Liquid chromatographic determination of epimerization of chlortetracycline residue to 4-epi-chlortetracycline residue in animal feed, using McIlvain's buffer as extractant.
A method for studying McIlvain's solution as a factor in epimerization of chlortetracycline in animal feed has been developed. McIlvain's solution (McBuffer) was used previously to extract oxytetracycline (OTC), tetracycline-HCl (TC-HCl), and chlortetracycline-HCl (CTC-HCl) from animal feed because it gave the best recoveries for all 3 tetracyclines; however, the McBuffer solution caused epimerization of CTC-HCl to 4-epi-chlortetracycline (4-epi-CTC). Recovery results were 30-40% lower for CTC than for OTC and TC from the same sample extract. The levels of concentration tested for CTC and 4-epi-CTC were 10 ppm, the detection limits for both were 3 ppb, and the calibration curves were linear between 5 and 80 ppm for both CTC-HCl and 4-epi-CTC. The present study shows that CTC recoveries averaged 35% lower because of epimerization initiated by the use of McBuffer in the extraction procedure.
Martinez
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EE
Food and Drug Administration, Denver Federal Center, CO 80225.
Shimoda
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D000821:Animal Feed / Q000032:analysis*; D002021:Buffers; D002751:Chlortetracycline / Q000032:analysis*; D002853:Chromatography, Liquid; D004350:Drug Residues / Q000032:analysis*; D007202:Indicators and Reagents; D010118:Oxytetracycline / Q000032:analysis; D012015:Reference Standards; D013237:Stereoisomerism
D002021:Buffers; D007202:Indicators and Reagents; D002751:Chlortetracycline; D010118:Oxytetracycline