Gradient elution.

An accurate, precise and reproducible high performance liquid chromatographic method was developed for quantitative estimation of emtricitabine, efavirenz and tenofovir disoproxil fumarate simultaneously in tablet dosage forms. Separation of the drugs was achieved within 15.0 min on a Xterra RP-18 column (150 x 4.6 mm; 5µ) by gradient elution using mixtures of ammonium acetate buffer and acetonitrile as the mobile phase. The analytes in the eluate were monitored at 260 nm. The retention times obtained for emtricitabine, efavirenz and tenofovir disoproxil fumarate were 4.611, 9.098 and 7.512 min respectively. The calibration curves were linear over the range of 20.11-60.33 µg/mL for emtricitabine, 60.28-180.45 µg/mL for efavirenz and 30.13-90.18 µg/mL for tenofovir disoproxil fumarate. 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 excipients or endogenous substances.

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.