SEMI-ON-LINE MICROWAVE-ASSISTED DIGESTION OF SHELLFISH TISSUE FOR THEDETERMINATION OF SELENIUM BY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

An electrothermal atomic absorption spectrometric method for the deter mination of selenium in shellfish tissue at the microgram per gram lev el, following digestion of the sample in a continuous system including a microwave oven, is proposed. In the presence of palladium, the pyro lysis temperature for selenium can be raised to 1100 degrees C, and th e signal is increased to a greater extent than with other reported che mical modifiers. The proposed method allows the determination of selen ium in the range 25-250 mu g l(-1) (2.5-25 mu g l(-1) Se after 10-fold dilution in the how manifold). The precision achieved, expressed as t he relative standard deviation, was 6.8% for within-run assays and 12. 5% for between-run assays. The pow system is characterized by its simp licity (no special device is needed to process evolved gases during sa mple digestion). Samples can be introduced into the system as slurries made from unlyophilised fresh shellfish tissue (there is no differenc e between the mean results for unlyophilised and lyophilised samples).