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.

Optimized determination of lorazepam in human serum by extraction and high-performance liquid chromatographic analysis.

The present research was designated to evaluate a rapid and sensitive method for determining low concentrations of the highly active drug lorazepam in serum. Isolation of the drug from biological fluid after addition of nordazepam as the internal standard was achieved using a simple liquid-liquid extraction with dichloromethane and the extracted compounds were quantified by high-performance liquid chromatography. Chromatographic separation on a reversed phase column containing a stationary phase with low silanol activity resulted in a perfectly symmetrical peak with a tailing factor of 1.0. The limit of quantitation in serum is 2.5 ng mL(-1) for both lorazepam and internal standard. The procedure is rapid and sensitive enough for determination of lorazepam in serum.

Capillary gas chromatography determination of benzaldehyde arising from benzyl alcohol used as preservative in injectable formulations.

A simple, precise and accurate capillary gas-liquid chromatographic procedure has been developed to determine benzaldehyde, the toxic oxidation product of the widely used preservative and co-solvent benzyl alcohol, in injectable formulations of the non-steroidal anti-inflammatory drugs, diclofenac and piroxicam, as well as in Vitamin B-complex injection solutions. Following liquid-liquid extraction with chloroform, separation and quantification are achieved on a fused silica capillary column (25 m x 0.53 mm i.d.) coated with 0.5 microm film of OV-101. 3-Chlorobenzaldehyde was used as internal standard with flame-ionization as the detection mode. The ability of the system to resolve benzaldehyde peak from interfering components is good. The method displays excellent linearity over the concentration range 0.5-100 microg/ml of benzaldehyde and a precision of better than 2.5% from intra- and inter-day analyses. The quantification limit for benzaldehyde is 0.4 microg/ml. Levels of benzaldehyde in generic diclofenac and piroxicam injection formulations were found to be seven to 15 times higher than in reference formulations, and double in generic Vitamin B-complex injection formulations.

Polarographic determination of benzaldehyde in benzyl alcohol and sodium diclofenac injection formulations.

A rapid and sensitive polarographic method was developed for qualitative as well as quantitative analysis of the neurotoxic contaminant benzaldehyde in Na-diclofenac injections and in benzyl alcohol used for parental formulations. A well-defined differential pulse (DP) polarographic peak or a sampled direct current (SDC) wave was obtained at -1.39 V (vs. silver-silver chloride reference electrode) in Britton-Robinson buffer (pH 9.15) and at -1.41 V in 0.1 M LiCl solution. The reduction step involves a two-electron process, corresponding to the formation of benzyl alcohol. No peaks were observed in the anodic branch of the cyclic voltammogram, emphasizing the occurrence of an irreversible process. The peak current versus concentration relationship was found to be linear up to 50 microg/ml with the detection limit of 10 ng/ml and quantitation limit of 30 ng/ml. The relative standard deviations (S.D.) obtained for concentration levels of benzaldehyde as low as 25 microg/ml with the SDC and DP methods were 1.5 and 0.78% (n=10), respectively. Benzyl alcohol and Na-diclofenac are not electrochemically active, and metabisulfite reductions at -0.664 and -1.240 V do not interfere with the benzaldehyde reduction peak. The proposed methods (DP and SDC polarography) have been applied satisfactorily to the determination of benzaldehyde traces in benzyl alcohol and in different pharmaceutical products such as Na-diclofenac injectable formulations.