Rapid determination of ciprofloxacin in urine by matrix isopotential synchronous spectrometry

Abstract

A simple, rapid and sensitive synchronous fluorescence method is proposed for the determination of ciprofloxacin in urine. The combination of matrix isopotential synchronous fluorescence (MISF) and first derivative techniques provides good analytical results. MISF spectra are obtained by calculating an isopotential trajectory in the three-dimensional fluorescence spectrum of urine solutions. This trajectory is chosen so that it passes by the fluorescence maxima of ciprofloxacin (λ_ex = 277 nm and λ_em = 444 nm). Analyses were carried out in an ethanol–water medium (10% v/v), with an apparent pH of 4.8 kept constant by using a sodium acetate/acetic acid buffer solution. The linear range of concentration was between 40 and 400 ng mL⁻¹. Exhaustive statistical analyses were made of all calibration graphs. The detection limit according to the error propagation theory was 5.6 ng mL⁻¹ and the detection limit proposed by Clayton was 13.5 ng mL⁻¹. The repeatability of the method was determined for two series of ten solutions containing 40 and 180 ng mL⁻¹ of ciprofloxacin in urine, respectively. By applying the IUPAC definition, the relative errors were 9.5% and 2.0%, while, based on error propagation, the relative errors were 6.3% and 1.2%, respectively.