Analytical Methodologies to Assess the Micro/Nanoplastics within the Environment

Analysis of micro/nanoplastics in ecological matrix still remains a difficult task. Range of analytical techniques, tools and procedures are explored for isolation, identification and quantification of plastics. On the basis of diversity in plastics, analytical techniques can vary from physical (visual classification, microscopy) to chemical (spectroscopy, chromatography) techniques. Moreover, few researchers suggest isolation and identification of plastic on the basis of plastic size, density and hydrophobicity. The isolation and identification techniques have significant impact on quantification of plastics from environmental matrix. Typically, in micro/nanoplastics, quantification is highly dependent on the precision and accuracy of the separation techniques [32-34]. Variously commonly used analytical techniques for isolation, identification and quantification of plastics are thoroughly described in Table 1.1, with the key advantages and limitations.

TABLE 1.1 Analytical Techniques for Analyzing and Understanding Micro/Nanoplastics from Different Matrices

Technique

Advantages

Limitations

References

Thermal analysis with mass

spectrometry

  • 1. Easy identification of microplastics
  • 2. Identification using thermal degradation behavior
  • 3. No requirement of pretreatment for analysis and require only 5-200 pg of samples
  • 4. Thermal extraction and desorption (TED) with mass spectrometry (MS) permits the simultaneous identification of multiple samples
  • 1. Destructive techniques
  • 2. Do not allow the physical characterization of samples
  • 3. Expensive in nature

[35-37]

Raman

spectroscopy

  • 1. Non-destructive spectroscopic method
  • 2. Involve use of rotational and vibrational interactions
  • 3. Provides a structural fingerprint for micro/ nanoplastics in different environmental matrices
  • 4. Enables the identification within minutes
  • 5. In combination with other sophisticated analytical techniques (e.g., confocal microscopy, atomic force microscopy), can provide better visual analysis
  • 1. May require pretreatment or purification before sample analysis
  • 2. May need standardization prior to sample analysis
  • 3. Needs specialized staff for analysis and interpretation

[34,38^40]

Infrared

spectroscopy

  • 1. Precisely identify'' the physicochemical interactions between micro/nanoplastics and different matrices
  • 2. Highly specific and reveals characteristic band patterns for individual plastic particles
  • 3. Complementary technique to Raman spectroscopy and vice versa
  • 4. Can easily accommodate other functionalities such as focal plane array (FPA)-based FTIR and attenuated total reflectance (FTIR-ATR)
  • 5. Available as portable machines
  • 1. Time consuming
  • 2. Organic matrices may add to misidentification of plastics spectra
  • 3. Better analysis and outcomes need dry samples

[33,41|

Microscope- assisted visual screening

  • 1. Inexpensive and easy to perform
  • 2. Used for pre-sorting of samples
  • 1. May lead to over- or underestimation
  • 2. No data on chemical arrangement

[42-44]

Plastics’ physical (size, shape and morphology) properties and chemical (composition, functional moieties and chemical class) characteristics are the crucial features during analysis. Any analytical technique that consistently measures both the properties is highly appropriate for plastic analysis. However, it is very tricky to achieve identification of both characteristics using a single analytical method. Most of the techniques from Table 1.1 involve analytical techniques which are regularly utilized in physical, mechanical and biological fields. Exploring analytical principles from these domains could assist in the design and development of novel systems to respond to difficulties in micro/nanoplastics analysis. Thus, use of hyphenated analytical techniques (coupling of two or more analytical techniques) is highly applicable. Hyphenated analytical techniques that include elemental analysis and imaging to attain the chemical and physical identification may offer a possible future direction for plastics identification. Apart from these techniques, for most of the chromatographic/spectroscopic methods, we need to develop new and suitable libraries for plastic analysis based on chemical and physical characteristics for optimum identification. These types of libraries will provide quick decoding of the signals during analysis and ease the overall interpretation and data collection process. Simply, it will help to reduce identification time and efforts [32-34].

 
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