Development of a Targeted Metabolomics Method for Environmental Toxicants Using Mass Spectrometry

Abstract

The aim of this study was to develop a mass spectrometry-based targeted-metabolite quantification method that can be utilized to investigate the metabolic effects of environmental toxicants on organisms. We employed an ultra-high performance liquid chromatography quadrupole time-of-flight mass spectrometer (UHPLC-QTOF-MS) to obtain accurate m/z ratios and chromatographic retention times for the target metabolites. Optimization of mobile phase compositions, concentration gradients, additive types, and QTOF-MS source parameters was performed to achieve an optimal chromatographic separation of the metabolites representing different chemical classes and polarities. While 77 metabolites eluted near the void volume during the initial chromatographic run due to their hydrophilic nature, 7 metabolites were retained only on a C18 column. To address the challenges posed by highly polar metabolites, we implemented a hydrophilic interaction liquid chromatography (HILIC) column on which 85 metabolites were detected in electrospray ionization (ESI) positive and negative modes. We observed higher MS signals using a combination of 10 mM ammonium formate, 0.1% ammonium hydroxide, and 0.1 % formic acid as mobile phase modifiers.