Atomic absorption spectrophotometric determination of dibutyltin dilaurate in finished feeds: collaborative study.

Dibutyltin dilaurate is administered in the feed as an active drug for the removal of large roundworms, cecal worms, and several species of tapeworms from chickens and turkeys. The drug is extracted from finished feed with warm CHCl3, the CHCl3 extract is filtered, and a 25 ml aliquot is concentrated in the presence of methanol until all traces of CHCl3 are removed. The methanol solution is diluted and filtered to remove feed interferences, and then aspirated into an atomic absorption spectrophotometer with a triple-slot burner head, using an air/acetylene flame. The instrument response to tin at 286.3 nm is recorded. Recoveries of 100.5-101.9% tin were obtained for laboratory-prepared feeds. This method was collaboratively studied. The average recovery for dibutyltin dilaurate from 3 feed samples for 8 collaborators was 98.3% with an average coefficient of variation of 5.83%. The method has been adopted as official first action.