Detection of norfloxacin and monitoring its effect on caffeine catabolism in urine samples

A multi-walled carbon nano tube (MWCNT) modified pyrolytic graphite (MPG) electrode is prepared and applied to detect norfloxacin (NFX) based on its electrochemical reduction. The experimental parameters affecting the NFX determination were optimized in terms of MWCNT amount, pH, reaction time, and square wave frequency. The dynamic range for the NFX analysis ranged between 1.2 and 1000 mu M with a detection limit of 40.6 +/- 3.3 nM. The effect of NFX on the catabolism of caffeine has been studied by determining its concentration in the urine samples after the prolonged administration of NFX using the MPG electrode. The results show that the catabolism of caffeine is inhibited by similar to 65% after five days of NFX administration, consequently the caffeine concentration in the urine sample is increased, which is reflected in terms of similar to 2.5 times increase in the peak current of caffeine. The determinations of NFX and caffeine were selective and the method was successfully applied in biological fluids and pharmaceutical tablets for the test compound analysis. In future this method can be useful for the selective determination of NFX and studying its effect on caffeine catabolism. (C) 2013 Elsevier B.V. All rights reserved.