Simultaneous analysis of inorganic and organic lead, mercury and selenium by capillary electrophoresis with nitrilotriacetic acid as derivatization agent

A capillary electrophoresis (CE) method for the simultaneous speciation of three elements in organic and inorganic species was developed. Nitrilotriacetic acid (NTA) was used as the off-column derivatization agent to form UV-absorbing complexes with the analytes. It was also added to the running electrolyte for the separation and detection. Besides, micellar electrokinetic chromatography (MEKC) was performed with sodium dodecyl sulfate (SDS) for the adjustment of electrophoretic mobility. A theoretical model, with the consideration of pH, SDS and NTA in the electrolyte buffer, was designed to describe the migration behavior of the analytes. Good agreement was obtained when the model was used to explain the experimental results. The aspect of improvement in detection was also evaluated, and SDS was found capable of enhancing the detection sensitivity for the or organometallic compounds. Further improvement of determination was achieved by amplified field sample injection. It permitted a 40 to 600 fold on-line enrichment for five analytes. Detection limits down to 0.2 ng/ml were obtained. (C) 1998 Elsevier Science B.V.