Macromolecular weight averages of plastic fragments sampled during the composting experiment

The evolution of the macromolecular mass averages and the dispersity of the fragments sampled during the composting process was analyzed with Size-Exclusion Chromatography (SEC). It was performed using a Gilson pump (France) coupled to a Waters autosampler and refractometric index detector (Waters, France). The separation was carried out on a system consisting of a guard column (PLgel 5 µm) and three columns (two columns PLGel 5 µm MIXED-C and one column PLgel 3 µm MIXED E, Agilent Technologies) maintained at 40 °C in a column oven (Waters, France). The flow rate of the CHCl3 was 1 mL/min. The calibration curve was established using three standard kits (EasiVials, 2 mL) containing each four narrow polystyrene standards of molecular weight between 4.69∙103 and 5.68∙106 g/mol (Agilent Technologies). Data treatment was done using Empower 3 software (Waters). Samples were prepared by dissolution of the uncleaned solids in dried CHCl3 (app. 20 mg/mL) at room temperature or after heating at 40 °C without stirring at least 4 h. The supernatant was sampled after sedimentation of the insoluble phase and filtered before analysis with the help of 0.45 µm Teflon syringe filters. Because of the biodegradation of the materials during the process, the less and less sample mass was available. If enough sample available, the preparations were done several times (at least in duplicate).