Procedimento de deconvolução de picos e uso de voltametria de onda quadrada para a determinação de levamisol em amostras de cocaína

Abstract

This work presents the use of screen-printed carbon electrodes (SPEs) for the detection and quantification of levamisole (LEV) in cocaine sample (COC), using as electrochemical technique the square-wave voltammetry and as auxiliary tool the mathematical deconvolution procedure to improve the separation of the peaks. The deconvolution was necessary because overlap of the voltammetric peaks of levamisole and cocaine occurs, which makes impossible the detection of LEV. The initial studies showed the electrochemical behavior of COC and LEV using this type of electrode and Britton-Robinson (0.04 mol L-1) supporting electrolytes in different pH values. The pH 8.0 was defined the best working pH for the further analysis. The oxidation peaks for COC and LEV were at +0.85 and +0.96V, respectively. In addition, cyclic voltammograms indicated irreversible oxidation processes of LEV and COC on this type of electrode. The optimization of the square wave voltammetry parameters shows that using a frequency of 8 s-1, amplitude of 10 mV and potential step of 1 mV, it was possible to obtain the best separation of the peaks for subsequent application of the deconvolution procedure. The individual voltammetric responses of the LEV were found to be similar when using the deconvolution procedure for the separation of the COC and LEV peak. Thus, a linear response to LEV detection was obtained in the concentration range of 25 – 125 μmol L-1 (r = 0.997) with a detection limit of 0.017 μmol L-1. The analysis of sample seized by the Federal Police was satisfactory and the results obtained were statistically similar to those obtained by the Federal Police.