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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.

A high performance liquid chromatographic method characterized by its rapidness and sensitivity was developed and validated for quantitation of Cilostazol (CIL) and Telmisartan (TEL) in raw material, their synthetic mixture using isocratic technique and monolithic C8 column (3 mm × 4.6 mm i.d., 2 μm pore size highly porous). The mobile phase composed of acetonitrile:0.03 M dihydrogen phosphate buffer (40:60, v/v) at pH 4.5. Quantification was achieved through UV detection at 257 nm using flow rate of 1 mL/min, and Dipyridamole (DIP) was used as internal standard. DIP, CIL, and TEL, retention times were 2.2, 3.9 and 5.1 min. respectively. Peak area ratios of each drug to Dipyridamol internal standard were plotted against concentration of each drug and linear relations were obtained in the range of 0.5-15 μg/mL for CIL 0.25-20 μg /mL for TEL. The method was successfully utilized for the assay of CIL and TEL synthetic mixture. Stability-indicating assay methods (SIAM) were mentioned for separation of CIL in presence of its degradation products. Cilostazol was subjected to acid and alkali hydrolysis, oxidation and photochemical degradation. It was stable under acidic, basic and ultraviolet degradation conditions, but undergoes oxidative degradation, therefore the drug was separated from its oxidative degradation product using our proposed high performance liquid chromatographic and derivative ultraviolet spectrophotometric methods. The first derivative method (D1) depend on measuring the amplitude values at 227 and 257 nm for Cilostazol and oxidative degradate, respectively. From calibration plots, linearity was obtained in the range of 1-35 μg/mL for Cilostazol and 2-50 μg/mL for oxidative degradate. Chromatographic separation of Cilostazol from its oxidative degradate was proceeded using the same mobile phase at pH 3.3. All methods were validated statistically as per International Conference on Harmonization (ICH) recommendations for the studied drugs and Cilostazol oxidative degradate in the concentration range of the suggested methods se ion-pair liquid chromatography was described.

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 stability-indicating reversed-phase liquid chromatographic method for the determination of atenolol was developed. Different chromatographic conditions were carefully studied to optimize the parameters for the evaluation of the studied drug. The chromatographic assay involved the use of a C8 Column (250 mm×4.6 mm i.d., 5 μm) with a simple mobile phase composed of acetonitrile:methanol:0.02 M phosphate buffer, pH 5 (20:20:60) at a flow rate of 1 ml/min and UV detection at 226 nm. Pindolol was used as an internal standard. The method showed good linearity over the range of 0.05-10 μg/mL with a detection limit of 0.01 μg/mL and a quantitation limit of 0.03 μg/mL. The proposed method was successfully applied for the analysis of atenolol in three commercial tablets with average percent recoveries of 100.14 ± 1.04, 100.20 ± 0.92, 100.00 ± 0.91 and 100.75 ± 0.67, respectively. Several co-formulated and co-administered drugs did not interfere with the proposed method. The results were statistically compared with those obtained by the official method and were found to be in good agreement. The stability-indicating capability of the method was also tested after accelerated degradation of atenolol in acidic and basic media and after freezing and heating treatments.

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