A New Derivatization Reagent for HPLC-MS Analysis of Biological Organic Acids

Small molecules containing carboxylic acid functional groups are ubiquitous throughout biology, playing vital roles in biological chemistry ranging from energy metabolism to cellular signaling. This paper describes a new derivatization reagent, 4-bromo-N-methylbenzylamine, which was selected for its potential to derivatize mono-, di- and tri-carboxylic acids, such as the intermediates of the tricarboxylic acid (TCA) cycle. This derivatization procedure facilitated the use of positive electrospray ionization (ESI) tandem mass spectrometry (MS/MS) detection of derivatized species allowing for clear identification thanks to the easily recognizable isotope pattern of the incorporated bromine. A liquid chromatography (LC)-MS/MS method was developed which provided limits of detection between 0.2 and 44 μg L^-1 in under 6 min, depending on the analyte and total analysis time. This method was successfully applied in both in vitro and in vivo models.