ANALYSIS OF LECITHIN IN COSMETICS BY REVERSED-PHASE LIQUID-CHROMATOGRAPHY ELECTROSPRAY TANDEM MASS-SPECTROMETRY

A rapid, sensitive and selective method by reversed-phase liquid chrom atography (LC) with electrospray ionization (ESI) mass spectrometry (M S) was employed for the determination of lecithin in a cosmetic raw ma terial for quality control of the product formulation. The mixture of the phosphatidylcholine, phosphatidyl-ethanolamine, and phosphatidylin ositol in lecithin was separated using aqueous methanol-acetonitrile s olvent with a reversed-phase LC column, and detected as forms of pseud omolecular ions. Using this LC/ESI-MS technique, simultaneous separati on and detection of phospholipid classes and molecular species within each class were achieved for the first time. Additionally informative fragmentation patterns were obtained by employing LC/ESI-MS/MS in both positive and negative ionization modes to identify these fatty acid c hains and polar head groups in each molecular species of the phospholi pids. (C) 1998 John Wiley & Sons, Ltd.