Modified Carbon Paste Electrode And Its Adsorptive Voltammetric Determination Of Trace Antimony

A new chemically modified carbon paste electrode has been developed to replace drop mercury and other solid electrodes by electrochemical means. At the same time, the conditional tests of adsorptive stripping voltammetry as well as the electrode reaction mechanism of Sb(III) have been determined. For the first time, a highly sensitive adsorptive stripping voltammetry method which does not need any pretreatment for the direct and rapid determination of traces of Sb(III) in the complex solutions has been advanced. The rapid process control analysis of Sb in relevant production has been realized. In addition, the traces of Sb in the biosamples have been advanced by this method with satisfactory results.The conclusions obtained from lots of condition experiments are as follows: The modified carbon paste electrode with bromopyrograll red has favorable repeatability and longevity of service. An electroactive complex of Sb(III) with BPR is formed and accumulated on the surface of the electrode in a stirring biphthalate of potassium (KHP)-HCl and CuCl solutions(pH=2.5) at 0.0v(vs.SCE) for 2 minute. After it is reduced at -0.4v for 30s without stirring, the voltammogram is then recorded by applying an anodizing scan from -0.2v to +0.3v at 250mv/s, and the second derivative peak current is obtained at +0.1v. Under the optimal conditions, linear relationship between the second derivative peak current and Sb(III) concentration is obtained in the range of 8.0 X 10-9~2.0 X 10-7mol/L,and the determination limit is 2.0 X 10-9mol/L . The study on the electrode reaction mechanism shows that the transfered number of electrons is 3, and the transfered number of protons is 2. The electrode reaction is irreversible, and the composition of electroactive complex is BPR:Sb(III)=1:1.With the reducibility of Cu+ of CuCl to reduce Sb(V) to Sb(III), total amounts of antimony is determinated. Regarding the variability of the components in the solutions of zinc by wet process, the complexity of the interference factors, and the accumulation effect, the constant-volume -standard- addition -calculation method is applied for eliminating the errorsarising from the accumulation effect of the coexistence ions and the larger changes of the sample components and their concentrations. Compared with the traditional- standard- addition - method, the constant- volume -standard-addition -calculation method does not need zero blank value, and is not be severely limited by the concentration and volume of the standard solution, and has simple models.All the reagents are innocuous, low-cost and easy to be obtained.The method is convenient to operate with high sensitivity, selectivity and rapidity. It has been successfully applied to the determination of traces of Sb in the solution of zinc electrolyte, it is also a new electroanalysis method to determinate the traces of Sb in the pork livers and the pork kidneys.