High Sensitivity Internal Reflection Spectroelectrochemistry for Direct Monitoring of Diffusing Species Using Signal Averaging

Internal reflection spectrometry (IRS) at optically transparent electrodes (OTE) appears to be an excellent technique for quantitative studies of species produced or perturbed electrochemically within a distance δ of the electrode surface. Quantitative applications employing IRS at OTE, however, require an understanding of the sensitivity variation of absorbance. This variation was formulated as a sensitivity factor, N_eff, in the quantitative relationships describing absorbance and could be correlated with the optical constants of the system and the Fresnel equations describing the reflectivity. Further, the absorbance as a function of time during an electrochemical potential perturbation could be quantitatively analyzed, and good agreement was found with experimental results. Signal to noise ratios were greatly improved by signal averaging techniques, and small changes (<10^–5unit) could be resolved at very short times (ca. 10 μsec).