Comments on 'On the calculation of surface concentration from the measurement by the radiotracer 'electrode lowering' technique' by D. Poskus

Quantitative aspects of surface concentration measurements of radiolabeled adsorbates by the thin-gap measuring technique developed by our group have been discussed recently by Poskus (see D. Poskus, J. Electroanal. Chem. 442 1998 5). It was argued that surface concentrations obtained by us were und erdetermined since the backscattering factor of beta-radiation used in our work was too high versus a similar, but more recently obtained value by the quoted author. In response, we have reanalyzed our measuring conditions wi th a special emphasis on the backscattering phenomena involved in the exper iment. Without contradicting the author's conclusions, the reported results indicate that the backscattering factor used in our formula linking radiat ion data and surface concentrations was correct, Apparently. in the scintil lation-counter mode of the measurements, such a backscattering factor invol ves a simultaneous detection of reflected light from scintillation events a nd backscattered beta-radiation emitted by the radioactive preparate. Conve rsely, the Poskus measurements conducted by the use of a gaseous counter de termine the second component only. Using a new, experimentally determined b ackscattering factor and a Au(111) electrode, we present a comparison betwe en sulfate adsorption data obtained by the use of the thin-gap technique an d Auger electron spectroscopy and prove, once again, the accuracy of our da ta. (C) 1999 Elsevier Science S.A. All rights reserved.