Contaminants and Artifacts in Extraction

Other extraneous lipid-like materials can be introduced accidentally into lipid samples from a variety of sources. Plastic ware of all kinds (other than that made from Teflon) can be especially troublesome and is best avoided, since plasticizers (diesters of phthalic acid usually) very easily leach out by organic solvents. They tend to co-chromatograph with some lipids or cause ion suppression, so they may 

Spread confusion and obscure compounds of interest in lipidomic analysis. They are especially troublesome in GC analyses of fatty acid methyl esters. Conversely, it has been shown that lipids can themselves dissolve in some plastics, leading to selective losses of less polar constituents [50]. 

Manufacturers of fine chemicals are fallible, and all laboratory reagents can on occasion contain impurities that may cause problems in analytical procedures. It is necessary to exercise vigilance to detect and eliminate these at an early stage. Further lipid contaminants can arise from such obscure sources as fingerprints, and from a host of materials in everyday use in laboratories, including cosmetics, hair preparations, hand creams, soaps, polishes, the exhausts from vacuum pumps, lubricants, and greases, if they are used carelessly. 

Artifactual enzymatic hydrolysis of lipids, catalyzed by tissue enzymes, can be promoted by the solvents used for extraction. This is especially troublesome with plant tissues, in which PLD activity (both hydrolytic and transphosphatidylase) is stimulated by some solvents. The problem is usually circumvented by a pre-extraction with isopropanol, which deactivates the enzyme. It is also possible to obtain an artifactual enzyme-catalyzed acylation of some lipids (such as glycosyldiacylglycerols) in certain circumstances [52]. 

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