Determination of antimony on clay-PVA modified glassy carbon electrode

Due to antimony toxicity several methods have been developed for antimony detection including electrochemical [1,2]. In this paper the use of clay-PVA modified electrodes for determination of antimony was studied. Clay from Wyoming deposit was Na-enriched (Na-W) and used for synthesis of clay-poly(vinyl alcohol) composites. Two different poly(vinyl alcohol)-PVA to Na-W ratios were used for composite preparation. The composites were synthesized with 10 wt% and 20 wt% of PVA. The composites were characterized by X-Ray Powder Diffraction and Scanning Electron Microscopy. Both Na-W and composites were dispersed in Nafion® solution prior to depositing on the surface of the glassy carbon electrode (GCE) in order to obtain uniform film [3]. Modified electrodes were denoted as GCE-Naf/Na-W, GCE-Naf/NaW-PVA and GCE-Naf/NaW-PVA2 respectively. For comparison purpose the GCE electrode modified only with layer of Nafion was prepared and designated as GCE-Naf. The applicability of the obtained modified GCE for determination of antimony-Sb(III) concentration was studied. The square wave voltammograms (SWV) were recorded in the potential window of -0.4 to 0.3 V vs Ag/AgCl electrode with following parameters: pulse amplitude = 20 mV, scan increment = 5 mV and frequency = 10 Hz. The electrochemical detection of antimony Sb(III) was performed in acidic environment. The experiments were performed in antimony concentration range from 2.5 to 200 mM. The peak at around -100 mV vs. Ag/AgCl was obtained for all electrodes. Although the presence of clay and clay composites on the electrode surface led to widening of width at half of peak, the currents obtained these electrodes were several times higher than the currents obtained for GCE-Naf in the same concentration range. The presence of clay-PVA composites on electrode surface further improved applicability of GCE in Sb(III) detection. The addition of 10 wt% of PVA in clay composite resulted in increase of peak current and linear response of peak current vs. Sb(III) concentration in broader concentration range. Further addition of PVA up to 20% reduced peak current response, although linearity was preserved in the same concentration range. The dependence of peak current at -100 mV on Sb(III) concentration showed linear behavior in the concentration range of 2.5-100 μM for GCE-Naf/NaW electrode with slope of 0.055 μA/ μM. The linear behavior for PVA modified clay was obtained in concentration range of 2.5-200 μM with slopes of 0.118 μA/μM and 0.056 μA/μM for GCE-Naf/NaW-PVA and GCE-Naf/NaW-PVA2, respectively