Influence of sample pre-treatment on the determination of As and Se in Antarctic krill by HG-ICP-AES

Three digestion procedures for Antarctic krill samples were compared for th e reliable determination of two environmentally significant trace elements. A dry ashing (DA) procedure with magnesium nitrate and two microwave (MW) acid assisted digestion methods (with HNO3/H2O2 and HNO3/HF) were tested fo r decomposing the certified reference material MURST-ISS-A2 (antarctic kril l) for the subsequent determination of As and Se by HG-ICP-AES. Microwave p rocedures, namely MW1 and MW2, were insufficient to digest As and Se in thi s marine organism. The recoveries achieved were: 37.3% +/- 2.2% (MW1) and 3 0.9 +/- 1.6% (MW2) for As: 43.2 +/- 2.0% (MW1) and 41.61.8% (MW2) for Se. O n the other hand, the results obtained using the dry ashing method at 500 d egreesC were consistent with the reference values with recoveries around 10 0%. The optimum working conditions and the order of sample, NaBH4 and KI mi xing during the simultaneous hydride generation of As and Se were studied. Under optimised conditions detection limits of As and Se ranged between 22 and 50 ng g(-1) for the three methods tested. In all cases precisions were better than 7%.