Haloxyfop determination by gas chromatography/tandem mass spectrometry in eggs

Haloxyfop is a pre/post-emergence herbicide with known organ toxicities and teratogenic effects in mammals. The European Union Commission on Food Safety has an established maximum residue limit of 10 μg/kg in all agricultural products including eggs. A sensitive highly specific method would be of value in determination of haloxyfop residues in foodstuffs such as eggs.

The Michigan State University Veterinary Diagnostic Lab (MSU VDL) developed a method for the extraction of haloxyfop from eggs based on popular QuEChERS (quick, easy, cheap, effective, rugged, and safe) methodologies, essentially providing acetonitrile extracts following treatment with high ionic strength additives. Extracts derivatized with trimethylsilyl (TMS) groups were examined by gas chromatography/tandem mass spectrometry using developed multiple reaction monitoring (MRM) methodology.

The MSU VDL received eggs from chickens exposed to 760 μg/kg haloxyfop in flaxseed. Haloxyfop-TMS m/z 374→73 MRM setting enabled quantitation across the 1-50 ppb range in comparison with an ibuprofen MRM transition as internal standard.

The determined limit of quantitation was 2.5 ng/g, and the method successfully identified haloxyfop residues in five of six batches of the chicken eggs, with nonzero values ranging from 2.7 to 14.5 ng/g. These values were consistent with flaxseed incorporation into the diet at 4-7% and known excretion into eggs at 2-3% of daily haloxyfop exposure, and establish the utility of the method in identifying regulatory noncompliance and adulteration of food sources.