Researchers Develop Fast Screening Method For Water Testing

The technique applies a principle similar to that used in drug testing: samples are screened for the presence of a suspicious substance and only those that test positive are sent for further analysis.

Until now, there have been few screening methods for use by companies and environmental agencies charged with monitoring the nation's water supplies. Accurate water sampling of a large water system such as a river may require testing of as many as 100 samples from different locations in the river. Currently, each sample receives a full analysis, taking several hours per sample to complete.

"The problem with doing a full analysis on every sample is that you can spend hours analyzing a sample only to find out that it's below Environmental Protection Agency limits," said Anthony Andrews, an assistant professor of chemistry at Ohio University. "With our method, you won't get an exact result of the type or amount of contaminants in the water sample, but you'll know whether the sample is contaminated above or below EPA limits."

The method created by Andrews and former chemistry graduate student Glen Jackson can detect toxins at a level of just one-billionth of a gram per liter of water, well below current EPA standards, Andrews said.

The idea behind their technique may be simple, but the application is a bit complex. A fiber coated with a special chemical layer is dipped into a water sample. Any toxic molecules in the sample will be drawn to the chemical layer, preferring it over water. The molecule-covered fiber is placed in a gas chromatograph for separation. The injection port in the chromatograph is heated to about 250 degrees Celsius, which drives the molecules from the chemical layer on the fiber to another column where the molecules are separated.

Once separated, the toxic molecules are sent through a chamber filled with free electrons, which are quickly snapped up by the molecules. An electrode in a detection unit monitors the current produced by the electrons. The larger the change in current as electrons are grabbed, the higher the number of toxic molecules in the sample.

For their studies, the researchers screened water samples from the Hocking River in Athens in Southeastern Ohio for organochlorine pesticides such as DDT. Andrews said the process could be used to screen for any number of harmful substances, although some modifications would be required.

"The system we used could be constructed in any basic analytical laboratory and there's no reason to believe it couldn't be modified to detect any aqueous contaminant," Andrews said.

Now that he knows the technique can be used effectively, Andrews said he will try to make the process even faster, hopefully getting the run time down to five minutes or less.

The research was published in a recent issue of the journal Analyst. Andrews holds an appointment in the College of Arts and Sciences.

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Contact: Anthony Andrews, (740) 593-1658; andrewsa@ohiou.edu

Written by Kelli Whitlock, (740) 593-0383; kwhitlock1@ohiou.edu