Study On Electroanalysis Methods Of The Shachongdan And Imidacloprid

A new method for detemiination of Shachongdan by oscilographic potentiometric titration is devoloped in this paper.lt is base on the potential difference between the redox reaction of bromate with bromide and the oxidation reaction of bromate and shachongdan. When the concentration of hydrochloric acid ,bmmid is 6,0.0042 and 0.02 lmol/L respectively, the relative standard deviation is smaller than 0.2%.The proposed method is sensitive ,simple ,fast and indifferent to solution color and precipitation. A method for the rapid determination of Shachongdan products by oscillographic titration was developed. The effect of the chemical covering, solution acidity, titration speed and terminal indicating method on the analysis results were studied. It was found that K2Cr207 was suitable for covering common reducing substances. The proposed method was rapid, accurate and precise, which was recommendable for the application and popularization in fctories. The polarographic and voltammetric characteristic of Shachongdan was studied with cyclic voltanirnetiy, linear sweep voltarnmetxy. A well-defined reduction peak of Shachongdan was got in the buffer solution of 0.2 molILHAc- 0.2 moliL NaAc(pH4.65).The peak potential is -0.94 V(vs SCE). It held good linear relationship(r=0.9978) between the peak current and the concentration of Shachongdan from 3Xl03to 5X105 molIL . The standard deviation was 0.220/0 with 5 X l0~ molIL Shachongdan in 6 parallel assays. The ranges of recovery were from 98.81% to 99.43% in the test of standard added. It was showed that the reaction process involved the adsorption of Shachongdan on the dropping mercury electrode and a in-eversible four electron reduction .A mechanism of electrochemical reduction of Shachongdan was proposed by the calculation on quantum chemistry on Shachongdan. In a suppoiting electrolyte containing 0.0 lmoIIL NH3桹.2moVLNH4CI at pH=8.0, Imidacloprid produce a sensitive adsorptive wave by single- sweep oscilloplarogrphy. The peak potential is -0.95V (vs.SCE).The linear relation holds between the peak current and the imidacloprid concentration in the range from l.2X l0~ moVL to 5.OX l0~ mol/L (r~).994l),The relative standard deviation of 4.00 X 1 0~moVL imidacloprid for 6 parallel determination was 1.38%. The recoveries of standard addition were in the range of l00.00/o~l01.l%. A sensitive method for the determination of intidaclopiid by single-sweep oscillopolarography was developed. The method has been applied to the determination of imidacloprid products with satisfactory result. The mechanism of electrode reduction was discussed.