The addition of fluoride to drinking water or toothpaste is widespread and is mainly used for dental health and as a preventative measure against bone diseases.
However, an excessively high concentration of fluoride can lead to health problems. Clear symptoms of this fluorosis, that occurs in developing countries in particular, are brownish-yellow stains on the teeth.
Fluorinated drinking water is not being monitored everywhere so that children in particular can ingest too much fluoride. BAM Federal Institute for Materials Research and Testing has developed a very simple rapid colour test, which can help determine the fluoride concentration more easily in the future.
A change in the colour of a paper strip shows how much fluoride is dissolved in the water, similar to a litmus test to determine the pH value. The concentration is indicated by yellow-green dots, the darker the spot, the more fluoride is present. A dye developed by BAM is used in the procedure.
"This BODIPY amidothiourea dye is applied as a small spot to a strip of nitrocellulose that responds to the fluoride ion" says Pichandi Ashokkumar, who, together with Knut Rurack, has developed the test.
The paper strip is then immersed in a glass of water for example. The analyst can read the concentration by the change in the perceived colour and the test strip is reusable because of the particular chemical dye chosen. As simple as it sounds, it was very difficult to implement because fluoride is bound to thiocarbamide by hydrogen bonds.
Bonding triggers an electron transfer, which weakens the dye’s fluorescence so that the dye will appear darker. "The trick then was to develop a process that, in spite of the aqueous environment, still binds the fluoride and not the water's oxygen to the thiocarbamide" says project manager Knut Rurack. As the tests indicate, the scientists have succeeded. In order to evaluate the colour change better than with the human eye, the test strip’s colour may also be detected with the built-in camera of a mobile phone.
Fluorination of drinking water is common practice. In Europe this is practiced in the UK, Ireland and Switzerland and the U.S. also fluorinates the drinking water. In 2011, the U.S. Environmental Protection Agency (EPA) reduced the benchmark for fluoride in drinking water from 1 to 0.7 parts per million (ppm) and thus joined other countries.
The detection limit of the new fluoride test is 0.2 ppm. The test was conducted using different water samples, including tap and sea water. "The test is not disturbed by other ions in tap water or salt water," says Rurack. However, too high a concentration of phosphate, as in some toothpastes, may cause problems. The scientists envisage a potentially large field of application for their testes especially in Asia and Africa.
Dr. rer. nat. Knut Rurack
Department 1 Analytical Chemistry; Reference Materials
"Test-Strip-Based Fluorometric Detection of Fluoride in AqueousMedia with a BODIPY-Linked Hydrogen-Bonding Receptor", Pichandi Ashokkumar, Hardy Weißhoff, Werner Kraus and Knut Rurack, Angew. Chem. Int. Ed. 2014, 53, 2225-2229
Dr. Ulrike Rockland | idw - Informationsdienst Wissenschaft
New findings help to better calculate the oceans’ contribution to climate regulation
14.11.2018 | Jacobs University Bremen gGmbH
How algae and carbon fibers could sustainably reduce the athmospheric carbon dioxide concentration
14.11.2018 | Technische Universität München
Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.
Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...
Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.
In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...
On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.
When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure
Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...
Physicists at ETH Zurich demonstrate how errors that occur during the manipulation of quantum system can be monitored and corrected on the fly
The field of quantum computation has seen tremendous progress in recent years. Bit by bit, quantum devices start to challenge conventional computers, at least...
09.11.2018 | Event News
06.11.2018 | Event News
23.10.2018 | Event News
14.11.2018 | Materials Sciences
14.11.2018 | Health and Medicine
14.11.2018 | Life Sciences