Determination of ethalfluralin in canola seed, meal, and refined oil by capillary gas chromatography with mass selective detection.

Ethalfluralin is a herbicide that is effective for weed control on a wide variety of crops, including canola. A method is described for the determination of ethalfluralin residues in canola seed, meal, and refined oil. Residues are extracted from canola sample matrixes with acetonitrile. An aliquot of the extract is diluted with water and purified by C(18) solid-phase extraction prior to analysis by capillary gas chromatography with mass selective detection. For all three sample matrixes, the method has a validated limit of quantitation of 0.02 microg/g and a limit of detection of 0.006 microg/g. Recoveries averaged 96 +/- 7% for canola seed, 87 +/- 6% for canola meal, and 89 +/- 5% for refined oil. In a magnitude-of-residue study, canola seed from field plots that had been treated with ethalfluralin at one to three times the maximum label rate for weed control were found to contain no detectable residue of the herbicide.