EDTA Assisted Highly Selective Detection of As3+ on Au Nanoparticle Modified Glassy Carbon Electrodes: Facile in Situ Electrochemical Characterization of Au Nanoparticles

A facile electrochemical characterization technique of Au nanoparticles (AuNPs) developed by Wang et al. ( Wang, Y.; Laborda, E.; Salter, C.; Crossley, A.; Compton, R. G. Analyst 2012 , 137 , 4693 - 4697 ) was used to track the variation in the particle size and density of AuNPs in situ and to assist in optimizing the conditions of analysis and catalysis. In this method, the combination of total surface area determined by Pb underpotential deposition (UPD) and the amount of Au obtained by anodic stripping of Au in HCl solution was used to evaluate the average diameter of AuNPs and the number of particles on the electrode. The detection of As3+ in aqueous solution by a AuNP modified glassy carbon electrode (Aunano@GCE) using the electrochemical characterization technique was examined. The AuNPs with a uniform shape and size, deposited onto the GCEs using multiple-scan cyclic voltammetry (MSCV), were suitable for the electrochemical evaluation. The calibration curve for the detection of As3+ had a dynamic range of 0.1-15.0 mu g L-1 (from 1.30 to 200 nM, y = 0.21x (in mu A L mu g(-1)) + 0.01 (R-2 = 0.999)) and showed a sensitivity of 0.21 mu A L mu g(-1) (16.15 mu A mu M-1). A detection limit as low as 0.0025 mu g L-1 (32.5 pM) was achieved. The chelating agent ethylenediaminetetraacetate (EDTA) selectively chelated with the interfering metal ions and effectively inhibited the interfering ions from competing with the ion of interest (As3+), in the preconcentration process. The presence of EDTA effectively eliminated interference from several metal ions, especially Cu2+ and Hg2+. This method was validated by analyzing the As3+ content in real water samples.