Fluorescent Molecules That Detect Metal Pollutants

Because excesses of certain metals in a person's diet pose a health threat, BYU researchers devised the molecules as an improved method of detecting and monitoring increased metal levels in the environment caused by mining, smelting, fossil fuel combustion and industrial use. Their work will be highlighted on the July 13 cover of the American Chemical Society's "Journal of Organic Chemistry" and in an accompanying article.

"Methods of tracking metal in water currently exist, but they're labor intensive and can be very slow," said co-author Paul B. Savage, associate professor of chemistry. "This research will let us create a sensor that continually measures metal in a sample of water as it flows by, making it easier to respond to any problems more quickly."

The article describes step-by-step how the team designed and created the molecules in the laboratory and reports how the molecules respond to zinc in the presence of ultraviolet light. The team has also recently published two papers about synthetic molecules created to indicate the presence of mercury and cadmium.

Exposure to high levels of mercury can result in nervous system damage, loosening of the teeth and corrosion and ulceration of the entire digestive tract. The Environmental Protection Agency has set a limit of 2 parts of mercury per billion parts of drinking water. Cadmium is a metal commonly found in industrial workplaces where ore is being processed or smelted. According to the EPA's Toxic Chemical Release Inventory, from 1987 to 1993 cadmium releases were primarily from zinc, lead and copper smelting and refining industries, with the largest releases occurring in Arizona and Utah. Chronic cadmium exposure has been linked to biological effects including renal dysfunction, calcium metabolism disorders and an increased incidence of certain forms of cancer. Zinc is an essential dietary element -- too little can cause health problems, but too much is harmful. Some of the signs of zinc overdose include gastrointestinal irritation, painful urination and low blood pressure.

To detect metals in water like zinc, BYU researchers first created compounds that seek out and bind to metal ions --those atoms with extra electrons. Next, they created small molecules that attach to the metal-binding compounds. The small molecules reveal the presence of bound metal ions by acting as fluorescent "reporters" -- when ultraviolet light is shined on them, the "reporters" glow brightly. If no metal ion is bound, the compounds remain dark. The color of the glow depends on the type and concentration of the metal ions present.

Plans are underway to develop a device that will allow industrial plants and water treatment facilities to track the concentration of metal ions in water and waste streams over time, said Savage.

"I'm very impressed with the quality of research from BYU," said Richard A. Bartsch, chair of the department of chemistry and biochemistry at Texas Tech University who has also researched flourescent sensors . "This study is a further extension their unique method of making doughnut-shaped molecules that can be used to detect metal ions, in this case zinc. I've been acquainted with BYU researchers for more than a decade and have the highest regard for their research."

The lead researcher was emeritus professor of chemistry Jerald S. Bradshaw. Assisting Bradshaw and Savage were BYU researchers Reed M. Izatt, R. Todd Bronson, Saowarux Fuangswasdi, Sang Chul Lee and collaborator Krzysztof E. Krakowiak.

"It's an honor for us to have our research highlighted on the cover of the Journal of Organic Chemistry," said Bradshaw.