of a field flow fractionation device into the detection system (e.g., UV/Vis or ICP-MS) are displayed as a temporal signal called a fractogram (similar to a chromatogram in chromatographic separation).

fringe rods: A set of four short rods operated in the RF-only mode, positioned at the entrance of a quadrupole mass analyzer. Their function is to minimize the effect of the fringing fields at the entrance of a quadrupole mass analyzer and thus improve the efficiency of transmission of ions into the mass analyzer. They are usually straight, but it has been suggested that curved fringe rods might reduce background levels.

fusion mixture: A compound or mixture added to solid samples as an aid to get them into solution. Fusion mixtures are usually alkaline salts (e.g., lithium metaborate, sodium carbonate) that are mixed with the sample (in powdered form) and heated in a muffle furnace to create a chemical/thermal reaction between the sample and the salt. The fused mixture is then dissolved in a weak mineral acid to get the analytes into solution.

G

gamma-counting spectrometry: A particle-counting technique that uses the measurement of the radioactive decay of gamma particles. Also refers to particle-counting techniques, gas dynamics: In ICP-MS, it refers to the flow and velocity of the plasma gas through the interface region. It dictates that the composition of the ion beam immediately behind the sampler cone be the same as the composition in front of the cone because the expansion of the gas at this stage is not controlled by electrodynamics. This happens because the distance over which ions exert influence on one another (the Debye length) is small compared to the orifice diameter of the sampler or skimmer cone. Consequently, there is little electrical interaction between the ion beam and the cone and relatively little interaction between the individual ions in the beam. In this way, gas dynamics ensures that the compositional integrity of the ion beam is maintained throughout the interface region, getter (gas purifier): A device that “cleans up” inorganic and organic contaminants in pure gases. The getter usually refers to a metal that oxidizes quickly, and when heated to a high temperature (usually by means of RF induction), evaporates, and absorbs/reacts with any residual impurities in the gas.

GFAA: An abbreviation for graphite furnace atomic absorption.

graphite furnace atomic absorption (GFAA): An electrothermal atomization (ETA) analytical technique that specifically uses a graphite tube (in place of the normal flame) to generate ground-state analyte atoms. The sample is first injected into the tube, which is heated up slowly to remove the matrix components. Further heating then generates ground-state atoms of the analyte, which absorb light of a particular wavelength from an element- specific, hollow cathode lamp source. The amount of light absorbed is measured by a monochromator (optical system) and detected by a photomultiplier or solid-state detector, which converts the photons into an electrical pulse. This absorbance signal is used to determine the concentration of that element in the sample. Typically used for ppb-level determinations. Also refers to electrothermal atomization (ETA), grounding mechanism: A way of eliminating the secondary discharge (pinch effect) produced by capacitive (RF) coupling of the load coil to the plasma. This undesired coupling between the RF voltage on the load coil and the plasma discharge produces a potential difference of a few hundred volts, which creates an electrical discharge (arcing) between the plasma and sampler cone of the interface. This mechanism varies with different instrument designs, but basically involves grounding the load coil to make sure the interface region is maintained at zero potential.

H

half-life: The time required for half the atoms of a given amount of a radioactive substance to disintegrate. This principle is used in particle-counting measuring techniques.

heating zones: The zones that describe the different temperature regions within a plasma discharge, where the sample passes through. The most common zones include the preheating zone (PHZ), where the sample is desolvated; the initial radiation zone (IRZ), where the sample is broken down into its molecular form; and the normal analytical zone (NAZ), where the sample is first atomized and then ionized.

HEN: An abbreviation for high-efficiency nebulizer.

hexapole: A multipole containing six rods, used in collision/reaction cell technology.

HGAA: An abbreviation for hydride generation atomic absorption.

high-efficiency nebulizer (HEN): A generic name given to a nebulizer that is very efficient, with very little wastage. Usually used to describe direct injection or microconcentric-designed systems, which deliver all or a very high percentage of the sample aerosol into the plasma discharge.

high-resolution mass analyzer: A generic name given to a mass spectrometer with very high resolving power. Commercial designs are usually based on the double-focusing magnetic sector design.

high-sensitivity interface (HSI): High-sensitivity interfaces (HSIs) are offered as an option with most commercial ICP-MS systems. They all work slightly differently but share similar components. By using a slightly different cone geometry, higher vacuum at the interface, one or more extraction lenses, or modified ion optic design, they offer up to ten times the sensitivity of a traditional interface. However, their limitations are that background levels are often elevated, particularly when analyzing samples with a heavy matrix. Therefore, they are more suited for the analysis of clean solutions, high-solids nebulizers: Nebulizers that are used to aspirate higher concentrations of dissolved solids into the ICP-MS. The most common types used are the Babbington, V-groove, and cone-spray designs. Not widely used for ICP-MS because of the dissolved-solids limitations of the technique, but are sometimes used with flow injection sample introduction techniques.

hollow ion mirror: A more recent development in ion-focusing optics. The ion mirror, which has a hollow center, creates a parabolic electrostatic field to reflect and refocus the ion beam at right angles to the ion source. This allows photons, neutrals, and solid particles to pass through it, while allowing ions to be reflected at right angles into the mass analyzer. The major benefit of this design is the highly efficient way the ions are refocused, offering extremely high sensitivity and low background across the mass range, homogenized sample beam: The laser beam in an excimer laser, which produces a much flatter beam profile and more precise control of the ablation process, hydride generation atomic absorption (HGAA): A very sensitive analytical technique for determining trace levels of volatile elements such as As, Bi, Sb, Se, and Те. Generation of the elemental hydride is carried out in a closed vessel by the addition of a reducing agent, such as sodium borohydride, to the acidic sample. The resulting gaseous hydride is swept into a special heated quartz cell (in place of the traditional flame burner head), where atomization occurs. Atomic absorption quantitation is then carried out in the conventional way, by comparing the absorbance of unknown samples against known calibration or reference standards.

hydrogen atom transfer: An ion-molecule reaction mechanism in a collision/reaction cell where a hydrogen atom is transferred to the interfering ion, which is converted to an ion at one mass higher.

hyperbolic fields: The four rods that make up a quadrupole are usually cylindrical or elliptical in shape. The electrical fields produced by these rods are typically hyperbolic in shape, hyper skimmer cone: The name for an additional cone used in one commercial ICP-MS interface design, used in order to tighten the ion beam entering the ion optics.

I

ICP: An abbreviation for inductively coupled plasma.

ICP-OES: An abbreviation for inductively coupled plasma optical emission spectrometry.

IDL: Refers to instrument detection limit.

impact bead (nebulizer): A type of spray chamber more commonly used in atomic absorption spectrometers. The aerosol from the nebulizer is directed onto a spherical bead, where the impact breaks the sample into large and small droplets. The large droplets fall out due to gravitational force, and the smaller droplets are directed by the nebulizer gas flow' into the atomization/excitation/ionization source.

inductively coupled plasma (ICP): The high-temperature source used to generate ions in ICP-MS. It is formed w'hen a tangential (spiral) flow' of argon gas is directed between the outer and middle tube of a quartz torch. A load coil (usually copper) surrounds the top end of the torch and is connected to an RF generator. When RF power (typically, 750-1,500 W) is applied to the load coil, an alternating current oscillates within the coil at a rate corresponding to the frequency of the generator. The RF oscillation of the current in the coil creates an intense electromagnetic field in the area at the top of the torch. With argon gas flowing through the torch, a high-voltage spark is applied to the gas, causing some electrons to be stripped from their argon atoms. These electrons, which are caught up and accelerated in the magnetic field, then collide with other argon atoms, stripping off still more electrons. This collision- induced ionization of the argon continues in a chain reaction, breaking down the gas into argon atoms, argon ions, and electrons, forming what is known as an “inductively coupled plasma (ICP) discharge” at the open end of the plasma torch, inductively coupled plasma optical emission spectrometry (ICP-OES): A multielement technique that uses an inductively coupled plasma to excite ground-state atoms to the point where they emit wavelength-specific photons of light, characteristic of a particular element. The number of photons produced at an element-specific wavelength is measured using high-resolving optical components to separate the analyte wavelengths and a photon-sensitive detection system to measure the intensity of the emission signal produced. This emission signal is directly related to the concentration of that element in the sample. Commercial instrumentation comes in two configurations: a traditional radial view, where the plasma is vertical and is viewed from the side (side-on viewing), and an axial view, where the plasma is positioned horizontally and is viewed from the end (end-on viewing), infrared (IR) lasers: Laser ablation systems that operate in the IR region of the electromagnetic spectrum, such as the Nd:YAG laser, which has its primary wavelength at l,064nm. instrument background noise: Square root of the spectral background of the instrument (in cps), usually measured at mass 220 amu, where there are no spectral features. Also refers to background signal, background noise, and detection limit, instrument background signal: Spectral background of the instrument (in cps), usually measured at mass 220 amu, where there are no spectral features. Also refers to background signal, background noise, and detection limit.

