DETERMINATION AND CONFIRMATION OF IDENTITIES OF FLUMEQUINE AND NALIDIXIC, OXOLINIC, AND PIROMIDIC ACIDS IN SALMON AND SHRIMP

A previously published liquid chromatographic (LC) method for determin ing residues of flumequine (FLU) and nalidixic (NAL), oxolinic (OXO), and piromidic (PIR) acids in catfish tissue was applied to salmon and shrimp muscle. Identities of all 4 residues in salmon and shrimp were confirmed by gas chromatography/mass spectrometry (GC/MS). The tissue is homogenized with acetone, the acetone extract is defatted with hexa ne, and the quinolones are extracted into chloroform, The extract is f urther purified by first partitioning into base and then back-extracti ng from a solution acidified to pH 6.0. Analytes are determined by LC with simultaneous UV and fluorescence detection. Muscle tissue was for tified with each quinolone at 5, 10, 20, 40, and 80 ng/g. Average reco veries and relative standard deviations (RSDs) for salmon, which repre sent an average of the 5 levels for each analyte, ranged from 75.9 to 90.8% and from 2.25 to 6.40%, respectively, Average recoveries and RSD s for shrimp ranged from 81.3 to 91.2% and from 7.34 to 10.7%, respect ively, Identities of OXO, FLU, NAL, and PIR were confirmed in extracts of salmon and shrimp tissue fortified at 10 ng/g by determination of decarboxylated quinolones by GC/MS, Four diagnostic ions were monitore d for OXO, FLU, and PIR, and 5 ions were monitored for NAL, All ion re lative abundances were within 10% of those calculated for standard dec arboxylated quinolones, Optimum conditions for decarboxylation and GC/ MS confirmation are given.