Thin-layer chromatographic separation and in situ fluorimetric determination of ofloxacin in plasma and pleural fluid

A thin-layer chromatographic assay for the determination of ofloxacin in human plasma and pleural fluid is described. After extraction of ofloxacin from samples with dichloromethane, chromatography was performed on thin-layer plates (silica gel) with a mobile phase consisting of ethanol and water; the tank atmosphere was equilibrated with concentrated ammonia. The precision of the assay could be considerably increased along with the measured fluorescence intensity of ofloxacin by spraying the plate with a citric acid solution and dipping it into paraffin or using a mixture of both components. Peaks were quantified by densitometric evaluation of the chromatograms. The method shows a very low limit of detection (1 ng/ml) as well as good precision and linearity in the range 0.001-2.0 micrograms/ml for both plasma and pleural fluid.