Interfacing capillary electrophoresis with inductively coupled plasma mass spectrometry by direct injection nebulization for selenium speciation

Abstract

A demountable direct injection high efficiency nebulizer operating at low sample uptake rates was developed and used for coupling of capillary electrophoresis (CE) with inductively coupled plasma mass spectrometry (ICP-MS). When the nebulizer was used for continuous sample introduction, detection limits of 20 and 1 ng L−1 were obtained for 82Se and 103Rh, respectively, at sample uptake rates of 10–30 μL min−1, based on three times the standard deviation of blank solution (3σb, n = 10). The nebulizer was used as part of the interface for coupling of CE with ICP-MS and applied for speciation of aqueous selenium standards. The interface was operated in the self-aspirating mode with a sheath liquid uptake of 10 μL min−1. The CE-ICP-MS system resulted in baseline separation of selenate, selenite, selenocystine and selenomethionine within a total analysis time of 5.4 min. Detection limits were in the sub µg Se L−1 range, corresponding to absolute detection limits in the range 25–125 fg selenium. Repeatability (n = 6) expressed as relative standard deviations with respect to migration times, peak heights and peak areas were better than 1.6, 6.7 and 6.0%, respectively.