Older Methods of Lipid Analysis

Naturally occurring lipid mixtures have a composition of such extreme complexity that the analysis by chemical methods of a group of these substances or the determination of a single compound in such mixtures, appears hopeless. Up to about ten years ago, lipid mixtures were characterised by totals like acid-, saponification-, iodine-, thio-cyanogen- and diene- numbers . The determination of the amount of non-saponifiable matter after alkaline hydrolysis was a standard method in the analysis of fats. Phospholipids and sulpholipids were quantitatively determined as inorganic phosphate and sulphate after combustion. These methods were supplemented by detection of subsidiary fat constituents like lipochromes, sterols and resin acids, with the help of colour reactions. 

Physical methods for characterising lipids comprised determination of melting and freezing point, density, hardness, viscosity, surface and interfacial tension, solubility, flash point and combustion point. These classicaF methods have been described in detail in the works of T. P. Hilditch [59] and H. P. Kaufmann [77]. 

Lipid samples of 1 to 100 g were required for these separation procedures. They usually achieved no more than the enrichment of a component or semi-quantitative fractionation. The efficiency of the fractionations was generally monitored spectroscopically. 

---