...From the pages of Agricultural Research magazine
QuEChERS Method Catches Pesticide Residues
QuEChERS (pronounced catchers) is not a cool, new
way of spelling the position we usually associate with masked, padded,
often grimy players toiling behind home plate during baseball and softball
It's actually a catchy name for a new approach to analyzing
pesticide residues in fruits and vegetables.
Steven J. Lehotay, an ARS
chemist at the Microbial Biophysics and Residue Chemistry Research Unit,
Eastern Regional Research Center in Wyndmoor, Pennsylvania, and a visiting
scientist, Michelangelo Anastassiades, from a government laboratory
in Stuttgart, Germany, developed the QuEChERS method, which stands for
quick, easy, cheap, effective, rugged, and safe. It can be used with
a wide range of pesticides and food types.
Current methods of extracting pesticide residues from
food samples and preparing them for analysis are time consuming, expensive,
and labor intensive. The new, streamlined approach makes it easier and
less expensive for analytical chemists to examine food.
Routine monitoring serves to enforce laws, protect the
consumer, provide data for risk assessment and pesticide reregistration,
ease international trade, market residue-free products, and help verify
organic food labeling.
The U.S. Department of Agriculture and other organizations
started the Pesticide Data Program in May 1991 to test commodities in
the U.S. food supply for pesticide residues.
Using QuEChERS, a single chemist can prepare a batch of
10 previously chopped samples in about 30 minutes with $1 worth of materials
per sample. This gives at least fourfold lower material costs and fourfold
greater sample throughput per analyst than traditional methods. Lehotay
says the method combines different steps, which means there is less
chance for error.
A single, easy-to-clean Teflon tube is the only item to
be washed and reused, eliminating all the glassware used in conventional
methods. Furthermore, less than 10 milliliters of solvent waste is generatedmuch
less than the 75-450 milliliters generated by other methods.
Key to the new approach is the development of a rapid
procedure called dispersive solid-phase extraction. This technique quickly
removes water and nontarget compounds with magnesium sulfate and a primary-secondary
More than half the produce samples tested in the United
States typically do not have measurable residues, and less than 1 percent
of tested samples exceed tolerance levels, according to the U.S. Food
and Drug Administration (FDA). Consumers should always wash, peel, or
cook produce to help remove residues.
The term "tolerance" is used to describe the
maximum amount of a given pesticide or its breakdown products allowed
to remain in or on food commodities. The U.S. Environmental Protection
Agency sets tolerance levels in the United States, and state and federal
monitoring programs enforce these legal limits.
Several monitoring laboratories, including a few in the
FDA, are evaluating QuEChERS. Lehotay believes that it will someday
substantially increase monitoring rates and lower costs of pesticide
residue analysis.By Jim
Core, Agricultural Research Service Information Staff.
This research is part of Food Safety (Animal and Plant
Products), an ARS National Program (#108) described on the World Wide
Web at www.nps.ars.usda.gov.
Steven J. Lehotay
is in the USDA-ARS Microbial Biophysics
and Residue Chemistry Research Unit, Eastern Regional Research Center,
600 East Mermaid Lane, Wyndmoor, PA 19038-8598; phone (215) 233-6433,
fax (215) 233-6442.
"QuEChERS Method Catches Pesticide Residues" was published in the July 2003 issue of Agricultural Research magazine.