instrument detection limit (IDL): It’s a way of assessing an instrument’s detection capability. It is often referred to as signal-to-background noise and for a 99% confidence level is typically defined as 3x standard deviation (SD) of ten replicates of the sample blank, integration time: The total time spent measuring an analyte mass (peak). Comprising the time spent dwelling (sitting) on the peak multiplied by the number of points used for peak quantitation multiplied by the number of scans used in the measurement protocol. Also refers to duty cycle, measurement duty cycle, peak measurement protocol, settling time, and dwell time.

interface: The plasma discharge is coupled to the mass spectrometer via the interface. The interface region comprises a water-cooled metal housing containing the sampler cone and the skimmer cone, which directs the ion beam from the central channel of the plasma into the ion optic region.

interface cones: Refers to the sampler and skimmer cones housed in the interface region. Also refers to interface and interface region.

interface pressure: The pressure between the sampler cone and skimmer cone. This region is maintained at a pressure of approximately 1-2 torr by a mechanical roughing pump, interface region: A region comprising a water-cooled metal housing containing the sampler cone and the skimmer cone, which directs and focuses the ion beam from the central channel of the plasma into the ion optic region.

interferences: A generic term given to a non-analyte component that enhances or suppresses the signal intensity of the analyte mass. The most common interferences in ICP-MS are spectral, matrix, or sample transport in nature.

internal standardization (IS): A quantitation technique used to correct for changes in analyte sensitivity caused by variations in the concentration and type of matrix components found in the sample. An internal standard is a non-analyte isotope that is added to the blank solution, standards, and samples before analysis. It is typical to add three or four internal standard elements to the samples to cover all the analyte elements of interest across the mass range. The software adjusts the analyte concentration in the unknown samples by comparing the intensity values of the internal standard elements in the unknown sample to those in the calibration standards. Because ICP-MS is prone to many matrix- and sample- transport-based interferences, internal standardization is considered necessary to analyze most sample types.

ion: An electrically charged atom or group of atoms formed by the loss or gain of one or more electrons. A cation (positively charged ion) is created by the loss of an electron, and an anion (negatively charged ion) is created by the gain of an electron. The valency of an ion is equal to the number of electrons lost or gained and is indicated by a plus sign for cations and a minus sign for anions. ICP-MS typically involves the detection and measurement of positively charged ions generated in a plasma discharge.

ion chromatography (IC): A chromatographic separation technique used for determination of anionic species such as nitrates, chlorides, and sulfates. When coupled with ICP-MS, it becomes a very sensitive hyphenated technique for the determination of a wide variety of elemental ionic species.

ion energy: In ICP-MS, it refers to the kinetic energy of the ion, in electron volts (eV). It is a function of both the mass and velocity of the ion (KE = /2MV1). It is generally accepted that the spread of kinetic energies of all the ions in the ion beam entering the mass spectrometer must be on the order of a few electron volts to be efficiently focused by the ion optics and resolved by the mass analyzer.

ion energy spread: The variation in kinetic energy of all the ions in the ion beam emerging from the ionization source (plasma discharge). It is generally accepted that this variation (spread) of kinetic energies must be on the order of a few electron volts to be efficiently focused by the ion optics and resolved by the mass analyzer.

ion flow: The flow of ions from the interface region through the ion optics into the mass analyzer.

ion-focusing guide: An alternative name for the ion optics.

ion-focusing system: An alternative name for the ion optics.

ion formation: The transfer of energy from the plasma discharge to the sample aerosol to form an ion. By traveling through the different heating zones in the plasma, where the sample is first dried, vaporized and atomized, and then finally converted to an ion.

ion kinetic energy: Refers to ion energy.

ion lens: Often referred to as a single-lens component in the ion optic system. Also refers to ion optics.

ion lens voltages: The voltages put on one or more lens components in the ion optic system to electrostatically steer the ion beam into the mass analyzer. Also refers to ion optics.

ion mirror: A more recent development in ion-focusing optics. With this design, a parabolic electrostatic field is created with a hollow ion mirror to reflect and refocus the ion beam at right angles to the ion source. The ion mirror is an electrostatically charged ring, which is hollow in the center. This allows photons, neutrals, and solid particles to pass through it, while allowing ions to be reflected at right angles into the mass analyzer. The major benefit of this design is the highly efficient way the ions are refocused, offering extremely high sensitivity across the mass range with very little compromise in oxide performance. In addition, there is very little contamination of the ion optics because a vacuum pump sits behind the ion mirror to immediately remove these particles before they have a chance to penetrate further into the mass spectrometer.

ion optics: Comprises one or more electrostatically charged lens components that are positioned immediately after the skimmer cone. They are made up of a series of metallic plates, barrels, or cylinders, which have a voltage placed on them. The function of the ion optic system is to take ions after they emerge from the interface region and steer them into the mass analyzer. Another function of the ion optics is to reject the nonionic species such as particulates, neutral species, and photons and prevent them from reaching the detector. Depending on the design, this is achieved by using some kind of physical barrier, positioning the mass analyzer off axis relative to the ion beam, or electrostatically bending the ions by 90° into the mass analyzer.

ion packet: A “slice of ions” that is sampled from the ion beam in a time-of-flight (TOF) mass analyzer. In the TOF design, all ions are sampled through the interface cones, but instead of being focused into the mass filter in the conventional way, packets (groups) of ions are electrostatically injected into the flight tube at exactly the same time. Whether the orthogonal (right-angle) or axial (straight-on) approach is used, an accelerating potential is applied to the continuous ion beam. The ion beam is then “chopped” by using a pulsed voltage supply to provide repetitive voltage “slices” at a frequency of a few' kilohertz. The “sliced” packets of ions are then allowed to “drift” into the flight tube, where the individual ions are temporally resolved according to their differing velocities.

ion repulsion: The degree to which positively charged ions repel each other as they enter the ion optics. The generation of a positively charged ion beam is the first stage in the charge separation process. Unfortunately, the net positive charge of the ion beam means that there is now a natural tendency for the ions to repel one another. If nothing is done to compensate for this repulsion, ions of higher mass-to-charge ratio wall dominate the center of the ion beam and force the lighter ions to the outside. The degree of loss will depend on the kinetic energy of the ions—ions w'ith high kinetic energy (high-mass elements) will be transmitted in preference to ions with medium (mid-mass elements) or low kinetic energy (low-mass elements).

ionization source: In ICP-MS, the ionization source is the plasma discharge, which reaches temperatures of up to 10,000 К to ionize the liquid sample.

ionizing radiation counting techniques: Particle-counting techniques such as alpha, gamma, and scintillation counters that are used to measure the isotopic composition of radioactive materials. However, the limitation of particle-counting techniques is that the half-life of the analyte isotope has a significant impact on the method detection limit. This implies that they are better suited for the determination of short-lived radioisotopes, because meaningful data can be obtained in a realistic amount of time. They have also been successfully applied to the quantitation of long-lived radionuclides, but unfortunately require a combination of extremely long counting times and large amounts of sample to achieve low levels of quantitation.

ion-molecule chemistry: A chemical reaction between the analyte or interfering ion and molecules of the reaction gas in a collision/reaction cell. A reactive gas, such as hydrogen, ammonia, oxygen, methane, or gas mixtures, is bled into the cell, wdiich is a catalyst for ion-molecule chemistry to take place. By a number of different reaction mechanisms, the gaseous molecules react w'ith the interfering ions to convert them into either an innocuous species different from the analyte mass or a harmless neutral species. The analyte mass then emerges from the cell free of its interference and is steered into the analyzer quadrupole for conventional mass separation. In some cases, the chemistry can take place between the gaseous molecule and the analyte to form a new' analyte ion free of the interfering species.

