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A simple theoretical model is presented for the reduction of a singly charged cation under conditions where migration is important and the cation is coupled to a neutral species through a chemical equilibrium, AB = A(+) + B(-). Only the steady-state transport-limited current, I(l), is considered. Simple algebraic equations describe the ratio of I(l) to the diffusion-limited current, I(d), as it depends on the degree of dissociation, determined by the ratio of equilibrium constant to formal concentration, K(AB)/C*(AB). The ratio I(l)/I(d) is found to depend on the ratio of electrolyte to equilibrium concentration of A(+) in bulk solution just as for the well-known result for the case without the equilibrium (i.e., K(AB) → ∞). The results are in accord with published experimental data for weak acids. Agreement and disagreement with other theoretical treatments of this problem are discussed. The main results are for 1:1 supporting electrolytes; extensions are made to 2:1, 1:2, and 2:2 supporting electrolytes.

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A new method for detection of nerve gases, Sarin and Soman, was proposed on the basis of their catalyzed hydrolysis by metal chelate compounds and potentiometric detection of the byproduct, fluoride ion. Diisopropyl fluorophosphate (DFP) was used as a nerve gas mimic. The copper ion chelates shift the potential of the fluoride ion-selective electrode to more positive stable potential, which is beneficial for lowering the detection limit. In the presence of DFP, the electrode potential decreases rapidly with time due to the catalyzed hydrolysis of DFP and the production of fluoride ion. This method is sensitive, selective, and reproducible. The detection limit for DFP is 2 x 10(-6) M with a potential drop between 40 and 60 mV.