The Versatile Sampling Methods of Infrared Microspectroscopy
This chapter examines the basic experiments which can be done with an infrared microscope, along with the unwanted optical effects from microscopic samples, how they affect each experiment, and how to correct them by proper sampling. It then addresses sample purity and homogeneity. The chapter discusses additional instrumental parameters affecting performance and other special sampling techniques. Most microscopic sampling is performed on solids, particles, or fibers which, although they are small in diameter, are too thick for one to obtain representative spectra without reducing their pathlength. In macroscopic infrared spectroscopy, this consideration often may not pose a problem, since a solid sample is usually prepared for infrared spectroscopy by dilution with solvent, salt, or mineral oil. The sampling technique of flattening to reduce pathlength will help to reduce diffraction effects by enlarging the sample area. Sample purity is a major concern in microspectroscopy since contaminants are not adequately diluted by the sample on a microscopic scale.