Dispersive micro-solid phase extraction based on graphene oxide for the ultrasensitive determination of Cd by slurry sampling microplasma optical emission spectrometry

Abstract

For the first time, a dispersive micro-solid phase extraction (D-µSPE) based on graphene oxide was employed for the ultrasensitive determination of Cd by a solution anode glow discharge optical emission spectrometry (SAGD OES). It was possible to extract Cd from a dilute mixture of alkali and alkaline earth metals (Ca, K, Mg, and Na) with 100 % efficiency. It was found that in contact with microplasma, Cd bounded on the GO surface can be converted to its volatile species. As a result, it was possible to omit the elution step (a slurry sample was introduced), which allowed shortened time of sample preparation and reduced the risk of contamination. Using the Design of Experiments (DoE) approach, the effect of different variables, i.e., interferent concentration, GO concentration, number of GO rinsing repetitions, and HNO3 concentration, was studied in detail. Using the D-µSPE-SAGD OES, matrix effects were remarkably reduced and improvement in the tolerance of Cd to alkali metals by a factor of 25 was reached. Moreover, coupling with D-µSPE lowered the limit of detection (LOD) of Cd by 2 times (resulting in the LOD of 0.003 µg L−1). Under optimal operating conditions, D-µSPE-SAGD OES was successfully employed for the ultra-trace analysis of food and environmental samples characterized by a high-alkali metals content, i.e., wine and seawater. As compared to competitive methods recently reported in the literature, D-µSPE-SAGD OES is distinguished by the simplicity of the measurement system and the fact that the nanosorbent used is commercially available.