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A specific and sensitive liquid chromatography-tandem mass spectrometry method was developed and validated for the determination of the anticoagulant rodenticide diphacinone (DPN) in mouse and rat liver. Tissue samples were extracted with a mixture of water and acetonitrile containing ammonium hydroxide. The extracted sample was cleaned up with a combination of liquid-liquid partitioning and dispersive solid phase extraction. Chromatographic separation was achieved using a Waters X-Bridge BEH C-18 LC column (50 mm, 2.1 mm ID, 2.5 μm particle size) with detection on a triple quadrupole mass spectrometer in multiple reaction monitoring (MRM) mode. The monitored transition for DPN was m/z 339.0 → 167.0 for quantitation and 339.0 → 172.0 and 339.0 → 116.0 for confirmation. The linear range was 0.5 to 375 ng/mL. The average precision of DPN, represented by the relative standard deviation of the observed concentrations, was 7.2% (range = 0.97% - 20.4%) and the average accuracy, represented by the relative error, was 5.8% (range = 1.06% - 14.7%). The recovery of DPN fortified at 3 different levels averaged 106% in rat liver and 101% in mouse liver. The established method was successfully used to determine DPN residue levels in Polynesian rats (Rattus exulans) and mice (Mus musculus) fed two different formulated baits containing DPN. The observed residue levels were consistent with values observed in other rodent studies. However, the amount of bait consumed was lower for the novel baits evaluated in this study. [ABSTRACT FROM AUTHOR]

The eradication or control of invasive small Indian mongooses from islands likely requires toxic baiting when removal by trapping proves insufficient. The one toxic bait currently registered for mongooses in the United States has relatively low palatability and efficacy for mongooses. Developing and registering a new pesticide can be very expensive, while funding for developing toxicants for mongooses is limited. Once registered, use of a toxic bait may be hindered by other factors, such as public opposition to an inhumane toxicant, poorer efficacy than expected, or if the toxic bait is difficult for applicators to apply or store. Therefore, we conducted a product feasibility assessment comparing the registration and use potential of toxic baits for mongooses containing either bromethalin, diphacinone, para-aminopropiophenone (PAPP), or sodium nitrite (SN). We estimated that a diphacinone bait would be the cheapest and fastest to register, and more application methods may be allowed compared to the others. On the negative side, we ranked diphacinone as the least humane toxicant of the four, largely due to a prolonged time to death following exposure and onset of symptoms. However, this interval also increases the probability that the antidote can be administered following an accidental exposure. If an alternative toxicant is required, use of a bromethalin, PAPP, or SN bait would likely be limited to bait stations or burrow baiting due to primary risks to non-target species. A bromethalin bait would be the cheapest and fastest to register of the three, particularly if a bait that is already commercially available proved efficacious for mongoose. However, we ranked bromethalin lower than PAPP or SN for overall humaneness. A PAPP bait would be slow and the most expensive to register. An SN bait would be challenging to formulate into a palatable bait with a reasonable shelf life. Although we focused on the U.S., mongooses are invasive in many parts of the world and the regulatory and use requirements for pesticides in other countries are generally comparable. In addition, our feasibility assessment can serve as a template or starting point for managers considering development of toxicant products for vertebrate pests. [ABSTRACT FROM AUTHOR]