Gas chromatographic analysis of plasma lipids

The brief review points out the improved resolution and quantitation of plasma lipids that is possible on nonpolar capillary columns of short length. The main advantage over packed columns used previously is the higher recovery of the longer chain triacylglycerols, the lower temperature and time requirements for completion of the analysis, and the greater ease of column conditioning and certainty of obtaining a satisfactory column. The greater resolution of all components has resulted in a better definition of lipid classes along with a complete resolution of specific molecular species, which was not possible on the packed columns. The successful demonstration of the suitability of polar capillary columns for high-temperature GLC of plasma lipids promises further improvements in the plasma lipid profiling by GLC in the future. The polar capillary column resolves the glycerolipids and ceramides according to both carbon and double-bond number and results in an essentially complete separation of molecular species, except where peak overlaps occur. In combination with preliminary TLC resolution of the lipid classes, polar capillary GLC provides the most extensive resolution of plasma lipids yet achieved. A total of 200 peaks representing over 200 molecular species can be readily recognized and quantitatively measured. Neither the nonpolar nor the polar capillary columns are capable of resolving the reverse isomers or enantiomers, which overlap completely on both columns. Both column types are suitable for GC/MS work, although a mass spectrometric examination of the peaks is required only for confirmation of their identity. Direct analyses of plasma lipids on the polar capillary columns provide extensive information about the composition of the lipid classes and molecular species. Furthermore, the polar capillary column profiles of plasma lipids can be obtained with conventional equipment over a period of 30 min. At the moment these profiles would appear to be best suited for the assessment of dietary and potential physicochemical effects on plasma lipoproteins. With more complete understanding of plasma lipid biochemistry, these profiles might provide useful metabolic information.