isobar (or isobaric): Used in the context of atomic principles, it refers to two or more atoms with the same atomic mass (same number of neutrons) but different atomic number (different number of protons). Also refers to isobaric interferences.

isobaric interferences: The word “isobaric” is used in the context of atomic principles and refers to two or more atoms with the same atomic mass but different atomic number. In ICP-MS, they are a classification of spectrally induced interferences produced mainly by different isotopes of other elements in the sample, creating spectral interferences at the same mass as the analyte.

isotope: A different form of an element having the same number of protons in the nucleus (i.e., same atomic number) but a different number of neutrons (i.e., different atomic mass). There are 275 isotopes of the 81 stable elements in the periodic table, in addition to over 800 radioactive isotopes. Isotopes of a single element possess very similar properties, isotope dilution: An absolute means of quantitation in ICP-MS based on altering the natural abundance of two isotopes of an element by adding a known amount of one of the isotopes. The principle works by spiking the sample solution with a known weight of an enriched stable isotope. By knowing the natural abundance of the two isotopes being measured, the abundance of the spiked enriched isotope, the weight of the spike, and the weight of the sample, it is possible to determine the original trace element concentration. It is considered one of the most accurate and precise quantitation techniques for elemental analysis by ICP-MS. isotope ratio: The ability of ICP-MS to determine individual isotopes makes it suitable for an isotopic measurement technique called “isotope ratio analysis.” The ratio of two or more isotopes in a sample can be used to generate very useful information, such as an indication of the age of a geological formation, a better understanding of animal metabolism, and the identification of sources of environmental contamination. Similar to isotope dilution, isotope ratio analysis uses the principle of measuring the exact ratio of two isotopes of an element in the sample. With this approach, the isotope of interest is typically compared to a reference isotope of the same element, but can also be referenced to an isotope of another element.

isotope ratio precision: The reproducibility or precision of measurement of isotope ratios is very critical for some applications. For the highest-quality isotopic ratio precision measurements, it is generally acknowledged that either magnetic sector or time-of-flight (TOF) instrumentation offers the best approach over quadrupole ICP-MS. isotopic abundance: The percentage abundance of an isotope compared to the element’s total abundance in nature. Also refers to natural abundance and relative abundance of natural isotopes.

К

KE: An abbreviation for kinetic energy.

KED: An abbreviation for kinetic energy discrimination.

kinetic energy (KE): The energy possessed by a moving body due to its motion. It is equal to one- half the mass of the body times the square of its speed (velocity): KE = V2MV2. For kinetic energy as applied to moving ions, refers to ion energy.

kinetic energy discrimination (KED): In collision/reaction cell technology, it is one way to separate the newly formed by-product ions from the analyte ions. It is typically achieved by setting the collision cell potential (voltage) slightly more negative than the mass filter potential. This means that the collision by-product ions generated in the cell, which have a lower kinetic energy as a result of the collision process, are rejected, whereas the analyte ions, which have a higher kinetic energy, are transmitted to the mass analyzer.

L

laser ablation: A sample preparation technique that uses a high-powered laser beam to vaporize the surface of a solid sample and sweep it directly into the ICP-MS system for analysis. It is mainly used for samples that are extremely difficult to get into solution or for samples that require the analysis of small spots or inclusions on the surface.

laser absorption: The “coupling” efficiency of the sample with the laser beam in laser ablation work. The more light the sample absorbs, the more efficient the ablation process becomes. It is generally accepted that the shorter-wavelength excimer lasers have better absorption characteristics than the longer-wavelength IR laser systems for UV-transparent/opaque materials such as calcites, fluorites, and silicates and, as a result, generate smaller particle size and higher flow of ablated material.

laser fluence: A term used to describe the power density of a laser beam in laser ablation studies. It is defined as the laser pulse energy per focal spot area, measured in J/cm2. It is related to laser irradiance, which is the ratio of the fluence to the width of the laser pulse.

laser irradiance: A term used to describe the power density of a laser beam in laser ablation studies. Laser irradiance is the ratio of the laser pulse energy per focal spot area (i.e., fluence) to the width of the laser pulse. Also refers to laser fluence.

laser sampling: Refers to laser ablation.

laser vaporization: Refers to laser ablation.

laser wavelength: The primary wavelength of the optical components used in the design of a laser ablation system.

linear plane array detectors: Solid-state detector technology used to measure the mass spectrum in a simultaneous manner (recently commercialized in the Mattauch-Herzog magnetic sector instrument).

load coil: Another name for the RF coil used to generate a plasma discharge. Also refers to RF generator.

low-mass cutoff: This is a variation on bandpass filtering in a collision/reaction cell, which uses slightly different control of the filtering process. By operating the cell in the RF-only mode, the quadrupole’s stability boundaries can be tuned to cut off low masses where the majority of the interferences occur.

low-temperature plasma: An alternative name for cool or cold plasma.

M

magnetic field: A region around a magnet, an electric current, or a moving charged particle that is characterized by the existence of a detectable magnetic force at every point in the region and by the existence of magnetic poles. In ICP-MS, it usually refers to the magnetic field around the RF coil of the plasma discharge or the magnetic field produced by a quadrupole or an electromagnet.

magnetic sector mass analyzer: A design of mass spectrometer used in ICP-MS to generate very high resolving power as a way of reducing spectral interferences. Commercial designs typically utilize a very powerful magnet combined with an electrostatic analyzer (ESA). In this approach, known as the double-focusing design, the ions from the plasma are sampled. In the plasma, the ions are accelerated to a few kilovolts into the ion optic region before they enter the mass analyzer. The magnetic field, which is dispersive with respect to ion energy and mass, then focuses all the ions with diverging angles of motion from the entrance slit. The ESA, which is only dispersive with respect to ion energy, then focuses all the ions onto the exit slit, where the detector is positioned. If the energy dispersion of the magnet and ESA are equal in magnitude but opposite in direction, they will focus both ion angles (first focusing) and ion energies (second focusing) when combined together. Also refers to electrostatic analyzer.

mass analyzer: The part of the mass spectrometer where the separation of ions (based on their mass-to-charge ratio) takes place. In ICP-MS, the most common type of mass analyzers are quadrupole, magnetic sector, and time-of-flight (TOF) systems.

mass calibration: The ability of the mass spectrometer to repeatedly scan to the same mass position every time during a multielement analysis. Instrument manufacturers typically quote a mass calibration stability specification for their design of mass analyzer based on the drift or movement of the peak (in atomic mass units) position over a fixed period of time (usually 8h).

mass calibration stability: Refers to mass calibration.

mass discrimination: Sometimes called “mass bias.” In ICP-MS, it occurs when a higher- concentration isotope is suppressing the signal of the lower-concentration isotope, producing a biased result. The effect is not so obvious if the concentrations of the isotopes in the sample are similar, but can be quite significant if the concentrations of the two isotopes are vastly different. If that is the case, it is recommended to run a standard of known isotopic composition to compensate for the effects of the suppression, mass filter: Another name for a mass analyzer.

mass-filtering discrimination: A way of discriminating between analyte ions and the unwanted by-product interference ions generated in a collision/reaction cell, mass resolution: A measure of a mass analyzer’s ability to separate an analyte peak from a spectral interference. The resolution of a quadrupole is nominally 1 amu and is traditionally defined as the width of a peak at 10% of its height.

mass scanning: The process of electronically scanning the mass separation device to the peak of interest and taking analytical measurements. Basically, two approaches are used: singlepoint peak hopping, in which a measurement is typically taken at the peak maximum, and the multipoint-scanning approach, in which a number of measurements are taken across the full width of the peak. Also refers to ramp scanning, integration time, dwell time, settling time, peak measurement protocol, and peak hopping, mass separation: The process of separating the analyte ions from the non-analyte, matrix, solvent, and interfering ions with the mass analyzer, mass separation device: Another name for a mass analyzer.

mass shift mode: A mode used with a “triple quadruple collision/reaction cell instrument.” In this configuration, Q1 and Q2 are set to different masses. Similar to the “on-mass mode,” Q1 is set to the precursor ion mass (analyte and on-mass polyatomic interfering ions), controlling the ions that enter octapole collision/reaction cell. However in the mass-shift mode, Q2 is then set to mass of a target reaction product ion containing the original analyte. Mass-shift mode is typically used when the analyte ion is reactive, while the interfering ions are unre- active with a particular collision/reaction cell gas. mass spectrometer: The mass spectrometer section of an ICP-MS system is generally considered to be everything in the vacuum chamber from the interface region to the detector, including the interface cones, ion optics, mass analyzer, detector, and vacuum pumps, matching network (RF): The matching network of the RF generator compensates for changes in impedance (a material’s resistance to the flow of an electric current) produced by the sample’s matrix components or differences in solvent volatility. In crystal-controlled generators, this is usually done with mechanically driven servo-type capacitors. With free- running generators, the matching network is based on electronic tuning of small changes in the RF brought about by the sample, solvent, or matrix components, mathematical correction equations: Used to compensate or correct for spectral interference in ICP-MS. Similar to interelement corrections (IECs) used in ICP-OES, they work on the principle of measuring the intensity of the interfering isotope or interfering species at another mass, which is ideally free of any interferences. A correction is then applied, depending on the ratio of the intensity of the interfering species at the analyte mass to its intensity at the alternate mass.

