Attenuated total reflection fluids

For IR sensing, three transducer principles are standard classical transmission for (sufficiently) transparent samples, (diffuse) reflection for opaque samples, in particular solids and strongly turbid liquids and attenuated total reflection (ATR), in particular for strongly absorbing samples and fluids with varying amounts of suspended solids or gas bubbles. 

Y. Cheng, N. Boden, R. J. Bushby, S. Clarkson, S. D. Evans, P. F. Knowles, A. Marsh, and R. E. Miles, Attenuated total reflection Fourier transform infrared spectroscopic characterization of fluid lipid bilayers tethered to solid supports, Langmuir 14, 893-844 (1998). 

Protein-lipid interactions and particularly peptide-lipid interactions have been studied in supported bilayers by attenuated total reflection (ATR) FTIR spectroscopy. A slightly dated, but still valid comprehensive review on this method applied to supported bilayers has been published (20). Because IR light probes the vibrational properties of different classes of covalent bonds, this method is useful to examine lipids, peptides, and interactions between the two in the same sample. The most common parameter for assessing lipid structure and order is to study the stretching vibrations of the lipid acyl chains, for example as a function of peptide concentration or temperature. Such studies have lead to the conclusion that fusion peptides from viruses increase the lipid chain order of fluid phase bilayers and that... 

Figure 66. Typical attenuated total reflectance infrared spectrum of an invert emulsion oil-based drilling fluid. (Reproduced with permission from reference 182. Copyright 1994.)...

---