Improved determination of individual molecular species of phosphatidylcholine in biological samples by high-performance liquid chromatography with internal standards

Separation and quantitation of phospholipids and their ether analogues by high-performance liquid chromatography

The common mobile phase hexane/isopropanol/water used for separation of phospholipids on high-performance liquid chromatography silica columns poses several problems, such as incomplete separation and rapid column deterioration. By inclusion of 5 mM ammonium sulfate in the aqueous phase, we were able to substantially improve the chromatographic resolution and obtain complete separation of phosphatidylcholine, phosphatidylethanolamine, lysophosphatidylcholine, lysophosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, cardiolipin, phosphatidylglycerol, and sphingomyelin. In addition, ammonium sulfate prevented column degeneration and greatly improved reproducibility. A new quantitation method for alkenylacyl, alkylacyl, and diacyl forms of phospholipids was also developed based on derivatization with [(3)H]acetic anhydride. Separation and quantitation of the radioactive acetyl diradylglycerols were performed by straight-phase HPLC coupled to a radioactive flow detector and enabled detection of the various ether analogues at the picomole level with high reproducibility. The described methods are mild and nondestructive and can therefore be easily combined with analysis of either molecular species or fatty acid and aldehyde composition of the individual phospholipids.

Reversed-phase separations of nitrogenous phospholipids on an octadecanoyl poly(vinyl alcohol) phase

Molecular species of nitrogenous phospholipids (PLs) phosphatidylcholine (PC), phosphatidylethanolamine (PE), PE-derivatives and sphingomyelin (SP) were separated on an octadecanoyl poly(vinyl alcohol) (ODPVA) column by reversed-phase HPLC with UV and evaporative light scattering detection (ELSD). Mobile phases employed variable proportions of acetonitrile, methanol and water. HPLC-UV of the polar lipids yield components with peak intensities somewhat different from those obtained by HPLC-ELSD despite discernible similarity in the peak profiles observed in the two detection systems. Incorporation of ammonium hydroxide in mobile phases resulted in a decrease in analyte retention. The mobile phase basicity effect on capacity factors of PE species was significantly greater than that of PC counterparts. The new ODPVA-HPLC-ELSD technique was applied to the analysis of PC and PE molecular species in vegetable oils.

Molecular species analysis of phospholipids

The elucidation of phospholipid molecular species composition provides detailed structural information concerning various lipids and thus offers descriptions of crucial determinants of membrane physical and biological properties. Various methods differing in labor intensity, mode of separation and detection, type of calibration, as well as other factors, have been published. Thus precision and accuracy are expected to vary considerably between methods. Qualitative and quantitative aspects of different procedures for molecular species analysis of individual phospholipid classes are discussed in this review. Special emphasis has been given to the characterization of biological tissue samples.