Highly polar compounds – II

The monitoring of highly polar compounds – particularly in low concentrations (ng/L range) – presents a great challenge. Compared with known, classical environmental pollutants (e.g., PCBs, pharmaceuticals, pesticides), there is a knowledge gap for highly polar compounds with regard to analytical methods, monitoring, regulation and water treatment. The objective of this project was to develop a sample pre-treatment to enhance the sensitivity of the existing HILIC and mixed-mode non-target screening for highly polar compounds, with a specific focus on halogenated methanesulphonic acids, including F3-MSA.

Enhancing sensitivity in identification of highly polar compounds

Highly polar compounds – also known as Persistent and Mobile Organic Compounds (PMOCs) – can easily spread in water and the soil. They are moreover often difficult to remove during wastewater and drinking water treatment. This makes them especially important for the water sector.

A HILIC and a mixed-mode non-target screening method were developed within the Joint Research Programme of KWR and the water utilities (Joint Research Programme).  These are suitable both for the semi-quantitative monitoring of known highly polar compounds, such as metformin and melamine-(derivatives), and for the screening and possible identification of unknown highly polar compounds.

HILIC and mixed-mode chromatography require the use of relatively high buffer concentrations in the mobile phase. For many compounds this produces a substantial signal suppression. This ultimately renders the method less sensitive (> 0.1 µg/L). In addition, with HILIC the peak shape is not optimal for many compounds, which also adversely affects the sensitivity. Given the urgency presented by these compounds, a lower detection limit is necessary.

Sample pre-treatment for lowering of HILIC screening detection limits

This project developed a sample pre-treatment for highly polar compounds, with a specific focus on small (per)fluoro compounds. Several methods are probably needed for the analysis of an as large as possible group of highly polar and ionogenic compounds, from permanently negatively-charged compounds to permanently positively-charged compounds.

The method develop increases the sensitivity of the existing HILIC and mixed-mode screening, and is being applied in a monitoring campaign to relevant samples from the Dutch and Belgian water cycle. Screening is being carried out for known and unknown compounds, the identification of new compounds, and the conduct of a toxicological risk assessment for the compounds detected. This will ultimately provide a better understanding of the presence of highly polar compounds in the water cycle and of its significance.

The project also involved participation in the supervisory group of the NWO-STW TooCOLD (Toolbox for studying the Chemistry Of Light-induced Degradation) project. Knowledge generated by the TooCOLD project is valuable for research into the chemical analysis of polar (transformation) products.

Improved screening and risk assessment

The developed sample pre-treatment improves the current method for the screening of highly polar compounds. In conjunction with the monitoring campaign, this provides insight into the presence of and the risk represented by highly polar and ionogenic compounds in specific drinking water sources in the Netherlands and Belgium. The project thus makes an important contribution to the monitoring of chemical drinking water quality.