Submitted to: Analytica Chimica Acta
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/27/2004
Publication Date: 8/20/2004
Citation: Schneider, M.J., Chen, G. 2004. Time-resolved luminescence screening assay for tetracyclines in chicken muscle. Analytica Chimica Acta. Interpretive Summary: Tetracyclines are a group of broad-spectrum antibiotics that are used in both medical and veterinary applications. Use of antibiotics in animals used for food has generated concern as the presence of these residues in food may lead to increased microbial resistance in humans. Efficient methods are thus needed to monitor levels of these residues in food. We have developed a screening assay for tetracyclines in chicken muscle that is effective at the low maximum residue level (100 ng/g) set by the E. U.. In this approach, chicken samples are rapidly extracted with buffer, the extracts are cleaned up by solid phase extraction, and the levels of the tetracyclines present are then measured using a very sensitive technique, time resolved luminescence. Fortification experiments showed good recoveries were obtained. No overlap was observed between the luminescence intensity of control chicken extracts and those fortified with 100 ng/g chlortetracycline. The method was tested with a set of fortified blind samples to illustrate its use as a screening assay. This procedure provides an alternative to microbial screening assays for tetracyclines and is a promising tool for use by regulatory agencies.
Technical Abstract: A time-resolved luminescence assay was developed for effective screening of tetracyclines in chicken muscle at the E.U. tolerance level of 100 ng/g. The method involves extraction of the tetracyclines with McIlvaine-EDTA buffer, centrifugation, solid phase extraction clean-up, formation of a Eu (III) complex and then measurement of the time-resolved luminescence signal at 615 nm (excitation at 388 nm). Fortified standard curves with tetracycline, oxytetracycline or chlortetracycline showed different sensitivities of the three analytes, in the following order: tetracycline > oxytetracycline> chlortetracycline. Examination of the least sensitive case, chlortetracycline, showed no overlap between the time-resolved luminescence of control chicken extracts and those which had been fortified with 100 ng/g chlortetracycline. The method was tested with blind control and fortified samples over the range of 20-500 ng/g chlortetracycline in order to illustrate its utility. This method can provide an alternative to microbial screening assays.