Quantification of Microplastics in environmental samples using pressurized liquid extraction and Pyr-GC/MS

Fast and reliable quantification of microplastics in environmental samples is currently a challenging task. To enable monitoring of microplastics, a fast and robust method in sample preparation and subsequent analysis is of extraordinary need and urgency. Therefore, the combination of pressurized liquid extraction and Pyr-GC/MS has been developed. The fully automated extraction includes a pre-extraction via methanol for matrix elimination and a subsequent main extraction for microplastics using tetrahydrofuran to enrich microplastics on silica gel which is hence analyzed by means of Pyr-GC/MS.

Several commonly occurring organic matrices known to result in GC interferences were tested to be eliminated by pressurized liquid extraction.  For the most frequently used synthetic polymers PE, PP, and PS extraction efficiencies of 113-131, 80-98, and 70-118 %, respectively, and limits of quantification down to 0.005 mg/g were achieved.

The developed method was validated and applied to environmental samples with complex matrices such as roadside soils, potting soils, and sewage sludge. In all these matrices PE, PP, and PS were detected with contents ranging from 0.8 to 3.3, 0.01 to 0.36, and 0.06 to 0.61 mg/g. However, calcined sea sand spiked with wood, leaves, and humic acids, respectively, were found to interfere with PE quantification (0.140, 0.210, and 0.050 mg/g). Reduction of these interferences will be further evaluated.