Functioning of antimony film electrode in acid media under cyclic and anodic stripping voltammetry conditions

Abstract

New insights into the functioning, i.e. electrochemical behaviour and analytical performance, of in situ prepared antimony film electrodes (SbFEs) under square-wave anodic stripping (SW-ASV) and cyclic (CV) voltammetry conditions are presented by studying several key operational parameters using Pb(II), Cd(II) and Zn(II) as model analyte ions. Five different carbon- and metal-based substrate transducer electrodes revealed a clear advantage of the former ones while the concentration of the precursor Sb(III) ion exhibited a distinct influence on the ASV functioning of the SbFE. Among six acids examined as potential supporting electrolytes the HNO3 was demonstrated to yield nearly identical results in conducting ASV experiments with SbFE as so far almost exclusively used HCl. This is extremely important as HNO3 is commonly employed acidifying agent in trace metal analysis, especially in elemental mass spectrometry measurements. By carrying out a systematic CV and ASV investigation using a medium exchange protocol, we confirmed the formation of poorly soluble oxidized Sb species at the substrate electrode surface at the end of each stripping step, i.e. at the potentials beyond the anodic dissolution of the antimony film. Hence, the significance of the cleaning and initializing the surface of a substrate electrode after accomplishing a stripping step was thoroughly studied in order to find conditions for a complete removal of the adhered Sb-oxides and thus to assure a memory-free functioning of the in situ prepared SbFE. Finally, the practical analytical application of the proposed ASV method was successfully tested and evaluated by measuring the three metal analytes in ground (tap) and surface (river) water samples acidified with HNO3. Our results approved the appropriateness of the SbFE and the proposed method for measuring low μg L(-1) levels of some toxic metals, particularly taking into account the possibility of on-field testing and the use of low cost instrumentation.