CLOSED-VESSEL NITRIC-ACID MICROWAVE DIGESTION OF POLYMERS

A simple, closed-vessel microwave digestion method has been developed for several polymer samples. A 0.15-g sample of high density polyethyl ene, polystyrene, polyethylene/polypropylene blend, and polyethylene p recursor was digested in 4 mL nitric acid in a high-pressure (75 bar) closed-vessel digestion bomb. The digestate was filtered and analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES). Depending on the polymer, 1-18 elements were determined in the three sample types. Detection limits were in the low parts-per-billion range , and precision was better than 5% relative standard deviation for mos t metals. The accuracy of the method was determined by performing spik e recoveries for 1-15 test elements. Recoveries were in the 90-100% ra nge for all elements. The digestion technique eliminated the need for harsh acid mixtures (including H2SO4 and HF) that are routinely used f or polymer samples.