Capillary electrophoresis of some tetracycline antibiotics coupled with reductive fast cyclic voltammetric detection

The separation and quantitative performance parameters for tetracycline, chlortetracycline and oxytetracycline antibiotics were investigated by capillary zone electrophoresis coupled with fast cyclic voltammetric detection. Optimization of pH and complexation with a boric acid-sodium tetraborate buffer provided good resolution of all compounds. Detection by electrochemical reduction using fast on-line cyclic voltammetric detection with a Hg-film mu m-electrode gave detection limits (2Xpeak-to-peak baseline noise) of 7.10(-7) mol/l for tetracycline and chlortetracycline, and 1.5.10(-6) for oxytetracycline. The influence of electrode material, potential range and scan rate was examined and discussed. Optimal electrochemical detection was obtained Hg-film electrode with a waveform than consisted of an initial constant potential of -0.6 V for 200 ms followed by a cyclic voltammetry (CV) scan at 300 V/s from -0.6 V to a vertex potential of 1.7 V. The analytic signal was obtained by plotting the integrated values of the CV current from each applied waveform as a function of time. The calibration plot (peak areas) for each separated peak was found to be linear over over three-orders of magnitude. (C) 1999 Elsevier Science B.V. All rights reserved.