Monitoring and determination of sulfonamide antibiotics (sulfamethoxydiazine, sulfamethazine, sulfamethoxazole and sulfadiazine) in imported Pangasius catfish products in Thailand using liquid chromatography coupled with tandem mass spectrometry

• Ultrasonic and LC-MS/MS was employed to determine SAs in Pangasius catfish.
• The highest concentration were 10.97, 6.23, 11.13 ng/g for SMD, SMT, SDZ.
• The highest concentration of SMX was found at 245.91 ng/g, higher than EU standard.
• All samples contaminated with SMX also contained SMT.
• More than one antibiotic was used for Pangasius catfish in the country of origin.

This research aimed to monitor the concentrations of sulfamethoxydiazine (SMD), sulfamethazine (SMT), sulfamethoxazole (SMX) and sulfadiazine (SDZ) in imported Pangasius catfish products in Thailand. The residues of the four sulfonamides (SAs) were analyzed by extraction process and liquid chromatography coupled with tandem mass spectrometry. The highest concentrations found were 10.97 ng/g for SMD, 6.23 ng/g for SMT, 11.13 ng/g for SDZ and 245.91 ng/g for SMX, which was higher than the European Union (EU) standard (100 ng/g). Moreover, all samples contaminated with SMX also contained SMT, indicating that more than one antibiotic was used for production in the country of origin. Because Thai standards for antibiotics in food have not been completely set, all contaminated discovered would not be considered to be an illegal food, in which antibiotic residues may affect human health in the long term. Therefore, antibiotic residues in Pangasius catfish products should be continually regulated and monitored.