Mathieu stability plot: A graphical representation of the stability of an ion as it passes through the rods of a multipole mass separation device. It is a function of the ratio of the RF to the DC current placed on each pair of rods. A plot of these ratios of multiple ions traveling through the multipole shows which ions are stable and make it through the rods to the detector and which ions are unstable and get ejected from the multipole. The most well-defined stability boundaries are obtained with a quadrupole and become more diffuse with higher-order multipoles such as hexapoles and octopoles.

matrix interferences: There are basically three types of matrix-induced interferences. The first, and simplest to overcome, is often called a “sample transport or viscosity effect” and is a physical suppression of the analyte signal brought on by the level of dissolved solids or acid concentration in the sample. The second type of matrix suppression is caused when the sample matrix affects the ionization conditions of the plasma discharge, which results in varying amounts of signal suppression depending on the concentration of the matrix components. The third type of matrix interference is often called “space-charge matrix suppression.” This occurs mainly when low-mass analytes are being determined in the presence of larger concentrations of high-mass matrix components. It has the effect of defocusing the ion beam, and unless any compensation is made, the high-mass matrix element will dominate the ion beam, pushing the lighter elements out of the way, leading to low sensitivity and poor detection limits. The classical way to compensate for matrix interferences is to use internal standardization.

matrix separation: Usually refers to some kind of chromatographic column technology to remove the matrix components from the sample before it is introduced into the ICP-MS system.

Mattauch-Herzog magnetic sector design: One of the earliest designs of double-focusing magnetic sector mass spectrometers. In this design, which was named after the German scientists who invented it, two or more ions of different mass-to-charge ratios are deflected in opposite directions in the electrostatic and magnetic fields. The divergent monoenergetic ion beams are then brought together along the same focal plane. Recently commercialized using a simultaneous-based direct charge array detector.

MDL: Refers to method detection limits.

measurement duty cycle: Also known as the duty cycle, it refers to a percentage of actual quantitation time compared to total integration time. It is calculated by dividing the total quantitation time (dwell time x number of sweeps x replicates x elements) by total integration time ([dwell time+settling/scanning time] x number of sweeps x replicates x elements).

membrane desolvation: Can be used with any sample introduction technique to remove solvent vapors. However, it is typically used with an ultrasonic or microconcentric nebulizer to remove the solvent from a liquid sample. In this design, the sample aerosol enters the membrane desolvator, where the solvent vapor passes through the walls of a tubular micro- porous PTFE or Nafion membrane. A flow of argon gas removes the volatile vapor from the exterior of the membrane, while the analyte aerosol remains inside the tube and is carried into the plasma for ionization.

method detection limit (MDL): The MDL is broadly defined as the minimum concentration of analyte that can be determined from zero with 99% confidence. MDLs are calculated in a similar manner to IDLs, except that the test solution is taken through the entire sample preparation procedure before the analyte concentration is measured multiple times.

microconcentric nebulizer: Is based on the concentric nebulizer design, but operates at much lower flow rates. Conventional nebulizers have a sample uptake rate of about 1 mL/min with an argon gas pressure of 1 L/min, whereas microconcentric nebulizers typically run at less than 0.1 mL/min and typically operate at much higher gas pressure to accommodate the lower sample flow rates.

microflow nebulizer: A generic name for nebulizers that operate at much lower flow rates than conventional concentric or cross-flow' designs. Also refers to microconcentric nebulizer.

micro-porous membrane: A tubular membrane made of an organic micro-porous material such as Teflon or Nafion, used in membrane desolvation. The sample aerosol enters the desolvation system, where the solvent vapor passes through the walls of the tubular membrane. A flow of argon gas then removes the volatile vapor from the exterior of the membrane, while the analyte aerosol remains inside the tube and is carried into the plasma for ionization.

microsampling: A generic name given to any front-end sampling device in atomic spectrometry that can be used for the preparation, pretreatment, and delivery of the sample to the spec- trometric analyzer. The most common type of microsampling device used in ICP-MS is the flow injection technique, which involves the introduction of a discrete sample aliquot into a flowing carrier stream. Using a series of automated pumps and valves, procedures can be carried out online to physically or chemically change the sample or analyte, before introduction into the mass spectrometer for detection.

microwave digestion: A method of digesting difficult-to-dissolve solid samples using microwave technology. Typically, a dissolution reagent such as a concentrated mineral acid is added to the sample in a closed acid-resistant vessel contained in a specially designed microwave oven. By optimizing the current, temperature, and pressure settings, difficult samples can be dissolved in a relatively short time compared to traditional hot plate sample digestion techniques.

microwave dissolution: An alternative name for microwave digestion.

microwave-induced plasma (MIP): The most basic form of electrodeless plasma discharge. In this device, microwave energy (typically, 100-200 W) is supplied to the plasma gas from an excitation cavity around a glass/quartz tube. The plasma discharge in the form of a ring is generated inside the tube. Unfortunately, even though the discharge achieves a very high power density, the high excitation temperatures only exist along a central filament. The bulk of the MIP never goes above 2,000-3,000 K, which means it is prone to very severe matrix effects. In addition, it is easily extinguished when aspirating liquid samples, so it has a found a niche as a detection system for gas chromatography.

MIP: An abbreviation for microwave-induced plasma.

molecular association reaction: An ion-molecule reaction mechanism in a collision/reaction cell, where an interfering ion associates with a neutral species (atom or molecule) to form a molecular ion.

molecular cluster ions: Species that are formed by two or more molecular ions combining together in a reaction cell to form molecular clusters.

molecular spectral interferences: Another name for polyatomic spectral interferences, which are typically generated in the plasma by the combination of two or more atomic ions. They are caused by a variety of factors, but are usually associated with the argon plasma/nebu- lizer gas used, matrix components in the solvent/sample, other elements in the sample, or entrained oxygen/nitrogen from the surrounding air.

monodisperse particulates: Nanoparticles, which are predominantly one size.

M/S mode: A mode used in a “triple quadrupole” collision reaction cell where the first quadrupole acts as a simple ion guide allowing all ions through to the collision/reaction cell, similar to a traditional single-quad ICP-MS system that uses a collision cell.

M/S M/S mode: A mode used in a “triple quadrupole” collision reaction cell, where the first quadrupole is operated with a 1 amu fixed band pass window, allowing only the target ions to enter the collision/reaction cell. This process can be implemented in two different ways: either the “on-mass” or “mass shift” modes.

multicomponent ion lens: An ion lens system consisting of several lens components, all of which have a specific role to play in the transmission of the analyte ions into the mass filter. To achieve the desired analyte specificity, the voltage can be optimized on every ion lens and is usually combined with an off-axis mass analyzer to reject unwanted photons and neutral species.

multichannel analyzer: The data acquisition system that stores and counts the ions as they strike the detector. As the ions emerge from the end of the quadrupole rods, they are converted into electrical pulses by the detector and stored by the multichannel analyzer. This multichannel data acquisition system typically has 20 channels per mass, and as the electrical pulses are counted in each channel, a profile of the mass is built up over the 20 channels, corresponding to the spectral peaks of the analyte masses being determined.

multichannel data acquisition: The process of storing and counting ions in ICP-MS. Also refers to multichannel analyzer.

multipole: The generic name given to a mass filter that isolates an ion of interest by applying DC or RF currents to pairs of rods. The most common type of mass analyzer multipole used in ICP-MS is the quadrupole (four rods). However, other higher orders of multipoles used in collision/reaction cell technology include hexapoles (six rods) and octopoles (eight rods).

m/z: Another way of expressing mass-to-charge ratio.

