VALIDATED MICELLAR ELECTROKINETIC CAPILLARY CHROMATOGRAPHY METHOD FORQUALITY-CONTROL OF THE DRUG SUBSTANCES HYDROCHLOROTHIAZIDE AND CHLOROTHIAZIDE

A stability-indicating, quality control analysis method was developed and validated for the diuretic drug substances hydrochlorothiazide (HC TZ) and chlorothiazide (CTZ). Micellar electrokinetic capillary chroma tography employing the anionic detergent sodium dodecyl sulfate at 30 mM in 20 mM sodium berate buffer pH 9.5 was utilized to separate and q uantify the active drug substance HCTZ from CTZ and the common impurit y, 4-amino-6-chloro-1,3-benzenedisulfonamide (DSA). A 100 mu m I.D. un coated fused-silica capillary was necessary to provide the sensitivity , i.e. 1 mu g/ml, for quantification of the DSA impurity. In this stud y, the linearity, precision, selectivity, accuracy, reproducibility an d limit of quantitation for the method were investigated for HCTZ, CTZ and DSA. As the first validation of a drug substance method by capill ary electrophoresis in this laboratory, unusual care was taken to insu re reliability and ruggedness with multiple instruments, capillaries a nd analysts. Precision and reproducibility in the range of 1% R.S.D. w as achieved by controlling subtle injection factors. These included mi nimizing the time in which the capillary ends were not immersed in buf fer or sample during the injection process and minimizing the number o f assays for each anode or inlet buffer vial. Stacking induced by diff erences in ionic strength between sample and capillary buffer was redu ced by using a sample buffer concentration similar to that bf the capi llary buffer. Although stacking accomplished by using lower sample buf fer concentrations increased sensitivity, reproducibility was decrease d. Achievement of the 1% R.S.D. precision level means that many qualit y control assays for drugs with good absorbance characteristics can be validated with HPLC reproducibility and CE efficiency. These micellar electrokinetic capillary chromatography methods conform to the USA an d European Pharmacopoeial validation guidelines.