Internal Reflection Spectroscopy

Abstract

The history of internal reflection spectroscopy (IRS), also known as attenuated total reflection spectroscopy (ATR), began nearly two centuries ago with the observation by Newton [l] of an evanescent field in a lower index of refraction medium in contact with a higher index of refraction medium in which a propagating wave of radiation undergoes total internal reflection (TIR). However, the exploitation of this phenomenon for the production of absorption spectra did not begin until the pioneering development work of Harrick [2, 31 and Fahrenfort [4]. After the disclosure on the technique in the literature in 1960, a flurry of publications exploiting it for a wide variety of applications ensued. By 1967 a large body of literature existed which was sufficient to justify a monograph by Harrick [5] and a review by Wilks and Hirschfeld [6], These publications thoroughly reviewed the history and applications of IRS up until that time. Although the IRS technique appeared to promise a ready solution for a wide range of problems which were difficult or intractable by other techniques, such as transmission IR, its general use was hampered by doubts about its reproducibility and capability to be quantitative, Some of the problems which diminished the use of the IRS technique include sample contact to the internal reflection element (IRE) 7-91, spectrometer requirements [101, and data-handling requirements [111.