A new universal high-performance liquid chromatographic method for determination of 1,4-benzodiazepines as bulk drugs and in pharmaceutical formulations.

A universal high-performance liquid chromatographic method was developed for the simultaneous determination of seven frequently prescribed 1,4-benzodiazepines in bulk powder or formulated in tablets or capsules. Peak tailing commonly reported with HPLC method developed for benzodiazepines, is completely omitted with this new method. The assay procedure consisted of pulverization, extraction into methanol, filtering, diluting and injecting of aliquots of clear filtrate into a reversed phase column with a very low silanol activity. The mobile phase consisted of a mixture of methanol and 0.05 mol x L(-1) buffer solution of ammonium dihydrogen phosphate (50:50, v/v) adjusted to pH 5.8. The effluent was monitored by UV detection at 254 nm and delivered at a flow rate of 1.6 mL x min(-1). The new method has been applied for quantifying of 1,4-benzodiazepines in different commercial formulations with recoveries ranging from 99.0 (+/- 1.98) to 102.0 (+/- 1.58)%. The excipients present in tablets and capsules did not interfere with the developed method. The applicability of the method for content uniformity and dissolution tests has been also investigated and the results were considered satisfactory. The developed method is rapid and sensitive, and is suitable for routine control of pharmaceutical dosage forms.

New high-performance liquid chromatographic method for serum analysis of oxazepam: application to bioequivalence and pharmacokinetic study.

A rapid and sensitive high-performance liquid chromatographic method was developed and validated for determination of oxazepam in serum. Oxazepam was isolated from biological fluid using a simple liquid-liquid extraction with dichloromethane. Nordazepam was used as the internal standard. The chromatographic separation was accomplished using a 125 x 4-mm (inner diameter) stainless-steel (5 microm) Perfectsil Target ODS-3 reversed phase column with a mobile phase consisting of ammonium dihydrogen phosphate buffer (0.05 mol x L(-1), pH 5.8) and methanol (50:50, v/v), running at a flow rate of 1.5 ml x min(-1). The absorbance of the fluent was monitored at 254 nm. The developed method resulted in totally symmetrical peaks. It has been applied to assess the pharmacokinetics of oxazepam. Also the bioequivalence of two different oxazepam preparations following oral administration in healthy volunteers was assessed by this method.