Sample Handling in Infrared Spectroscopy — An Overview
Infrared Spectroscopy is a useful analytical technique because of its enormous versatility. Spectra can be obtained, often nondestructively, on samples in all three states of matter — gases, liquids, and solids. This chapter presents an overview of the techniques for sample handling. The first consideration is the intensity of the bands in the spectrum. The density of a sample in the vapor phase is much less than that of the same sample in its condensed phase. So, in order to get a spectrum of suitable intensity, it is necessary to resort to cells with much longer pathlengths than are used for liquids and solutions. The phenomenon of attenuated total reflection in the visible region of the spectrum was reported by Isaac Newton, but it remained until the early 1960s before it came into use as a sampling technique for infrared spectroscopy. The thickness of a sample will need to be the same whether the technique is macro or micro sampling.