Simultaneous determination of lomefloxacin, fenbufen and felbinac in human plasma using high performance liquid chromatography

Development of a UPLC-MS/MS method for the determination of lomefloxacin in rabbit aqueous humor and its application to a pharmacokinetic study

Lomefloxacin is a kind of synthetic fluoroquinolone antibiotic, which is used for the treatment of infectious diseases. In this study, a rapid and efficient liquid chromatography-tandem mass spectrometric assay was developed to determine the concentration of lomefloxacin in rabbit aqueous humor quantitatively. Aqueous humor samples were extracted by protein precipitation. Ofloxacin was chosen as internal standard. The chromatographic separation was achieved on a Kinetex C18 (50mm×2.10mm, 2.6μm, Phenomenex Corp, USA) column, with a gradient of methanol (0.1% formic acid) and water (0.1% formic acid). Multiple reaction monitoring (MRM) with positive ionization mode was used for the mass analysis. The validation of this method was based on the European Medicines Agency (2011) [1] and US FDA Guidelines (2001) [2]. The calibration range of aqueous humor samples was 5-1200ng/mL with r=0.9990 (n=6). For all QC samples, Inter-and intra-run precisions were less than 15% and accuracies were between 80%-120%. In conclusion, the assay was rapid, sensitive and able to determinate the lomefloxacin in rabbit aqueous humor accurately. At the same time, this method was successfully applied to study the pharmacokinetics of lomefloxacin hydrochloride eye drops and lomefloxacin hydrochloride ophthalmic gel in rabbit aqueous humor.

Determination of quinolones in plasma samples by capillary electrophoresis using solid-phase extraction

The potential of capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography (MEKC) have been investigated for the separation and quantitative determination of 10 quinolone antibiotics. The influence of different conditions, such as the buffer and pH of the electrolyte, the surfactant and the ion-pairing agents added to the electrolyte and the organic modifier were studied. A buffer consisting of 40 mM sodium tetraborate at pH 8.1 containing 10% (v/v) methanol was found to be a highly efficient electrophoretic system for separating lomefloxacin, enoxacin, norfloxacin, pipemidic acid, ofloxacin, piromidic acid, flumequine, oxolinic acid, cinoxacin and nalidixic acid. A solid-phase extraction method to remove the sample matrix (pig plasma samples) was developed on a C(18) cartridge using a mixture of methanol-water (70:30, v/v). The method is specific and reproducible and mean recoveries were in the range 94.0+/-4.2% and 123.3+/-4.1% for pig plasma samples over the range used. A linear relationship between concentration and peak area for each compound in pig plasma samples was obtained in the concentration range 5-20 mg l(-1) and detection limits were between 1.1 and 2.4 mg l(-1).

Analysis of fluoroquinolones in biological fluids by high-performance liquid chromatography

High-performance liquid chromatographic methods for the analysis of fluoroquinolones in biological fluids are reviewed. In particular, sample preparation and handling procedures, chromatographic conditions, and detection methods are discussed. A summary of published high-performance liquid chromatographic assays for individual fluoroquinolones is included.