Simultaneous determination of malondialdehyde and ofloxacin in plasma using an isocratic high-performance liquid chromatography/fluorescence detection system

This study establishes the applicability of using high-performance liquid chromatography (HPLC) with fluorescence detection for the simultaneous determination of malondialdehyde (MDA) and ofloxacin (OFL). The MDA and OFL were separated through a reverse-phase C18 column (250 mm x 4.6 mm) at a flow rate of 1.0 mL min(-1) and then detected using a fluorescence detector (excitation: 532 nm; emission: 553 nm). The separation conditions were optimized by varying the concentration and pH of the phosphate buffer and the percentage of organic solvent; the optimal mobile phase was a mixture of 50 mM phosphate buffer (adjusted to pH 5.8 with potassium hydroxide) and methanol (45:55, v/v). The retention times of MDA and OFL were 3.6 and 5.9 min, respectively, with detection limits (at a signal-to-noise ratio of 3) of 0.015 and 4.0 mu M, respectively. This method afforded linear responses between the MDA and OFL concentrations and the HPLC peak areas within the ranges 0.15-2.43 mu M and 0.06-1.0 mM, respectively. The precisions of the determinations of MDA and OFL, measured in terms of relative standard deviations, were 1.6-5.0% and 1.9-3.6%, respectively, for intra-day assays and 1.0-4.3% and 0.3-1.8%, respectively, for inter-day assays. The average recoveries of MDA and OFL spiked in plasma were 100.4% and 98.8%, respectively. To the best of our knowledge, this paper describes the first practical analytical approach toward simultaneously monitoring the levels of MDA and OFL in plasma. The OFL-induced oxidative stress measured using this method indicated that OFL treatment did not markedly increase the level of MDA. (C) 2008 Elsevier B.V. All rights reserved.