1. Sulfadiazine, 2 μg mL-1; 2. sulfamerazine, 0.48 μg mL-1; 3. sulfametoxydiazine, 1 μg mL-1; 4. sarafloxacin, 2 μg mL-1; (a) 0~5 min: 25% B; 5~7 min: 25% B→30% B; 7~11 min: 30% B; 11~13 min: 30% B→25% B. (b) 0~5 min: 25% B; 5~7 min: 25% B→35% B; 7~11 min: 35% B; 11~13 min: 35% B→25

Figure 2: Chromatograms of the analyte standard solutions using gradient programs.