Determination of sulphonamides in foods by liquid chromatography with postcolumn fluorescence derivatization

A postcolumn fluorimetric derivatization procedure for the detection and simultaneous determination of several sulphonamides using liquid chromatography was developed. The derivatization method involves the reaction of the sulpha drugs with o-phthaldialdehyde and beta-mercaptoethanol. The chromatographic elution programme consisted of an initial isocratic step with acetonitrile-water (3:97) for 5 min followed by a linear gradient up to a 40:60 mixture over 15 min. The proposed method was applied to routine quality control analysis to ensure the absence of sulphonamides in foods, resulting in an overall mean recovery of 95% (n = 45) at fortification levels of 0.04, 0.1 and 0.5 mu g/ml.