Abstract:

A method was established for the simultaneous determination of bipyrazone and cypyrafluone in wheat by solid-phase extraction and high performance liquid chromatography-tandem mass spectrometry. Bipyrazone and cypyrafluone in wheat samples were extracted by acidified acetonitrile, salted out by sodium chloride and anhydrous magnesium sulfate, cleaned up by HLB solid phase extraction column, separated by ACQUITY UPLC BEH C18 column with gradient elution of water (containing 0.1% formic acid) and acetonitrile (containing 0.1% formic acid) as the mobile phase, detected by positive electrospray ionization using multiple reaction monitoring (MRM) mode and finally quantified by external standard method of matrix calibration curve. Good linear relationship displays in the concentration range of 2-100 μg·L^-1 for bipyrazone and cypyrafluone with correlation coefficient (r) greater than 0.998. The limits of detection of them are 2 μg·kg^-1, and the limits of quantitation are 6 μg·kg^-1. At three spiked concentration levels of 6, 20 and 50 μg·kg^-1, the average recoveries of bipyrazone are 93.9%-99.6%, with relative standard deviations (RSDs) of 2.2%-4.8%, and the average recoveries of cypyrafluone are 83.6%-90.7%, with RSDs of 1.4%-4.5% (n=6). The method is sensitive, accurate and suitable for determination of bipyrazone and cypyrafluone in wheat.

Key words: solid-phase extraction, high performance liquid chromatography-tandem mass spectrometry, bipyrazone, cypyrafluone, wheat