Effect of ammonium fluoride as a mobile phase additive on quantitativity of fatty acids in electrospray ionization-liquid chromatography-tandem mass spectrometry.

Fatty acids (FAs) are essential molecules in biological systems and have crucial roles for fundamental components of cellular membranes, energy stores and mediators for cellular functions. The growing importance of FAs has also paid attention to analytical methods for the determination of FA contents in various samples accurately. Liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis is a powerful tool due to less time for sample preparation and analysis. This analytical approach enables to quantify levels of FA and other lipid classes in various samples simultaneously without derivatization. In the present study, the effects of ammonium salts on the sensitivity of FAs in LC-MS/MS analysis were evaluated. First, authors performed the comparison of FA analysis with different mobile phases, which contain ammonium formate, ammonium fluoride, ammonium acetate or ammonium carbonate. Interestingly, the mobile phase containing ammonium fluoride enhanced the sensitivity of targeted FA species more than other ammonium salts. Second, the difference of quantativity of FA species was examined. It was indicated that both carbon chain length and the number of double bonds affect ionization of FA species. Finally, the method of FA analysis based on ammonium fluoride was applied to FA profiling of lotus root. It is indicated that mobile phase containing ammonium fluoride enabled to evaluate FA contents with highly sensitivity in LC-MS/MS analysis.