Liquid chromatographic method for determination of furazolidone in premixes and complete feeds: collaborative study

A liquid chromatographic (LC) method for determining furazolidone in finished feeds and premixes was collaboratively studied. Finished feed sample is extracted with acetone-water (93 + 7) on a Goldfisch apparatus, extracting solvent is removed, and the residual material is dissolved in warm DMF. A solution of tetraethylammonium bromide is added, the fat layer is removed, and the sample is clarified by filtration and injected onto a reverse phase LC system with detection at 365 nm. Premixes, extracted by shaking with DMF and diluted so that the final furazolidone concentration is about 55 micrograms/mL, are chromatographed and detected the same as finished feed samples, using a mobile phase of acetonitrile-2% acetic acid (20 + 80). Ten commercial feed samples were preweighed and supplied to 14 collaborators. The 5 matched pairs were chosen to represent the following allowed levels: 0.0055, 0.022, 0.033, 2.2, and 22%. Two familiarization samples at the 0.0055 and 11% levels were also supplied. Instructions called for a single analysis of each sample. Two results were eliminated by the Dixon test. The coefficients of variation, following treatment by the ranking test, ranged from 2.0 at the 22% level to 6.5 at the 0.0055% level. Calculated F-values are not significant (P greater than 0.01) except for the 0.0055% level samples extracted overnight. This method has been adopted official first action.