The determination of selenium in serum and urine by inductively coupled plasma mass spectrometry: comparison with Zeeman graphite furnace atomic absorption spectrometry

An inductively Coupled Plasma Mass Spectrometric (ICPMS) method for the det ermination of selenium in both serum and urine is described. Se-78 is used analytically in spite of (ArAr)-Ar-38-Ar-40 isobaric interference at mass 7 8. Initially Se-82 was monitored but, limited isotope abundance and therefo re limited detection capability for urine selenium precluded continued use. An ethanol-Triton X-100-nitric acid diluent was used to dilute serum and u rine and enhance selenium ionization so that both serum and urine can be an alyzed with the same calibration curve. Results derived by the ICPMS method were compared with Zeeman Graphite Furnace Atomic Absorption Spectrometry (ZGFAAS) using nickel as the matrix modifier. Detection limits for ZGFAAS a nd ICPMS using mass 78 are 2.9 and 0.25 mu g/l, respectively. ICPMS and ZGF AAS instrument responses were recorded for additions of inorganic selenium, trimethylselenonium iodide, seleno-Dr-methionine, and seleno-Dr-cystine to urine and serum. ICPMS slopes for all compounds added to urine and serum w ere found to be nearly identical. ZGFAAS response for each compound was mor e variable than ICPMS. ZGFAAS response for trimethylselenonium iodide was a pproximately 3-fold lower than for the other compounds. ZGFAAS regression s lopes and correlation coefficients were 0.72 and 0.8139 for reference urine samples. ICPMS regression slope and correlation coefficient vs. the refere nce target values were 0.95 and 0.9700 for the same urines. Regressions slo pes and correlation coefficients for reference sera were 1.01 and 0.9912 fo r ICPMS and 1.12 and 0.9648 for ZGFAAS. We conclude that ICPMS produced mor e accurate results than ZGFAAS for selenium in serum and urine. (C) 1999 El sevier Science B.V. All rights reserved.