Chromatographic resolution of drug analogues: 3-hydroxy-3-methylglutarylcoenzyme A reductase inhibitors (statins).

A high performance liquid chromatographic method for the simultaneous determination both qualitative and quantitative of cholesterol lowering statin drugs in pharmaceutical formulations has been developed. The most important advantage of developed method is that all seven statin drugs can be determined on a single chromatographic system without modification in detection wavelength. An organic modifier addition (25% v/v methanol) in the presence of buffer (20mM ammonium acetate; pH 4.0 adjusted with dilute acetic acid) played a key role in the resolution of statin drugs in gradient elution with acetonitrile. The drugs were separated on a Purospher Star 4.6mm × 25cm, 5µm, C18 column maintained at 25°C with 1mLmin(-1) flow rate using ultra violet detection at 240nm. Good separation (Rs > 2.5) was achieved in a short analysis allowing simultaneous determination of all seven statins. The effect of variation in flow rate, detection wavelength and column oven temperature was also studied. The proposed method was statistically validated in terms of precision, accuracy, linearity, specificity and robustness. The newly developed method proved to be specific, robust and accurate for the quantification of seven statins in commercial pharmaceutical formulations.

Chromatographic resolution of angiotensin II receptor antagonists (sartans).

First time a simple, sensitive and unified quantification method has been developed to analyze the complete class of angiotensin II receptor antagonists which are used in the treatment of hypertension either alone or in combination with some other drugs. The most important advantage of developed method was that the eight separate drugs can be determined on a single chromatographic system without modifications in detection wavelength and mobile phase. The drugs were separated on a Purospher Star 4.6mm×25cm, 5µm, C18 column maintained at 40°C with 1mLmin(-1) flow rate using ultra violet detection at 254nm. Good separation (Rs>2.0) was achieved in a short analysis allowing simultaneous determination of all eight sartans. The effect of variation in flow rate, detection wavelength and column oven temperature was also studied. The proposed method was statistically validated in terms of precision, accuracy, linearity, specificity and robustness. The newly developed method proved to be specific, robust and accurate for the quantification of eight sartans in commercial pharmaceutical formulations.

Estimation of sulfolax and antimicrobial preservatives in laxative drops.

A simple, fast, precise, economic, selective and accurate HPLC method for simultaneous estimation of sorbicacid, sodium picosulphate and methyl parabensodium in laxative drops has been developed and subsequently validated. Chromatographic separation was achieved using gradient elution with mix phosphate buffer pH 7.0 and acetonitrile. The column used was purospherstar C18, 5 µm, 25 cm × 4.6mm kept at 25°C with 1 ml/min flow rate using detection (PDA) at 263 nm. The retention times of sorbicacid, sodium picosulphate and methyl paraben sodium were found to be 4.6, 7.4 and 11.4 minutes respectively. The proposed method was found to be linear over a concentration range of 8-12 µg/ml for sorbic acid, 60-90 µg/ml for sodium picosulphate and 16-24 µg/ml formethyl paraben sodium respectively. The recovery was found to be 99.13-101.68% for sorbic acid, 99.81-100.21% for sodium picosulphate and 99.84-100.09% for methyl paraben sodium respectively. The limit of detection (LOD) for sorbicacid, sodium picosulphate and methyl parabensodium were found to be 0.032 µg/ml, 0.337 µg/ml and 0.131 µg/ml respectively and limit of quantitation (LOQ) for sorbicacid, sodium picosulphate and methyl parabensodium were found to be 0.097 µg/ml, 1.023 µg/ml and 0.399 µg/ml respectively. The method was validated with respect to specificity, precision, accuracy, linearity and robustness according to guidelines of ICH.