VALIDATION OF METHODS FOR THE DETERMINATION OF ALUMINUM IN FISH GILLSBY INAA AND ICP-MS

In a European study of fish death in mixing zones of rivers with diffe rent acidities a reliable determination of Al and other elements in gi lls from freshwater fish was required, and both INAA and ICP-MS were s tudied as candidate reference methods. INAA requires minimum sample ha ndling with a correspondingly small risk of contamination and no blank value; however, a careful study was needed of both nuclear interferen ce from P and the increased detection limit caused by other major elem ents in the sample, before reliable results for Al could be ascertaine d. ICP-MS requires dissolution of the sample with a resulting risk of contamination and a significant reagent blank; while sensitivity was g ood, the interference from N created problems for sample decomposition in the microwave oven. Our experience with actual samples indicates t hat both methods suffer from considerable contamination problems, requ iring that samples be handled in a clean bench with superpure reagents . Nuclear interference was determined experimentally by irradiating st oichiometric P-compounds with and without a Cd-shield; the observed in terference of 1 mu g Al from 50 mg of P was found to require no correc tion in almost all cases. The accuracy of results was ascertained by a nalyzing SRM 1577 Bovine Liver.