Desenvolvimento de um método analítico portátil baseado em impressão 3D para a determinação de secnidazol em amostras apreendidas

Abstract

Secnidazole (SCZ) or α,2-dimethyl-5-nitro-1H-imidazol-1-ethanol is a 5-nitroimidazole-based drug with antiprotozoal and antimicrobial activity used in the treatment of trichomoniasis, giardiasis, amoebiasis and bacterial vaginosis. The identification and quantification of these substances are crucial for preventing counterfeiting and adulteration. Additionally, the detection of residual substances in seized drugs can assist law enforcement agencies in locating clandestine laboratory. In this dissertation, the electrochemical performance of an electrode produced via 3D printing technology was evaluated for SCZ determination. The working electrode was printed using a commercial conductive filament composed of carbon black (CB) and polylactic acid (PLA). Initially, the performance of the 3D printed electrode was investigated without and with chemical/electrochemical treatment in an alkaline medium (NaOH 0.5 mol L-1), with a significant improvement observed after the treatment. After optimization studies, the supporting electrolyte at pH 2 (BR buffer) was chosen due to the best electrochemical performance in the electrochemical reduction of SZC (reduction peak at -0.31 V). The square wave voltammetry technique was selected to determine SCZ using the following parameters: amplitude: 40 mV, step: 5 mV and frequency: 40 Hz. The calibration curve was obtained under optimized conditions and showed good linearity in the concentration range between 2.5 and 250.0 µmol L-1 (r2= 0.998) with limits of detection (LOD) and quantification (LOQ) calculated at 0.25 and 0.82 µmol L-1, respectively. Relative standard deviations (RSD) smaller than 3.8 and 2.3% were found in the repetitive (n = 10) analysis of solutions containing 10.0 and 100.0 µmol L-1 of SCZ, respectively. The printed CB/PLA electrode showed good inter-electrode reproducibility (RSD = 4,2%, n = 3). The proposed method was successfully used to determine SCZ in pharmaceutical and seized samples, presenting statistically similar results to those obtained by HPLC-DAD. The method was also used to determine four pharmaceutical samples seized by the Civil Police of Brasília, achieving statistically similar results to those found by the HPLC-DAD method. The great advantage of the proposed method is the possibility of in situ analyzes or in places with minimal infrastructure.