August 2001

From Virginia Tech

Researchers building a trap for chromium six

BLACKSBURG, Aug. 26, 2001 -- Chromium three is an essential dietary mineral. Chromium six, as Erin Brokovich learned, can make you sick. Discovering which one is in your ground water is problematic, because six can decay to three by the time a water sample reaches the lab.

Virginia Tech researchers are testing an innovative method for capturing and preserving chromium six until it can be tested. They will present their research at the 222nd national meeting of the American Chemical Society Aug. 26-30 in Chicago.

Heavy metals can seep into groundwater from any number of sources -- such as from old landfills after a heavy rain. For the last 30 years, the EPA has been particular about how much metal can be in the water and analytical chemists have learned how to determine concentrations at very low levels. There are problems in looking at the form of a metal, however.

In the case of chromium three and chromium six, the number relates to the number of electrons on the molecule. Chromium six is carcinogenic because it is highly reactive -- interacting with the body's chemistry and functions, says Gary Long, chemistry professor at Virginia Tech.

"If you have a site with chromium contamination and you want to find out what form it is and whether it is in the groundwater, you could dig wells to sample the water. If you could do analysis immediately, you could avoid the problems that plague us in the lab," says Long. "The problem is that chromium six can be reduced to chromium three by light, organic material, or pH. Even if you work hard to get the samples, by the time you get to the lab, they no longer represent the real situation."

Now, Cherese D. Winstead-Allen, a Ph.D. student in chemistry at Virginia Tech, and Long are working on a method to trap chromium six on a plastic membrane in the field and preserve it until it can be tested in the lab. This is the first approach to work at the point of collection to preserve chemical information, Long says. The form of chromium cannot change once it's in the trap.

Chromium six is smaller than three. "Since three is bigger, it can't be trapped by our membrane system," says Long. "You can't trap a fox in a trap only big enough for a mouse."

The device, called a Selective Ion Trap (SIT), looks like a 35 mm film canister with a membrane at each end. Winstead-Allen explains that the SIT uses a polymer-based liquid membrane for the selective sorption and stabilization of specific oxidation states of chromium.

The multi-layer sampler can be used by people with no more training than their certification for drilling and sampling. There are no instruments to hook up. The new sampling device would be used with existing sampling technology.

The sampler is still being tested in the lab. The researchers have determined how to make the membranes and how they work best, and are beginning soil column tests.

Winstead-Allen and Long will present their research in the poster, "Selective ion trap for chromium III and chromium VI (ANYL 130)," at 7 p.m. Sunday, Aug. 26, in the Hyatt Regency Chicago Riverside Center. She began her research to detect ground water contamination while a master's student at Hampton University. Her hometown is Dover, Del. The research is funded by Winstead-Allenís National Science Foundation training grant, the Globalizing Interdisciplinary Research Incentive Grant, and the Graduate Research Development Program at Virginia Tech.


Cherese Winstead-Allen, PhD Candidate, Department of Chemistry Virginia Polytechnic Institute and State University (Virginia Tech) Blacksburg, VA 24061

540-231-8220 (w)

Dr. Gary L. Long, Associate Professor of Chemistry, Virginia Tech 540-231-7575 email:

This article comes from Science Blog. Copyright © 2004

Archives 2001 E