Liquid chromatographic determination of nicarbazin in feeds

A new liquid chromatographic method has been developed for determination of nicarbazin in feeds. Approximately 40 g feed is extracted with 200 mL acet onitrile-water (80 + 20, v/v). An aliquot of the extract is filtered and as sayed using a reversed-phase isocratic method that measures the 4,4'-dinitr ocarbanilide moiety of nicarbazin at a wavelength of 340 nm, For medicated feeds, the method uses a standard linear range of 5 to 100 mu g/mL. For low er levels, a linear range of 50 to 150 ng/mL can be used. The method has a limit of detection of 250 ng/g and a limit of quantitation of 500 ng/g in a 40 g feed sample. Recovery was 99.1%, with a range of 95.2 to 101.8%. In t he typical U.S. dosing range of 27 to 113.5 g/ton, the precision of the met hod based on one analyst, one day, and 2 weighings ranged from 2.8% (113.5 g/ton) to 4.7% (27 g/ton).