N

nanomaterials: Nanomaterials can occur in nature, such as clay minerals and humic acids; they can be incidentally produced by human activity such as diesel emissions or welding fumes; or they can be specifically engineered to exhibit unique optical, electrical, physical, or chemical characteristics. Also refers to engineered nanomaterials (ENMs).

nanometrology: The measurement and characterization of nanoparticles.

nanoparticles (NP): Particles that are released from engineered nanomaterials when they enter the environment.

natural abundance: The natural amount of an isotope occurring in nature. Also refers to isotopic abundance.

natural isotopes: Different isotopic forms of an element that occur naturally on or beneath the earth’s crust.

Nd:YAG laser: Nd:YAG is an acronym for neodymium-doped yttrium aluminum garnet, a compound that is used as the lasing medium for certain solid-state lasers. In this design, the YAG host is typically doped with around 1% neodymium by weight. Nd:YAG lasers are optically pumped using a flashlamp or laser diodes and emit light with a wavelength of 1,064 nm in the infrared region. However, for many applications, the infrared light is frequency-doubled, frequency-tripled, frequency-quadrupled, or frequency-quintupled by using additional optical components to generate output wavelengths in the visible and UV regions. Typical wavelengths used for laser ablation/ICP-MS work include 532 nm (doubled), 266 nm (quadrupled), and 213 nm (quintupled). Pulsed Nd:YAG lasers are usually operated in the so-called “Q-switching” mode, where an optical switch is inserted in the laser cavity, waiting for a maximum population inversion in the neodymium ions before it opens. Then, the light wave can run through the cavity, depopulating the excited laser medium at maximum population inversion. In this Q-switched mode, output powers of 20 MW and pulse durations of less than 10 ns are achieved.

nebulizer: The component of the sample introduction system that takes the liquid sample and pneumatically breaks it down into an aerosol using the pressure created by a flow of argon gas. The concentric and cross-flow designs are the most common in ICP-MS.

neutral species: Species generated in the plasma torch that have no positive or negative charge associated with them. If they are not eliminated, they can find their way into the detector and produce elevated background levels.

neutron: A fundamental particle that is neutral in charge, found in the nucleus of an atom. It has a mass equal to that of a proton. The number of neutrons in the atomic nucleus defines the isotopic composition of that element.

Nier-Johnson magnetic sector design: Nier-Johnson double-focusing magnetic sector instrumentation is the technology that all modern magnetic sector instrumentation is based on. Named after the scientists who developed it, Nier-Johnson geometry comes in two different designs, the “standard” Nier-Johnson geometry and “reverse” Nier-Johnson geometry. Both these designs, which use the same basic principles, consist of two analyzers: a traditional electromagnet analyzer and an electrostatic analyzer (ESA). In the standard (sometimes called “forward”) design, the ESA is positioned before the magnet, and in the reverse design, it is positioned after the magnet, ninety (90)-degree ion lens: A design of ion optics that bends the ion beam 90°.

NP: Refers to nanoparticles.

О

octapole: A multipole mass-filtering device containing eight rods. In ICP-MS, octopoles are typically used in collision/reaction cell technology, off-axis ion lens: An ion lens system that is not on the same axis as the mass analyzer. Designed to stop particulates, neutral species, and photons from hitting the detector, on-mass mode: A mode used with the “triple quadrupole” collision/reaction cell. In this configuration, Q1 and Q2 are both set to the target mass. Q1 allows only the precursor ion mass to enter the cell (analyte and on-mass polyatomic interfering ions). The octapole collision/reaction cell then separates the analyte ion from the interferences using the reaction chemistry of a reactive gas, while Q2 measures the analyte ion at the target mass after the on-mass interferences have been removed by reactions in the cell, oxide ions: Polyatomic ions that are formed between oxygen and other elemental components in the plasma gas, sample matrix, or solvent. They are generally not desirable because they can cause spectral overlaps on the analyte ions. Oxide formation is typically worse in the cooler zones of the plasma, and as a result, can be reduced by optimizing the RF power, nebulizer gas flow, and sampling position.

P

parabolic field: Shape of the magnetic fields produced by a quadrupole.

particle-counting techniques: Include alpha, gamma, and scintillation counters that are used to measure the isotopic composition of radioactive materials. However, the limitation of particle-counting techniques is that the half-life of the analyte isotope has a significant impact on the method’s detection limit. This means that to get meaningful data in a realistic amount of time, they are better suited for the determination of short-lived radioisotopes. They have been successfully applied to the quantitation of long-lived radionuclides, but unfortunately require a combination of extremely long counting times and large amounts of sample to achieve low levels of quantitation.

peak hopping: A quantitation approach in which the quadrupole power supply is driven to a discrete position on the analyte mass (normally the maximum point), allowed to settle (settling time), and a measurement taken for a fixed amount of time (dwell time). The integration time for that peak is the dwell time multiplied by the number of scans (scan time). Multielement peak quantitation involves peak hopping to every mass in the multielement run. Also refers to measurement duty cycle and peak measurement protocol.

peak integration: The process of integrating an analytical peak (mass). Also refers to integration time, peak measurement protocol, and measurement duty cycle.

peak measurement protocol: The protocol of scanning the quadrupole and measuring a peak in ICP-MS. In multielement analysis, the quadrupole is scanned to the first mass. The electronics are allowed to settle (settling time), left to dwell for a fixed period of time at one or multiple points on the peak (dwell time), and signal intensity measurements are taken (based on the dwell time). The quadrupole is then scanned to the next mass and the measurement protocol repeated. The complete multielement measurement cycle (sweep) is repeated as many times as is needed to make up the total integration per peak and the number of required replicate measurements per sample analysis, peak quantitation: The process of quantifying the peak in ICP-MS using calibration standards.

Also refers to peak hopping, peak integration, and peak measurement protocol.

Peltier cooler: A thermoelectric cooler using the principle of generating a cold environment by creating a temperature gradient between two different materials. It uses electrical energy via a solid-state heat pump to transfer heat from a material on one side of the device to a different material on the other side, thus producing a temperature gradient across the device (similar to a household air-conditioning system), peristaltic pump: A small pump in the sample introduction system that contains a set of mini rollers (typically, 12) all rotating at the same speed. The constant motion and pressure of the rollers on the pump tubing feeds the sample through to the nebulizer. Peristaltic pumps are usually used with cross-flow nebulizers.

photon stop: A grounded metal disk in the ion lens system that is used as a physical barrier to stop particulate matter, neutral species, and photons from getting to the detector, physical interferences: An alternative term used to describe sample transport- or viscosity-based suppression interferences.

pinch effect: An effect caused by an undesired electrostatic (capacitive) coupling between the voltage on the load coil and the plasma discharge, which produces a potential difference of a few hundred volts. This capacitive coupling is commonly referred to as the pinch effect and shows itself as a secondary discharge (arcing) in the region where the plasma is in contact with the sampler cone.

piston pump: A pump using a small piston or syringe to introduce the sample to the nebulizer (used instead of a peristaltic pump). They typically produce a more stable signal, plasma discharge: Another name for an inductively coupled plasma (ICP). plasma source: Refers to the RF hardware components that create the plasma discharge, including the RF generator, matching network, plasma torch, and argon gas pneumatics, plasma torch: Another name for the quartz torch that is used to generate the plasma discharge. The plasma torch consists of three concentric tubes: an outer tube, middle tube, and sample injector. The torch can either be one piece, where all three tubes are connected, or have a demountable design, in which the tubes and the sample injector are separate. The gas (usually argon) that is used to form the plasma (plasma gas) is passed between the outer and middle tubes at a flow rate of 12-17 L/min. A second gas flow (auxiliary gas) passes between the middle tube and the sample injector at 1 L/min, and is used to change the position of the base of the plasma relative to the tube and the injector. A third gas flow (nebulizer gas) also at 1 L/min brings the sample, in the form of a fine-droplet aerosol, from the sample introduction system and physically punches a channel through the center of the plasma. The sample injector is often made from other materials besides quartz, such as alumina, platinum, and sapphire, if highly corrosive materials need to be analyzed.

