Abstract: The analysis method on six sulfonamides in milk, namely sulfamerazine, sulfamethazine, sulfamethoxazole, sulfamonomethoxine, sulfadimethoxine and sulfadiazine was studied. Milk containing sulfonamides was extracted with chloroform -acetone mixture (2:1, V/V) twice. The extract was combined and evaporated to dry, then dissolved in methanol-0.08% acetic acid (60:40, V/V). Purified by hexane, the extract was analyzed in HPLC in a C18 column with methanol-acetic acid-H2O as eluent. Sulfonamide residues were detected by a UV detector and their concentrations were determined with calibrated curves. A good linear relationship exists for all residues in concentration range of 0.01～1.0 mg/L, while the detection limit for sulfadiazine and sulfamerazine and sulfamethazine is 0.010 mg/L and for sulfadimethoxine and sulfamonomethoxine and sulfadimethoxine 0.015 mg/L. The analysis procedure needs total time less than 3 h with an addition recovery for sulfonamides about 69.4%～ 123.5% and coefficient of variation less than 8%. The method is rapid, simple and accurate.

Key words: sulfonamide, milk, analysis, RP-HPLC