Desenvolvimento de procedimento eletroanalítico para a determinação de midazolam em amostras forenses usando eletrodo de diamante dopado com boro

Abstract

Midazolam (MID) is an imidazobenzodiazepine commonly used as tranquilizer, sedative hypnotic and anticonvulsant drug. MID differs from other benzodiazepines, because of its fast absorption and solubility in aqueous solutions, which enables its use in many types of beverage samples as a facilitated-sexual or date rape drug, also known “Good night, Cinderela”. In this work, we described a simple, portable and low-cost method for fast screening and selective determination of MID in beverages samples (vodka, whisky and red wine). Differential-pulse voltammetry, boron-doped diamond electrode (BDD), and Britton-Robinson (BR) buffer (pH = 2.0) were selected as electrochemical technique, working electrode and supporting electrolyte, respectively. Different linear response ranges (4-25 µmol L-1 and r = 0.997; 1-10 µmol L-1 and r = 0.995; 1-15 µmol L-1 and r = 0.998) and limits of detection (0.46, 0.43 and 0.33 µmol L-1) were obtained for the analysis of samples as vodka, whisky, red wine, respectively. The precision and accuracy were satisfactory considering the low relative standard deviation values (RSD < 6.3%, n= 15) and the values obtained in the recovery studies (88-103%). In order to compare the performance (LOD, LOQ and selectivity) between two MID electrochemical processes, the reduction peak was also explored using the same technique, work electrode and the supporting electrolyte for the oxidation peak. The parameters of differential pulse voltammetry for the reduction peak were optimized: modulation amplitude: 70 mV; step potential: 5 mV and modulation time: 25 ms, being possible to compare with the analytical characteristics of the oxidation and reduction process of the MID. Finally, the proposed method was also adapted to a robust portable electrochemical system (BIA, batch injection analysis) which has great potential for rapid point-of-care testing (rapid screening tests).