Organic and inorganic selenium speciation in urine by on-line vesicle mediated high-performance liquid chromotography-focused microwave digestion-hydride generation-inductively coupled plasma mass spectrometry

A vesicle mediated high performance liquid chromatographic (HPLC)-microwave digestion (MW)-hydride generation (HG) system coupled on-line with atomic absorption spectrometry (AAS) and inductively coupled plasma mass spectrometry (ICP-MS) has been assessed for selenium species separation and detection, Selenocystine, selenomethionine, selenoethionine, selenourea, Se-IV and Se-VI are separated by vesicle mediated chromatography prior to on-line selenocompounds microwave digestion with a KBrO3-HBr mixture to generate Se-IV continuously, which is finally transformed into SeH2, in a continuous manner with a merging flow of sodium tetrahydroborate(III). Analytical characteristics of this coupling are compared with those obtained coupling HPLC-ICP-MS via conventional nebulisation, Detection limits (DLs) obtained for selenocystine, selenomethionine, selenoethionine, selenite and selenate in spiked human urine, when ICP-MS was used as detector, ranged between 1.0 and 5.3 mu g l(-1) (51-267 pg), while precision ranged between +/- 3.4 and +/- 8.4%. This continuous system, vesicle mediated HPLC-MW-HG-atomic detection, allows the separation and detection of selenocystine, selenourea, selenomethionine, selenoethionine, selenite and selenate in human urine. The analytical versatility of such coupling (with ICP-MS as the atomic detector) allows basal selenium speciation in urine, Three different normally occurring selenium species in human urine, simply diluted (1 + 1), have been found, The relative sophistication of the vesicle mediated-HPLC-MW-HG-ICP-MS interface, versus HPLC-ICP-MS via conventional nebulisation, can be justified because of its considerably higher sensitivity for most of the selenocompounds assayed, lower matrix interferences and the possibility of simultaneous interference free Se-77 and Se-78 monitoring.