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 120 s. 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 %.