Rajantie, Hanna Katarina; (2001) Electrochemical titrations with dual microband electrodes. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The main objective of this thesis is to present a generator-collector mode titration with dual parallel microband electrodes and a miniaturisation of an electroanalytical method. The system is based on manipulation of the mass transport, which is accomplished by using screen-printed microband electrodes, controlling the fluxes of reactive material and vibrating the electrodes in order to stir the solution and to renew the boundary conditions. An analysis method that is easy-to-use, rapid and sensitive is developed. The titrant is generated electrochemically at the generator electrode by applying a current, and instead of balancing the molar amounts, the fluxes of reactive material are balanced. The end-point is detected either amperometrically or potentiometrically by the appearance of the titrant at the collector electrode: the more analyte is present in the solution the greater the generator current required to reach a certain threshold value of the collector current or the open-circuit potential, and the longer it takes to achieve this value. The method is applied to, e.g., determination of L-ascorbic acid (vitamin C) with ferricyanide and titration of thiosulfate and sulfite with iodine using gold microband electrodes. Silver microband electrodes are employed here for a potentiometric titration where the titrant is electrogenerated by dissolving the generator electrode material and the open-circuit potential of the collector is measured. The use of silver microbands is demonstrated by determination of halides, cyanide and thiosulfate with Ag(I). The accuracy of these titrations is ±10 %, and it is mostly limited by the reproducibility of the present fabrication method of the electrodes. The results prove that the method is effective with a simple instrumental set-up, and the actual time needed for common titrations is significantly decreased. A comprehensive basis for further applications and other analytical systems is demonstrated.

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