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In this study, a solid-phase extraction (SPE)-high performance liquid chromatography (HPLC)-ultra violet (UV) method was developed for the determination of rivaroxaban (RIV), an oral anticoagulant drug, in human plasma samples. The concentration of RIV in plasma samples was increased 7.5 times and the interference coming from matrix components was avoided by using SPE. The extracted samples of RIV were analyzed by using an HPLC-UV method. RIV was approved in 2008 and many studies have been published in recent years in order to investigate its pharmacokinetic profile in various groups. In light of this information, it is clear that the RIV pharmacokinetic profile should be investigated in further studies; the HPLC-UV method presented in this study might be an easy method to apply, as it is a cheap and rapid alternative to HPLC-MS-MS for this purpose. A Phenomenex Luna 5-µm C18 100 Å LC column (250 × 4.6 mm) was used for the separation of RIV and prednisolone (internal standard). The total analysis time was <6 min. The method was validated according to the FDA guidelines and can be proposed for pharmacokinetic studies of RIV.

Rivaroxaban, an anti-clotting medication, acts at a crucial point in the blood-clotting process and stops the formation of blood clots. In this study, RP-HPLC method was developed for the determination of rivaroxaban in tablets (Xarelto ® (10 mg)). Phenomenex Luna 5 µm C18 100 Å LC Column (250 x 4.6 mm) was used at 40 o C. Isocratic elution was performed with ACN:Water (55:45 v/v) mixture. The flow rate was 1.2 mL min -1 and UV detection was at 249 nm. Internal standard (Caffeine) and rivaroxaban were eluted within 2.21 and 3.37 minutes, respectively. The developed method was validated according to the ICH guidelines and found to be linear within the range 0.005 -40.0 µg mL -1 . The method was accurate, precise, robust and rapid. Thus, it was applied successfully for the quality control assay of rivaroxaban in tablet dosage form.Uniterms: HPLC. Rivaroxaban. Validation. System suitability. Stability-indicating. Pharmaceutical dosage form.Rivaroxabana, fármaco anticoagulante, atua em um ponto crucial no processo de coagulação do sangue e impede a formação de coágulos sanguíneos. Neste estudo, desenvolveu-se método de RP-HPLC para a determinação de rivaroxabana em comprimidos (Xarelto ® (10 mg)). Utilizou-se coluna LC (250 x 4,6 mm) Phenomenex Luna C18 5 mm 100 Å a 40 o C. Realizou-se eluição isocrática com ACN: água (55:45 v/v). O fluxo foi de 1,2 mL min-1 e a detecção de UV foi a 249 nm. Padrão interno (cafeína) e rivaroxabana eluíram em 2,21 e 3,37 minutos, respectivamente. O método desenvolvido foi validado de acordo com as diretrizes do ICH e mostrou-se linear na faixa 0,005-40,0 mg mL -1 . O método foi exato, preciso, robusto e rápido. Assim, foi aplicado com êxito para o ensaio de controle de qualidade da Rivaroxabana na forma de comprimidos.Unitermos: HPLC. Rivaroxabana. Validação. Adequação do sistema. Indicador de estabilidade. Forma farmacêutica.

