High-performance liquid chromatography-tandem mass spectrometry for the determination of sulfonamides in eggs

High-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) me- thod was developed for the determination of ten sulfonamides (SAs) in hen eggs. Conditions for reversed-phase HPLC and electrospray ionization MS/MS in the positive ion mode were optimized monitoring two characteristic mass transitions for each analyte. The egg samples were extracted with acetonitrile and defatted with n-hexane. Further solid-phase clean-up on a Strata-X polymeric cartridge was performed to obtain an extract suitable for the HPLC-MS/MS analysis. The calibration curves showed acceptable linearity in the concentration range from 1 to 45 µg/kg with correlation coefficients (r 2 ) above 0.992. Using two labelled internal standards (sulfamethazine- 13 C 6 and sulfamethoxazole- 13 C 6 ) the mean recoveries of SAs from egg samples spiked at 10 µg/kg were in the range of 91-146%. The applicability of this technique was dem - onstrated by the analysis of hen eggs available from local poultry farms. Among the 10 samples analyzed, none of them were found positive for the sulfonamides studied.