Using Hot Water as a Solvent
|Concerns about food and environmental quality underscore the need for quick, nontoxic analysis of food contaminants. That's why Agricultural Research Service scientists are developing cleaner analytical methods that use nontoxic solvents and a new technique called subcritical water extraction.
In laboratory studies, ARS postdoctoral research chemist Meredith S.S. Curren in Peoria, Illinois, is testing subcritical water extraction to remove potential contaminants from meat samples. Working under the direction of ARS chemist Jerry W. King at the National Center for Agricultural Utilization Research, Curren starts with highly purified water and heats it under pressure to 212 °F. That's as hot as water in a teakettle gets before boiling. Then she flows the hot, compressed water through a meat sample that's been mixed with an adsorbent to extract the pesticide residue.
Curren is using subcritical water extraction to remove atrazine from beef kidney samples. Atrazine is an herbicide widely used to control weeds in Midwest corn and soybean fields. The tolerance level for atrazine in livestock meat, fat, and meat byproducts is 20 parts per billion. But this level may change after the U.S. Environmental Protection Agency reviews atrazine for its potential as a food and environmental contaminant.
Federal agencies like USDA's Food Safety and Inspection Service need safer analytical methods like this one to check pesticide levels in foods. Traditional extraction techniques use toxic organic solvents, which are costly and unsafe for laboratory workers and the environment. These solvents also require safe disposal, which adds to the cost of their use. Filtered, purified water systems, however, are inexpensive and don't require a disposal system.
"Besides being safer for the lab worker, our method is faster than other analytical techniques," says Curren. She streamlined the technique by performing extraction and sample cleanup concurrently. Cleanup of lipids and proteins from the sample is required since the subcritical water extracts other components in addition to the target pesticide. The total time for analyzing atrazine in beef kidney with this new method is about 90 minutes. In a single day, the researchers can analyze a minimum of 20 samples.
The hot-water extraction method can also be used to analyze samples for other pesticides and antibiotics and their metabolic breakdown products. Use of this method by food-testing laboratories will ensure that the food we eat continues to be among the safest in the world.—By Linda McGraw, Agricultural Research Service Information Staff.
Meredith S. S. Curren and Jerry W. King are in the USDA-ARS New Crops and Processing Technologies Research Unit, National Center for Agricultural Utilization Research, Peoria, IL 61604; Curren's phone (309) 681-6236, King's phone (309) 681-6203, fax (309) 681-6686.
"Using Hot Water as a Solvent To Analyze Atrazine in Meat" was published in the October 2001 issue of Agricultural Research magazine.