polyatomic spectral interferences: Another name for molecular-based spectral interferences, which are typically generated in the plasma by the combination of two or more atomic ions. They are caused by a variety of factors, but are usually associated with the argon plasma/ nebulizer gas used, matrix components in the solvent/sample, other elements in the sample, or entrained oxygen/nitrogen from the surrounding air. polydisperse particulates: Nanoparticles that are many different sizes and dimensions, precursor ion: Usually refers to a polyatomic or isobaric interfering ion that is formed in the plasma as opposed to a product (or by-product) ion that is formed in the collision/reaction cell, product ion: Usually refers to a product (or by-product) ion that is formed in the collision/reaction cell as opposed to a precursor interfering ion (polyatomic or isobaric) that is formed in the plasma.

proton: A stable, positively charged fundamental particle that shares the atomic nucleus with a neutron. It has a mass 1,836 times that of the electron, proton transfer: A reaction mechanism in a collision/reaction cell in which the interfering polyatomic species gives up a proton, which is then transferred to the reaction gas molecule to form a neutral atom.

pulse counting: Refers to the conventional mode of counting ions with the detector measurement circuitry. Depending on the type of detection system that is used, an ion emerges from the quadrupole and strikes the ion-sensitive surface (discrete dynode, Channeltron, etc.) of the detector to generate electrons. These electrons move down the detector and generate more secondary electrons. This process is repeated at each stage of the detector, producing a pulse of electrons that is finally captured by the detector’s collecting and counting circuitry.

Q

QID: Refers to quadrupole ion deflector.

quadrupole: The most common type of mass separation device used in commercial ICP-MS systems. It consists of four cylindrical or hyperbolic metallic rods of the same length (15-20cm) and diameter (approximately 1cm). The rods are typically made of stainless steel or molybdenum and sometimes coated with a ceramic coating for corrosion resistance. A quadrupole operates by placing both a DC field and a time-dependent AC of RF 2-3 MHz on opposite pairs of the four rods. By selecting the optimum AC/DC ratio on each pair of rods, ions of a selected mass are then allowed to pass through the rods to the detector, whereas the others are unstable and ejected from the quadrupole.

quadrupole ion deflector (QID): A commercial ion optics design that bends the ion beam at right angles.

quadrupole power supply: Another name for the electronic components that control the RF and DC voltages to change the mass-filtering characteristics.

quadrupole scan rate: Scan rates of commercial quadrupole mass analyzers are on the order of 2,500 amu/s. The quadrupole scan rate and the slope at which the RF and DC voltages of the quadrupole power supply are scanned will determine the desired resolution setting. A steeper slope translates to higher resolution, whereas a shallower slope means poorer resolution.

quadrupole stability regions: The region of the Mathieu stability plot where the trajectory of an ion is stable and makes it through to the end of the quadrupole rods. All commercial ICP-MS systems that utilize quadrupole technology as the mass separation device operate in the first stability region, where resolving power is typically on the order of 500-600. If the quadrupole is operated in the second or third stability regions, resolving powers of 4,000 and 9,000, respectively, have been achieved. However, improving resolution using this approach has resulted in a significant loss of signal and higher background levels.

quantitative methods: The different kinds of quantitative analyses available in ICP-MS, which include traditional quantitative analysis (using external calibration, standard additions, or addition calibration), semiquantitative routines (semiquant), isotope dilution (ID) methods, isotope ratio (IR) measurements, and classical internal standardization (IS).

quartz torch: The standard plasma torch used in ICP-MS. Also refers to plasma torch.

R

radio frequency (RF) generator: The power supply used to create the plasma discharge. Hardware includes the RF generator, matching network, plasma torch, and argon gas pneumatics.

radioactive isotope: Sometimes known as “radioisotope,” a radioactive isotope is a natural or artificially created isotope of an element having an unstable nucleus that decays, emitting alpha, beta, or gamma rays until stability is reached. The stable end product is typically a nonradioactive isotope of another element.

ramp scanning: One of the two approaches for quantifying a peak in ICP-MS (peak hopping being the other). In the multichannel ramp scanning approach, a continuous smooth ramp of l - n channels (where n is typically 20) per mass is made across the peak profile. Mainly used for accumulating spectral and peak shape information when doing mass scans. It is normally used for doing mass calibration and resolution checks and as a classical qualitative method development tool to find out what elements are present in the sample and to assess their spectral implications on the masses of interest. Full-peak ramp scanning is not normally used for doing rapid quantitative analysis, because valuable analytical time is wasted taking data on the wings and valleys of the peak where the signal-to-noise ratio is poorest. For this kind of work, peak hopping is normally chosen.

reaction cell: A collision/reaction cell that specifically uses ion-molecule reactions to eliminate the spectral interference. Often used to describe a dynamic reaction cell (DRC).

reaction mechanism: The mechanism by which the interfering ion is reduced or minimized to allow the determination of the analyte ion. The most common collisional mechanisms seen in collision/reaction cells include collisional focusing, dissociation, and fragmentation, whereas the major reaction mechanisms include exothermic/endothermic associations, charge transfer, molecular associations, and proton transfer.

reactive gases: In ICP-MS, the term refers to gases such as hydrogen, ammonia, oxygen, methane, or those used to stimulate ion-molecule reactions in a collision/reaction cell (CRC) or collision/reaction interface (CRI).

relative abundance of natural isotopes: The isotopic composition expressed as a percentage of the total abundance of that element found in nature.

resolution: A measure of the ability of a mass analyzer to separate an analyte peak from a spectral interference. The resolution of a quadrupole is nominally 1 amu and is traditionally defined as the width of a peak at 10% of its height.

resolving power: Although resolving power and resolution are both a measure of a mass analyzer’s ability to separate an analyte peak from a spectral interference, the term “resolving power” is normally associated with magnetic sector technology and is represented by the equation R = ml Am, where m is the nominal mass at which the peak occurs and Am is the mass difference between two resolved peaks. The resolving power of commercial double-focusing magnetic sector mass analyzers is on the order of 1,000-10,000, depending on the resolution setting chosen.

response tables: The intensity values for known concentrations of every elemental isotope stored in the instrument’s calibration software. When semiquantitative analysis is carried out, the signal intensity of an unknown sample is compared against the stored response tables. By correcting for common spectral interferences and applying heuristic, knowledge-driven routines in combination with numerical calculations, a positive or negative confirmation can be made for each element present in the sample.

reverse Nier-Johnson double-focusing magnetic sector instrumentation: The technology that all modern magnetic sector instrumentation is based on. Named after the scientists who developed it, Nier-Johnson geometry comes in two different designs: the “standard” Nier- Johnson geometry and “reverse” Nier-Johnson geometry. Both these designs, which use the same basic principles, consist of two analyzers: a traditional electromagnet analyzer and an electrostatic analyzer (ESA). In the standard (sometimes called “forward”) design, the ESA is positioned before the magnet, and in the reverse design, it is positioned after the magnet.

RF generator: An alternative name for radio frequency generator.

right-angled ion lens design: A recent development in ion-focusing optics, which utilizes a parabolic ion mirror to bend and refocus the ion beam at right angles to the ion source.

The ion mirror incorporates a hollow structure that allows photons, neutrals, and solid particles to pass through it, while allowing ions to be deflected at right angles into the mass analyzer.

roughing pump: Traditional mechanical roughing or oil-based pumps are used in ICP-MS to pump the interface region down to approximately 1-2 torr and also to back up the turbomolecular pump used in the ion optics region of the mass spectrometer, ruby laser: Ruby laser systems operate at 694 nm in the visible region of the electromagnetic spectrum.

