Reversed-phase ion-pair liquid chromatographic determination of chlorophacinone residues in animal tissues

Retention time of chlorophacinone in black-tailed prairie dogs informs secondary hazards from a prairie dog rodenticide bait

BACKGROUND

Secondary toxicity in mammals and birds that consume animals containing residues of anticoagulant rodenticides represents a persistent conflict between conservation, agriculture and environmental contamination. Chlorophacinone residues in black-tailed prairie dogs (Cynomys ludovicianus) represent a secondary exposure hazard to predatory and scavenging avian and mammalian species in the Central Plains of the United States, especially considering efforts to re-establish black-footed ferrets (Mustela nigripes). Rozol(®) Prairie Dog Bait (chlorophacinone 0.005%) is registered to control black-tailed prairie dogs in ten states throughout the midwestern and western United States.

RESULTS

We fed Rozol Prairie Dog Bait to captive black-tailed prairie dogs for 2 days and analyzed their livers and whole bodies (without livers) for chlorophacinone residue on days 3, 5, 7, 9, 11, 14, 18 and 27 post-exposure. We found the greatest levels of residues in livers (x‾ = 5.499 mg kg(-1) ) and whole bodies (x‾ = 1.281 mg kg(-1) ) on day 3. Residues in both tissues declined rapidly over time, with estimated half-lives of approximately 6 days post-exposure. However, a risk assessment of secondary toxicity to non-target mammals indicated acute risks for mammalian species up to 27 days post-exposure and negligible risks for birds.

CONCLUSION

The results suggest that the greatest risk of secondary toxicity occurs ≤14 days post-application of Rozol Prairie Dog Bait and declines thereafter. This corresponds to the time when chlorophacinone residues are high, and prairie dogs exhibit signs of intoxication and are perhaps most susceptible to predation and scavenging. These results confirm that Rozol Prairie Dog Bait should not be used in areas where black-footed ferrets or other sensitive species occur. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Pindone residues in rabbit tissues: implications for secondary hazard and risk to non-target wildlife

Context Pindone is used to control rabbits in Australia and New Zealand, but the secondary non-target risks presented by pindone-poisoned rabbits are poorly known. Aims We aimed to generate new data on residual concentrations of pindone in poisoned rabbits for use in a review of the secondary poisoning risks posed to non-target animals in New Zealand. Methods Laboratory rabbits were offered pellet bait containing 0.25 g kg–1 pindone in three trials to simulate a range of bait uptake scenarios: single exposure and low or high chronic exposure. Residual pindone concentrations measured in body tissues of laboratory rabbits that had ingested known exposures of pindone were compared with those in wild rabbit carcasses collected after three pindone-baiting operations. Residues in the faeces of some laboratory rabbits were also measured. Key results Highest concentrations of pindone residues were in the liver and fat tissue of poisoned rabbits, with consistently lower concentrations in muscle tissue. A dose–response relationship between pindone exposure and liver residue concentrations was found only at the highest chronic exposures. Rabbit carcasses collected after field-baiting operations had generally higher pindone residue concentrations than did laboratory rabbits that had ingested known lethal amounts of bait. Unmetabolised pindone was excreted in rabbit faeces. Conclusions The occurrence of the highest residual pindone concentrations in rabbit liver was consistent with the known tissue distribution of anticoagulants in mammals; however, the co-occurrence of similar-range pindone concentrations in rabbit fat has not been previously described. Re-ingestion of soft faecal pellets (caecotrophy) in rabbits that have eaten pindone bait may function as a secondary exposure to increase or prolong their oral exposure to pindone. Some rabbits poisoned following field pindone-baiting operations are likely to have consumed well in excess of a lethal amount of bait. Implications Concentrations of residual pindone in fat and liver of poisoned rabbits suggest that secondary poisoning hazard to some non-target predators and scavengers is high. The lack of field-based assessments of the non-target impacts of pindone is a marked information gap that needs to be addressed.

