Efficient and rapid method for extraction of intact phospholipids from sediments combined with molecular structure elucidation using LC-ESI-MS-MS analysis

This paper presents the application of an efficient method for extraction and fractionation of intact phospholipids (PLs) from complex sediment matrices and elucidation of their molecular structure by normal-phase HPLC - ESI- MS - MS. Flow-blending extraction was tested with different solvent mixtures and the best recovery of all PLs classes from the sediment matrix was achieved by using methanol - dichloromethane - buffer, 2: 1: 0.8. The applied LC - ESI- MS system has linearity of R(2) = 0.98 and a detection limit of 0.5 ng/PL, sufficient for reliable identification of complex mixtures of PLs. MS - MS analyses using a triple-quadrupole mass spectrometer enables detection of individual PL side-chain composition and, hence, characterization of the living organisms contributing to the sedimentary organic material. Parallel GC - MS analysis of the hydrolysed phospholipid fatty acids supports the characterized fatty acid patterns determined from intact PLs. The PL inventory of different investigated lacustrine surface sediments shows predominantly high abundance of phosphatidylglycerols and phosphatidylethanolamines and phosphatidyl-mono- and dimethyl-ethanolamines with fatty acyl side-chains typically known from bacteria. In a sample from Lake Baikal intense signals of bacterial 14: 0-acyl-PGs were also identified, for the first time in sediments as far as we are aware.