J.V.L.N. Seshagiri Rao

The authors proposed a simple, rapid and sensitive liquid chromatography / tandem mass spectrometry assay method for the determination of nateglinide in human plasma using carbamazepine as internal standard (IS). Analyte and the IS were extracted from the human plasma via liquid-liquid extraction using ethyl acetate. The chromatographic separation was achieved on a C18 column by using a mixture of 0.1% formic acid buffer –acetonitrile buffer (20:80, v/v) as the mobile phase at a flow rate of 0.8 mL/min. The calibration curve obtained was linear (r2 ³ 0.99) over the concentration range of 10.0–10005 ng/mL. Method validation was performed as per FDA guidelines and the results met the acceptance criteria. The proposed method was found to be applicable to pharmacokinetic studies.

An accurate and precise high performance liquid chromatographic method was developed for quantitative estimation of bosentan in tablet dosage forms. Chromatographic separation of the drug was achieved on a Kromasil C18 column (150 x 4.6 mm; 5µ) by eluting with a mobile phase consisting of phosphate buffer (pH 4.0) and acetonitrile (30:70 v/v) at a flow rate of 1.0 mL/min. The drug in the eluate was monitored by U V detection at 270 nm. The retention time obtained for the drug was 3.54 min. The calibration curve plotted was linear over the range of 25-175 µg/mL of the drug. The validation of the method was done following the ICH guidelines. The proposed method could be applied for determination of bosentan in its tablet dosage forms without any interference from excipients. The method is suitable for routine quality control analysis of bosentan formulations.

An accurate, precise and reproducible high performance liquid chromatographic method was developed for the simultaneous estimation of lamivudine, zidovudine and nevirapine in pharmaceutical dosage forms. Phenomenex C18 column (250 x 4.6 mm; 5µ) was employed for the separation of drugs. A mixture of 0.02 M trichloroacetic acid (6.8 pH) and methanol in the ratio of 40:60 v/v was used as the mobile phase and pumped at a flow rate of 1ml/min. The detection wavelength was set at 265 nm. The linearity of quantification was observed in the range of 7.5-112.5, 10-150 and 15-225 μg/ml for lamivudine, zidovudine and nevirapine respectively. The proposed method was validated according to ICH guidelines. The method was found to be suitable for simultaneous and accurate determination of these drugs in tablet dosage forms without any interference from the excipients.

An accurate, precise and reproducible high performance liquid chromatographic method was developed for quantitative estimation of telmisartan in bulk drug samples and tablet dosage forms. Chromatographic separation of the drug was achieved on a Kromasil C18 column (150 x 4.6 mm; 5µ) using a mixture of phosphate buffer (pH 4.0) and acetonitrile (40:60 v/v) as the mobile phase at a flow rate of 1.0 mL/min. Under optimized conditions, the retention time of the drug was found to be 2.887 min. Good detecting sensitivity for the analyte was observed at 224 nm. The quantitation calibration curve for the drug was linear over the range of 20-60 µg/mL. The performance of the proposed method was validated as per ICH guidelines. The method was proved to be suitable for the estimation of telmisartan in tablet dosage forms. Key words: Telmisartan, Estimation, Tablets, HPLC.

An accurate, precise and reproducible high performance liquid chromatographic method was developed for quantitative estimation of abacavir, lamivudine and zidovudine simultaneously in tablet dosage forms. Separation of the drugs was achieved within 15.0 min on a Hichrom RP-select B column (250 x 4.6 mm; 5µ) by gradient elution using mixtures of 0.02M ammonium acetate and methanol as the mobile phase. The analytes in the eluate were monitored at 250 nm. The retention times obtained for abacavir, lamivudine and zidovudine were 12.172, 1.884 and 4.378 min respectively. The calibration curves were linear over the range of 25-200 µg/mL for abacavir, 12.5-100 µg/mL for lamivudine and 25-200 µg/mL for zidovudine. The performance of the method was validated according to ICH guidelines. The method was found to be suitable for accurate determination of these drugs in tablet dosage forms without any interference from the excipients or endogenous substances. Key words: Abacavir, Lamivudine, Zidovudine, Determination, HPLC, Gradient elution.