What is ATR? (Attenuated Total Reflectance) - METTLER TOLEDO - EN

Attenuated Total Reflectance (ATR) is one of the most used sampling technologies for FTIR Spectroscopy. The reason for the ubiquitous use of ATR is that it enables solids and liquid samples to be analyzed neatly - simplifying the measurement of virtually all substances. In contrast with transmission, the other widely used sampling method, the measurement path length is independent of the thickness of the sample. ATR is an internal reflection-based method, and the sample path length is dependent on the depth of penetration of the infrared energy into the sample. A solid sample can be 100 microns thick or 100 mm thick and the recorded infrared spectrum will basically look the same. If a fluid or slurry sample is in contact with the ATR surface, the infrared spectrum of the liquid portion is recorded. It is this latter phenomena that makes ATR so powerful for chemical reaction monitoring.

Attenuated Total Reflectance methodology is an ideal complement to FTIR Spectroscopy for in situ, real-time analysis and monitoring of chemical reactions. Reaction mixtures are typically optically dense to mid-infrared radiation. The restricted depth of penetration of infrared energy into the reaction solution that is in contact with the ATR sensor allows high-quality FTIR spectra to be recorded. An ATR-FTIR sensor fabricated of appropriate material, which is mounted at the end of a tubular probe or as part of flow cell, enables reactions to be analyzed whether in batch or continuous flow mode, respectively. Suitable FTIR-ATR sensors for analyzing chemical reactions must have the requisite index of refraction to enable internal reflection, but also must perform in harsh chemical environments without degrading. Both diamond and silicon are excellent sensor materials for FTIR-ATR analysis of chemistry and the choice of which to use is dependent on the type of chemistry and the infrared peak positions that need to be tracked.

ATR-FTIR spectroscopy: https://www.mt.com/us/en/home/applica...

FTIR spectroscopy: https://www.mt.com/us/en/home/applica...

FTIR vs Raman spectroscopy: https://www.mt.com/us/en/home/applica...

Raman spectroscopy: https://www.mt.com/us/en/home/applica...

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