Screening of sulphonamides in egg using gas chromatography-mass-selective detection and liquid chromatography-mass spectrometry.

A rapid extraction and clean-up procedure for sulphonamide antibiotics in eggs suitable for both GC-MSD and LC-MS end determinations has been developed. The drugs were extracted using acetonitrile, acidified using acetic acid and cleaned-up using cation- and anion-exchange. For determination by GC-MSD, extracts were derivatised with diazomethane followed by pentafluoropropionic acid anhydride. For LC-MS extracts were taken up in water and used directly. The methodology developed was validated at the 100 and 25 microg kg(-1) levels, equivalent to the MRL and one quarter of the MRL. Results for the GC-MS procedure were quantitated against deuterated sulphadiazine with relative recoveries ranging from 54% for sulphachloropyridazine to 135.5% for sulphamethazine. Recoveries for the LC-MS procedure ranged from 33% for sulphaguanidine to 92% for sulphamethazine and sulphadimethoxine.