Single-run capillary electrophoretic speciation of iodide and iodine

Abstract

A new, capillary electrophoretic (CE) technique for single-run determination of iodine and iodide is described. The method is based on the CE separation of iodine and iodide species followed by selective in-capillary derivatization of iodine to iodide with sulfite. The optimal conditions for the separation and derivatization reaction were established by varying electrolyte introduction time and SO 3 2−/I 2 concentration ratio. Triiodide formation from iodide and iodine causes an additional peak broadening of the iodide. The optimized separations were carried out in 0.02 mol l −1 Tris–HCl electrolyte (pH 8.5) using direct UV detection at 214 nm. The calibration curves were linear in the concentrations range 1×10 −5 to 1×10 −3 mol l −1 for I − and 2×10 −5 to 5×10 −4 mol l −1 for I 2 with correlation coefficients higher than 0.998. The detection limits were 2×10 −6 mol l −1 for I − and 8×10 −6 mol l −1 for I 2. The proposed method was applied to the rapid speciation of iodide and iodine in commercially available antiseptics such as povidone-iodine and ethanolic iodine solutions.