Separation and simultaneous determination of nalidixic acid, hydroxynalidixic acid and carboxynalidixic acid in serum and urine by micellar electrokinetic capillary chromatography

Separation in capillary electrophoresis is governed by various factors, inc luding buffer type, buffer concentration, pH, temperature, voltage and mice lles. Through proper adjustment of these parameters, nalidixic acid and its two major metabolites, 7-hydroxynalidixic and 7-carboxynalidixic, could be separated by micellar electrokinetic capillary chromatography using an ele ctrophoretic electrolyte consisting of 50 mM berate buffer (pH 9) containin g 25 mM sodium dodecyl sulphate and 10% acetonitrile. A linear relationship between concentration and peak area for each compound was obtained in the concentration range 0.15-100 mu g ml(-1), with a correlation coefficient gr eater than 0.999 and detection limits in the 0.2-0.7 ng ml(-1) range. Intra - and inter-day precision values of about 0.8-1.2% RSD (n = 11) and 1.3-2.0 % RSD (n = 30), respectively, were obtained. The method has been applied to the analysis of nalidixic acid and its two major metabolites in serum and urine with limits of sensitivity lower than 0.8 ng ml(-1). (C) 1999 Elsevie r Science B.V. All rights reserved.