Fractionation of soybean phospholipids by preparative high-performance liquid chromatography with sorbents of various particle size.
Normal-phase high-performance liquid chromatography was used on a preparative scale to seperate phosphatidylethanolamine (PE), phosphatidylinositol (PI) and phosphatidylcholine (PC) phospholipids from soybean. Separation was achieved using mixtures of three solvents, hexane, methanol and isopropanol. The optimized mobile phase compositions were experimentally determined while operating in a linear gradient mode using 15, 5-20, 25-40, and 40-63 microm preparative particles as well as 4 microm analytical particles. A gradient mobile phase was established on a commmercially available analytical Nova-Pak column such that hexane linearly decreased from 85 to 0 as isopropanol and methanol linearly increased in two gradient steps from 10 to 30 and 5 to 70 respectively. The total run time was 25 min at a flow-rate of 1.5 ml/min. A slight change in mobile phase composition was required to increase the resolution of phospholipids. The 15 microm particle size gave the best separation of the preparative particle sizes examined based on their resolutions between PE and PI and PI and PC. Finally, the retention factors of PE and PC were correlated in terms of mobile phase composition.
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.
The Invariance of the Vacuum is the Invariance of the World
The following theorem is demonstrated: If the vacuum is invariant under the group generated by the space integral of the time component of a local vector current, then the Hamiltonian is invariant also. A similar theorem holds for the group generated by the space integral of a space component of a local axial-vector current.