High Performance Liquid Chromatographic Determination of the Ternary Mixture of Caffeine, Dipyrone and Drotaverine Hydrochloride in Tablet Dosage Form.

This work describes a simple, rapid, and reliable HPLC method for the simultaneous determination of caffeine (CAF), dipyrone (DIP) and drotaverine hydrochloride (DRV). Chromatographic separation was achieved using a reversed phase Waters Symmetry C18 (3.9×150 mm, 5 μm particle size) column with gradient elution of the mobile phase composed of 0.05 M orthophosphoric acid and acetonitrile. The gradient elution started with 15% (by volume) acetonitrile ramped up linearly to 60% in 3 min then kept at this percentage till the end of the run. The flow rate was 1mL/min. Quantification was based on measuring peak areas at 210 nm. The analytes were resolved with retention times 1.47, 2.39 and 7.17 min for DIP, CAF and DRV, respectively. Analytical performance of the proposed procedure was validated with respect to system suitability, linearity, ranges, precision, accuracy, robustness, detection and quantification limits. The linearity ranges were 10-200, 5-100 and 5-100 μg/mL for DIP, CAF and DRV, respectively. The validated HPLC method was applied to the simultaneous determination of the three drugs in several laboratory-prepared mixtures of different ratios. Finally, laboratory made tablets containing the three drugs were assayed using the developed procedure where no interfering peaks were encountered from the tablet additives.

Spectrophotometric Determination of Rabeprazole Sodium Using Two Charge Transfer Complexation Reactions.

This work presents two simple and direct spectrophotometric methods for determination of rabeprazole sodium (RB) through charge transfer complexation reactions. The first method is based on the reaction of the drug with p-chloranilic acid (p-CA) in acetonitrile to give a red colored product with maximum absorbance at 518 nm. The second method is based upon the interaction of RB and 7,7,8,8‐tetracyanoquinodimethane (TCNQ) in acetone resulting in the formation of a bluish-green complex measured at 845 nm. Factors affecting the color development were studied and optimized. The proposed colorimetric procedures were effectively validated with respect to linearity, ranges, precision, accuracy, robustness, detection and quantification limits. Regression analysis for the calibration curves of the formed color products with p-CA and TCNQ showed good linear relationships over the concentration ranges of 20–200 and 2–16 μg/mL respectively. The method was successfully applied to the assay of rabeprazole enteric coated tablets with good accuracy and precision. Assay results were statistically compared to a reference HPLC method where no significant differences were observed between the proposed methods and reference method.