Speciation of selenium compounds by open tubular capillary electrochromatography-inductively coupled plasma mass spectrometry

We introduce a T-type interface and a crossflow nebulizer to find ways to combine CEC with inductively coupled plasma MS (ICP-MS) detection for selenium speciation. For CEC separation, we employed a macrocyclic polyamine-bonded phase capillary as the separation column and a bare fused-silica capillary filled with the make-up liquid (0.05 M HNO3). The effect of nebulizer gas flow rate, make-up liquid flow, type, concentration and pH of the mobile phase on the separation have been studied. Tris buffer of 50 mM at pH 8.50 gave the best performance for selenium speciation. The reproducibility of the retention time indicated that sample injection by electrokinetic and nebulizer gas flow was better than that by self-aspiration alone. The detection limits for selenate, selenite, selenocystine and selenomethionine were found to be 2.40, 3.53, 12.86 and 11.25 ng/mL, respectively. Due to the high sensitivity and element-specific detection, as well as the high selectivity of the bonded phase, quantitative analysis of selenium speciation in urine was also achieved.