One of the most useful applications of internal reflection spectroscopy (ATR) is in microsampling. Not only can it be applied to the analysis of samples that are small in physical size such as a chip of paint or a small blemish on a surface, but it is a convenient and sensitive method for examining microsamples that can be spread over a considerable area. Examples are residues from the evaporation of solutions, condensed GC fractions, and thin coatings or weathered layers on surfaces. In this study we will discuss two different methods of internal reflection microsampling: (1) large plate, thin layer sampling and (2) condensed beam sampling.
A. C. Gilby, John Cassels, and P. A. Wilks, "Internal Reflectance Spectroscopy. III. Micro Sampling," Appl. Spectrosc. 24, 539-543 (1970)