Measurement of the temporal transferability of indoxacarb to cotton gloves from spot-on treated dogs.

The objectives of the studies reported herein were to (1) determine the minimum number of petting simulations required to load the maximum amount of test substance (indoxacarb) residue onto cotton gloves (the sampling medium) from spot-on treated dogs; and (2) using the number of petting simulations that resulted in maximal transfer, to conduct a second study that measured amount of residue dislodged via petting a dog as a function of the time interval after application. Maximal percent transfer of indoxacarb from spot-on treated dogs occurred after 10 repetitive petting simulations (consisting of 3 directional pet strokes each) and was approximately 1-2% of amount applied. Temporal measurements of mean indoxacarb transferability followed an exponential decay function, beginning at approximately 2% transfer on the day of application, and declining to 0.08% by d 30 post treatment.

Determination of florfenicol amine in channel catfish muscle by liquid chromatography.

A method for quantifying florfenicol amine (FFA) in channel catfish muscle was validated according to U.S. Food and Drug Administration guidelines. FFA is the proposed marker residue for the veterinary antibiotic florfenicol in catfish muscle for regulatory surveillance purposes. The method includes acid hydrolysis followed by sample cleanup with ethyl acetate extraction, basification, solid-phase extraction, and quantitation by liquid chromatography with UV detection. The assay was validated at 5 concentrations in the range of 0.075-35 microg/g muscle. The overall mean recovery of FFA from fish tissues fortified at these concentrations ranged from 85.7 to 92.3%, 4.8-17.2% relative standard deviation (RSD). The assay limit of detection was 0.044 microg/g muscle based on analysis of control muscle. Catfish muscle samples containing incurred florfenicol residues were analyzed in quintuplicate with RSD < 5%. Acid hydrolysis has previously been demonstrated to convert florfenicol and its known metabolites to FFA and to release a significant amount of FFA from nonextractable florfenicol residues in tissues containing incurred residues in other species. By using acid hydrolysis, this method should yield a more accurate estimate of the total florfenicol-related residue level in muscle tissue from florfenicol-treated catfish than could be achieved by solvent extraction alone.