Determination of Free Fatty Acids in Tibet Folk Medicine Potentilla anserina L. Using a New Labeling Reagent by LC with Fluorescence Detection and Identification with Online Atmospheric Chemical Ionization-MS Identification

A sensitive method for the determination of free fatty acids using 1,2-benzo-carbazole-9-ethyl-p-toluenesulfonate (BCETS) as tagging reagent with fluorescence detection has been developed. BCETS could easily and quickly label fatty acids in the presence of the K2CO3 catalyst at 80 A degrees C for 30 min in N,N-dimethylformamide solvent. In this study, fatty acids from the extracted Potentilla anserina L. plant sample were sensitively determined. The corresponding derivatives were separated on a reversed-phase Eclipse XDB-C-8 column by LC in conjunction with gradient elution. The identification was carried out by post-column APCI-MS in positive-ion detection mode. BCETS-fatty acid derivatives gave an intense molecular ion peak at m/z [M+H](+), the collision-induced dissociation spectra of m/z [M+H](+) produced the specific fragment ions at m/z [M'+CH2CH2](+), m/z 216.6 and m/z [MH-H2O](+) (here, M': corresponding molecular mass of the fatty acids). The fluorescence excitation and emission wavelengths of the derivatives were at lambda (ex) 279 nm and lambda (em) 380 nm, respectively. Linear correlation coefficients for all fatty acid derivatives are more than 0.9994. Detection limits, at a signal-to-noise ratio of 3:1, are 10.79-34.19 fmol for the labeled fatty acids.