EVALUATION OF ONLINE COUPLING SIZE-EXCLUSION CHROMATOGRAPHY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY FOR SELENIUM SPECIATION

Chromatographic effluents were on-line analyzed by Zeeman-ETAAS, using a flow-through cell placed in a graphite furnace autosampler as inter face. To obtain high sampling rates, the use of fast graphite furnace programmes was studied. Conventional programmes of 96 s were reduced t o 18 s by using hot injection (120 degrees C) and reducing the charrin g step to 2 s. The increase of the injection volume from 20 to 60 mu l lengthened the programme to 46 s. Nickel had to be added to get a com parable response for both inorganic and organic selenium species (sele nite and selenomethionine) and to reduce the interferent effect produc ed in presence of the chromatographic eluent (TRIS 0.01 mol l(-1) NH4N O3 0.1 mol l(-1), pH 7). The optimized conditions were applied to the speciation of selenium in human erythrocyte lysates by size exclusion LC-ETAAS. Using a high performance size exclusion column selenium coul d be assigned to proteins of 100 and 35 kDa. Detection limits in the r ange of 1 ng (2 mu g l(-1) for 500 mu l injection volume) were obtaine d for the combined technique.