Determinação eletroanalítica individual e simult nea das fluoroquinolonas, levofloxacina e norfloxacina, empregando meio micelar e procedimento de deconvolução

Abstract

The fluroquinolones are some of the most prescribed class of drugs, being used on many bacterial infections treatment, both in humans and animals. However, in some cases, its broad spectrum of activity may take it so harmful as the disease. Moreover, they may be absorbed on the unmetabolized form by the tissues of animal origin and/or excreted in biological samples. It may cause the contamination of the food eaten by humans, which may cause, among others damages, in a drug resistance. Therefore, in this task two new alternative methods were proposed to determine, simultaneously, the fluoroquinolones levofloxacin (LEVO) and norfloxacin (NOR) in several matrices. For this purpose, the square wave voltammetry (SWV) was used as electroanalytical technique and as a tool to help on separation of the peaks, the mathematical deconvolution procedure which was done on the Microcal Origin® software. The deconvolution was necessary, because, although these fluroquinolones were easily detected individually, the same was not applied on the mixture of both, due to an overlap of voltammetric peaks. The initial studies were done on the surface of the glassy carbon electrode (GCE), in different supporting electrolytes and presence of surfactants, on an attempt to obtain voltammograms with voltammetric peaks, satisfactorily separated. The optimized conditions to GCE were adapted and used on screen-printed carbon electrodes (SPCE). In both the electrodic surfaces, the voltammograms were characterized by two peaks, the first observed in 1.04V (GCE) and 0.73V (SPCE), assigned on oxidation of LEVO, and the second observed on 1.14V (GCE) and 0.87V (SPCE), assigned on oxidation of NOR. After optimization of the conditions for the GCE, obtained linear response to fluroquinolones detection in the concentration range of 2.00×10-6 to 2.00×10-5 mol L-1 (r = 0.999, n = 10) with a limit of detection of 2.97×10-7 mol L-1 (LEVO) and 7.90×10-7 mol L-1 (NOR). For SPCEs, the voltammetric response was linear in the concentration range of 2.50×10-7 to 3.00×10-5 mol L-1 (r = 0.999, n = 7) with a limit of detection of 3.20×10-8 mol L-1 (LEVO) e 8.30×10-7 mol L-1 (NOR). The electroanalysis of human and bovine urine samples were satisfactory, enabling the quantification of these fluoroquinolones with recovery values between 90.2% and 101.3% to LEVO and between 88.1% e 107.1% to NOR when used the GCE and between 96.8% and 101.1% to LEVO and between 98.0% and 100.8% to NOR, when using the SPCE. Thus, the aims of this work were attended, with promising analytical performance for simultaneous determination of LEVO and NOR on the surface of SPCE and GCE.