A team of chemists at University of Burgos in Spain have produced a sheet that acts similarly to litmus paper, but it changes its colour in the presence of water contaminated with mercury. And if being able to see this with a naked eye is not ground-breaking enough for you, when the new membrane is photographed with a mobile phone device, the concentration of the toxic metal can even be quantified.
The problem of water contamination with mercury is particularly severe in developing countries, where it poses serious health risks. It is introduced to the environment through industrial emissions and mining waste.
High concentrations of the toxic metal in humans is due to consumption of contaminated fish. Numerous reports, such as the Global Mercury Assessment 2013, focus on testing the concentrations of the metal in streams and rivers.
The new technique developed by the scientists provides a cheap and easy way to measure the metal concentrations in water. The study was just published in the journal ‘Analytical Methods’ with a lead author José Miguel García.
The method of detection is very simple. The fine sheet that the researchers created should only be placed in the water. If there is presence of mercury above the determined limits, the sheet turns red.
In addition to this, a simple photograph of the sheet, taken with a digital camera of a mobile device, allows an accurate estimation of the exact concentrations. The only requirement is to have an image treatment software, many of which are readily available online and free, to see the color coordinates.
The florescent organic compound ‘rhodamine’ within the membrane acts as a sensor for mercury. It is insoluble in water, but required additional chemical fixes of the hydrophilic polymre structure so that it swells when put in water. In this way, the sensory molecules remain in the aqueous medium and interact with the toxic metal.
The composition of the sheet can also be adjusted to specific parameters. The team calibrated it according to the limits established by the Environmental Protection Agency (EPA) of the United States: 2 ppb (parts per billion) of divalent mercury –Hg(II).
In addition to this, the team developed methods for other elements- including iron and cyanide. They tested the quality of Spanish drinking water and concluded that it is “excellent.”
The technique allows a rapid detection of mercury concentrations in spills, or in its presence in fish.