We use fluorescence to identify counterfeit money. Could we use a very similar technique to assess the quality of fresh water? K. Khamis and colleagues suggest tryptophan-like fluorometers to do so. In their paper, they discuss a novel way of measuring pollutants thanks to this procedure, and also propose novel mathematical models to better conduct in situ experiments, thus avoiding the storage and transportation of samples.
When water is polluted with sewage or farm waste, the amount of dissolved organic matter (DOM) increases. Organic matter contains sugars, lipids, nucleic acids and proteins. The latter are biomolecules which have a very interesting property: fluorescence. Folded proteins are fluorescent, mainly because of the tryptophan residues, and they can absorb and emit light at 280 nm and 350 nm, respectively. As a consequence, fluorescence may be directly correlated with the quantity of organic waste dissolved in water.
However, very few fluorescence sensors have been developed to measure OM in freshwater, mostly because freshwater systems are quite dynamic in space and time. Moreover, certain factors such as temperature or suspended inorganic particles often alter the measurements. Temperature allows electrons to return to their ground-energy state without emitting any fluorescence. Additionally, soil particles can scatter light and reduce the fluorescence signal by up to 80%.
But Khamis and his team did not see a problem in this. On the contrary, they saw this fact as an opportunity to develop new tryptophan-like sensors and state-of-the art algorithms to minimize the effect of quenchers like temperature or soil particles. Researchers located in situ detectors near Birmingham to study urban streams and near Nottingham to study groundwater; they also took a wide set of samples which were analyzed in the lab.
The data obtained from these analyses was then compared to the in situ measurements. Using these two different groups of data, they elaborated mathematical models to compensate the effect of quenchers. These algorithms were fundamental to ensure the accuracy of the quantifications. When the corrections were applied, in situ and lab results appeared to correlate much better.
Thanks to these amazing results, scientists may soon be able to develop cheap, small sized, highly accurate tryptophan-like pollution sensors for freshwater. These detectors could be easily used in the field, hence completely eliminating the need to collect, preserve, store and carry around thousands of samples.
To access the full article, download a copy for free* by clicking the link below:
In situ tryptophan-like fluorometers: assessing turbidity and temperature effects for freshwater applications
K. Khamis, J. P. R. Sorensen, C. Bradley, D. M. Hannah, D. J. Lapworthc and R. Stevens
Environ. Sci.: Processes Impacts, 2015, 17, 740-752
Fernando Gomollon-Bel is a PhD Student at the ISQCH (CSIC–University of Zaragoza). His research focuses on asymmetric organic synthesis using sugars as chiral-pool starting materials towards the production of fungical transglycosidase inhibitors.
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