High performance liquid chromatogaphic determination of mixtures of benzoic acid and sorbic acid and methyl paraben and propyl paraben in some soft drinks and pharmaceutical formulations

A rapid, specific and accurate reversed phase HPLC method was developed and validated for the determination of cited compounds in bulk powder samples and commercial pharmaceutical and food products. HPLC was performed with a Pecosphere C18 column "Perkin-Elmer" [33 x 4.6 mm, 3 mum] with a mobile phase of methanol: water [60: 40] for the determination of the two parabens with UV detection at lambda 255 nm and methanol-phosphate buffer pH 45 [8: 92] for the determination of the two acids with UV detection at lambda 235 nm. The influence of pH of phosphate buffer and its ratio in mobile phase was discussed. The typical linear range extended from 1-10 mug/ml for methyl paraben, 1-12 mug/ml for propylparaben, 5-50 mug/ml for sorbic acid and 5-100 mug/ml for benzoic acid. The results were evaluated by a linear regression analysis

Determination of clorazepate dipotassium via its iodobismuthate complex

A spectrophotometric method and two titrimetric methods for the determination of clorazepate dipotassium via its Iodobismuthate complex are described. These methods depend on, the reaction of clorazepate dipotassium with potassium bismuth iodide which give an orange precipitate. Determination of clorazepate dipotassium in the precipitated complex is done iodometrically using standard potassium iodate solution or complexometrically using standard EDTA solution and xylenol orange indicator. Alternatively, the complex is dissolved in ethyl alcohol and its absorbance is measured at 322 nm. The three methods were successfully applied for the determination of authentic samples of clorazepate dipotassium in the concentration range of 5-25 mg [for the titrimetric method and 40-120 mcg [for the spectrophotometric method]. The mean percentage recoveries were found to be 99.61 +/- 0.81, 99.80 +/- 0.48 - and 99.97 +/- 0.50 for the three methods, respectively. The proposed methods described were successfully applied for the determination of clorazepate dipotassium in tranxene capsules and the validity of the suggested procedures was assessed by applying the standard addition technique

Spectrofluorometric determination of clorazepate dipotassium in presence of its degradation product

A sensitive spectrofluorimetric procedure for the quantitative determination of the intact molecule of clorazepate dipotassium and its degradation product, without separation, was described. The method depends upon the difference of the fluorescence behavior of clorazepate dipotassium and its acidic degradation product; namely, 2-amino, 5-chlorobenzophenone. The concentration of both components are computed from their calculated regression equations. The efficiency of the method has been evaluated by analyzing mixtures of a reference sample of clorazepate dipotassium and controlled, acid-degraded samples; the results obtained are found to concord with both. The method is applied to clorazepate dipotassium bulk powder and to its pharmaceutical formulation, "Tranxene capsules" with an accuracy of 99.7 + 0.58. The proposed procedure is simple, accurate, precise, and less time consuming than the others

Titrimetric determination of piroxicam and diclofenac sodium using N-bromosuccinimide

A simple volumetric method for the determination of each of piroxicam and diclofenac sodium is suggested based on the reaction with N- bromosuccinimide [NBS]. The direct titration with NBS is only successful for piroxicam in glacial acetic acid medium using methyl orange as indicator. However, the indirect titration is described for both piroxicam and diclofenac sodium, in which the drug solution is allowed to react with a known excess of standard NBS solution for the specified time and the excess NBS is back titrated iodometrically. The different factors affecting the titrations are discussed. The method determines 1.2 mg of piroxicam in the direct titration with a mean accuracy of 100.4 +/- 1.03% and determines 2-12 mg of piroxicam and 1-15 mg of diclofenac sodium in the indirect titration with mean accuracies of 100.0 +/- 0.53% and 100.1 +/- 0.78%, respectively