Electrochemical sensing of cysteine using a novel carbon black and cobalt phthalocyanine composite

Abstract

In this work, a novel composite material using carbon black and cobalt phthalocyanine (CoPc/CB) was produced. Characterizations by spectroscopic techniques (Raman and infrared), scanning electron microscopy, and X-ray diffraction confirmed the formation of the composite material. The proposed material was cast on the glassy carbon electrode surface, and its electrochemical sensing properties were checked using cysteine (CYS), an important amino acid widely used in medicine, food additives, and cosmetics, as a model molecule. Studies by cyclic voltammetry revealed that the modified electrode caused considerable electrocatalytic effects (detection at a potential close to 0.1 V) and enhanced in peak current compared to the unmodified electrode. A wide linear range (1—150 µmol/L) and adequate detectability (LOD = 0.75 µmol/L) were achieved by Batch Injection Analysis (BIA) with amperometric detection. Repeatability tests (n = 20) at two concentration levels (20 and 40 µmol/L) confirmed the precision of the method (RSD < 11 %). Interestingly, even under high flow conditions, good stability of the electrode modification was noticed. The proposed method was applied to determine CYS concentration in pharmaceutical samples, where adequate recovery values (89 and 110 %) and results statistically similar to those achieved by capillary electrophoresis indicated the accuracy and reliability of the electrochemical analyses.