Micropollutants are synthetic or natural compounds that end up in aquatic environments, usually at low concentrations. These compounds can include pharmaceutical and chemical waste, as well as pesticide residue. The accurate detection and removal of micropollutants is critical to ensuring that communities have access to safe drinking water. Scientists can also make use of micropollutant-extracting techniques to assess the environmental state of rivers and seas, and to ensure that items such as medical equipment are in pristine condition. “Extracting micropollutants from water samples usually involves the use of toxic solvents,” notes NanoEX project coordinator Detlef Lohse, from the Department of Science and Technology at the University of Twente, the Netherlands. “Sample preparation is not only environmentally unfriendly; the process can also be very time-consuming.” This is in part because multiple steps in sample preparation are required. In addition to using up a lot of manpower, traditional extraction techniques can lead to errors and mistakes, as well as difficulties in reproducing findings.
The NanoEX project, funded by the European Research Council, sought to address these sampling challenges by developing a means of simplifying and streamlining the whole process. At the core of the project was the concept of nano-extraction. Building on the findings of a previous ERC-funded project, called DDD (Diffusive Droplet Dynamics), Lohse and his colleagues successfully immobilised and ‘fixed’ nanodroplets – oil droplets in water measurable on the nanoscale – onto a solid surface. The team was confident that their nano-based technique would make it easier and simpler to identify and extract micropollutants. “The process works like this,” explains Lohse. “We first form these nanodroplets on a substrate, inside a narrow chamber. The sample solution, which might potentially contain micropollutants, is then injected into the chamber. The contaminants – insoluble in water – are soluble in the oil droplets and are thus ‘extracted’ into the droplets.” Importantly, these small nanoscale droplets are ‘pinned’ to the substrate. This means that they remain on the substrate, even as the sample solution flows through the chamber. “After this, we can then detect if there are extracted compounds in the droplets, by applying techniques sensitive to micropollutants to the nanodroplets on the surface,” says Lohse. “Alternatively, we can collect the small droplets from the chamber, and analyse them by using common analytical instruments in a lab.”
Accurate micropollutant analysis
Lohse and his team believe that the technique pioneered in the NanoEX project will greatly simplify the sample preparation process for sensitive chemical analysis, and also improve the accuracy of the findings. The technique can already be used for ensuring water quality and carrying out environment analyses, as well for forensics and medical diagnostic purposes. Research institutes, analytical chemists and public health authorities all stand to benefit. “Next steps include simplifying how we collect these small droplets from the substrate,” says Lohse. “At the moment, we need to carefully bring them together, to form a larger droplet for analysis. There is a risk here that we might leave some droplets behind.” Nonetheless, Lohse and his team are confident that they are on the right path. “Many compounds can be extracted by the NanoEX technique,” he adds. “Another benefit is that the technique can be applied in tandem with almost any analytic instruments that you would find in a research lab.”
NanoEX, micropollutants, water, aquatic, medical, nanodroplets, contaminants