End-column amperometric detection of aesculin and aesculetin by capillary electrophoresis

Determination of aesculin (AL) and aesculetin (AT) by capillary electrophor esis with end-column amperometric detection using a 33 mu m microdisk carbo n fiber electrode is described. The HDVs, the effect of pH, buffer concentr ation, injection voltage, injection time and separation voltage on the peak current response (i(p)) of the analytes and the number of theoretical plat es (N) were studied. The method has high sensitivity and good reproducibili ty. Under the optimum condition - 10 mM, pH 9.00 phosphate buffer, 4 s at 9 kV injection, separation at 15 kV and +1.0 V as the detection potential - low detection limits (S/N = 3) of 0.06 and 0.3 mu M were obtained for AL an d AT, respectively. The calibration curve was linear over three orders of m agnitude. The relative standard deviations (n = 15) of peak current and mig ration time were 3.9% and 4.6%, and 0.96% and 0.75% for 15 consecutive inje ctions of 5 mu M AL and AT, respectively. The use of this method for the se paration and detection of the two compounds present in the traditional Chin ese medicine and human urine samples is also reported. (C) 1999 Elsevier Sc ience B.V. All rights reserved.