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Three rapid, accurate and very simple derivative spectrophotometric methods for RIV and CLP assay in their binary mixture and tablet dosage forms were developed. Method (I) is first derivative spectrophotometric method, derivative amplitudes were measured at the zero crossing wavelength of 289 and 249.5 nm for estimation of RIV and CLP, respectively. The linearity is over the range 2.0 - 20.0 μg/ml for RIV and 5.0 - 60.0 μg/ml for CLP with LOD of 0.211 and 0.361 μg mL-1 and LOQ of 0.641 and 1.095 μg mL-1 for RIV and CLP, respectively. Method (II) is ratio derivative spectrophotometric method. The ratio spectra of each drug were derived by dividing its spectra on a constant concentration of the other drug as a divisor. Derivative amplitudes were measured at 256 nm for RIV and at 214.5 nm for CLP over the same linearity range as the first method with LOD of 0.137 and 0.485 μg mL-1 and LOQ of 0.417 and 1.471 μg mL-1 for RIV and CLP, respectively. Method (III) is absorbance ratio method, absorbance of both drugs were recorded at two wavelengths λ1 (232) iso-absorptive point and λ2 (249) λmax of RIV. The final concentrations were obtained by applying the Q equations. The method was linear over the same concentration range as the first method with LOD of 0.272 and 0.485 μg mL-1 and LOQ of 0.826 and 1.471 μg mL-1 for RIV and CLP, respectively. The proposed methods were validated as per ICH guidelines. The proposed methods were successfully applied to both drugs analysis in their laboratory prepared co formulated tablet. Statistical comparison of the obtained results with those of the reference method show good agreement and confirm that there were no significant difference in the accuracy and precision between the proposed and reference one respectively.

A selective and short time consuming cost effective micellar high performance liquid chromatographic technique is created for the separation and simultaneous assay of two antiplatelet drugs, Rivaroxaban (RIV) with Clopidogrel (CLP). The developed and validated method is characterized by its simplicity, sensitivity and rapidness. Chromatographic study is performed on a 3 mm × 4.6 mm i.d., 2 μm pore size highly porous monolithic (chromolith® reversed phase) column to obtain good chromatographic separation using a mixture of 0.185 M sodium dodecyl sulphate (SDS), 8% n-propanol, 0.3% triethylamine (TEA) as a mobile phase, adjusted at pH 4.0 using 0.02 M orthophosphoric acid and pumped at a flow rate of 1 mL/min. using UV detector at 235 nm. The internal standard (IS) of choice was Raloxifen (RAL) and separation was performed at room temperature. Good linearity for the proposed method was obtained over the ranges of 0.3-9.0 μg/mL and 0.5-25.0 μg/mL with limits of detection (LOD) of 0.05, 0.16 μg/mL and limits of quantitation (LOQ) of 0.16, 0.49 μg/mL for rivaroxaban and clopidogrel, respectively and retention time was 1.9 and 5min., respectively. Simultaneous analysis of the studied drugs in their laboratory prepared mixture and tablet was done as an application for the proposed method showing satisfactory results. Also biological fluids were assayed using the proposed method for the determination of rivaroxaban in human plasma and for both drugs in human urine with no need for previous extraction. The data obtained by the proposed method was statistically evaluated and compared with the reference one showing good accuracy and precision of the proposed method.

Two simple and sensitive kinetic methods were developed for the determination of ribavirin in bulk and in its pharmaceutical preparations using alkaline potassium permanganate as an oxidizing agent. The methods are based upon a kinetic investigation of the oxidation reaction of the drug at room temperature for fixed times of 20 and 30 minutes. In the first method, the absorbance of the colored manganate ion was measured at 610 nm, while in second method the reduction in the absorbance of permanganate was measured at 525 nm. The absorbance concentration plots were linear over the range of 3-15 μg/ml with detection limits of 0.028 μg/ml in the first method and 0.229 μg/ml for the second method. The proposed methods were applied successfully for the determination of the drug in its pharmaceutical formulations, the percentage recoveries were 100.15 ± 1.34, 100.06 ± 0.86 in the first method, and 99.60 ± 0.54, 100.43 ± 0.82 in the second method. The results obtained were compared statistically with those obtained by the official method and showed no significant differences regarding accuracy and precision.

A micellar liquid chromatographic method was developed for the simultaneous analysis of a binary mixture of norfloxacin and tinidazole (NOR and TIN) in dosage forms and human plasma. The analysis was carried out using a Waters Symmetry® C18 column (250 mm x 4.6 mm i.d., 5 µm particle size). The running mobile phase consisting of 0.15 M sodium dodecyl sulphate (SDS), 0.3 % triethylamine (TEA), 5 % n-propanol, the pH was adjusted to 4 by addition of 0.02 M orthophosphoric acid pumped at a flow rate 1.0 mL/min with UV at 275 nm. Calibration curves were linear over the range 1-28 and 1.5-42 µg/mL for NOR and TIN, respectively. The quantification limits were 0.7 and 1.0 µg /mL for NOR and TIN respectively. The proposed method was successfully applied for the simultaneous determination of NOR and TIN in human plasma without prior precipitation of protein. The mean percentage recoveries of bioavailability test in human plasma (n = 3) were 90.31 ± 4.22 and 90.05 ± 1.3 for NOR and TIN, respectively., Colegio de Farmacéuticos de la Provincia de Buenos Aires