A comparison of three bioassay techniques for the detection of chloramphenicol residues in animal tissues

In two experiments a total of six young steers were injected intramuscularly with 11mg/kg chloramphenicol (CAP) twice daily for 3 days. Another steer was injected with double the dose, and two steers were left untreated. Eighteen hours after the last CAP injection all steers were euthanized. Samples of kidney, liver, and muscle were collected. No microbial inhibition was obtained with any of the tissues with the swab test on premises (STOP). Only kidney from the steer given 22 mg of CAP/kg was positive by the microbial inhibition test. All muscle samples were positive for CAP by thin-layer chromatography/bioautography (TLCB). The CAP detection limit was 0.6 ppm for TLCB and 5 ppb for a gas chromatographic CAP method. Levels of CAP in muscle and liver decreased when stored at -20 degree C.