Potential-modulated reflectance spectroscopy of the methyl orange transfer across the water|1,2-dichloroethane interface

The kinetics of methyl orange transfer across the water/1,2-dichloroethane interface is studied by potential-modulated reflectance (PMR) and ac-impedance. The frequency dependence analysis of both techniques provide complementary information about charge transfer kinetics and the potential distribution across the interface. The PMR signal is obtained under total internal reflection from the liquid/liquid interface. It is concluded that the PMR responses are originated from the ac flux of ion crossing the interface, and therefore provide a direct analysis of the faradaic responses. This technique is also less sensitive to uncompensated resistance effects in comparison to the admittance analysis. In the case of methyl orange transfer, a standard apparent rate constant of (4.5 +/- 0.7) 10(-2) cm s(-1) and a transfer coefficient of 0.40 +/- 0.03 were estimated from the frequency dependence of the PMR. (C) 1998 Elsevier Science S.A. All rights reserved.