Determination of volatile elements in biological materials by isotopic dilution ETV-ICP-MS after dissolution with tetramethylammonium hydroxide or acid digestion

Isotopic dilution for the determination of Ag, Cd, Hg, Pb and Tl in biologi cal materials by ETV-ICP-MS is proposed. The sample was simply dissolved wi th tetramethylammonium hydroxide (TMAH) or acid digested in a microwave fur nace, with an on line matrix separation. When the dissolution was employed, Ir was used as a chemical modifier for Hg and Pb and Pd was used for Cd an d Tl. No modifier was used for Ag. The pyrolysis temperatures were taken fr om pyrolysis temperature curves. The on line preconcentration was performed in a flow injection system with solenoid valves and was based on the analy te complexation with ammonium diethyldithiophosphate and sorption of the co mplexes on C-18 bonded to silica gel in a minicolumn. For the digested samp le submitted to the analyte preconcentration procedure, a modifier, Ir, was only used for Hg. For the other analytes, since a low pyrolysis temperatur e, 300 degrees C, was employed, no modifier was added. The isotopic dilutio n calibration was applied to two certified materials, bovine liver and dog fish muscle, dissolved with TMAH or acid digested, and to another two certi fied materials, corn bran and rice flour, acid digested and submitted to an alyte preconcentration. The obtained concentration values agree with the ce rtified ones, showing that this calibration procedure leads to accurate res ults in the determination of low concentrations of volatile elements. Due t o simplicity, the dissolution with TMAH is very attractive. (C) 2000 Elsevi er Science B.V. All rights reserved.