Traditional analytical chemistry of fatty acids and their derivatives

Industrial fatty acids and their derivatives are generally manufactured under strict quality control and sold under rigid specifications. The purchase specifications are normally prescribed by a series of traditional “wet” analytical methods. These methods include acid value, saponification value, iodine value, hydroxyl value, water content, and others. Occasionally, other information is specified; this may include for tall oil fatty acids, rosin content, and free glycerol in monoglycerides, diene value for drying fatty acids, and conjugated fatty acids for specialized fatty acids. The most common fatty acid derivatives of the industrial fatty acids are anionic and nonionic surfactants and the nitrogen derivatives such as amines and quaternary ammonium salts. Rigid quality control is also applied to these compounds. The amine value and the determination of primary, secondary, and tertiary amines are the key analytical methods applied to amine derivatives. Quaternary ammonium compounds present unique problems; these are in a present state of methods improvement. Physical property test methods are often used to characterize fatty acids. Though simple in concept, they are often the most difficult to meet in purchase specifications. Examples of these tests are viscosity, titer, color, color stability, flash and fire point.