A BRIDGING STUDY BETWEEN LIQUID-CHROMATOGRAPHY AND MICROBIAL INHIBITION ASSAY-METHODS FOR DETERMINING AMOXICILLIN RESIDUES IN CATFISH MUSCLE

A bridging study was conducted to establish the correlation between a liquid chromatographic (LC) method and a microbial inhibition (MI) met hod for analysis of amoxicillin residues in catfish muscle. The LC pro cedure involved precolumn derivatization with formaldehyde followed by Le separation with fluorescence detection. The MI procedure used Baci llus 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 significa nt differences were found between the methods when all data were inclu ded in statistical computations. The linear correlation of LC means ve rsus MI 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 MI for amoxicillin residues at less th an or equal to 10 ng/g. For practical purposes, values obtained by the 2 methods can be considered equivalent.