A simple, rapid and reproducible HPLC method was developed for the simultaneous determination of amlodipine and valsartan in their combined dosage forms, and for drug dissolution studies. A C18 column (ODS 2, 10 μm, 200 x 4.6 mm) and a mobile phase of phosphate buffer (pH 3.6 , 0.01 mol L-1):acetonitrile: methanol (46:44:10 v/v/v) mixture were used for separation and quantification. Analyses were run at a flow-rate of 1 mL min-1 and at ambient temperature. The injection volume was 20 μL and the ultraviolet detector was set at 240 nm. Under these conditions, amlodipine and valsartan were eluted at 7.1 min and 3.4 min, respectively. Total run time was shorter than 9 min. The developed method was validated according to the literature and found to be linear within the range 0.1 - 50 μg mL-1 for amlodipine, and 0.05 - 50 μg mL-1 for valsartan. The developed method was applied successfully for quality control assay of amlodipine and valsartan in their combination drug product and in vitro dissolution studies.
Desenvolveu-se método de HPLC rápido e reprodutível para a determinação simultânea de anlodipino e valsartana em suas formas de associação e para os estudos de dissolução dos fármacos. Utilizaram-se coluna C18 (ODS 2, 10 μm, 200 x 4,6 mm) e fase móvel tampão fosfato (pH 3,6, 0,01 mol L-1):acetonitrila: metanol para a separação e a quantificação. As análises foram efetuadas com velocidade de fluxo de 1 mL min-1 e à temparatura ambiente O volume de injeção foi de 20 μL e utilizou-se detector de ultravioleta a 240 nm. Sob essas condições, anlodipino e valsartana foram eluídas a 7,1 min e 3,4 min, respectivamente. O tempo total de corrida foi menor que 9 min. O método desenvolvido foi validado de acordo com a literatura e se mostrou linear na faixa de 0,1-50 μg mL-1 para anlodipino e de 0,05-50 μg mL-1 para valsartana. O método desenvolvido foi aplicado com sucesso para ensaios de controle de qualidade de associações de anlodipino e valsartana e nos estudos de dissolução in vitro

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A simple, sensitive, and selective square-wave voltammetric method was developed for the determination of pantoprazole. The influence of the nature of the supporting electrolyte solution, pH, modulation amplitude, frequency, and scan increment was examined by square-wave voltammetric method for pantoprazole. The best results were obtained in Britton-Robinson buffer of pH 5.0. The peak currents were measured with hanging mercury drop electrode at 2987 mV vs. Ag/ AgCI. The calibration curve for pantoprazole was found as linear at a concentration range from 0.15 to 25.23 mg mL 21 . The limit of detection and the limit of quantification of pantoprazole were 0.048 mg mL 21 and 0.15 mg mL 21 , respectively. The validation parameters of the proposed method were evaluated. The method was applied to the pharmaceutical formulation and to both spiked plasma and the plasma of patients orally administered pantoprazole. A spectrophotometric method reported in the literature was utilized as a comparison method. There were no significant differences between the results obtained by two methods.

In this study, the electrochemical behaviour of rosuvastatin calcium, which is a hydroxy methyl glutaryl Co-A inhibitor (a member of the statin group), used for the treatment of hypercholesterolemia and dyslipidemia was investigated using cyclic voltammetry (CV) and chronoamperometry (CA) methods. According to these studies it is assumed that the reaction is a diffusion-controlled process and irreversible. The results from the CA were calculated using Cottrell's equation and the diffusion coefficient was found to be 5.79 Â 10 À5 AE 0.22 Â 10 À5 cm 2 s À1 . It was calculated that 2 electrons were transferred. For the determination of rosuvastatin calcium from the pharmaceutical preparations, a square wave voltammetry (SWV) method was selected and developed because it is more sensitive and faster than the other voltammetric methods. Rosuvastatin calcium's reduction peak was seen at À1184 mV in pH 5 acetate buffer with a hanging mercury drop electrode (HMDE) used as the working electrode, an Ag/AgCl with saturated 3 M KCl reference electrode and a platinum wire counter electrode. 70 Hz frequency, 4 mV scan increment and 25 mV pulse amplitude were chosen as optimum parameters. This method was validated according to the ICH guidelines on analytical method validation processes. Linearity for rosuvastatin calcium was found between 0.20 and 10.00 mg mL À1 . While the limit of detection for rosuvastatin calcium was 0.07 mg mL À1 , the limit of quantitation was 0.20 mg mL À1 . As a result of these validation studies, the selective, accurate and precise square wave voltammetric method, which gives sensitive and repeatable results, was applied to the determination of rosuvastatin calcium from pharmaceutical preparations. The results obtained from the developed method were compared with a spectrophotometric method and a capillary electrophoresis method reported in the literature and no significant difference was found statistically. Fig. 1 Chemical structure of rosuvastatin calcium.