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Use your cell phone to detect mercury levels in water

Chemists say they've manufactured a sheet that changes color when dipped in mercury-tainted water, and that taking a picture of the sheet with a mobile phone or digicam can quantify the toxin's concentration.

A digital camera can detect the differences in the colors of various membranes submerged in mercury-tainted water.
J. M. Garcia et al.

It may not make your list of must-have camping gear, but a new sheet that detects mercury levels in water may prove useful to those who live or work downstream from industrial and mining sites (such as gold mines and coal-fired powered plants) and want to drink the local water.

When dipped in water for five minutes, the sheet, manufactured by chemists at the University of Burgos in Spain, signals the presence of mercury by turning red -- a process that can be seen with the naked eye.

Take a picture of that sheet with a digital camera, and you can learn the specific concentration of the mercury, a metal that is liquid at room temperature and has been found to cause long-term neurological issues after accumulating in the brain.

The researchers, who've just published their findings in the journal Analytical Methods, say they used the open access GIMP program to see the color coordinates, which are then compared with reference values to determine mercury concentration.

The sheet itself houses a fluorescent organic compound called rhodamine to detect the metal. "Rhodamine is insoluble in water," the researchers say in a news release. "But we chemically fix it to a hydrophilic polymer structure in such a way that when put into water it swells and the sensory molecules are forced to remain in the aqueous medium and interact with mercury."

They add that they can calibrate the sheet to change color according to different limits, i.e., have it turn red only when it exceeds the safety limit set by the Environmental Protection Agency.

In January, reps from more than 140 countries gathered in Geneva to establish the Minamata Convention, a global binding regulation that's named after the city in Japan where more than a thousand people lost their lives in the 1900s to mercury poisoning.

The United Nations Environment Program recently released a report called the Global Mercury Assessment 2013, which found that gold mines and coal-fired power plants in developing countries are the largest contributors to the rise in mercury emissions, and that the largest source of human exposure is through fish consumption. In the past century, mercury levels have doubled in the shallowest 100 yards of the world's oceans.

While the researchers call the water quality in their native country of Spain "excellent" owing to "highly efficient controls," they say they'd use this technique to study mercury levels in fish and detect the metal in certain spills.