Determination of selenoethionine by flow injection-hydride generation-atomic absorption spectrometry/high-performance liquid chromatography-hydride generation-high power nitrogen microwave-induced plasma mass spectrometry

A simple direct flow injection hydride generation atomic absorption spectrometric method was developed using sodium tetrahydroborate and hydrochloric acid for the determination of selenoethonine (Seet) that excluded any chemical pretreatment prior to hydride generation. The detection limit (3 sigma of blank) of the method was 0.25 ng ml(-1) selenium (standard solutions in Milli-Q water), The reproducibility (R.S.D. of three analyses performed on three different days) and the repeatability (R.S.D. of seven successive analyses) of the method were 9.2% for 5.05 ng ml(-1) and 2.8-9.5% for 20.0-1.00 ng ml(-1) of standard selenium (Milli-Q water), respectively. The calibration graph was linear up to 20.0 ng ml(-1). This HG method is very promising and was successfully applied for the on-line estimation of Seet (spiked) in human urine with using high-performance liquid chromatography-hydride generation-high power nitrogen microwave-induced plasma mass spectrometry (HPLC-HG-N-2-MIP-MS). The separation was performed on a GS-220 gel-permeating column with a 25 mM tetramethylammonium hydroxide + 25 mM malonic acid buffer (pH 7.5), which showed 26-30% signal suppression due to less volatile hydride formation from Seet among the mobile phases examined. The recovery of Seet that was prepared in the above mobile phase is about 74% as that of the Seet prepared in Milli-Q water. In the PRP-X100 anion-exchange column with the 15 mM phosphate (pH 7.0) mobile phase, Seet eluted out after 600 s keeping a broad peak with enlarging the baseline signal. The concentration of selenite found in the human urine was 3.6 +/- 0.2 mug l(-1) and that agreed well with the high-performance liquid chromatography inductively coupled plasma mass spectrometry (HPLC-ICP-MS) value (3.8 +/- 0.2 mug l(-1)). (C) 2001 Elsevier Science B.V. All rights reserved.