The effect of digestion temperature on matrix decomposition using a high pressure asher

A high pressure asher system was employed for the nitric acid digestion to two standard reference materials (NIST SRM 1547 Peach Leaves and NIST SRM 1 632v Coal). The effect of the final ashing temperature (180-300 degrees C) upon the extent of digestion was investigated. The organic matrix decomposi tion products are monitored by high performance liquid chromatography. For the peach leave samples, the isomers of nitrobenzoic acid appear as the maj or products at low temperature. They degrade at elevated temperatures to a variety of by-products, until only one product is left after digestion at 3 00 degrees C. The coal sample has a much more complicated post-digestion ma trix that is also reduced to a single component at the maximum ashing tempe rature, are determined by inductively coupled plasma optical emission spect rometry. In most cases, the recovery for a variety of test metals varies be tween 90 and 110%, regardless of ashing temperature.