A method for the determination of lasalocid, an antibiotic and coccidiostat, in grease and fat is described. The manufacture of lasalocid produces a grease-like residue as a waste byproduct. Recently this byproduct has been shown to have been illegally introduced into the animal feed
chain. Therefore, a quantitative and confirmatory procedure to analyse for lasalocid in this matrix is needed. A portion of grease/oil sample was extracted into hexane-washed acetonitrile, and a portion of the extract was then applied to a carboxylic acid solid-phase extraction (SPE) column
for concentration and clean-up. The SPE column was washed with additional hexane-washed acetonitrile and ethyl acetate/methanol, after which lasalocid was eluted with 10% ammoniated methanol. The eluate was evaporated to dryness, redissolved in (1:1) acetonitrile–water and filtered through
a PTFE syringe filter. Confirmation and quantitation of lasalocid in the final extract employed a triple quadrupole LC-MS/MS. The method was applied to grease and oil samples containing from 0.02 to 34 000 mg kg−1 of lasalocid.
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Document Type: Research Article
Denver Laboratory, US Food and Drug Administration (USFDA), Denver, CO, USA
Animal Drugs Research Center, US Food and Drug Administration (USFDA), Denver, CO, USA
Publication date: August 3, 2015