A Simple Method for Quantifying Polycarbonate and Polyethylene Terephthalate Microplastics in Environmental Samples by Liquid Chromatography–Tandem Mass Spectrometry

Microplastics (MPs) have frequently been found in the environment. However, studies of the quantification methods for MPs are still needed. Plastics are polymers with different degrees of polymerization. In this study, alkali-assisted thermal hydrolysis was applied to depolymerize two plastics containing ester groups, polycarbonate (PC) and polyethylene terephthalate (PET), in a pentanol or butanol system. By determining the concentrations of the depolymerized building block compounds, i.e., bisphenol A and p-phthalic acid, we quantified the amounts of PC and PET MPs in environmental samples. Recoveries of 87.2–97.1% were obtained for the PC and PET plastic particles spiked in the landfill sludge. The method was successfully applied to determine the occurrence of PC and PET MPs in samples of sludge, marine sediments, indoor dust, digestive residues in mussel and clam, and sea salt and rock salt. High concentrations of 246 and 430 mg/kg were determined for PC and PET type MPs, respectively, in an indoor dust. In addition, concentrations of 63.7 mg/kg for PC and 127 mg/kg for PET were detected in the digestive residues of a clam.