Analytical Sciences

Dual-Gradient Capillary Electrochromatography by Varying the Mobile Phase Composition and Applied Voltage

Tomoharu SAKAI, Hiroyuki NAKAGAWA, Shinya KITAGAWA, and Hajime OHTANI

Department of Materials Science and Engineering, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso, Showa, Nagoya 466-8555, Japan

Dual-gradient capillary electrochromatography (DG-CEC) was developed to provide superior performance with regard to the separation of ionized analytes; in this method, both the eluent composition and the applied voltage are varied during the separation procedure. As for the gradient in the eluent composition, a shift in the pH is employed to control not only the electrophoretic mobility, but also the retention factor of the analytes. The dual-gradient method was shown to be effective in increasing the resolution and reducing the chromatographic period of ionized analytes. Fourteen kinds of o-phthalaldehyde labeled amino acids were separated within 8 min using DG-CEC with multistage enlargement in the applied voltage. The separation efficiency increased particularly for highly retained amino acids in the dual-gradient, as compared to those in the ordinary single-gradient for the eluent.

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