Determination of zinc phosphide residues in corn (Zea mays) grain, fodder, and forage

In five US states representative of commercial corn production, zinc phosphide baits were deployed for rodent control in corn fields, and subsequent residues were determined in grain, fodder, and forage samples. Results showed that dilutions of the solid zinc phosphide materials with a variety of solids resulted in unacceptably high variation. The most promising carrier was found to be propylene glycol. The method limit of detection was determined to be 7, 10, and 6 ng in ground grain, ground silage, and ground fodder, respectively. Losses of 15.6, 44.8, and 32.1% were found for grain, silage, and fodder, respectively, after storage.