Derivatization strategy for semi-quantitative analysis of medium- and long-chain fatty acids using multiple reaction monitoring

Medium- and long-chain fatty acids (MLFAs) are essential energy sources in cells and possess vital biological functions. Characteristics of MLFAs in biosamples contributes to the understanding of biological process and finding potential biomarkers for relevant diseases. However, there are obstacles of the MLFAs determination due to their poor ionization efficiency in mass spectrometry and structural similarity of the MLFAs. Herein, a derivatization strategy was applied by labeling with d0-N, N-dimethyl-6,7-dihydro-5H-pyrrolo [3,4-d] pyrimidine-2-amine (d₀-DHPP) and detecting with ultra-high performance liquid chromatography combined with tandem mass spectrometry (UHPLC-MS/MS) in multiple reaction monitoring (MRM) mode. The parallel isotope labeled internal standards were generated by tagging d₆-DHPP to MLFAs. The simple and rapid derivatization procedure and mild reaction conditions greatly reduced the potential of MLFA degradation during the processing procedure. With the methodology, the chromatographic performance was greatly improved, and the mass spectrum response was enhanced up to 1, 600 folds. Finally, the developed derivatization method was applied to serum samples to analyze the alteration of MLFAs induced by 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) exposure in breast cancer nude mice. The semi-quantitative results demonstrated that the BDE-47 exposure significantly influenced the MLFA metabolism in mice.