Determinação eletroquímica de norfloxacina em fármacos, fluidos biológicos e soluções eletrolisadas usando um eletrodo de diamante dopado com boro pré-tratado catodicamente

An electrochemical method for the determination of norfloxacin (NOR) in pharmaceutical formulations and synthetic biological fluids as well as for the monitoring of the concentration of NOR during its electrooxidation was developed using a boron-doped diamond electrode (BDD) coupled to square-wave voltammetry (SWV). A cathodically pretreated BDD electrode, a platinum foil, and anAg/AgCl (3.0 mol L–1KCl) electrode were used as working, counter, and reference electrodes, respectively. The obtained analytical curve showed a wide linear concentration range (1.00 –400 μmol L–1NOR), with a detection limit of 0.25 μmol L–1. The comparison of the results obtained for the determination of NOR in drugs using the developed method with those from a HPLC-UV-vis methods howed no differences between them at a confidence level of 95% (ttest). The selectivity of the developed method was investigated testing possible interferents typically found in this type of sample, and is all cases the RSD valueswere lower than 6%. Hence, thedeveloped method was applied in the determination of NOR in biological fluids (synthetic urine and human physiologic saline solution) doped with 3, 30, and 100 μmol L–1NOR. The obtained recovery results were adequate: in the range of 95 to 108% and 105 to 118 %, for urine and human physiologic saline solution, respectively. Finally, NOR electrooxidation was performed using aBDD anode in a filter-press flow reactor [1] while the decrease in [NOR] after given degradation times was followed by HPLC and SWV. For both methods, a similar decay of [NOR] vs. t was observed during 3 h of degradation; then the value of [NOR] became constant and close to zero, indicating that complete degradation of the compound. From the obtained results, we concluded that the developed electroanalytical method using a cathodically pretreated BDD electrode coupled with SWV can be used for the quantification of NOR in pharmaceutical formulations, with results similar to the reference method (HPLC). Similarly, good results were also obtained in the determination of NOR in synthetic human urine and serum samples, indicating the possible use of the developed method for determination of NOR in real biological fluids. Furthemore, the electrooxidation of NOR was successfully monitored using the proposed method, withresults similar to those of areference HPLC method.