Column-Switching High-Performance Liquid Chromatographic Determination of Ciprofloxacin in Serum using Amberlite XAD-7

A small precolumn (40 x 2 mm i.d.) packed with Amberlite XAD-7 facilitates the determination of ciprofloxacin in serum by permitting direct injection of a relatively small volume (100 μL) of diluted serum. A 0.05 M phosphate buffer (pH 7.0) washes out the plasma components. Acetonitrile-Methanol-5 mM tetrabutylammonium bromide (adjusted to pH 2.0 with phosphoric acid) (10:5:85, v/v) subsequently elutes the drug from the precolumn through the analytical column. This method shows excellent precision with good sensitivity and speed, and a detection limit of 0.1 μg/mL. The total analysis time per sample was less than 15 min, and the mean coefficients of variation for intra- and inter-assay were both less than 4.8%. The method has been successfully applied to serum samples from dogs and rats receiving oral administration of ciprofloxacin.