Trace determination of cadmium content in Malaysian herbs using graphene-ionic liquid-modified screen-printed carbon electrodes

Abstract

A simple and effective method of square-wave anodic stripping voltammetry (SWASV) with screen-printed carbon electrodes (SPCEs) was used to determine the cadmium concentration in Malaysian herb samples. The optimization process involved the selection of an optimized pH, an acetate buffer as a supporting electrolyte, the deposition potential, deposition time and the surface modification process on an SPCE surface. The optimum conditions were a pH of 4.5, a deposition potential of-1.4 V and a deposition time of 120s. The SPCE surface was modified with the fabrication of the graphene-ionic liquid composite as the sensing layer. Four herb samples were tested, where herbs A, D, M and C contained 0.0035, 0.0237, 0.0267 and 0.0251 ppm of cadmium, respectively. The sensitivity of the proposed sensor was compared with an inductively coupled plasma-optical emission spectroscopy (ICP-OES). The relative standard deviation (RSD) between the sensor and the ICP-OES indicated that the sensor was sensitive, as RSD was below 20% with range of 7.93% to 18.28%.