Determination of MCPA residue in wheat using high performance liquid chromatography tandem mass spectrometry

A method for the determination of MCPA residue in wheat samples was developed using high performance liquid chromatography tandem mass spectrometry(HPLC-MS/MS).The preparation procedure of sample was also applied to determine the MCPA residue in soil(with HPLC-UVD).The sample was extracted with 0.04 mol/L NaOH,adjusted pH value below 3 with phosphoric acid.Liquid-liquid partitioning with ethyl acetate,and further cleanup by graphitized carbon black(GCB) were followed.The mass spectrometer with interface of electro-spray in negative ion mode(ESI-) was operated in multi-reaction monitoring(MRM) mode.The precursor/product ion transitions(199/141 m/z) were monitored.Average fortified recoveries ranged from 75.0%-112.1% with relative standard deviations 2.7%-14.8% in plants,wheat and straw samples.Lower Practical Levels(LPL) were 0.5 mg/kg for straw,0.05 mg/kg for wheat,and 0.5 mg/kg for wheat plants,respectively.The method was used to determine MCPA residues in various matrices from supervised residue field trials in China.