A. Narasa Raju

Determination of lovastatin and simvastatin in pharmaceutical dosage forms by MEKC.

A micellar electrokinetic chromatographic (MEKC) method was developed for the quantification of lovastatin and simvastatin, cholesterol lowering agents in pharmaceutical dosage forms. Lovastatin and simvastatin were separated using an electrolyte system consisting of 12% acetonitrile (v/v) in 25 mM sodium borate buffer pH 9.3 containing 25 mM sodium dodecyl sulphate (SDS) with an extended light path capillary (48.5 cm x 50 microm i.d, 40 cm to detector). The method has been validated and proven to be rugged. Calibration curves were linear over the studied ranges with correlation coefficients greater than 0.996. A limit of detection of 3.2 microg/ml and a limit of quantitation of 10.6 microg/ml were estimated for both the drugs. The proposed method was found to be suitable and accurate for the determination of these drugs in commercial formulations.

Enantiospecific resolution of rabeprazole by liquid chromatography on amylose-derived chiral stationary phase using photo diode array and polarimetric detectors in series ☆

A simple and rapid liquid chromatographic method for enantioselective separation and determination of R-(+) and S-(-) enantiomers of rabeprazole in drugs and pharmaceuticals using photo diode array (PDA) and polarimetric detectors connected in series was developed. Chiralpak AD-H (250mmx4.6mm) 5mum column packed with amylose tris(3,5-dimethylphenyl carbamate) as a stationary phase and the mobile phase containing n-hexane:ethanol:2-propanol(75:15:10, v/v/v) in an isocratic mode has yielded baseline separation with resolution greater than 3.0 at 40 degrees C. Effects of ethanol, 2-propanol and temperature on separation were studied for optimum resolution. Lansoprazole sulphone was used as an internal standard (IS) for quantitative determination of individual enantiomers in bulk drugs as well as pharmaceutical formulations. The method was validated in terms of accuracy, precision and linearity according to ICH guidelines. The linearity of the method was studied in the range of 0.5-50mug/ml and the r(2) was >0.9997. The inter- and intra-day precision of assay were determined (R.S.D.<1%) and the recoveries were in the range of 99.63-100.22% with <1% R.S.D. The limits of detection (LOD) and quantification (LOQ) were 0.02mug/ml and 0.07mug/ml for both the enantiomers, respectively.

Isolation and characterization of a potential process related impurity of phenazopyridine HCl by preparative HPLC followed by MS-MS and 2D-NMR spectroscopy.

During the process development of phenazopyridine HCl bulk drug, a potential impurity was detected in the routine impurity profiles by HPLC. Using MS-MS and multidimensional NMR techniques, the trace level impurity was unambiguously identified to be 3-phenyl-5-phenylazo-pyridine-2,6-diamine after its isolation from phenazopyridine HCl by semi-preparative HPLC. The formation of the impurity was discussed. To our knowledge, it is a novel impurity not reported elsewhere.