MICROWAVE DIGESTION OF FISH TISSUE FOR SELENIUM DETERMINATION BY DIFFERENTIAL-PULSE POLAROGRAPHY

In KIO3-NH3-NH4Cl medium, the selenium complex Se(O)SO32-, resulted fr om the reaction of selenite and sulphite in acid solution, gave a cata lytic wave, which was applied to the determination of selenium in fish by differential pulse polarography. The sample was decomposed using t he HNO3/H2SO4/H2O2 digestion mixture in a closed PTFE digestion vessel with microwave heating. The detection limit was 0.06 mug/dm3. The cal ibration curve was linear up to 8 mug/dm3. Selenate present was reduce d with hot hydrochloric acid to selenite. The recoveries of the seleni te and selenate in two spiked samples investigated ranged from 91 to 1 04%. The NIES CRM No. 6 mussel was analyzed and the results obtained a greed well with the reference value (reference value: 1.5 mug/g; found : 1.43 +/- 0.05 mug/g). The results obtained by differential pulse pol arography were in good agreement with those found by hydride generatio n atomic absorption spectrometry.