Validation of an FT-IR microscopy method for the determination of microplastic particles in surface waters

For analysis of microplastic (MP) particles in aquatic or solid compartments, standardized methods are required, yet data obtained by current methods are of limited comparability. Current methods include Fourier-transform Infrared (FT-IR) microscopy, Raman microscopy or thermo-analytical methods and attempts to compare data-sets from these methods have largely failed. Only little quality data based on validated methods and appropriate quality standards is available. Thus, reports of presence and numbers of MP still vary significantly from each other without a reliable indicator which of the reported data fulfils data acceptable quality requirements. A methodology for the determination of MP via FT-IR microscopy is introduced and critically discussed regarding mandatory validation parameters and applicability. Furthermore, advantages and challenges of this method are put into relation to other spectroscopic and spectrometric techniques.