Effect of Pressure on Diffuse Reflectance Infrared Spectra of Compressed Powders

Abstract

The effect of compressing powdered samples on their diffuse reflectance infrared spectra is discussed. The scattering coefficient decreases with applied pressure, the magnitude of the increase being dependent on the nature of the sample. For pure powdered organic samples, such as caffeine, the increase in f(R∞) can be dramatic. By subjecting powdered samples to a pressure which is not enough to cause them to become transparent, the packing density becomes more uniform and band intensities become more reproducible. The relative intensity of neighboring bands in any region of the spectrum does not change appreciably with applied pressure.