Analytical Sciences

Ofloxacin Determination in Urine, Serum and Pharmaceuticals Using an Automatic Flow Potentiometric System

Adriana M. PIMENTA,* M. Renata S. SOUTO,** Rita I. L. CATARINO,* M. Fernanda C. LEAL,* and José L. F. Costa LIMA***

*REQUIMTE, CEBIMED, Faculty of Health Sciences, University Fernando Pessoa, Rua Carlos da Maia, 296, 4200–150 Porto, Portugal
**CBQF, CEBIMED, Faculty of Health Sciences, University Fernando Pessoa, Rua Carlos da Maia, 296, 4200–150 Porto, Portugal
***REQUIMTE, Applied Chemistry Laboratory, Department of Chemical Sciences, Faculty of Pharmacy, University of Porto, Rua de Jorge Viterbo Ferreira, 228, 4050–313 Porto, Portugal

An automatic system was developed to determine ofloxacin in biological fluids and pharmaceutical formulations. Drug detection was carried out by a potentiometric membrane sensor based on [bis(trifluoromethyl)phenyl]borate as molecular-recognition material. The tubular shaped detector system was solidly attached to the manifold, creating a high-throughput stable setup (50 samples per hour) appropriate for routine antibiotic assessment. Under the optimized flow conditions, the sensor displayed a mean detection limit of 1 × 10⁻⁵ M, a linear response over the concentrations of 2 × 10⁻⁵ to 5 × 10⁻³ M (slope of 57.4 mV decade⁻¹) and a wide working pH range (2.1 – 6.6). The procedure was successfully applied to ofloxacin analysis in pharmaceuticals (relative deviation lower than 6%) and biological fluids at levels usually found after drug administration of clinical doses (recoveries between 91 and 106%). No significant interference from common excipients found in commercial formulations and inorganic ions usually present in biological fluids was noticed.

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