S

S/B: An abbreviation for signal-to-background ratio.

sample aerosol: Refers to aerosol.

sample digestion: The process of digesting a sample by traditional hot plate, fusion techniques, or microwave technology to get the matrix and analytes into solution.

sample dissolution: The process of dissolving a sample by traditional hot plate, fusion techniques, or microwave technology to get the matrix and analytes into solution.

sample injector: The central tube of the plasma torch that carries the sample aerosol mixed with the nebulizer gas. It can be a fixed part of the quartz torch or it can be separate (demountable) and be made from other materials, such as alumina, platinum, and sapphire, for the analysis of highly corrosive materials.

sample introduction system: The part of the instrument that takes the liquid sample and puts it into the plasma torch as a fine-droplet aerosol. It comprises a nebulizer to generate the aerosol and a spray chamber to reject the larger droplets and allow only the smaller droplets into the plasma discharge.

sample preparation: The entire process of preparing the sample for aspiration into the ICP mass spectrometer.

sample throughput: The rate at which samples can be analyzed.

sample transport interferences: A term used to describe a physical suppression of the analyte signal caused by matrix components in the sample. It is more exaggerated with samples having high levels of dissolved solids, because they are transported less efficiently through the sample introduction system than aqueous-type samples. Also refers to physical interferences.

sampler cone: A part of the mass spectrometer interface region, where the ion beam from the plasma discharge first enters. The sampler cone, which is the first cone of the interface, is typically made of nickel or platinum and contains a small orifice of approximately 0.8-1.2 mm diameter, depending on the design. The sampler cone is much more pointed than the skimmer cone.

sampling accessories: Customized sample introduction techniques optimized for a particular application problem or sample type. The most common types used today include the following: laser ablation/sampling (LA/S), flow injection analysis (FIA), electrothermal vaporization (ETV), desolvation systems, direct injection nebulizers (DIN), and chromatography separation techniques.

scan time: The mass analyzer scan time is the time it takes to scan from one isotope to the next.

Scott spray chamber: A sealed spray chamber with an inner tube inside a larger tube. The sample aerosol from the nebulizer is first directed into the inner tube. The aerosol then travels the length of the inner tube, where the larger droplets fall out by gravity into a drain tube and the smaller droplets return between the inner and outer tube, where they eventually exit into the sample injector of the plasma torch.

secondary discharge: Another term used for the pinch effect.

secondary (side) reactions: Reactions that occur in a collision/reaction cell that are not a part of the main interference reduction mechanism. If not anticipated and compensated for, secondary reactions can lead to erroneous results.

semiquant: An abbreviated name used to describe semiquantitative analysis.

semiquantitative analysis: A method for assessing the approximate concentration of up to 70 elements in an unknown sample. It is based on comparing the intensity of a small group of elements against known response tables stored in the instrument’s calibration software. By correcting for common spectral interferences and applying heuristic, knowledge-driven routines in combination with numerical calculations, a positive or negative confirmation can be made for each element present in the sample.

settling time: The time taken for the mass analyzer electronics to settle before a peak intensity measurement is taken for the operator-selected dwell time. The dwell time can usually be selected on an individual mass basis, but the settling time is normally fixed because it is a function of the mass analyzer and detector electronics.

shadow stop: A grounded metal disk that stops particulate matter, neutral species, and photons from getting to the detector. It is considered a part of the ion optics and is sometimes called a photon stop.

side reactions: Reactions that occur in a collision/reaction cell that are not a part of the main interference reduction mechanism. If not anticipated and compensated for, secondary reactions can lead to erroneous results.

signal-to-background ratio (S/B): The ratio of the signal intensity of an analyte to its background level at a particular mass. When considering the noise of the background signal (standard deviation of the signal), it is typically used as an assessment of the detection limit for that element. Also refers to detection limit, background signal, and background noise.

single-particle ICP-MS: A technique used to characterize nanoparticles. The method involves introducing nanoparticle (NP)-containing samples, at very dilute concentration, into the ICP-MS, and collecting time-resolved data.

single-point peak hopping: A quantitation in which the quadrupole power supply is driven to a discrete position on the analyte mass (normally the maximum point), allowed to settle (settling time), and a measurement taken for a fixed amount of time (dwell time). The integration time for that peak is the dwell time multiplied by the number of scans (scan time). Multielement peak quantitation involves peak hopping to every mass in the multielement run. Also refers to measurement duty cycle and peak measurement protocol.

skimmer cone: A part of the mass spectrometer interface region where the ion beam from the plasma discharge first enters. The skimmer cone, which is the second cone of the interface, is typically made of nickel or platinum and contains a small orifice of approximately 0.5-0.8mm diameter, depending on the design. The skimmer cone is much less pointed than the sampler cone.

solvent-based interferences: Spectral interferences derived from an elemental ion in the solvent (e.g., water and acid) combining with another ion from either the sample matrix or plasma gas (argon) to produce a polyatomic ion that interferes with the analyte mass.

SOP: Standard operating procedure.

space charge effect: A type of matrix-induced interference that produces a suppression of the analyte signal. This occurs mainly when low-mass analytes are being determined in the presence of larger concentrations of high-mass matrix components. It has the effect of defocusing the ion beam, and without compensation, the high-mass matrix element will dominate the ion beam, pushing the lighter elements out of the way, leading to low sensitivity and poor detection limits. The classical way to compensate for a space-charge matrix interference is to use an internal standard of similar mass to the analyte.

speciation analysis: In ICP-MS, it is the study and quantification of different species or forms of an element using a chromatographic separation device coupled to an ICP mass spectrometer. In this configuration, the instrument becomes a very sensitive detector for trace element speciation studies when coupled with high-performance liquid chromatography (HPLC), ion chromatography (IC), gas chromatography (GC), or capillary electrophoresis (CE). In these hybrid techniques, element species are separated on the basis of their chromatograph retention/mobility times and then eluted/passed into the ICP mass spectrometer for detection. The intensity of the eluted peaks is then displayed for each isotopic mass of interest in the time domain.

spectral interferences: A generic name given to interferences that produce a spectral overlap at or near the analyte mass of interest. In ICP-MS, there are two main types of spectral interference that have to be taken into account. Polyatomic spectral interferences (or molecular-based spectral interferences) are typically generated in the plasma by the combination of two or more atomic ions. They are caused by a variety of factors, but are usually associated with the argon plasma/nebulizer gas used, matrix components in the solvent/sample, other elements in the sample, or entrained oxygen/nitrogen from the surrounding air. The other type is an isobaric spectral interference, which is caused by different isotopes of other elements in the sample creating spectral interferences at the same mass as the analyte.

SP-ICP-MS: Refers to single-particle ICP-MS.

spray chamber: The component of the sample introduction system that takes the aerosol generated by the nebulizer and rejects the larger droplets for the more desirable smaller droplets.

SRM: An abbreviation for standard reference materials.

stability: The ability of a measuring device to consistently replicate a measurement. In ICP-MS, it usually refers to the capability of the instrument to reproduce the signal intensity of the calibration standards over a fixed period of time without the use of internal standardization. Short-term stability is generally defined as the precision (as % RSD [relative standard deviation]) of ten replicates of a single or multielement solution, whereas long-term stability is defined as the precision (as % RSD) of a fixed number of measurements over a 4-8-hour time period of a single or multielement solution. However, stability in mass spectrometry can also refers to mass calibration stability, which is the ability of the mass spectrometer to repeatedly scan to the same mass position every time during a multielement analysis.

stability boundaries/regions: The RF/DC boundaries of the Mathieu stability plot where an ion is stable as it passes through a quadrupole mass-filtering device. Also refers to Mathieu stability plot.

standard additions: A method of calibration that provides an effective way to minimize sample-specific matrix effects by spiking samples with known concentrations of analytes. In standard addition calibration, the intensity of a blank solution is first measured. Next, the sample solution is “spiked” with known concentrations of each element to be determined. The instrument measures the response for the spiked samples and creates a calibration curve for each element for which a spike has been added. The calibration curve is a plot of the blank subtracted intensity of each spiked element against its concentration value. After creating the calibration curve, the unspiked sample solutions are then analyzed and compared to the calibration curve. Depending on the slope of the calibration curve and where it intercepts the X-axis, the instrument software determines the unspiked concentration of the analytes in the unknown samples.

standard reference materials (SRM): Well-established reference matrices that come with certified values and associated statistical data which have been analyzed by other complementary techniques. Their purpose is to check the validity of an analytical method, including sample preparation, instrument methodology, and calibration routines, to achieve sample results that are as accurate and precise as possible and can be defended under intense scrutiny.

standardization methods: Refers to the different types of calibration routines available in ICP-MS, including quantitative analysis (external calibration and standard additions), semiquantita- tive analysis, isotope dilution, isotope ratio, and internal standardization methods.

syringe pump: Refers to piston pump.

