Application of internal universal calibration for determination of fully dissociated species in capillary electrophoresis using indirect UV detection and electrokinetic injection

Although the electrokinetic injection suffers from quantitation problems arising from mobility and matrix bias, the application of electrokinetic injection and indirect photometric detection may provide a very simple, sensitive and universal determination of fully dissociated components. In this work a survey of the possibilities of quantitative analysis using EK injection with indirect UV detection is given and a simple procedure (internal universal calibration) for accurate quantitative determination of traces using EK injection is proposed. It was shown that the thiosulfate as an internal universal standard (IUS) can be applied for quantitative determination of fully dissociated analytes (e.g. Br−, Cl−, NO2−, NO3−, SO42−, S2O32−) whose mobilities (migration times) do not differ from the mobilities of monitoring ion (chromate), counter-ion (potassium) and IUS with more than 10%. The proposed calibration procedure provides concentration data, which deviate generally less than 5% extent from the actual true values. The validity and the applicability of the method was studied in the analysis of samples containing different amount of matrix material.