ATR FT-IR spectroscopy is a widely used technique for surface analysis. A less common FT-IR method is CIRCLE ATR, which was originally designed to study aqueous systems that are difficult to analyze due to strong water absorbance in transmission measurements. Recent studies of styrene/acrylic acid copolymer dissolved in aqueous solvent show that with the use of this technique it is possible to detect very low concentrations of solute (0.001 w/w). For our purposes this technique was modified for application to surface studies of flexible films and fibers.
Ann M. Tiefenthaler and Marek W. Urban, "Surface Studies of Polymer Films and Fibers by CIRCLE ATR FT-IR," Appl. Spectrosc. 42, 163-166 (1988)