Determination of Chlormequat and Mepiquat Residues in Food by High Performance Liquid Chromatography-Tandem Mass Spectrometry

A high performance liquid chromatography-electrospray ionization tandem mass spectrometric(HPLC-ESI MS/MS) method was developed for the determination of two plant growth regulators,e.g.chlormequat and mepiquat,in rice,wheat flour,pear,tomato and ketchup samples.The samples were extracted with methanol-water(1∶1,by volume) and cleaned up on a Strata-X-C solid-phase extraction column.The target compounds were separated on an Agilent ZORBAX RX-SIL(1.8 μm,3.0 mm×100 mm) chromatographic column by equivalently elution using acetronitrilie-10 mmol/L ammonium acetate(containing 0.1% formic acid) as mobile phase.The residues of chlormequat and mepiquat were determined under the electrospray positive ionization(ESI+) and multiple reaction monitoring(MRM) mode,and quantified by the matrix-matched external standard method.The calibration curves for chlormequat and mepiquat showed good linearities in the range of 0.20-10 μg/L with correlation coefficients(r2) no less than 0.999 0.The limits of quantitation(S/N≥10) and limits of detection(S/N≥3) were in the range of 0.05-0.15 μg/kg and 0.02-0.05 μg/kg,respectively.The average recoveries of chlormequat and mepiquat from rice,wheat flour,pears,tomato and ketchup matries at three spiked levels of 0.20,5.0,10 μg/kg were in the range of 82%-102% and 80%-103%,respectively,with relative standard deviations of 3.8%-9.6% and 1.9%-10.0%,respectively.The method was sensitive and accurate,and could meet the requirements for the determination of chlormequat and mepiquat in foods.