A stability-indicating MEKC method was developed and validated for the simultaneous determination of aliskiren (ALI) and hydrochlorothiazide (HCTZ) in pharmaceutical formulations using ranitidine as an internal standard (IS). Optimal conditions for the separation of ALI, HCTZ and its major impurity chlorothiazide (CTZ), IS and degradation products were investigated. The method employed 47 mM Tris buffer and 47 mM anionic detergent SDS solution at pH 10.2 as the background electrolyte. MEKC method was performed on a fused-silica capillary (40 cm) at 28°C. Applied voltage was 26 kV (positive polarity) and photodiode array (PDA) detector was set at 217 nm. The method was validated in accordance with the ICH requirements. The method was linear over the concentration range of 5-100 and 60-1200 μg/mL for HCTZ and ALI, respectively (r(2) >0.9997). The stability-indicating capability of the method was established by enforced degradation studies combined with peak purity assessment using the PDA detection. Precision and accuracy evaluated by RSD were lower than 2%. The method proved to be robust by a fractional factorial design evaluation. The proposed MEKC method was successfully applied for the quantitative analysis of ALI and HCTZ both individually and in a combined dosage tablet formulation to support the quality control.

A reversed-phase liquid chromatography (RP-LC) method is validated for the determination of aliskiren in tablet dosage form. The LC method is carried out on a Waters XBridge C(18) column (150 × 4.6 mm i.d.), maintained at 25°C. The mobile phase consisted of acetonitrile:water (95:5, v/v)/phosphoric acid (25 mM, pH 3.0) (40:60, v/v), run at a flow rate of 1.0 mL/min, with photodiode array detector set at 229 nm. The chromatographic separation is obtained with aliskiren retention time of 3.68 min, and it is linear in the range of 10-300 μg/mL (r = 0.9999). The limits of detection and quantitation are 2.38 and 7.93 μg/mL, respectively. The specificity and stability-indicating capability of the method are proven through degradation studies, which also showed that there is no interference of the formulation excipients, showing that peak is free from any coeluting peak. The method showed adequate precision, with a relative standard deviation (RSD) values lower than 0.92%. Good values of accuracy were also obtained, with a mean value of 99.55%. Experimental design is used during validation to calculate method robustness. The proposed method is applied for the analysis of the tablet dosage forms, contributing to improve the quality control and to assure the therapeutic efficacy.

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A stability indicating reversed-phase liquid chromatography method is developed and validated for the determination of norfloxacin in a new formulation of extended-release tablets. The LC method is carried out on a Luna C(18) column (150 x 4.6 mm) maintained at 40 degrees C. The mobile phase is composed of phosphate buffer (0.04 M, pH 3.0)-acetonitrile (84:16, v/v) run at a flow rate of 1.0 mL/min and detection at 272 nm. The chromatographic separation was obtained within 10 min, and it is linear in the concentration range of 0.05-5 microg/mL. Validation parameters, such as the specificity, linearity, precision, accuracy, and robustness, were evaluated, and results were within the acceptable range. Moreover, the proposed method was successfully applied for the assay of norfloxacin in the developed formulations.

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Rev. bras. hematol. hemoter. 2006;28(1):28-32.

A simple, stability-indicating capillary zone electrophoresis (CZE) method was developed and validated for the analysis of fesoterodine (FESO) in tablets. Optimal conditions for the separation of FESO and its degradation products were investigated. The method used 10 mM sodium phosphate buffer at pH 6.5 as the background electrolyte with an applied voltage of 30 kV (positive polarity).The capillary length was 80.5 cm (72 cm to the detector), and the detection wavelength was 208 nm. The method was validated in accordance with the International Conference on Harmonization requirements, which involved specificity, linearity, precision, accuracy, robustness, LOD, and LOQ. The stability-indicating capability of the method was established by stress degradation studies combined with peak purity assessment using photodiode array detection. The method was linear over the concentration range of 2-100 microg/mL (r2 = 0.9998) of FESO. Intraday and interday precision and accuracy evaluated by RSD, respectively, were all lower than 2%. The LOD and LOQ were 0.57 and 1.90 microg/mL, respectively. The method proved to be robust by a fractional factorial design evaluation. The proposed CZE method was successfully applied for the quantitative analysis of FESO in extended-release tablets to support its QC.