N-alkylpyridinium quaternization combined with liquid chromatography-electrospray ionization-tandem mass spectrometry: A highly sensitive method to quantify fatty alcohols in thyroid tissues

A highly sensitive method was developed for the identification and quantification of fatty alcohols in biological tissues. In the presence of pyridine-d(0) and triflic anhydride (Tf2O), fatty alcohols were converted into permanently charged N-alkylpyridinium ions. Stable isotope-labeled derivatives were generated by pyridine-d(5) and added as internal standard (IS). The mixture was analyzed by liquid chromatography coupled to positive electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). This method was optimized and validated in terms of reaction time, derivatization efficiency, stability, desalting, and ion suppression effect. Besides, fatty alcohols exhibited good linear relationship (r2 > 0.993) over the concentration range of 10 ng mL(1)-1 mu g mL(1). The limits of detection (LODs) were lowered from previously reported 0.1 ng mL(1) to 0.25 pg mL(1). Precision (RSD% < 15.6%), accuracy (93.0-107.2%), matrix effect, and recovery (in thyroid tissues) were validated as well. Finally, this method was applied for the analysis of ten even carbon-numbered fatty alcohols (C8-C24) in human thyroid procedure achieved a sufficient enhancement of sensitivity. Furthermore, the exact concentrations of total (free and esterfied) fatty alcohols in human thyroid tissues were measured.