Simultaneous analysis of thirteen diuretics residues in bovine milk by ultra‐performance liquid chromatography/tandem mass spectrometry

A simple, rapid, sensitive and specific method used to screen and confirm multi-class diuretics residues in whole bovine milk is described. Thirteen drugs of four different classes including carbonic anhydrase inhibitors, loop, thiazide and potassium-sparing diuretics were extracted from whole milk by acetonitrile followed by further purification with hexane. The analytes were separated using an ACQUITY UPLC BEH C18 column and detected by electrospray ionization tandem mass spectrometry (ESI-MS/MS). MS data acquisition was performed by a time-scheduled multiple reaction monitoring program, selecting two ion transitions for each target compound. The overall average recoveries based on matrix-fortified curves fortified with diuretics at three levels ranged from 80.6 to 108.8% with the coefficients of variation ranging from 2.6 to 19.7% (n = 6). The limits of quantitation (LOQs) of diuretics in bovine milk were 5.0 microg/kg for spironolactone and 0.5 microg/kg for other analytes, respectively.