Speciation of selenomethionine and selenocystine using online micro-column containing Cu(II) loaded nanometer-sized Al2O3 coupled with ICP-MS detection

A flow injection online speciation procedure by using micro-column packed with Cu(II) loaded nanometer-sized Al2O3 coupled to inductively coupled plasma mass spectrometry (ICP-MS) for the separation and determination of selenomethionine (SeMet) and selenocystine (SeCys2) has been developed. The main factors affecting the separation and preconcentration of SeMet and SeCys2 including pH value, sample flow rate, eluent concentration, eluent volume and flow rate, and interfering ions have been investigated. It was found that SeCys2 could be selectively retained by micro-column packed with Cu(II) loaded nanometer-sized Al2O3 at pH 4.0, and the retained SeCys2 could be eluted by 1.0 mol L−1 HNO3, while SeMet was not retained and passed through the micro-column directly at this pH. Both SeMet and SeCys2 could be quantitatively adsorbed by the micro-column at pH 9.0, and the retained SeMet and SeCys2 could be easily eluted with 1.0 mol L−1 HNO3. The content of SeMet was obtained by subtracting the SeCys2 from the total content of seleno amino acids. With the enrichment factor of 7.8 and 7.7, the limits of detection (LODs) for SeMet and SeCys2 were found to be 24 pg Se mL−1 and 21 pg Se mL−1, respectively. The relative standard deviations (RSDs) for SeCys2 and SeMet with seven replicate determinations of 1.0 ng mL−1 SeMet and SeCys2, were 2.1% and 1.6%, respectively, the sampling frequency of 8 h−1 was obtained. The proposed method was applied to the speciation of SeMet and SeCys2 in selenized yeast, human urine and serum with satisfactory results.