Voltammetric analysis of cocaine hydrochloride at carbon paste electrode chemically modified with N,N′-ethylene-bis-(salicylideneiminato) manganese(II) Schiff base complex

This article describes a method that uses a carbon paste chemically modified with N,N'-ethylene-bis-(salicylideneiminato) manganese(II) to detect cocaine hydrochloride by linear sweep voltammetry (LSV) in aqueous medium containing 0.1 mol L-1 KCl as supporting electrolyte. The potential scans were run from 0.4 to 0.9 V (vs Ag/AgCl), at 100 My s(-1). The carbon paste chemically modified with the [Mn(salen)] complex had to be heated at 60 degrees C for paste agglutination. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were conducted to assess the thermal stability of the [Mn(salen)] complex, which remained stable up to 300 degrees C. Scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) analyses showed that the [Mn (salen)] complex was evenly and homogeneously distributed on the chemically modified electrode surface. The possible mechanism of electronic exchange between cocaine hydrochloride and the electrode surface was proposed: cocaine hydrochloride reduction at the working electrode surface produced the radical center dot C-OH due to reduction of the carbonyl group (C = 0) stabilized by interaction of its free electron with orbital d electrons present in the manganese(II) Schiff base complex. Cathodic activity was verified at 0.8 V (vs Ag/AgCl). Cocaine hydrochloride detection presented linear dependence from 1 to 100 mu mol L-1 with linear correlation coefficient of 0.9995 +/- 0.0006, average amperometric sensitivity of 0.3367 mu mol L-1 , limit of detection (LOD) of 0.9349 mu mol L-1. and limit of quantification (LOQ) of 3.11 mu mol L-1. Notably, the [Mn(salen)] complex used in herein presented higher amperometric sensitivity than the complexes published so far, which is an important contribution to the development of techniques for cocaine detection.