Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/1/2005
Publication Date: 3/10/2006
Citation: Chen, G., Liu, L.S., Smith, E. 2006. Antibiotic screening in animal muscle without centrifugation and filtration. Pittcon 2006 Abstract. #2030-4
Technical Abstract: Analysis of antibiotic residues in foods of animal origin requires multi-step sample preparation including homogenization, extraction, enrichment and cleanup. Besides interfering chemical species, tissue particulates must be excluded by centrifugation and filtration to minimize scattering and attenuation in spectrometry. To simplify sample preparation, we proposed earlier a methodology that hyphenates sorbent extraction and solid-matrix time-resolved luminescence (SMTRL), and applied it successfully to tetracycline screening in milk. In this work its application is extended to antibiotics in animal tissues, illustrated by oxytetracycline (OTC) screening in catfish muscle. After homogenization in an EDTA solution, NaCl is added to the homogenate, in which three 10x6 mm glass-back C18 strips are immersed for 20 min for extraction and enrichment. Cleanup is carried out next by a 3-min water immersion and an one-pass water spray. Following reagent spotting and desiccation, TRL is measured directly on the sorbent surface. The integrated signal intensity shows a linear dependence r(2) = 0.9966) in a 0-4 µg/g OTC range and a typical <15% RSD. To screen OTC at 2 µg/g, the FDA regulatory tolerance level, a threshold is set at mean minus 3 standard deviation of 15 TRL data points at 2 µg/g. The method is friendly to both analysts and the environment since no organic solvent is needed. By eliminating centrifugation and filtration, equipment and labor costs are saved, sample throughput is greatly improved, and field assay becomes possible using a portable fluorometer.