LIQUID-CHROMATOGRAPHIC DETERMINATION OF FLUORESCENT DERIVATIVES OF 6 SULFONAMIDES IN BOVINE SERUM AND MILK

A rapid and sensitive liquid chromatographic (LC) method with fluorome tric detection was developed to detect sulfadiazine, sulfathiazole, su lfamethazine, sulfamonomethoxine, sulfamethoxazole, and sulfadimethoxi ne residues in bovine serum and milk. p-Aminobenzoic acid (PABA) was a dded as an internal standard. The sulfonamides were extracted from sam ples and derivatized with fluorescamine, and 50 mu L was injected into a Nova-Pak C-18 LC column and eluted with acetonitrile-10 mM potassiu m phosphate (30 + 70, v/v). The sulfonamides were detected fluorometri cally (excitation, 390 nm; emission, 475 nm), and their retention time s ranged from 6.2 to 16.5 min without interference from coextractives. The detection limit for standard sulfonamide solution was 0.1 ng/mL; the calibration curves were linear between 1 and 100 ng/mL in the pres ence of PABA as internal standard, Recovery rates of sulfonamides from spiked samples (1 and 10 ppb) were 95.4-107.2 and 81.4-89.6% for seru m and 80.7-91.1 and 62.6-84.1% for milk, respectively.