The steady growth in the production and use of chemicals is leading to an increased presence of these compounds in drinking water and drinking water sources. Target screening is no longer sufficient for the monitoring of all these compounds. There is a need for methods that can detect a multiplicity of chemicals simultaneously and in low concentrations: suspect- and non-target screening (NTS).
With NTS a sample is measured using a generic measurement method (HPLC-HRMS), which detects all compounds that can be separated and ionised by the selected chromatography and electrospray ionisation (ESI). The results are then screened using a ‘suspect’ list of compounds that can be expected to be present in the sample. The remaining unidentified compounds (features) are identified using NTS on the basis of the exact mass, isotope patterns, retention time, the fragmentation spectrum and the information available in the databases. To confirm the outcome and achieve level 1 confidence, the compound must be compared to a reference standard (Schymanski et al. 2014).
Method development at KWR
We work continually on extending and optimising our NTS methods in order to be able to better identify and, ultimately, also quantify more compounds. A key concern is the measurement of highly polar compounds, which are mobile and thus very relevant for drinking water, since they can easily end up in the groundwater and are hard to remove in water treatment plants. These compounds are moreover difficult to analyse. We have developed a chromatographic method, consisting of Hydrophilic Interaction Chromatography (HILIC) and mixed-mode LC, for the analysis of these compounds. The transformation products formed in the water treatment plant also present a challenge to drinking water quality, which is why we have developed a method using NTS to better monitor them.
Apart from method development we also work on the implementation of the new techniques. We transmit our knowledge to users and students by means of webinars, workshops, presentations and publications.