Abstract

A procedure is described for open vessel pulse microwave wet ashing system. In wet ashing procedure organic matrix in biological tissues is digested in acid. This step must precede trace metal analysis by atomic absorption spectroscopy. Conventional wet ashing procedure using hot plate takes several hours. Digestion of animal and plant tissues by 5.0 ml, 10.0 ml or 20.0 ml of $\rm H\sb2SO\sb4$ (95.0-98%)/HNO$\sb3$ (69-71%) (v/v) (1:1) acid mixture were effectively achieved by pulse microwave treatment using domestic grade microwave oven. Samples are subjected to 10s (method A) or 6s (method B) microwave heating followed by dormant time of 3 minutes for a total microwave heating time of less than 20 minutes. Data will be presented to show how conditions were chosen. The temperature of digestion mixture was maintained $<$100$\sp\circ$C. The effect of pulse time variation and acid mixture volume variation was studied in detail.