Development of Screen Printed Electrodes Chemically Modified with Schiff Base Films for Application in Forensic Chemistry
In this work, chemically modified screen printed electrodes (CM-SPE) using different Schiff base films were employed in the voltammetric investigation of cocaine, 3,4 - methylenedioxymethanphetamine (MDMA), and morphine. Dip coating process was chosen for the surface chemical modification. Three different electrode plateforms were employed: carbon, gold, and platinum. with methanolic solution containing different Schiff base complexes with subsequent drying step at room temperature. The voltammetric measurements were carried out in 50:50 v/v methanol:water solution containing 0.05 mol L-1 KCl and 0.1 mol L-1 LiCl as a supporting electrolyte without oxygen elimination by inert gas flow. The best results were obtained with carbon electrodes. Cocaine exhibits a well defined irreversible anodic peak current (ipa) at a potential (Epa) of 0.85V vs Ag/AgCl.
Voltammetric parameters such as Eprec, v, and tprec were optimized in this study, being obtained the values of -0.80V (vs Ag/AgCl), 120 s, and 100 mV s-1, respectively. The optimized amount of the chemical modifier was found to be 30 mg per electrode. Detection and quantification limits were obtained in 110 and 390 mmol L-1, respectively. Additionally, intra and inter-day repeatability of 2.61% and 3.77%, were obtained for cocaine determination. It was possible to obtain a transductor for cocaine in presence of morphine and MDMA with high specificity in trace levels.
The author acknowledges FAPESP (2013/17630-7) and CAPES (25/2014 Pro-Forenses) for financial suport.