Quantification of Dissolved Metabolites in Environmental Samples through Cation-Exchange Solid Phase Extraction (CX-SPE) paired with Liquid Chromatography-Mass Spectrometry

ABSTRACT: Small, biologically produced, organic molecules called metabolites play key roles in microbial systems where they directly mediate exchanges of nutrients, energy, and information. However, the study of dissolved polar metabolites in seawater and other environmental matrices has been hampered by analytical challenges including high inorganic ion concentrations, low analyte concentrations, and high chemical diversity. Here we show that a cation-exchange solid phase extraction (CX-SPE) sample preparation approach separates positively charged and zwitterionic metabolites from seawater and freshwater samples, allowing their analysis by liquid chromatography-mass spectrometry (LC-MS). We successfully extracted 69 known compounds from an in-house compound collection and evaluated the performance of the method by establishing extraction efficiencies and limits of detection (pM to low nM range) for these compounds. CX-SPE extracted a range of compounds including amino acids and compatible solutes, resulted in very low matrix effects, and performed robustly across large variations in salinity and dissolved organic matter (DOM) concentration. We compared CX-SPE to an established solid phase extraction procedure (PPL-SPE) and demonstrate that these two methods extract fundamentally different fractions of the dissolved metabolite pool with CX-SPE extracting compounds that are on average smaller and more polar. We use CX-SPE to analyze four environmental samples from distinct aquatic biomes, producing some of the first CX-SPE dissolved metabolomes. Quantified compounds ranged in concentration from 0.0093 nM to 49 nM and were composed primarily of amino acids (0.15 – 16 nM) and compatible solutes such as TMAO (0.89 – 49 nM) and glycine betaine (2.8 – 5.2 nM).

ORGANISM(S): Other

TISSUE(S): Water

SUBMITTER: Joshua Sacks  

PROVIDER: ST002292 | MetabolomicsWorkbench | Tue Aug 30 00:00:00 BST 2022

REPOSITORIES: MetabolomicsWorkbench