Analysis of Veterinary Drug Residues in Imported and Domestic Crawfish Using Liquid Chromatography—Mass Spectrometry

Aquaculture production has greatly increased over the past few decades, and will continue to grow as the world fisheries become overfished and demand for seafood increases. With increased production comes more intense cultivation methods and heavy use of formulated feeds that may contain veterinary drug residues. Currently no antibiotics are allowed in the U.S. for crawfish aquaculture; yet, detectable levels of various antibiotics have been found in imported seafood samples.The FDA is responsible for testing aquaculture products entering the United States, but only has the capabilities to test a minimal amount of those imports. Additionally, for crawfish there is only one published FDA method to test for chloramphenicol, and they have yet to publish a method to test for multiple veterinary drug residues. Therefore, the objective of this study was to develop a method that could test various antibiotics in commercially available frozen crawfish, and use that method to test imported and domestic crawfish. Crawfish were obtained from the Aquaculture Research Station at Louisiana State University, and were used as blank crawfish to validate a method to test for chloramphenicol, florfenicol, enrofloxacin, ciprofloxacin, and sarafloxacin using liquid chromatography—mass spectrometry. In short, the tissue was extracted with dilute acetic acid and acetonitrile with added sodium chloride. After centrifugation, the extract was evaporated to dryness with nitrogen and reconstituted in mobile phase. The extract was passed through a syringe and 0.2μm PVDF membrane filter into an auto-sampler vial. A Waters Acquity TQD LC/MS/MS operated in the positive and negative ion mode; ciprofloxacin, enrofloxacin, and sarafloxacin in positive ion mode, and florfenicol and chloramphenicol in negative ion mode. Results indicated acceptable method performance characteristics for selectivity, linearity, accuracy (recovery), precision (RSD), and MDL and LOQ. Though ciprofloxacin did show some of the lowest recoveries, and chloramphenicol did have quite high RSD values. Retail samples tested negative for most of the veterinary drug residues with the exception of chloramphenicol in one Louisiana brand at an average concentration of 0.91 ng/g, and in a Chinese brand at an average concentration of 0.52 ng/g