In natural waters and in culture media, the bioavailability of trace metals to microorganisms depends on their binding to a variety of weak and strong complexing agents.  See also  Metal Uptake by Phytoplankton  and
The Role of Metals in Nitrogen Cycling in Soils.  In nature, these organic compounds include humic substances, intracellular molecules released by cell lysis, and ligands released by microorganisms for the purpose of metal detoxification or uptake. Most available data on these complexing agents come from electrochemical measurements that provide information on their concentrations and binding strengths but not on their chemical identity. To elucidate the chemical nature of this unknown pool of individual ligands we develop and apply new approaches including high-resolution liquid-chromatography electrospray mass-spectrometry using Orbitrap platforms.