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Summary

A novel stability-indicating reversed-phase (RP) HPLC method has been developed and validated for quantitative analysis of eplerenone in the bulk drug and in a pharmaceutical dosage form. Use of a 250 mm × 4.6 mm, 5-μm particle, C18 column with 55:45 (v/v) 50 mM ammonium acetate buffer (pH 7)-acetonitrile as isocratic mobile phase enabled separation of the drug from its degradation products. UV detection was performed at 240 nm. The method was validated for linearity, accuracy (recovery), precision, specificity, and robustness. The linearity of the method was excellent over the range 10–100 μg mL−1 (correlation coefficient 0.999). The limits of detection and quantification were 0.019 and 0.053 μg mL−1, respectively. Recovery of eplerenone from the pharmaceutical dosage form ranged from 100.97 to 101.25%. Eplerenone was subjected to stress conditions (hydrolysis (acid, base), oxidation, photolysis, and thermal degradation) and the stressed samples were analysed by use of the method. Degradation was observed in acid, base, and 30% H2O2. The drug was stable under the other stress conditions investigated. The degradation products were well resolved from main peak. The forced degradation studies prove the stability indicating power of the method.

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Abstract

A simple, sensitive, and rapid RP-HPLC method for analysis of enalapril in the presence of H2-receptor antagonists has been developed and validated. Enalapril maleate was separated from H2-receptor antagonists by use of a 250 mm × 4.6 mm, 5-µm particle, C18 column with 86:14 (υ/υ) methanol-water, pH adjusted to 3.5, as mobile phase, at a flow rate of 1.5 mL min−1. UV detection was performed at 227 nm. The retention times of enalapril maleate, ranitidine, cimetidine, and famotidine were 3, 5, 7, and 7.5 min, respectively. The detection limit for enalapril was 10 ng mL−1 and the calibration plot was linear in the range 2.5–50 µg mL−1. In-vitro interaction of enalapril with the commonly administered H2-receptor antagonists cimetidine, ranitidine, and famotidine in simulated gastric juice at different pH and 37°C was also studied by use of this method. These studies clearly indicated that most of these H2-receptor antagonists bind to enalapril causing drastic changes in the availability of the drug. The HPLC method is accurate, selective, sensitive, and reproducible.

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Acta Chromatographica
Authors: Jovana Tomić, Branka Ivković, Slavica Oljačić, Katarina Nikolić, Nevena Maljurić, Ana Protić, and Danica Agbaba

with optimization of the stability-indicating high-performance thin-layer chromatographic method (HPTLC), reversed-phase high-performance liquid chromatographic method (RP-HPLC), and spectrophotometric method for the separation of ivabradine and its

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A new, rapid, and specific reversed phase high-performance liquid chromatographic (RP-HPLC) method involving precolumn derivatization with benzoyl chloride was developed and validated for the estimation of γ-aminobutyric acid (GABA) in rat brain tissue preparations. The derivatization product of GABA was identified by melting point, infrared, and proton nuclear magnetic resonance (1H NMR) spectroscopy to be n-benzoyl GABA. Various parameters which influenced derivatization and elusion were optimized. The chromatographic system consisted of C-18 column with ultraviolet (UV)—photodiode array detection ranging from 210 to 400 nm. Elution with an isocratic mobile phase consisting of 0.025 M disodium hydrogen phosphate buffer—methanol (65:35, v/v; pH 6) at a flow rate of 1 mL min−1 yielded sharp and specific peak of n-benzoyl GABA within 7 min. The method was validated with respect to the linearity, accuracy, precision, sensitivity, selectivity, and stability, wherein the benzoyl derivative of GABA showed stability for 2 months. The lower limit of detection was 0.5 nmol L−1. This novel derivatization procedure for the estimation of GABA with benzoyl chloride was also applied for rat brain tissue preparations that gave highly specific peak and good component recovery. The results show that the method for the determination of GABA by benzoylation using RP-HPLC has good linearity, accuracy, precision, sensitivity, and specificity and is simple and economical to perform.

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A fast, simple, and sensitive reversed-phase high-performance liquid chromatography (RP-HPLC) method has been developed and fully validated for the determination of moxifloxacin (MXF) in rat plasma. MXF and gatifloxacin (internal standard, I.S.) were extracted from plasma by single-step protein precipitation with acidified acetonitrile. Chromatographic separation was accomplished in less than 8 min on an Atlantis ® T3 column with 0.4% aqueous triethylamine–methanol–acetonitrile (60:35:5, v/v/v) solution as mobile phase. Detection was achieved by fluorescence (λ excitation = 295 nm, λ emission = 500 nm), and the calibration curves were found to be linear over the plasma concentration range of 10–2,500 ng mL−1 with a mean correlation coefficient (r) of 0.9946 (n = 6). The intra- and inter-assay imprecision (% CV) was less than 2.4 and 3.3%, respectively, and the accuracy was >90%. The mean extraction recoveries for MXF and I.S. from plasma were 77 and 82%, respectively. The method was also validated for specificity, sensitivity, and stability; all the results were within the acceptable range. The proposed method was then successfully applied to the quantitative analysis of MXF in rat plasma samples, being a valuable and high-throughput assay to support ongoing pharmacokinetic studies on this promising anti-infective agent.

