Comprehensive monitoring of organic micro-pollutants in drinking water sources relies on non-target screening using liquid chromatography and high-resolution mass spectrometry (LC-HRMS). Identification of pollutants is typically based on accurate mass and tandem mass spectrometry (MS/MS) data by matching against entries in compound databases and MS/MS spectral libraries. This method routinely identifies the so-called “known unknowns”, i.e. pollutants that are present in the databases. However, the detection method is blind to pollutants that are not listed in these libraries. Examples of these “unknown unknowns” are emerging pollutants and transformation products that are formed in chemical, biological or photo-degradation processes.
Infrared ion spectroscopy is a powerful method, developed by researchers at HFML-FELIX, that uses the infrared free electron laser FELIX to measure an infrared fingerprint of compounds in a mass spectrometer, providing an orthogonal diagnostic for molecular structure identification of the “unknown unknowns”. Nonetheless, even with the help of the infrared fingerprint, the identification of species in surface water samples is challenging because of the gigantic number of chemical compounds that might be present in river water.
