Effect of Long-time Heating for Polyvinyl Chloride and Polypropylene Resin Pellet Certified Reference Materials for Heavy Metal Analysis.

The effect of long-time heating for both polyvinyl chloride (PVC) and polypropylene (PP) resin pellet certified reference materials (CRMs) for heavy metal analysis, which contained Cd, Cr, Hg and Pb, was examined in the present study. The temperature of the drying oven was 80°C, which was used for drying these CRMs before analysis, and the long-time heating was carried out for up to 480 h. As a result, a relative decrease in mass of ca. 0.3% was observed for both CRMs. Moreover, a decrease in concentration of ca. 10% was observed for Cr, even though the concentrations for other elements did not change during the long-time heating. Since the chemical form of Cr was an organometallic compound with lower melting point, it was considered that concentration decreased due to the heat.