Over the last years, the analysis of small-molecules by high-resolution liquid-chromatography-mass spectrometry (LC-MS) instrumentation has become widely available and affordable. The new technology is game-changing because it allows molecular characterization of small molecules with high sensitivity in extremely complex real-world samples, such as soil or seawater extracts.
Using high-resolution LC-MS/MS, we developed a direct approach to discover and characterize metal chelating agents by exploiting the stable isotope patterns of many metals and known MS/MS signatures of siderophores (Baars et al. 2014, 2016). However, LC-MS has limitations: The detection is dependent on the structure of the compounds, and some analytes show poor chromatography and ionization. Thus, we are developing workflows for combining LC-MS with orthogonal separation techniques and other spectroscopic methods (particularly LC-UV/vis, LC-CAD, NMR). We use a new LC-inductively coupled plasma mass-spectrometry (LC-ICPMS) platform for quantitative speciation of metals and other elements independent of their molecular structure. We are are further developing methods for imaging of small molecules in microbiome interactions with different detection techniques, such as Matrix-assisted laser desorption electrospray ionization (MALDESI) mass spectrometry (Sampson, J. S.; Hawkridge, A. M.; Muddiman, D.C. (2006)).