Microplastics in the Ecosystem: A Systematic Review of the Methods for Their Detection and Removal

Table 2

Table of microplastic detection methods.

Source	Identification method	Pretreatment	Concentration	Polymer type	Advantage	Limitation	Reference
Wastewater in Germany	Pyr-GC-MS	Filtration	100 μm, 50 μm, 10 μm	PE, PS	Recognition of compositions in samples; can simultaneously detect any additives present in the plastic	Destructive technology	[69, 70]
Plastic bottled water	FTIR	Sieve and wash with ethanol, freeze and oxidize with H2O2 or other chemicals, density separation, and sonication	6.5–100 μm	Polypropylene	Selective and reproducible (nondestructive) identification of polymer matrix, small sample quantities	It is not completely reliable with weathered samples, samples that have undergone degradation, or with samples containing mixed polymers	[23, 71]
Bottled mineral water	Raman spectroscopy	Cleaning with a 30% hydrogen peroxide (H2O2) solution, followed by filtration using a 47 mm diameter Whatman glass fiber filter and subsequent rinsing with deionized water	1–10 μm	PET, PE, PP	The Raman spectra of microplastics subjected to UV degradation remain virtually unchanged, and neither the shape nor the thickness of the particles affects the measurement	It is not entirely reliable on worn, colored, and degraded samples or on mixed polymer samples. Autofluorescence may mask the signal, and samples may be affected	[72, 73]
Marine mangrove	FTIR-ATR	Oxidation by density separation (30% H2O2)	<20 μm	PE, PP, PVC	It is primarily used to determine and describe MPs present in water and sediments. It is a cost-efficient method and does not require elaborate sample preparation or complex mathematical adjustments	The time required per particle is considerable (3 minutes per particle)	[70, 74]
Plastic water bottles	SEM-EDS	It needs to be deposited on an electrically conductive surface, using a thin layer of a conductive material, such as carbon (by vacuum evaporation) or gold and gold/palladium alloy (plasma sputter coating)	≥3 μm	PET, PE	It facilitates accurate identification of the size distribution, shape, and chemical composition of microplastic and nanoplastic particles	It can cause damage due to the electron beam and cause signs of degradation on the sample surface, resulting in high cost	[68, 75]
Water fountains in Qingdao	Micro-FTIR	Pass through a 0.45 μm nitrocellulose membrane using vacuum filtration	>10 μm	PVC, PE, PET	Particularly suitable for recognizing very small plastic particles	Measurement of irregularly shaped microplastic particles in environmental samples can generate spectra that are difficult to interpret due to refractive errors	[76, 77]
Wastewater	TGA-DSC	ZnCl2 solution was added. Then, the biomass residues were oxidized using H2O2 (30%)	<12 μm	PE, PP	Cost-effective and straightforwardly allows determination of polymer-type concentrations and simultaneous analysis of polymer types and additives	It is only possible to identify PE and PP through destructive analysis	[78, 79]
Rivers	TED-GC-MS	Pretreated with H2O2 (20%) for 48 hours and 8 days	—	PE, PP, PS, PET, PA	It allows the analysis of significant amounts of samples, up to 100 mg. It is a potentially rapid and quantitative technique for the detection and identification of MPs	The absence of suitable calibration curves prevents the determination of the absolute mass content in the reference sample. If there is an overlap with another compound, certain mass fragments may be altered	[80, 81]