Quantitative ATR spectroscopy: some basic considerations

Abstract

A comprehensive treatment of ATR spectra on the basis of the Lorentz-Lorenz law and Fresnel equations is given. The standard equation for the effective thickness is redefined showing how the lossy case deviates from the lossless case. A matrix effect due to the influence of the real part of the refractive index within an absorption band is demonstrated theoretically as well as experimentally. The concentration of a nonab-sorbing solute sample, i.e., glucose, is determined by ATR spectroscopy near the critical angle.