Analysis of Methylated Quaternary Ammonium Compounds Using Hydrophilic Interaction Liquid Chromatography Combined With Mass Spectrometry

Abstract

Liquid chromatography-mass spectrometry (LC-MS) is a powerful technique for the detection and quantification of methylated quaternary ammonium compounds (mQACs), such as acylcarnitines and methylated amino-acid-derived (betainized) compounds, in biological matrices. Due to their high polarity and permanent charge, mQACs present analytical challenges, particularly in achieving efficient chromatographic retention and resolution. Here, we focus on the application of hydrophilic interaction liquid chromatography combined with mass spectrometric (HILIC-MS), for the analysis of these compound classes in biological samples. We highlight practical considerations in their analysis, including their MS/MS fragmentation patterns and identification in positive electrospray mode (ESI)+, to support researchers working with mQACs in targeted or untargeted metabolomics studies.