Mercury is a deadly and persistent toxin in our environment, and one that is easily spread in our air and water from sources such as coal-burning power plants. And because a large segment of mercury contamination in humans comes through contaminated fish in polluted water, being able to determine the mercury content in water can help people avoid consuming both tainted fish and water.
But because current testing methods aren't simple or cheap, and samples have to be 'sent off' to a lab to be analyzed, a new easier method may really help broaden the scope of mercury testing in water.
Researchers at the University of Burgos, in Spain, have developed test sheets that change color when exposed to mercury in water, which will enable quick, cheap, and on-site mercury detection. The results of the test can be determined by eye (similar to Litmus test strips in science class), but for more accuracy, the sheet can be photographed with a mobile phone and compared with color reference values using an image editor program on the phone.
"Changes can be seen by the naked eye and anyone, even if they have no previous knowledge, can find out whether a water source is contaminated with mercury above determined limits." - José Miguel García
The test sheets contain rhodamine, a florescent organic compound which acts as the mercury sensor, and the make-up of the test sheets can be varied according to the parameters of the testing. The research team calibrated these sheets to change color when the mercury contamination in the water exceeds 2 parts per billion of divalent mercury -Hg(II), which is the limit set by the EPA for water intended for human consumption.
In many developing areas of the world, coal plants, industrial discharges and runoff from mineral extraction sites can all add to the mercury load in water, so having a fast and affordable method of determining the levels of mercury pollution could be a big step forward for human health.
The full results of the study are available in Analytical Methods: Sub-ppm quantification of Hg(II) in aqueous media using both the naked eye and digital information from pictures of a colorimetric sensory polymer membrane taken with the digital camera of a conventional mobile phone.