Organic Solvent Systems for31P Nuclear Magnetic Resonance Analysis of Lecithin Phospholipids: Applications to Two-Dimensional Gradient-Enhanced1H-Detected Heteronuclear Multiple Quantum Coherence Experiments

Abstract 31 P 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 (CHCl 3 /CH 3 OH/H 2 O–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 31 P 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 1 H– 31 P 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.