ABSTRACT
Vibrational spectroscopy has held a prominent place in the routine analysis of surfactants. There are three main categories of vibrational spectroscopy that provide useful structural information in the analysis of organic and inorganic molecules: mid-infrared (IR), Raman, and near-infrared spectroscopies. The mid-infrared region of the electromagnetic spectrum extends from approximately 4000 to 200 wavenumber, with nearly all organic and inorganic compounds absorbing radiation somewhere in this region. A practical description of infrared spectroscopy starts with the fundamental idea of absorption of light. Somewhat less traditional, but with a longer history in the surfactant industry, is Raman spectroscopy. Although a very popular technique before World War II, it eventually gave way to IR as the dominant vibrational spectroscopic technique subsequent to the war due to the sudden availability of cheap, sensitive mid-IR detectors. Solid materials are most often analyzed in the infrared as a ground powder mixed with a solid dispersing agent such as potassium bromide.
