Current Methods of Detection, Identification and Quantification of Micro- and Nanoplastics in Food and Other Samples

One of the major challenges for the detection and analysis of micro- and nanofragmented plastics is the lack of a standard operating procedure and quality assurance. Apart from that, there is no detailed and internationally agreed definition of micro- and nanoplastics. Currently, both conventional and advanced detection or identification methods are being utilized by scientists globally. In this chapter, a brief description of measurement principle and advantages and disadvantages of commonly used methods of detection have been summarized.

Further information may be found in Chapters 7 and 8 of this book.

Filtration Technique

It is one of the most basic methods for recovering microplastics from liquids like water and other solutions. The process is simple, cheap, categorizes particles according to size and is suitable for liquids. However, it comes with the limitation of clogging of pores of the filter, loss of particles with large pore size filters, and inaccurate data.

Floatation or Sedimentation Technique

Differences in the densities of inorganic materials present in microplastics is exploited to extract particulates of plastic by floating them out from salt solution, whose density is higher than plastic but lower than other solids and minerals present in them [80]. Particles can be made to sediment or float depending on their size, or density, because of the effect of gravitational force. The process can be accelerated by centrifugation. It separates microplastics from inorganic matter. However because the plastic particles need to be detached from the matrix material, the critical choice of the type of gradient is important.

Matrix Dissolution Technique

This technique is used to study the traces of fragmented plastics in animal tissues, organs and biofilms. The acid digestion technique used for the detection of trace elements has also been exploited for microplastics [81]. This method needs optimization to digest organic matter. There is a possibility that the plastic particles may get damaged or destroyed by acids. Alkaline digestion by NaOH or KOH has been reported for the detection of microplastics in biological matrices [82]. The process has been successfully used for a wide range of polymers because of the low risk of damaging or chemically modifying particulates. Biological materials are usually detected by the enzyme digestion technique. However, certain enzymes are specific to certain types of protein matrices, and thus it requires several sequential steps to remove the matrix components adequately.

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