Studies on the methanolysis of small amounts of purified phospholipids for gas chromatographic analysis of fatty acid methyl esters

The methanolysis of small amounts of purified phosphoglycerides and sphingomyelin was studied and a quantitative comparison of five methods for the methanolysis of standard phosphoglycerides was made. These methods were based on methanolysis with boron trifluoride-methanol, methanolic sodium methoxide (at ambient temperature and with heating) and methanolic sulphuric acid. A further method was based on saponification with methanolic sodium hydroxide and subsequent esterification with boron trifluoride- methanol. Under the experimental conditions, only the sodium methoxide-catalysed method at ambient temperature gave complete methanolysis of phosphoglycerides. For methanolysis of sphingomyelin, boron trifiuoride-methanol, methanolic sulphuric acid and methanolic hydrochloric acid were used. It was found that complete methanolysis of sphingomyelin takes 15 h at 90°C. Based on these results, procedures for the methanolysis of phosphoglycerides and sphingomyelin separated by high-performance liquid chromatography are presented.