Simultaneous determination of sulfa drugs and tetracyclines in feeds and animal tissues by high-performance liquid chromatography

This study aimed to develop a high-performance liquid chromatographic method for simultaneous determination of six sulfa drugs, three tetracyclines antibiotics and carbadox in feeds and animal tissues. Four successful conditions were established: 1. On LiChrosorb RP-C18 column with water: acetonitrile (95:5, v/v) s mobile phase and UV detector at 254 nm to separate SDA, SMM, STA, SDM, SMT and SQO. 2. On ultrasphere ODS Column with water: acetonitrile (85:15, v/v) as mobile phase and detected at UV 254 nm to separate SDA, SMM, STA, SMT, SQO and SDM. 3. On LiChrosorb RP-C18 column with water: isopropanol (93:7, v/v) as mobile phase and detected at UV 254 nm to separate STA, SMT, Carbadox, TC, OTC and CTC. 4. On Alltech RP-C18 column with water: dimethylformamide (72:28, v/v) as mobile phase and detected at UV 280 nm to separate STA, SMT, OTC, Carbadox and CTC. The recoveries of the drugs in feeds were between 85-99%; in animal tissues, 69-80%. Eleven out of 20 feed samples were found with prohibited sulfa drugs or tetracyclines added. One pork sample with OTC residue and two pig liver samples with total sulfa drugs residue exceeding the maximum tolerance limits were detected from the 21 meat samples analyzed. The lowest detection limits of residual drugs were between 1.0 - 5.0 ppb in feeds; 2.0 - 12 ppb in animal tissues.