Detection and confirmation of very long-chain polyunsaturated fatty acids in gilthead sea bream retina extracts using gas chromatography with atmospheric pressure chemical ionization source

Treball Final del Màster Universitari en Tècniques Cromatogràfiques Aplicades (Pla de 2013). Codi: SIY009. Curs acadèmic 2014-2015Long-chain and very long-chain polyunsaturated fatty acids (LC-PUFAs, C12–22; VLCPUFAs, C24–38), play an important role in retinal, brain and reproductive functions. Deficiencies in retinal LC-PUFAs and VLC-PUFAs, as well as mutations in the enzyme responsible for elongation of very long-chain fatty acids (ELOVL4), have been associated with retinal diseases. Gas chromatography coupled to mass spectrometry (GC-MS) with election ionization has been widely applied to study VLC-PUFA. The extensive fragmentation of this source is the main drawback for further tandem MS (MS/MS) experiments. In the present work, an atmospheric pressure chemical ionization (APCI) source coupled to a quadrupole time-of-flight analyzer has been tested to study the ionization and mass spectrometric behavior of ten fatty acid methyl esters (FAMEs). The protonated molecule ([M+H]+ ) became the base peak of the spectrum for all the studied compounds, promoted, furthermore, by the addition of a 1% formic acid solution in the source. The preservation of the molecule provides more sensitive and selective precursor ions in selected reaction monitoring (SRM) based methods. In addition, several specific fragment ions have been found for each FAME group. The application of GC-APCI- (Q)TOF to the screening analysis of gilthead sea bream retina extracts made possible the detection of several suspect VLC-PUFA. The reliable identification of the compounds was supported by accurate mass measurements, the isotopic pattern of 13C and the presence of two representative m/z ions in the spectrum