Detection of Copper Ions by a Simple, Greener and Cost Effective Sensor with GCE Modified with L-Tryptophan

Metal ions contamination is the leading cause of many health and environmental problems. In order to rectify and remediate the environment from metal ions contamination, simple, efficient and easy to fabricate sensors for the onsite detection of metals ions is obligatory. However, devising a practically applicable sensor that could be compatible to the environment which contains a plethora of other ions than the target metal ions, is very challenging. In this work we report a highly sensitive and selective yet simple and greener electrode for copper ions detection by modifying GCE with amino acid-L-tryptophan. The modifier brings about increase in active surface area of the GCE and effectively binds to the metal ions through the process of chelation utilizing its amino and carboxylic acid functional groups. Cyclic voltammetry (CV), square wave voltammetry (SWV) and square wave anodic stripping voltammetry (SWASV) along with electrochemical impedance spectroscopy (EIS) was conducted to investigate the surface of the electrode and its sensitivity towards detection of Cu1+ and Cu2+ ions. A number of experimental parameters such as pH, supporting electrolyte, concentration of the modifier, accumulation time and deposition potential were investigated to achieve best response of the metal ions towards the modified electrode. The designed sensor exhibited excellent electrocatalytic activity and sensitivity towards Cu1+ ions even in the presence of 5-fold higher concentration of different interferents. The LOD (Limit of detection) of 3.13 pM as determined by the calibration curve was found to be much lower than permissible values suggested by the WHO (World Health Organization) and US EPA (Environmental Protection Agency). % age recoveries as estimated from real water samples was found to be within 3% RSD value and proved the validity of the proposed methodology for the designed sensor. Computational studies were carried out using hyperchem 7.5 software with semi empirical PM3 method. The negative value of binding energy of the merged molecule i.e., -3024.181 kcal mol(-1) point towards significant interactions between L-tryptophan and Cu2+ ions which is evident from the change in physicochemical properties upon merging of L-tryptophan with Cu2+ ions. Our computational studies agree well with the experimental results. (C) 2020 The Electrochemical Society (ECS). Published on behalf of ECS by IOP Publishing Limited.