A DRIFTS accessory operates by directing the IR energy into a sample cup filled with a mixture of the sample and an IR transparent matrix (such as KBr). The IR radiation interacts with the particles and then reflects off their surfaces, causing the light to diffuse, or scatter, as it moves throughout the sample. The output mirror then directs this scattered energy to the detector in the spectrometer. The detector records the altered IR beam as an interferogram signal, which can then be used to generate a spectrum. Typically, a background is collected with the DRIFTS accessory in place and the cup filled with just the IR matrix. Excellent quantitative and qualitative data can be collected with proper sample preparation. However, transmission and ATR techniques are preferable to diffuse reflectance for quantitative data due to pathlength.
DRIFTS is commonly used for the analysis of both organic and inorganic samples that can be ground into a fine powder (less than 10 microns) and mixed in a powder matrix such as potassium bromide (KBr). Typical sample types include:
The DRIFTS technique can also be used with silicon carbide paper for the analysis of large intractable surfaces. Silicon carbide paper can be used to rub off a small amount of a variety of samples for analysis. This technique is a viable alternative to traditional sampling techniques for: