Development and application of a high-performance liquid chromatographic method for the determination of in vitro drug release of levodopa, carbidopa, and entacapone from a tablet formulation.

A simple, precise, and accurate high-performance liquid chromatographic method was developed and validated to determine percent drug release of levodopa (LEV), carbidopa (CAR), and entacapone (ENT) from its combination dosage form. A mixture of acetonitrile and buffer was used as the mobile phase for reversed-phase liquid chromatographic separation for determination of the in vitro drug release of LEV, CAR, and ENT. A dissolution test was conducted at 75 rpm with United States Pharmacopeia (USP) apparatus-II (paddle) by using pH 5.5 phosphate buffer as a dissolution medium. Three formulations, differing in strength, were evaluated. The developed method was validated for specificity, linearity, precision, accuracy, and solution stability. The specificity of the method was determined in the presence of placebo interference. The method was linear over the drug concentration ranges of 4-210 microg/mL for LEV, 1-52 microg/mL for CAR, and 6-280 microg/mL for ENT. Precision was established by determination of system precision, method precision, and intermediate precision. Accuracy values for the method ranged from 96.8 to 104.3% for LEV, from 97.2 to 101.3% for CAR, and from 99.5 to 102.8% for ENT. The developed method was suitable for estimating percent drug release of LEV, CAR, and ENT in terms of the dissolution test.

Validated column high-performance liquid chromatographic method for determination of aspirin and clopidogrel in combined tablets in the presence of degradation products formed under ICH-recommended stress conditions.

The development and validation of a column high-performance liquid chromatographic assay method for the determination of aspirin and clopidogrel in tablet formulation are described. The combination formulation was subjected to International Conference on Harmonization-recommended stress conditions. Separation of the drugs from the degradation products formed under stress conditions was achieved on an octasilyl (C8) column using 0.3% orthophosphoric acid-acetonitrile (65 + 35, v/v) mobile phase. The method was validated for specificity, linearity, limits of detection and quantification, precision, accuracy, and robustness. The method was found to be specific against placebo interference and during the forced degradation. The response was linear in the concentration range of 30.0-120.0 microg/mL for aspirin and 15.0-60.0 microg/mL for clopidogrel, with a correlation coefficient of 0.9999 for both. The relative standard deviation values for intra- and interday precision were <2.0%. The accuracy was between 99.12 and 99.83% for aspirin and 98.20 and 100.35% for clopidogrel. Stress testing showed degradation products that were well-separated from the parent compound, confirming the stability-indicating capacity of the method.

Development and validation of a stability-indicating column high-performance liquid chromatographic assay method for determination of nebivolol in tablet formulation.

A simple, precise, and accurate isocratic reversed-phase (RP) stability-indicating column high-performance liquid chromatographic (HPLC) assay method was developed and validated for determination of nebivolol in solid pharmaceutical dosage forms. Isocratic RP-HPLC separation was achieved on a Phenomenex Luna C8 (2) column (250 mm x 4.6 mm id, 5 microm particle size) using mobile phase composed of acetonitrile-pH 3.5 phosphate buffer (35 + 65, v/v) at a flow rate of 1.0 mL/min, and detection was performed at 280 nm using a photodiode array detector. The drug was subjected to oxidation, hydrolysis, photolysis, and heat to apply stress conditions. The method was validated for specificity, linearity, precision, accuracy, robustness, and solution stability. The method was linear in the drug concentration range of 40-160 microg/mL with a correlation coefficient of 0.9999. The repeatability relative standard deviation (RSD) for 6 samples was 0.69%, and the intermediate precision (RSD) for 6 samples was 1.39%. The accuracy (recovery) was between 98.57 and 99.55%. Degradation products produced as a result of stress studies did not interfere with detection of nebivolol, and the assay can thus be considered stability-indicating.

Determination of nebivolol and valsartan in a fixed-dose combination by liquid chromatography.

An accurate and reproducible liquid chromatographic assay method was developed and validated for the determination of nebivolol and valsartan in a capsule formulation. Buffer-acetonitrile (55 + 45, v/v) was used for reversed-phase liquid chromatography to determine the contents of nebivolol and valsartan in the combination-capsule dosage form. The method was validated by determining parameters such as specificity, linearity, limits of detection and quantitation, precision, accuracy, and robustness. The method was found to be specific against placebo interference. Linearity was evaluated over the concentration ranges of 2-8 micro/mL for nebivolol and 32-128 microg/mL for valsartan (the correlation coefficient was 0.9999 for both nebivolol and valsartan). Both the intraday and interday precision values of the system and the method were determined. The accuracy of the method ranged from 100.66 to 102.58% for nebivolol and from 101.17 to 101.85% for valsartan. The proposed method was found to be robust when slight but deliberate changes were made in the analytical conditions. The developed method was found suitable for the assay determination of nebivolol and valsartan in a capsule formulation.