A Bridging Study Between Liquid Chromatography and Microbial Inhibition Assay Methods for Determining Amoxicillin Residues in Catfish Muscle

Abstract A bridging study was conducted to establish the correlation between a liquid chromatographic (LC) method and a microbial inhibition (Ml) method for analysis of amoxicillin residues in catfish muscle. The LC procedure involved precolumn derivatization with formaldehyde followed by LC separation with fluorescence detection. The Ml procedure used Bacillus stearothermophilus as the test organism and was validated in this study before the bridging investigation. The 2 methods were compared for determination of both fortified and incurred samples. No significant differences were found between the methods when all data were included in statistical computations. The linear correlation of LC means versus Ml means had a slope of 0.972 and a negligible intercept (1.0 ng/g), with a correlation coefficient of 0.9962. LC was more specific and showed better sensitivity than Ml for amoxicillin residues at ≤10 ng/g. For practical purposes, values obtained by the 2 methods can be considered equivalent.

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A Bridging Study for Oxytetracycline in the Edible Fillet of Rainbow Trout: Analysis by a Liquid Chromatographic Method and the Official Microbial Inhibition Assay

Journal of AOAC International ◽

10.1093/jaoac/82.4.866 ◽

1999 ◽

Vol 82 (4) ◽

pp. 866-870 ◽

Cited By ~ 4

Author(s):

Guy R Stehly ◽

William H Gingerich ◽

Connie R Kiessling ◽

Cutting Jeffrey H

Keyword(s):

Rainbow Trout ◽

Fish Species ◽

High Performance ◽

Chromatographic Method ◽

Inhibition Assay ◽

Microbial Inhibition ◽

Liquid Chromatographic Method ◽

Residue Depletion ◽

Liquid Chromatographic ◽

Bridging Study

Abstract Oxytetracycline (OTC) is a drug approved by the U.S. Food and Drug Administration (FDA) to control certain diseases in salmonids and catfish. OTC is also a likely control agent for diseases of other fish species and for other diseases of salmonids and catfish not currently on the label. One requirement for FDA to extend and expand the approval of this antibacterial agent to other fish species is residue depletion studies. The current regulatory method for OTC in fish tissue, based on microbial inhibition, lacks sensitivity and specificity. To conduct residue depletion studies for OTC in fish with a liquid chromatographic method, a bridging study was required to determine its relationship with the official microbial inhibition assay. Triplicate samples of rainbow trout fillet tissue fortified with OTC at 0.3,0.6,1.2,2.4,4.8, and 9.6 ppm and fillet tissue with incurred OTC at approximately 0.75,1.5, and 3.75 ppm were analyzed by high-performance liquid chromatography (HPLC) and the microbial inhibition assay. The results indicated that the 2 methods are essentially identical in the tested range, with mean coefficients of variation of 1.05% for the HPLC method and 3.94% for the microbial inhibition assay.

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