High-performance liquid chromatographic method for the separation of enantiomeric gatifloxacin.

A high-performance liquid chromatographic method has been developed in normal-phase conditions for the separation of enantiomeric gatifloxacin, (+/-) 1-cyclopropyl-6-fluoro-8-methoxy-7-(3-methylpiperazin-1-yl)-4-oxo-quinoline-3-carboxylic acid, an antibiotic in bulk drug. The method involved the use of an amylose-based Chiralpak AD-H (150 mm x 4.6 mm, 5 microm) column using a mobile phase system containing n-hexane-ethanol-diethylamine (85:15:0.1% v/v). The conditions affording the best resolution were found by selection and variation of the mobile-phase compositions and the differences in separation capability of the method is noted. Relative standard deviation of retention times and peak areas were better than 0.2% and 0.4%, respectively, for precision. Gatifloxacin sample solution and mobile phase are found to be stable for at least 48 h.

Enantiomeric separation of Linezolid by chiral reversed-phase liquid chromatography.

A chiral liquid chromatographic method is developed for the enantiomeric resolution of Linezolid, (S)(-)-N-[[-3-(3-fluoro-4-(4-morpholinyl)phenyl]-2-oxo-5-oxazolidinyl] methyl] acetamide, an antibiotic in bulk drugs. The enantiomers of Linezolid are resolved on a Chiralcel OJ-RH column using a mobile phase system containing 150mM di-sodium hydrogen phosphate buffer (pH 4.5)-acetonitrile (86:14, v/v). The resolution between the enantiomers is found to be two. The developed method is extensively validated and proved to be robust. The limit of detection and limit of quantification of (R)-enantiomers are found to be 94 and 375 ng/mL, respectively, for 10 microL injection volume. The percentage recovery of (R)-enantiomer is ranged from 98.9 to 102.9 in bulk drug samples of Linezolid. Linezolid sample solution and mobile phase are found to be stable for at least 48 h. The proposed method is found to be suitable and accurate for the quantitative determination of (R)-enantiomer in bulk drugs.