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A novel simple, sensitive, and rapid isocratic reverse phase high-performance liquid chromatographic (RP-HPLC) method was developed for the quantitative determination of alosetron HCl, a 5-HT3 antagonist used in the treatment of severe irritable bowel syndrome (IBS) in females. The optimized chromatographic separation was achieved using a stationary phase of Phenomenex® kromasil C-18 (250 mm × 4.6 mm; 5 μm particle size) column, and mobile phase of 0.025 M disodium hydrogen orthophosphate buffer, pH adjusted to 3.0 with orthophosphoric acid, and acetonitrile in the ratio of 65:35 (v/v) with a flow rate of 1 mL min−1. The UV detection was carried out at 217 nm. The developed method provided linear responses within the concentration range 100–2000 ng mL−1, and regression analysis showed a correlation coefficient value (r 2) of 0.997. The HPLC method was validated as per International Conference on Harmonization (ICH) guidelines with respect to selectivity, precision, linearity, and robustness. Limit of detection (LOD) and limit of quantification (LOQ) were found to be 1 ng mL−1 and 5 ng mL−1, respectively.

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Summary

An isocratic RP-HPLC method has been developed and validated for simultaneous analysis of ambroxol hydrochloride (AMB) with cetirizine hydrochloride (CTZ) and of ambroxol hydrochloride (AMB) with levo-cetirizine dihydrochloride (LCTZ) in combined solid dosage forms. Formulations containing AMB with CTZ (tablets) and AMB with LCTZ (capsules) are used as antihistaminic H1 blockers. Chromatography was performed on a 250 mm × 4.6 mm, 5-μm particle size, C18 (ODS) column with a 45:30:30 (v/v) mixture of 30 mM aqueous ammonium sulphate (pH 5.5), acetonitrile, and methanol as mobile phase at a flow rate of 1 mL min−1. The detection wavelength was 230 nm and analysis was performed at room temperature. Hydrochlorothiazide was used as internal standard for both formulations. Plots of drug-to-internal standard peakarea ratios (response factor) against respective concentrations were linear in the range 3 to 20 μg mL−1 for AMB and in the range 1 to 11 μg mL−1 for CTZ and LCTZ. The method was precise (RSD < 2) and accurate for analysis of both drugs in pharmaceutical dosage forms. Statistical data and results from recovery studies were reported for both formulations.

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voltammetry (CV), capillary electrophoresis (CE), electrokinetic chromatography (EKC), thin-layer chromatography (TLC), and reversed-phase high-performance liquid chromatography (RP-HPLC). RP-HPLC represents a good alternative for the measurement of

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High-performance liquid chromatography (HPLC) is a widely used technique for the simultaneous detection and quantification of different drugs. The purpose of the current study was to develop a simple and cost-effective reversed-phase high-performance liquid chromatography (RP-HPLC) method for the simultaneous determination of tizanidine (TZN) HCl and meloxicam (MLX) in rabbit's plasma. Assay of TZN and MLX was performed after extraction of drug from plasma by liquid–liquid extraction technique using methanol and diethyl ether as protein precipitants. Isocratic elution was performed in a Kromasil® C18 column (dimension, 250 × 4.60 mm; particle size, 5 μm) with mobile phase consisting of methanol–water (8:2). Orthophosphoric acid was used to adjust the pH of the mobile phase 3.0, and detection was done at 228 nm. Flow rate was 0.8 mL/min with ambient temperature and average operating pressure of 1400 psig. Retention time of TZN was 2.612 min and that of MLX was 6.960 min with a resolution of 3.18. Both drugs showed satisfactory linearity in the range of 10 to 50 ng/mL with correlation coefficients (R 2) of 0.9989 and 0.9972 for TZN and MLX, respectively. The developed method was validated successfully for linearity, system suitability, intra-day and inter-day accuracy, and precision, robustness, and specificity following International Conference on Harmonization (ICH) guidelines. Conclusively, a precise, stable, reproducible, economical, and suitable method for estimation of pharmacokinetic evaluation was developed and validated.

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. Thus, they can be considered a great advantage for lipid analysts during method development [ 23 ]. However, many RP-HPLC–UV methods require high volume of blood which is difficult to be obtained from rat's blood. For example, 5 mL of human plasma [ 24

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