Unified alcoholysis-GC-MS/MS for simultaneous differentiation and quantification of polyester microplastics in water

Environmental waters now carry complex mixtures of polyester microplastics that vary in origin and biodegradability, including fossil-based and biodegradable polyesters, yet no method can simultaneously distinguish and individually quantify them. We present a unified alcoholysis method coupled with GC-MS/MS to quantify four polyester microplastics (PEMPs) in a single workflow. By selectively cleaving ester bonds in an alcohol medium, the method converts polylactic acid, polyethylene terephthalate, polyhydroxybutyrate and polybutylene succinate into four distinct, stable monomers. These monomers are directly determined by GC-MS/MS without derivatization. Under unified conditions (190 °C, 5 h), depolymerization efficiencies range from 15% to 90%. We calibrate directly between polymer mass and monomer signal intensity. Detection limits are 0.0462 μg/L for polylactic acid (PLA), 0.103 μg/L for polyethylene terephthalate (PET), 2.92 μg/L for polyhydroxybutyrate (PHB), and 0.695 μg/L for polybutylene succinate (PBS). Spiked recoveries in lake water are 90-115%. In six lake samples, PLA constitutes over 75% of total PEMPs. This fingerprint points to consumer packaging as the dominant source. By circumventing particle morphology constraints and delivering polymer-specific mass concentrations, the method opens a direct route for source apportionment of coexisting fossil-based and biodegradable polyester microplastics.