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.