SPECIATION OF ORGANIC SELENIUM-COMPOUNDS BY REVERSED-PHASE LIQUID-CHROMATOGRAPHY AND INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY - PART I - SECTOR FIELD INSTRUMENT WITH LOW-MASS RESOLUTION

The speciation of selenocystine, selenocystamine, selenomethionine and selenoethionine was studied by on-line coupling of high performance l iquid chromatography with inductively coupled plasma mass spectrometry with hydraulic high pressure nebulization (HHPN) for sample introduct ion employing a double-focusing magnetic sector field mass spectromete r in order to achieve the utmost sensitivity. Reversed-phase chromatog raphy was applied to separate the organic Se compounds. The eluent was 30 mM ammonium buffer adjusted to pH 3.0 in methanol-water (5 + 95 v/ v). The operating conditions for chromatographic separation (pH of the mobile phase, methanol content of the mobile phase, pH of the sample and sample uptake rate) were carefully optimized. With the developed p rocedure, detection limits below 0.02 ng ml(-1) were achieved, so that even low pg levels could be detected when applying sample volume of 2 00 mu l.