Simultaneous acid extraction of six trace metals from fish tissue by hot-block digestion and determination by atomic-absorption spectrometry
A simple and rapid digestion method is reported for the simultaneous acid extraction of chromium, copper, zinc, cadmium, nickel and lead from high-fat fish tissue. Samples are digested with nitric and sulphuric acids at 150 °C in a modified aluminium hot-block. The method is specially set up for fish sample sizes of up to 5 g, for low level detection of these elements. After digestion, acid extracts of the sample are analysed by direct flame atomic-absorption spectrometry for copper, zinc and chromium. The other three elements, cadmium, nickel and lead, are concentrated by chelation with ammonium tetramethylene dithiocarbamate followed by solvent extraction with isobutyl methyl ketone and determined by flame atomic-absorption spectrometry. The ease, rapidity and safety by which samples can be processed by this method make it suitable for the routine preparation of a large number of samples simultaneously.