ARS | Publication request: Use of a portable time-resolved fluorometer to determine oxytetracycline residue in four fruit crops

Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 30, 2010
Publication Date: February 1, 2011
Citation: Chen, G., Liu Guyu 2011. Use of a portable time-resolved fluorometer to determine oxytetracycline residue in four fruit crops. Food Chemistry. 127:264-269.

Interpretive Summary: Worldwide, oxytetracycline (OTC) is used in fruit and vegetable crops to prevent and treat bacteria diseases. In the U.S., the Environmental Protection Agency approved its use in apple, pear, peach, and nectarine; and set tolerance at 350 ng/g. OTC residues in 12 varieties of these fruits are determined by europium-sensitized luminescence (ESL) using a unique, portable instrument with microsecond resolution. After extracted in an acidic buffer and filtration, OTC is cleaned up. ESL’s high specificity results in low background noise, so in-situ quantitative analysis is possible without prior chromatographic separation. Linear response is observed over 10-10000 ng/g range, with 1.74-4.44 ng/g limit of detection. Over 82.0% recovery and reproducible results are achieved. The specificity of ESL technique allows elimination of chromatography; while portable instrumentation and simplified sample preparation enable in-situ analysis. Immediate results avail timely decision making; so hopefully market recall can be minimized and food safety improved.

Technical Abstract: Worldwide, oxytetracycline (OTC) is used in fruit and vegetable crops to prevent and treat bacteria diseases. In the U.S., the Environmental Protection Agency approved its use in apple, pear, peach, and nectarine, and set tolerance at 350 ng/g. OTC residues in 12 varieties of these fruits are determined by europium-sensitized luminescence (ESL) using a unique, portable instrument with us resolution. OTC is extracted in Na2EDTA-NaCl-McIlvaine buffer at pH 4, and after filtration, cleaned up using hydrophilic-lipophilic balance cartridges. ESL’s high specificity results in low background noise (24.7 ng/g), so in-situ quantitative analysis is possible without prior chromatographic separation. Linear response is observed (r2 = 0.9914-0.9998) over 3 orders of magnitude (10-10000 ng/g), with 1.74-4.44 ng/g limit of detection and 1.86% average relative standard deviation. Recovery is 82.0% and 83.3% at 100 and 350 ng/g, respectively.