Study On Simultaneous Determination Of Plant Growth Regulator Residues In Bean Sprout Based On Mass Spectrometry

BackgroundPlant growth regulators are a class of synthetic compounds with phytohormone activity. On behalf of their functions for enhancing quality and yield of agro-products, they are used in practical agricultural production widely. On one hand, they have brought great economic benefits of agriculture. On the other hand, they caused a threat to humans’ health at the same time. Series of reports relating to PGRs abuse have been revealed more frequently. It has become one of the major factors affecting our people in food safety area. Currently, focusing on PGRs, our country was lack of developing multiple residue analysis methods and establishing related limit standards. Thus,in order to solve this problem, it’s necessary to develop an novel analytical methods to simultaneously detect multiple PGRs in a simple, rapid and efficient way. ObjectiveThrough optimizing the pretreatment methods, chromatography and mass spectrometry conditions, this study developed a solid phase extraction-gas chromatography-mass spectrometry method and a Qu ECHERS-ultra performance liquid chromatography-tandem mass spectrometry method for spontaneously determination of five kinds of plant growth regulator residues in bean sprouts respectively. In addition, it provided theoretical basis and data supporting for the establishment of relevant national standards. Methods1. SPE-GC-MSHomogenatized samples were initially extracted with acetonitrile containing 0.5%(v/v) acetic acid via ultrasonic for 30 minutes in 50 ℃ and clean-up by using MCS cartridge. After methyl etherification in boron trifluoride diethyl etherate for 45 minutes in 70 ℃, samples were purged with nitrogen standing by injection. Target analytes were separated by gas chromatography with capillary column(HP-5MS, 30m×0.25 mm,0.25μm) and determined by a mass spectrometer with electron impact(EI) at selected ion monitoring(SIM) mode. The content was calculated by calibration matrix-external reference method.2. Qu ECHERS-UPLC-MS/MSHomogenatized samples were initially extracted with acetonitrile containing 0.5%(v/v) acetic acid and cleaned up by a Qu ECHERS reaction system consisting of Mg SO4 and C18.Target analytes were separated by WATERS ACQUITY UPLC HSS T3 column(100mm×2.1mm,1.7μm)with gradient elution using acetonitrile and 2mmol/L ammonium acetate solution as mobile phases. Negative electrospray ionization with multiple reactions monitoring mode was used for the mass detection. The matrix-matched external standard calibration curves were used for quantitative analysis. Results1. SPE-GC-MSBy optimizing pretreatment methods and instrument parameters, an integrated sample determination could be finished within 26 minutes. In the linear range of each analyte, the correlation coefficient was greater than 0.990. The limits of detection(LOD) were 3.0~8.0μg/kg and the limits of quantification(LOQ) were 10.0~25.0μg/kg. At different fortified levels,the corresponding recoveries were 81.4%~101.2% and the relative standard deviations were 2.4%~7.8%.2. Qu ECHERS-UPLC-MS/MSBy optimizing pretreatment methods and instrument parameters, an integrated sample determination could be finished within 6 minutes. In the linear range of each target analyte, the correlation coefficient was greater than 0.999. The limits of detection(LOD) of the method were 1.0~3.0μg/kg and the limits of quantification(LOQ) of the method were 3.0~10.0μg/kg. At different fortified levels, the corresponding recoveries were 82.1%~106.7% and the relative standard deviations were 3.2%~8.2%. Conclusion:Both of the methods that we developed were efficient, rapid, and accurate, which was suitable for the simultaneous determination demands of a trace level of the five PGRs residue in bean sprout.