Diffuse reflectance infrared fourier transform

Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS)^[1] is an infrared spectroscopy spectra technique used on powder samples with no preparation. The sample is added to a sample cup and the data is collected on the bulk sample. The infrared light on a sample is reflected and transmitted at different amounts depending on the bulk properties of material. The diffuse reflection is produced by the sample rough surfaces reflection of the light in all directions and is collected by use of an ellipsoid or paraboloid mirror. Shape, compactness, refractive index, reflectivity and absorption of the particles are all characteristic of the material being analyzed. If the sample is too absorbent, then it can be diluted with a nonabsorbent material such as potassium bromide, potassium chloride, etc. Particle size should be smaller than the wavelength of the incident light, so this would infer that it should be less than 5 microns for mid-range infrared spectroscopy. The spectra are plotted in units of log inverse reflectance (log 1/R) verses wavenumber. Alternative plots of Kubelka-Munk units can be used, which relate reflectance to concentration using a scaling factor.

References

1. ^ C.-P. Sherman Hsu, Ph.D. "Handbook of Instrumental Techniques for Analytical Chemistry" Prentice-Hall, New Jersey, 1997, 262.