Determination of levofloxacin in human urine with capillary electrophoresis and fluorescence detector

Abstract

In this study, we developed an analytical method for the enantioseparation of ofloxacin, using capillary electrophoresis with fluorescence detection. The optimum background electrolyte was obtained to be 60 mM hydroxylpropyl-β- cyclodextrin (HP-β-CD) in 50 mM phosphate buffer at pH 2.30. Under these conditions, the (+) and (-) ofloxacin were completely separated, with the detection limit of 10 nM when the sample was prepared in deionized water. The linear ranges of levofloxacin in deionized water and untreated urine were 10-7 to 5 × 10-3 M with R2 = 0.9989 and 5 × 10-6 to 5 × 10-3 M with R2 = 0.9943, respectively. We also applied this method to investigate the purity of a commercial drug. The results revealed that the ratio between (+)-ofloxacin and (-)-ofloxacin (levofloxacin) was 99.9:0.1, and there is about 93 mg levofloxacin per tablet (200 mg). The concentration of levofloxacin in patient's urine was founded to be 7.9 × 10-4 M, and the ratio between the two optical isomers was 99.3:0.7.