Researchers who presented their work on Tuesday, August 22 at the 254th National Meeting and Exposition of the American Chemical Society said they are utilizing the “coffee-ring effect” to make sense of the multiple components in a single drop of water.
This method is being perfected so that someday, the public could use it to test their own tap water.
The coffee-ring effect is the occurrence in which particles in a single droplet of water gather around the edges of the droplet as the water evaporates. “The residue patterns for tap water are like fingerprints that can be used to identify what's in a sample,” said Rebecca Lahr, Ph.D. Of Michigan State University.
Lahr said this experiment is relevant especially during a time when the U.S. is plagued with water contamination in cities such as Washington, D.C.; Charleston, West Virginia; Toledo, Ohio; and the most famous one in recent years, the lead contamination of the waters in Flint, Michigan. (Related: Los Angeles homes, schools and workplaces still heavily contaminated with lead.)
“If you are worried about your drinking water, it can be overwhelming to look at a water-testing fee schedule to decide which water tests to run. You have to know what you are looking for beforehand,” Lahr said.
After several experiments, the researchers got residue patterns for tap waters from communities across southern Michigan. They also made synthetic tap water solutions to imbibe the condition of community tap waters with varied amounts of hardness, alkalinity, chloride, copper, iron, sodium, sulfate, and total dissolved solids.
So at its present state, can the coffee-ring effect be used to understand the intricacies of the lead contamination of the Flint water supply?
“It's too early to say. The idea here is to develop a faster and cheaper way to screen samples to raise red flags when there should be further analyses performed. This method won't have the sensitivity of standard analytical techniques, but it's much cheaper,” Lahr said.
For the meantime, the coffee-ring effect can serve its purpose in the classroom, which is to get students curious and eager to learn more about environmental science. “I'm amazed by how powerful it is as an educational tool. Students bring in their own samples and quickly see the differences in the patterns left behind,” Lahr said.
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