Desenvolvimento de métodos eletroanalíticos simples, portáteis e de baixo custo para aplicações em análises forenses

Abstract

In this work it was demonstrated the use of electrochemical techniques in the development of simple, low cost and portable analytical methods applied to Forensic Chemistry. The Square Wave Voltammetry (SWV) and Multiple Pulse Amperometry (MPA) techniques were used in association with the Batch Injection Analysis (BIA) system for cocaine determination and screening process of the most common adulterants (caffeine, phenacetin, benzocaine, lidocaine, procaine, paracetamol and levamisole) in seized samples, in addition to sibutramine and ephedrine in food supplements and herbal supplements. In the methods proposed in this work, the samples require only one step of dissolution in the supporting electrolyte prior to injection into the BIA cell. A SWV scanning is then performed on the injected sample which is electrochemically oxidized on a boron doped diamond electrode (BDDE), resulting in an unique voltammetric profile. Using optimized experimental conditions, a linear range of 6 to 30 mg L-1 was obtained for cocaine, with a detection limit of 0.27 mg L-1. The accuracy of the method was evaluated comparing results obtained by gas chromatography. SWV and BDDE were also used to determine the presence of adulterants, such as, sibutramine and ephedrine in spiked samples and/or natural dietary supplements used for weight loss purposes. The detection and screening of sibutramine was possible even in highly complex samples such as multivitamins. Studies have shown a linear response for sibutramine from 5 to 50 mg L-1 and a detection limit of 0.08 mg L-1. The SWV method developed for sibutramine was also easily adaptable to the BIA system. The study for the determination of ephedrine in dietary, herbal supplements and urine was carried out using a BIA-SWV system. A linear range of 5 to 40 mg L-1 with detection limit of 0.13 mg L-1 was achieved for ephedrine in 0.1 mol L-1 acetic acid / acetate buffer, pH 4.75. The use of the screening protocols developed in this work have shown to be promising and interesting tools for applications in criminal and sports forensic analysis. Additionally, quantification methods were described for the species of interest in different samples.