Use hot water as a solvent to analyze contaminants in meat.

Concerns about food and environmental quality underscore the need for the rapid nontoxic analysis of food contaminants. That's why USDA-ARS scientists are developing cleaner analytical methods that use nontoxic solvents and subcritical water extraction to do the job.

ARS researchers (National Center for Agricultural Utilization Research, New Crops and Processing Technologies Research Unit, 1815 N. University St., Peoria, IL 61604) are testing a subcritical water extraction process that removes potential contaminants from samples of meat. Scientists start with highly purified water and heat it under pressure to 212 F. That's as hot as water gets before it boils. Then they flow the hot, compressed water through a sample of meat that's been mixed with an adsorbent to extract the pesticide residue.

The research team is using subcritical water extraction specifically to remove atrazine from beef kidney samples. Atrazine is an herbicide widely used to control weeds in some corn and soybean fields. The tolerance level for atrazine in livestock meat, fat and meat byproducts is 20 parts per billion (ppb). But this level may change after the U.S. Environmental Protection Agency reviews atrazine for its potential as a food and environmental contaminant.

The research has only been performed thus far on spiked samples in the laboratory. However, the method is complete and ready for testing on incurred or endogenous residues in real samples. Scientists see no reason why commercial testing would not follow if they are able to collaborate with interested partners.

The hot water mixture removes the contaminant from the kidney samples by dissolving the contaminant, once any bonds that have formed between the contaminant and the sample have been broken. The extraction solvent--the hot water-ethanol mixture--performs both these functions. The kidney sample is immersed in the solvent for several minutes before the solvent is flushed out of the extraction vessel, and this process is repeated three times. This allows more time for bond-breaking and dissolution to occur and helps to ensure complete recovery of the contaminant.

This technique has great potential for use with other contaminants. Ideally, one would use it for those contaminants that do not undergo any chemical reactions when they are exposed to the hot water-ethanol mixture. Besides being safer for the lab worker, the new method is faster than other analytical techniques. Investigators 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 method is about 90 minutes. In a single day, the researchers can analyze a minimum of 20 samples. The hot-water extraction process can also be used to analyze samples for other pesticides, antibiotics and their metabolic breakdown products.

Further information. Meredith Curren; phone: [phone]; fax: [phone]; email: [e-mail].