Steady-state amperometric and chronocoulometrlc experiments were carried out with a glassy carbon rotating disk electrode coated with a film of the perfluorinated Ion-exchange polymer Nafion, In order to investigate the transport of anionic, cationic, and neutral catechols through the film. The distribution constants of the compounds between film and solution (Kd) were measured, and the diffusion coefficients In the film (Df) were calculated. The film diffusion coefficients of catecholamines were found to be In the range (0.5 to 3.0) X 10'7 cm2 s_1. The selectivity constants were determined of the Nafion film for catecholamines relative to three monovalent cations Ll+, Na+, and K+. The competitive effects of. the buffer cations were found to decrease In the order expected from literature data on the Ion-exchange selectivity of Nafion. The buffer cation concentration has no Influence on the transport of neutral catechols through the film, and for anionic catechols the effect was opposite to that for cations. Other important factors for the detection In flow-through systems were also investigated, such as the influence of the film thickness, the pH, and the methanol concentration. From the results guidelines were formulated to obtain maximum selectivity for cationic analytes with Nafion-coated electrodes in liquid chromatography and flow-injection analysis.

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The application of manganese(V1) and copper (III) in strongly alkaline solutions as strong oxidizing reagents in flow injection analysis is described. Both reagents were prepared under batch conditions and fed to the flow from a stock solution. The reactions of most analytes tested with manganese (VI) required the use of a heated (65 'C) reaction coil. The main application appears to be for the determination of monosaccharides in the 1O-4-1O-6 mol 1-i range.