REVERSED-PHASE ION-PAIR CHROMATOGRAPHIC-SEPARATION OF SELENITE AND SELENATE WITH SELENIUM-SPECIFIC DETECTION

Tetraalkylammonium salts [R(3)R'N](+)X(-) (R = R', X: CH3, Cl; C2H5, Br; C3H7, Br; C4H9, H2PO4; C5H11, Br; R, R', X: CH3, C16H33, Br) were investigated as ion-pairing reagents for the reversed-phase ion-pair chromatographic separation of selenite and selenate. Other chromatographic parameters such as composition and pH of the mobile phase and concentration of the ion-pairing reagent were also investigated. The compatibility of the proposed chromatographic procedures with various selenium-specific detectors is discussed. The absolute detection limits were found to be 31 ng Se for selenite and 51 ng Se for selenate (100 mu l injection) with a solution of 5 mM tetrabutylammonium dihydrogen phosphate in 50:50 (v/v) methanol/water as mobile phase at a flow rate of 1 ml/min when a flame atomic absorption spectrometer was used as detector. The HPLC/FAAS system was employed for the determination of selenite in solutions serving as selenium supplement for animals.