T

thermoelectric cooling device: Better known as a Peltier cooler, it generates a cold environment by creating a temperature gradient between two different materials. It uses electrical energy via a solid-state heat pump to transfer heat from a material on one side of the device to a different material on the other side, thus producing a temperature gradient across the device (similar to a household air conditioner).

thermoelectric flow meter: A device to measure the liquid flow' through a nebulizer to check for any blockages or breakages.

time-of-flight mass spectrometry (TOFMS): A mass spectrometry technique based on the principle that the kinetic energy (KE) of an ion is directly proportional to its mass (m) and velocity (VO, which can be represented by the equation KE = '/2MV2. Therefore, if a population of ions with different masses is given the same KE by an accelerating voltage ([/), the velocities of the ions will all be different, depending on their masses. This principle is then used to separate ions of different mass-to-charge (m/z) in the time (?) domain, over a fixed flight path distance (D), represented by the equation mlz, = Wf-tD1. The simultaneous nature of sampling ions in TOF offers distinct advantages over traditional scanning (sequential) quadrupole technology for ICP-MS applications, where large amounts of data need to be captured in a short amount of time, such as the multielement analysis of transient peaks (laser ablation, flow' injection, etc.).

time-of-flight (TOF) mass spectrometry (axial design): There are basically tw'o different sampling approaches that are used in commercial TOF mass analyzers: the axial and orthogonal designs. In the axial design, the flight tube is in the same axis as the ion beam, w'hereas in the orthogonal design, the flight tube is positioned at right angles to the sampled ion beam. The axial approach applies an accelerating potential in the same axis as the incoming ion beam as it enters the extraction region. Because the ions are in the same plane as the detector, the beam has to be modulated using an electrode grid to repel the “gated” packet of ions into the flight tube. This kind of modulation generates an ion packet that is long and thin in cross section (in the horizontal plane), w'hich is then resolved in the time domain according to the different ionic masses. Also refers to time-of-flight mass spectrometry.

time-of-flight (TOF) mass spectrometry (orthogonal design): There are basically two different sampling approaches that are used in commercial TOF mass analyzers, the axial and orthogonal designs. In the axial design, the flight tube is in the same axis as the ion beam, whereas in the orthogonal design, the flight tube is positioned at right angles to the sampled ion beam. With the orthogonal approach, an accelerating potential is applied at right angles to the continuous ion beam from the plasma source. The ion beam is then “chopped” by using a pulsed voltage supply coupled to the orthogonal accelerator to provide repetitive voltage “slices” at a frequency of a few' kilohertz. The “sliced” packets of ions, w'hich are typically tall and thin in cross section (in the vertical plane), are then allowed to “drift” into the flight tube, where the ions are temporally resolved according to their differing velocities. Also refers to time-of-flight mass spectrometry.

TOFMS: An abbreviation for time-of-flight mass spectrometry.

torch design: Refers to the different kinds of commercially available torch designs.

trace metal speciation studies: Refers to speciation analysis.

transient signal (peak): A signal that lasts for a finite amount of time, compared to a continuous signal that lasts for as long as the sample is being aspirated. Transient peaks are typically generated by alternative sampling devices such as laser ablation, flow injection, or chromatographic separation systems where discrete amounts of sample are introduced into the ICP mass spectrometer.

triple cone interface: A commercial design of an ICP-MS interface that uses three cones. Also refers to hyper skimmer cone.

“triple quadrupole” collision/reaction cell: A commercial collision/reaction cell design that has an additional quadrupole prior to the collision/reaction cell multipole and the analyzer quadrupole. This first quadrupole acts as a simple mass filter to allow only the analyte masses to enter the cell, while rejecting all other masses. With all non-analyte, plasma and sample matrix ions excluded from the cell, sensitivity and interference removal efficiency is significantly improved compared to traditional collision/reaction cell technology coupled with a single quadrupole mass analyzer.

turbomolecular pump (turbo pump): A type of vacuum pump used to maintain a high vacuum in the ion optics and mass analyzer regions of the ICP mass spectrometer. These pumps work on the principle that gas molecules can be given momentum in a desired direction by repeated collision with a moving solid surface. In a turbo pump, a rapidly spinning turbine rotor strikes gas (argon) molecules from the inlet of the pump towards the exhaust, creating and maintaining a vacuum. In the case of ICP-MS, two pumps are normally used, a large pump for the ion optic region, which creates a vacuum of approximately 10~3 torr, and another small pump for the mass analyzer region, which generates a vacuum of 10-6 torr. However, some designs use a twin-throated turbo pump, in which one powerful pump is used with two outlets, one for the ion optics and one for the mass analyzer region.

twin-throated turbomolecular pump: In some designs of ICP mass spectrometer, a single twin- throated turbo pump is used instead of two separate pumps. In this design, one powerful pump is used with two outlets, one for the ion optics and one for the mass analyzer region.

U

ultrasonic nebulizer (USN): A type of desolvating nebulizer that generates an extremely fine- droplet aerosol for introduction into the ICP mass spectrometer. The principle of aerosol generation using this approach is based on a sample being pumped onto a quartz plate of a piezoelectric transducer. Electrical energy of 1-2MHz is coupled to the transducer, which causes it to vibrate at high frequency. These vibrations disperse the sample into a fine-droplet aerosol, which is carried in a stream of argon. With a conventional ultrasonic nebulizer, the aerosol is passed through a heating tube and a cooling chamber, where most of the sample solvent is removed as a condensate before it enters the plasma. However, commercial ultrasonic nebulizers are also available with membrane desolvation systems.

universal cell: The name applied to a commercial collision/reaction cell that offers the capability of either a collision cell using inert gases and KED or a DRC using highly reactive gases.

USN: An abbreviation for ultrasonic nebulizer.

UV laser: A generic name given to a laser ablation system that works in the ultraviolet region of the electromagnetic spectrum. The three most common wavelengths used in commercial equipment are all UV lasers. They include the 266 nm (frequency-quadrupled) Nd:YAG laser, the 213 nm (frequency-quintupled) Nd:YAG laser, and the 193 nm ArF excimer laser system. Also refers to excimer laser and Nd:YAG laser.

V

vacuum chamber: The region of the mass spectrometer that is under negative pressure created by a combination of roughing and turbomolecular pumps. As the ion beam moves from the plasma, which is at atmospheric pressure (760 torr), it enters the interface region between the sampler and skimmer cone (1-2 torr) before it is focused through the ion optic vacuum chamber region (10—4 torr) and eventually goes through the mass analyzer vacuum chamber (at 10~6 torr). Also refers to turbomolecular pump.

vacuum gauge: Used to measure the pressure in the different vacuum chambers of the mass spectrometer.

vacuum pump: A number of vacuum pumps are used to create the vacuum in an ICP mass spectrometer. Two roughing pumps are used, one for the interface region and another to back up the first turbomolecular pump of the ion optic region. Also, two turbomolecular pumps (or in some designs, one twin-throated pump) are used, one for the ion optics and another for the main mass analyzer region. Also refers to roughing pump, turbomolecular pump, and twin-throated turbomolecular pump.

Vapor-phase decomposition (VPD): A technique used to dissolve and collect trace metal impurities on the surface of a silicon wafer, by rolling a few hundred microliters of hydrofluoric acid (HF) over the surface.

visible laser: A laser that operates in the visible region of the electromagnetic spectrum. An example is the ruby laser, which operates at 694 nm.

W

wavelength: A name commonly used to identify an emission line in nanometers (nm) used in ICP optical emission spectroscopy. Also used to describe a type of laser ablation system (e.g., a ruby laser operating at a 694 nm wavelength) used to couple to an ICP-MS to analyze solid samples directly.

wet plasma: When a liquid sample is introduced or aspirated into the plasma, the plasma is called a “wet plasma.”

X

X-rays: A part of the electromagnetic spectrum that has a wavelength in the range of 0.01-10nm.

X-ray fluorescence: An analytical technique that uses the emission of characteristic “secondary” (or fluorescent) X-rays from a material that has been excited by bombarding with high- energy X-rays or gamma rays. The phenomenon is widely used for elemental analysis and chemical analysis, particularly in the study of solid materials such as metals, glass, ceramics, soils, and rocks.

ux” position: Refers to the alignment of the plasma torch in the lateral (sideways) position. Typically carried out to maximize sensitivity or to optimize sampling conditions for cool plasma use.

Y

“y” position: Refers to the alignment of the plasma torch in the longitudinal (vertical) position. Typically carried out to maximize sensitivity or to optimize sampling conditions for cool plasma use.

Z

“z” position: Refers to the alignment of the plasma torch in relation to the distance from the interface cone (in and out position). Typically carried out to maximize sensitivity or to optimize sampling conditions for cool plasma use.

 
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