HPLC DETERMINATION OF SULFADIAZINE RESIDUES IN COHO SALMON (ONCORHYNCHUS-KISUTCH) WITH CONFIRMATION BY LIQUID-CHROMATOGRAPHY WITH ATMOSPHERIC-PRESSURE CHEMICAL-IONIZATION MASS-SPECTROMETRY

High-performance liquid chromatography and postcolumn derivatization w ith fluorescamine were used to determine sulfadiazine (SDZ) residues i n muscle and skin from salmon dosed with Tribrissen. Determinations in the fish ranged from 0.2 to 21600 ng of SDZ/g; in each fish tested, t he concentration of SDZ in the skin was at least twice that in the mus cle. Liquid chromatography with atmospheric pressure chemical ionizati on mass spectrometry (LC-APCI/MS) was used to confirm SDZ residues. In -source collision induced dissociation was optimized to produce a mass spectrum containing the protonated molecule and four fragment ions. S ulfadiazine was confirmed in muscle fortified with 10 ng of SDZ/g and in muscle from fish dosed with SDZ by the accurate agreement of ion in tensity ratios generated from muscle compared with those generated fro m SDZ standard injections.