A binary mixture of fluoxetine HCl and olanzapine was determined by two different methods. The first method involved determination of fluoxetine HCl and olanzapine using reversed-phase liquid chromatography using acetonitrile:methanol:0.032 M ammonium acetate buffer (45:05:50, v/v/v) as the mobile phase at a flow rate of 1.5 ml/min. Quantitation was achieved with ultraviolet detection at 235 nm over concentration ranges of 0.2-4 and 0.1-2 μg/ml; mean accuracies were 101.16±0.59 and 99.79±0.56% for fluoxetine HCL and olanzapine, respectively. The second method was based on the high performance thin layer chromatography separation of the two drugs followed by densitometric measurements of their spots at 235 nm. The separation was carried out on Merck TLC aluminium sheets of silica gel 60 F254 using acetone:methanol:triethyleamine (5:3:0.5, v/v/v), as mobile phase. The linearity was found to be in the range of 300–1000 and 150–500 ng/spot; mean accuracies were 100.95±0.52 and 99.31±0.51% for fluoxetine HCl and olanzapine, respectively. The method was successively applied to tablets because no chromatographic interferences from the tablet excipients were found. The methods retained their accuracy and precision when the standard addition technique was applied. The results obtained by applying the proposed methods were statistically analyzed.

Simple, specific, accurate and precise method, namely, reverse phase high performance liquid chromatography was developed for estimation of duloxetine HCl in pharmaceutical formulations. For the high performance liquid chromatography method, Phenomenox C-18, 5 μm column consisting of 250×4.6 mm i.d. in isocratic mode, with mobile phase containing 0.01M 5.5 pH phosphate buffer: acetonitrile (60:40 v/v) and final pH adjust to 5.5±0.02 with phosphoric acid was used. The flow rate was 1.2 ml/min and effluent was monitored at 231 nm. The retention time was 5.61 min. The method was validated in terms of linearity, accuracy and precision. The linearity curve was found to be linear over 0.25-4 μg/ml. The limit of detection and limit of quantification were found to be 0.10 and 0.25 μg/ml respectively. The proposed method was successfully used to determine the drug content of marketed formulations.

A binary mixture of imipramine HCl and chlordiazepoxide was determined by three different spectrophotometric methods. The first method involved determination of imipramine HCl and chlordiazepoxide using the simultaneous equations and the second method involved absorbance ratio method. Imipramine has absorbance maxima at 251 nm, chlordiazepoxide has absorbance maxima at 264.5 nm and isoabsorptive point is at 220 nm in methanol. Linearity was obtained in the concentration ranges of 1-25 and 1-10 μg/ml for Imipramine HCL and Chlordiazepoxide, respectively. The third method involved determination of these two drugs using the first-derivative spectrophotometric technique at 219 and 231.5 nm over the concentration ranges of 1-20 and 2-24 μg/ml with mean accuracies 99.46±0.78 and 101.43±1.20%, respectively. These methods were successively applied to pharmaceutical formulations because no interferences from the tablet excipients were found. The suitability of these methods for the quantitative determination of the compounds was proved by validation.

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A binary mixture of trifluoperazine HCl and chlordiazepoxide was determined using reversed-phase liquid chromatography method using methanol:water (97:03, v/v) pumped at a flow rate of 1.0 ml/min. Quantification was achieved with ultraviolet detection at 262 nm over concentration ranges of 0.1-1 and 0.5-5 μg/ml; mean accuracies were 101.05±0.47 and 98.97±0.33 %, respectively. The method was successively applied to tablet dosage forms as no chromatographic interferences from the tablet excipients were observed. The method retained its accuracy and precision when the standard addition technique was applied.