Desenvolvimento de uma metodologia eletroanalítica para identificação e quantificação de cocaína em amostras apreendidas utilizando eletrodo de pasta de carbono modificado com nanotubos de carbono de paredes múltiplas

Abstract

Among drugs of abuse, cocaine is the second most used in the world due to its stimulant and psychoactive effects. Currently, it is classified, according to ANVISA (National Health Surveillance Agency), regulations as an illicit substance, being a frequent object of a seizure by police forces, in addition to causing serious social problems due to its abusive use. This study describes the development of an electroanalytical methodology using square wave voltammetry to quantify cocaine in seized samples using a low-cost technique associated with a single electrode of carbon paste modified with 10% MWNCT (Multi-Walled Carbon Nanotubes). The square wave voltammetry parameters were optimized (Es = 10 mV, a = 30 mV, and f = 15 Hz) using a Britton-Robinson buffer solution 0.1 mol L−1 (pH 10) as the supporting electrolyte. Cocaine showed an oxidation peak around 1.0 V, with low limits of quantification and detection (2.30 × 10−6 mol L−1 and 6.97 × 10−7 mol L−1, respectively), in the linear range from 2.36 × 10−6 mol L−1 to 1.38 × 10−5 mol L−1, with an R2 equal to 0.99. The results obtained in the intraday analytical curves present a standard deviation < 8%, indicating a good repetition of the proposed methodology, in addition to providing a quick and low-cost technique in favor of the police, allowing the production of the 10% MWNCT carbon paste for less than BRL 7.0 per analysis.