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Abstract
A time‐resolved luminescence (TRL) assay was developed for effective screening of tetracyclines in chicken muscle at the European Union (EU) maximum residue level of 100 ng g−1. The method involves extraction of the tetracyclines with McIlvaine–ethylenediamine tetraacetic acid (EDTA) buffer, centrifugation, solid‐phase extraction (SPE) clean‐up, formation of an Eu(III) complex, and then measurement of the TRL signal at 615 nm (excitation at 388 nm). Samples fortified with tetracycline (TC), oxytetracycline (OTC) or chlortetracycline (CTC) gave a linear response over the range of 0–1000 ng g−1, with relative sensitivities 5.4×, 2.4×, and 1×, respectively. Limits of detection for TC, OTC, and CTC were 3.5, 8, and 19 ng g−1, respectively. Examination of the least sensitive case, CTC, showed no overlap between the TRL of control chicken extracts and those that had been fortified with 100 ng g−1 CTC. The within‐day variation for these samples averaged 3.1% relative standard deviation (RSD), as did the day‐to‐day variation. The method was tested with blind control and fortified samples over the range of 20–500 ng g−1 CTC to illustrate its utility. Other veterinary drugs approved for chickens in the US (enrofloxacin, nicarbazin, tylosin) did not interfere. This method can provide a useful alternative to microbial screening assays for tetracyclines.
#Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture.
Acknowledgments
Limei Yun and Susan Braden are thanked for technical assistance, and Steve Lehotay for helpful discussions. John Phillips is thanked for his assistance with the statistical analysis.
Notes
#Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture.