Determination of Free Fatty Acids from Soil by LC-MS with Fluorescence Detection and Atmospheric Pressure Chemical Ionization Identification

A simple and highly sensitive method for the determination of fatty acids using liquid chromatography with fluorescence detection is described. Fatty acids were derivatized by a new novel pre-column derivatization reagent 1,2-benzo-3,4-dihydrocarbazole-9-ethanol before injection. Derivatives were sufficiently stable for efficient analysis by LC without pre-treatment. On a reversed-phase XDB-C(8) column, 19 kinds of fatty acids (C(1)-C(19)) derivatives were separated in conjunction with gradient elution and good baseline resolution. The precise determination of fatty acids from soil sample was achieved by post-column online mass spectrometric identification with atmospheric pressure chemical ionization source in positive mode. The established method exhibited good selectivity and excellent repeatability. The RSD (n = 6) for each fatty acid derivative were < 3%, detection limits (at signal-to-noise of 3:1) were 11.79-33.04 fmol.