Quantitative Analysis of Powdered Solids with FTIR-ATR

Infrared quantitative analysis is an everyday requirement for the analytical laboratory. While liquid solutions are a common sample, mixtures of powdered components also exist and it is often desirable to obtain a quantitative result without dissolution into a solvent. This paper outlines the development of quantitative analysis methods for two powdered mixtures. The traditional infrared analysis method for powdered samples is the collection of a KBr pellet spectrum of an aliquot of the powdered sample. However, preparation of KBr pellets requires some skill, especially for quantitative analyses. Attenuated Total Reflectance (ATR) accessories like a single-reflection micro-ATR provide a simple and effective alternative, suitable for the infrared analysis of powders. The powdered sample is simply placed onto the ATR crystal and the sample spectrum is collected. Pressure up to 75 psi is evenly applied to the sample lying on the diamond micro-ATR crystal during sample analysis. The sample is then cleaned from the crystal surface and the accessory is ready to collect additional spectra.