Crystallization chromatography of glycerides

Abstract

Mixtures of high-melting glycerides can be separated into their constituents by means of a chromatographic process resembling repeated fractional crystallization. Use is made of a column in which a temperature gradient is established, and of solvent mixtuies with gradually increasing solvent power. The principle of the method is briefly discussed, and examples are given of the analysis and purification of synthetic glycerides, and the isolation of "pure" triglycerides from natural products.Mixtures of high-melting glycerides can be separated into their constituents by repeated fractional crystallization. Even for simple mixtures a large number of crystallization steps is usually required. Application of a continuous method would have the obvious advantage that a large number of equilibration steps is possible in a single operation. Such methods are wellknown for the separation of constituents from a liquid mixture by distillation or liquid-extraction. Methods have recently been proposed 11 2p 3 to use the same principle in cases where one of the equilibrated phases is a solid.The principle of these methods is illustrated in Fig. 1. Consider a mixture of two components, A and B , which are completely miscible both in the liquid and in the solid state. If the liquid mixture of composition X I is slowly cooled, crustallization starts at a temperature T I and the precipitated solid has the composition x2. Now let the remaining liquid move slowly in the direction of lower temperatures, and the solid in the opposite direction. The composition of the liquid will follow the upper (liquidus) curve and that of the solid the lower (solidus) curve. If a sufficient number of equilibration steps is allowed, it should be possible to separate the mixture into its pure components.To operate this process the crystals should be separated from their mother liquor immediately after they have been formed. Three methods ~-C. A . Baker, R.