Ion chromatography tandem mass spectrometry for simultaneous confirmation and determination of indandione rodenticides in serum

This paper describes a simple method for the simultaneous determination and confirmation of the indandione rodenticides in serum. After samples were extracted with 10% (v/v) methanol in acetonitrile and cleaned by solid-phase extraction, chromatographic separation was performed on an IonPac AS11 analytical column (250 x 4.0 mm) using gradient KOH eluent with 10% (v/v) methanol as organic modifier. Confirmation was depended on the extensive fragmentation of the indandione molecule under MS/MS conditions which provides sufficient structural information. Quantification was performed by negative electrospray ionization in multiple reaction monitoring mode. All the method parameters were validated. It was confirmed that this method could be used in clinical diagnosis and forensic toxicology.

Determination of linear alkylbenzenes in fish tissue by gel permeation chromatography and gas chromatography-mass spectrometry

A gel permeation chromatographic (GPC) procedure is described for separation of the long-chain linear alkylbenzenes (LABs) from fish muscle tissues. This technique was found to remove the matrix interference significantly and thereby improve the sensitivity of detection of LABs in the extracts. Gas chromatography-mass spectrometry (GC-MS) was then used to quantitate LABs in different species of fish and also fish from different locations on a transect from the outfalls from the Orange County Sanitation Districts, in the coastal waters of Southern California. The results are consistent with the proximity of the (sewage) source. The data, thus, show that LAB contents in fish tissues, especially that from white croaker (Genyonemus lineatus) are useful in assessing exposure to sewage residues in the marine waters. This method of concentrating LABs by GPC could be applicable to all other similar biological matrices.

Reversed-Phase Ion-Pair High-Performance Liquid Chromatographic Quantitation of Difethialone Residues in Whole-Body Rodents with Solid-Phase Extraction Cleanup

A reversed-phase ion-pair high-performance liquid chromatographic method was developed for the determination of difethialone residues in laboratory rats (Rattus norvegicus). Difethialone was extracted from rat tissue with chloroform/acetone/formic acid. The extracts were cleaned up by a solid-phase extraction (SPE) procedure using both silica and aminopropyl SPE sorbents, concentrated, and analyzed by reversed-phase ion-pair high-performance liquid chromatography. Difethialone was quantitated via ultraviolet absorbance at 262 nm. A surrogate compound, brodifacoum, was used to correct for method performance. The mean surrogate-corrected recoveries for whole ground rodent fortified at 0.2, 1.0, and 20 µg/g difethialone were 92.3 +/- 7.7, 84.8 +/- 6.6, and 90.2 +/- 3.1%, respectively. The method limit of detection was 0.054 µg/g.

Identification of pesticide poisoning in wildlife

The Wildlife Incident Investigation Scheme investigates incidents of suspected poisoning of wildlife (also honey bees and companion animals) by pesticides in the United Kingdom. The approach to these investigations has evolved over the past 30 years. Field investigations, post-mortem examinations, toxicological data and experience of previous poisoning incidents assist in the selection and interpretation of appropriate chemical analyses. Several 'multi-residue' and several 'individual compound' analytical methods for pesticides in wildlife are currently in use; these are described.

High-performance liquid chromatographic strategies for the determination and confirmation of anticoagulant rodenticide residues in animal tissues

A comprehensive approach to the analysis of anticoagulant rodenticide residues in animal tissues based on high-performance liquid chromatography (HPLC) has been developed. Residues of warfarin, coumatetralyl, difenacoum, brodifacoum, bromadiolone, diphacinone and chlorophacinone were extracted with chloroformacetone (1:1, v/v). Extracts were cleaned-up by an integrated gel permeation and adsorption chromatographic procedure which divided the rodenticides into two groups. Residues were then determined and confirmed using normal-phase, ion-pair and weak ion-exchange HPLC techniques. Ion-pair gradient separation resolved all seven rodenticides in a single chromatographic analysis. UV detection methods were employed for all seven rodenticides. Use of a diode array detection system permitted additional confirmation of residues down to 0.1 mg kg-1 by matching UV spectra and derivatives of spectra. Sensitive fluorescence detection was possible for the coumarin-based rodenticides but not for diphacinone and chlorophacinone. Post-column pH-switching fluorescence detection methods were shown to be superior to other methods of fluorescence detection of coumarin-based rodenticides. Recoveries from spiked liver tissue were around 90% at levels from 0.05 to 1 mg kg-1. Detection limits of around 0.002 mg kg-1 for most rodenticides and of 0.01 mg kg-1 for warfarin could be achieved with animal tissue extracts.