Analysis of foods for lead, cadmium, copper, zinc, arsenic, and selenium, using closed system sample digestion: collaborative study.

A method for the determination of cadmium, lead, copper, arsenic, selenium, and zinc is presented. This method involves digesting a food sample with nitric acid under pressure and using aliquots of the solution for analysis by suitable techniques. Cadmium, lead, and copper are determined by anodic stripping voltammetry (ASV) after heating with equimolar sodium nitrate/potassium nitrate; arsenic and selenium are determined by atomic absorption spectrophotometry (AAS) after generation of their respective hydrides; zinc is determined by conventional AAS. The combined recoveries and reproducibilities (CVR) of the collaborative study on this multi-element analysis are: Cd, 89.14 (17.65) at 0.10-1.0 microgram/g; Zn, 96,53 (5.59) at 16.7 and 66.7 microgram/g; As, 99.50 (17.02) at 0.5 and 2.0 microgram/g; Se, 95.17 (16.52) at 0.5 and 2.0 microgram/g; Pb, 92.57 (15.22) at 0.3-3.0 microgram/g; Cu, 108.39 (18.30) at 1.0-10.0 microgram/g. The method has been adopted as official first action for cadmium, lead, arsenic, selenium, and zinc.