Organic solvent systems for P-31 nuclear magnetic resonance analysis of lecithin phospholipids: Applications to two-dimensional gradient-enhanced H-1-detected heteronuclear multiple quantum coherence experiments

P-31 NMR of lipid extracts is a reproducible, rapid, and nondegradative method for qualitative and quantitative analyses of phospholipid mixtures. This analysis, however, is hampered by the instability of the solvent system commonly used for NMR spectroscopy (CHCl3/CH3OH/H2O-EDTA). In this work we have investigated the effects of several monophasic solvent mixtures to overcome this disadvantage. Among these mixtures we have selected a solution of triethylamine, dimethylformamide, and guanidinium chloride (Et(3)N/DMF-GH(+)) as the most efficient system. In this solvent the chemical shift dispersion of the Slp signals is about four times the frequency range observed in the standard chloroform-methanol-water system. Moreover, the stability of this solvent, as a monophasic system, allows easy reproducibility of the analysis. The use of two-dimensional H-1-P-31 gradient-enhanced heteronuclear multiple quantum coherence experiments can further exploit the higher resolution of the signals obtained with this solvent system for the structure elucidation of known and unidentified phospholipids. (C) 1997 Academic Press.