DETERMINATION OF CHARGE-TRANSFER KINETIC-PARAMETERS USING AN AUTOMATED FLOW SYSTEM

The use of an automated flow system coupled to a mathematically rigoro us fitting routine is described for determination of the charge transf er kinetic parameters for members of the 1,4-benzodiazepines. The auto mated flow system offers increased productivity and reproducibility wh ich promote investigation of the model system under a variety of exper imental conditions. The values of the charge transfer parameters for r eduction of the adsorbed material were determined for a range of elect rode surface coverage, supporting electrolyte, and stripping parameter s. The interpretation is complicated by the artifact of IR drop, which affects the magnitude of the rate parameters but not the corresponden ce between the experimental and optimal theoretical voltammogram. The dependence of the charge transfer coefficient alpha on ionic strength indicated a supporting electrolyte concentration of 1.0 M to be a prop er compromise between solution resistivity and solution impurities. Va lues of the charge transfer coefficient and the rate constant (in reci procal seconds, referred to - 0.6 V vs. SCE) for the totally irreversi ble reduction of adsorbate were determined for alprazolam (0.674 +/- 0 .005, - 3.80 + 0.04), loprazolam (0.695 +/- 0.004, - 5.42 + 0.050), mi dazolam (0.721 +/- 0.007, - 2.74 +/- 0.05), and triazolam (0.750 +/- 0 .005, 4.10 +/- 0.05) respectively, in 1.0 M acetate buffer at 25-degre es-C.