Triacylglycerol molecular interactions

Fig. 3. Illustration of molecular interactions most irrfluential to structural stabilization of triacylglycerol crystals.

Two important factors controlling the efficiency of membrane separations are molecular size exclusion and chemical interaction between the membrane surface and the components of the fluid feed. The formation of micelles of phospholipids influences the separation in a positive way since monomers pass through the pores of the membrane more easily than micelles. Moreover, the adsorption of compounds on the membrane surface is often cited as the primary cause of fouling, resulting in blocking of pores. This phenomenon of adsorption is influenced by the polarity of the membrane surface and the polarity of the liquid medium in which are dissolved solutes to be separated. In nonpolar medium, as miscella of soybean oil dissolved in hexane, these authors reported that hydrophobic membranes showed greater tendency to adsorption of phospholipids and triacylglycerols of that hydrophilic membranes. 

As direct on-column injection can lead to a relatively rapid deterioration of the column through interactions of the liquid phase and the injection solvent or involatile impurities in the sample, an alternative has been devised in which a specially designed injection port takes over the function of the top part of the column. The sample is introduced into this inlet, which is cooled initially, and then its temperature is raised at a controlled rate so that the sample components are selectively vaporised. Injection systems of this type are relatively new and appear to be well suited to the analysis of lipids of high molecular weight, such as intact triacylglycerols. This is discussed further in Chapter 8. 

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