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Liquid chromatography coupled to electrospray mass spectrometry and tandem mass spectrometry has been used for the determination and quantification of 21 sulfonamides and two potentiators (ormethoprim, trimethoprim) in milk. Separation using high-performance liquid chromatography was achieved in less than 6 min for all compounds on a short (4.0 x 50 mm, 3 micron) reversed-phase column. After sample clean-up, time-scheduled single-ion monitoring (SIM) yielded detection of sulfonamides in milk from low ppb level to the ppt level. The strategy used to detect, confirm and quantify sulfonamides in milk samples was as follows: (a) pre-screening (and cp3firmation) of target and non-target sulfonamides by precursor ion scan and/or multiple reaction monitoring experiments using generic product ions; (b) quantification of identified target compounds by monitoring their protonated molecule ions in a time-scheduled SIM experiment; (c) further confirmation, if necessary, by selected reaction monitoring using characteristic product ions. |
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