Collaborative study of the 2,4-dinitrophenyl ether multiresidue method for use in determining four carbamate pesticides.

Eight laboratories tested the 2,4-dinitrophenyl ether method for determining carbamate pesticide residues by gas-liquid chromatography. Propoxur, carbofuran, carbanolate, and carbaryl in apples, corn, green beans, and a leafy vegetable (kale, collards, cabbage, or turnip greens) were determined at the fortification levels of 0.1, 0.2, and 0.5 ppm. Average recoveries of propoxur were 87-95%; carbofuran, 87-100%; carbanolate, 89-102%; and carbaryl, 77-92%. No serious background problems were encountered, other than that from field-incurred carbaryl residues in apples. The study revealed the need for certain precautions in determining carbaryl because of its instability in analytical operations. The method has been adopted as official first action.