Detection of low-level carbadox residues in animal feeds by high pressure liquid chromatography

The high pressure liquid chromatographic (HPLC) method is capable of detecting from 1 to 0.024 ppm methyl 3-(2-quinoxalinyl-methylene)carbazate-N1,N4-dioxide (carbadox). Carbadox is extracted from the feed with 2% NH4OH in acetone, passed through a liquid-liquid partition, subjected to HPLC, and detected by using a 365 nm detector. No feed materials or other active drug ingredients produced false positive results.