Screening tests for sulfa drugs and/or dinitrobenzamide coccidiostats and their monoamino metabolites in chicken livers.

Two procedures were developed for the simultaneous determination of 0.1 ppm sulfaquinoxaline and sulfadimethoxine, 1.0 ppm Zoalene and nitromide, and/or 0.1 ppm of their reduced coccidiostat metabolites from the same sample of chicken liver. Both methods include blender extraction of 5 g liver with chloroform-ethyl acetate (1 + 1), adsorption of the drugs and metabolites on neutral alumina, and subsequent elution with 0.2M carbonate buffer (pH 11.0). In Method A, all parent drugs and coccidiostat metabolites were partitioned into dichloromethane, following the addition of a small amount of tetrabutylammonium hydroxide (TBAH). The presence of the dinitrobenzamides was confirmed by the formation of a color with TBAH, which occurs when the solvent is concentrated (Zoalene = green; nitromide = red). Sulfa drugs and coccidiostat metabolites were detected by the Bratton-Marshall reaction after thin layer chromatographic (TLC) separation. Method B separates the individual classes by selective extraction techniques. The coccidiostats and their metabolites were extracted from the buffer eluate by ethyl acetate-dichloromethane (3 + 1) before ion pairing: sulfa drugs were extracted with dichloromethane after ion pairing with TBAH. The detection techniques were similar to those described for Method A.