Selective determination of inorganic selenium species in parenteral solutions using L-methionine as retaining agent in ETAAS

A time-based flow injection (FI) separation system coupled to electrothermal atomic absorption spectroscopy (ETAAS) has been developed for the determination of selenium in parenteral solutions. Selenate interacts with L-methionine, which is immobilized on controlled pore glass (CPG), at pH 3.0 and eluted with HCl (10% v/v). Total selenium content is determined directly by ETAAS without preconcentration and selenite is calculated by difference. The features of the separation system are: 100% efficiency of retention and an enhancement factor of 20 for a preconcentration time of 6 s (sample flow rate = 10 mL min(-1)) with HCl elution volumes of 50 mu L. The detection limit (3 sigma) was 6 ng L-1, and the relative standard deviation (n = 10) at the 0.1 mu g L-1 level is 3.0%. The method has high selectivity and was applied to the determination of Se (iv) and (vi) in parenteral solutions with satisfactory results.