@entity40676 Solid Phase Extraction Cleanup and Isotope Dilution Liquid Chromatography-Tandem Mass Spectrometry for the Determination of XXXX in Fish Muscles.

@entity40676 @entity14030 @entity21562 @entity6865 @entity6334 @entity70569
UNASSIGNED: Florfenicol (FFC) residues in foods are regulated as the sum of @entity21562 and its metabolites measured as @entity70569 ( @entity6334 ). An isotope dilution LC-MS/MS method utilizing @entity40676 ( @entity14030 ) SPE cleanup is established for the accurate determination of @entity6334 in fish muscles (i.e., salmon and tilapia) after acid catalyzed hydrolysis. Comparisons of the @entity14030 SPE cleanup procedure with other cleanup procedures such as mixed-mode cationic (MCX) SPE and solid supported liquid-liquid extraction were performed. Quantification of @entity6334 in fish muscles was accomplished by using matrix-matched calibration with @entity6334 -D3 as the internal standard. The method was validated with @entity6334 fortified fish muscles at three different levels (50, 100, and 200  g/kg). Conversion of FFC to @entity6334 by acid catalyzed hydrolysis was evaluated and found to be >= 88%. The recoveries of @entity6334 in fish muscles at the three fortification levels ranged from 89 to 106%, and @entity6865 were  <=9% in all cases. The LOD values in salmon and tilapia muscles were 0.13 and 1.64  g/kg, respectively. The LOQ values in salmon and tilapia muscles were 0.29 and 4.13  g/kg, respectively. This method is suitable for the application in routine control of FFC in fishes according to its residue definition.
