DETERMINATION OF SELENIUM BY INDUCTIVELY COUPLED PLASMA MASS-SPECTROMETRY UTILIZING A NEW HYDRIDE GENERATION SAMPLE INTRODUCTION SYSTEM

An inductively coupled plasma mass spectrometer with a newly designed continuous flow hydride generator was used for the determination of Se in biological materials. The design of the hydride generator was impo rtant in minimizing interference from HCl and in maximizing analytical sensitivity. Two sample preparation procedures incorporating either 3 .8 or 7.2 M HCl in the final sample solutions were compared. Interfere nce from Cu was eliminated by the addition of 0.2 M NaI to the sodium borohydride solution (3.8 M method) or by maintaining a high concentra tion of HCl in the sample solution (7.2 M method). The 3.8 M method ha d the advantage of minimizing exposure of expensive equipment to corro sive HCl fumes, whereas the 7.2 M method did not contaminate equipment with I and had no measurable sample-to-sample cross-contamination. In practice, cross-contamination from sample to sample in both methods w as negligible during analysis. An important factor in minimizing cross -contamination from sample to sample was the elimination of the air bu bble normally entrained between samples. Determination of isotopic tra cer enrichment was linear from 0 to 320% enrichment, which provided a broad range for isotope dilution analysis. A detection limit of 6.4 pg of Se was observed under optimum conditions, whereas a detection limi t of 1.3 ng of Se was found for routine analysis of 1-g samples of pla nt material. Selenium was accurately determined by isotope dilution an alysis in a variety of biological reference materials.