Quantitation of Caffeine by Capillary Zone Electrophoresis with End-Column Amperometric Detection at a Carbon Microdisk Array Electrode

Published: Journal of Chromatographic Science, ISSN 0021-9665 Volume 38, Number 1, January 2000, pp. 11-15

Quantitation of Caffeine by Capillary Zone Electrophoresis with End-Column Amperometric Detection at a Carbon Microdisk Array Electrode
Wenrui Jin, Daiqing Yu, Qian Dong, and Xiaoying Ye
Laboratory of Analytical Science, School of Chemistry, Shandong University, Jinan 250100, China

Capillary zone electrophoresis is employed for the determination of caffeine using end-column amperometric detection with a carbon fiber microdisk array electrode at a constant potential of 1.45 V versus a saturated calomel electrode. The optimum conditions of separation and detection are 0.152mM NaH₂PO₄–0.648mM Na₂PO₄ for the buffer solution, 20 kV for the separation voltage, 5 kV for the injection voltage, and 10 s for the injection time. The limit of detection is 2.9 x 10^–4mM or 1.2 fmol (signal-to-noise ratio = 2). The relative standard deviation is 0.68% for the migration time and 2.3% for the electrophoretic peak current. The method is applied to determining caffeine in human serum and a cola drink.

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