Study On The Analytical Methods Of Imidazolinone Pesticide Residues In Beans And Cereals

Imidazolinone pesticides are used widely nowadays,due to their broad-spectrum of activity,effectiveness and selectivity.With the increasing use of the pesticides in both crops and non-agricultural land,more attention is given to residues in crops and their harms on human health and the environment.Many countries have established the Maximum Residue Limits of imidazolinone for beans and cereals,which make our country faced with more technical barriers of grain export.Therefore,it is urgent and significant to establish a simple,rapid and selective method to determine imidazolinone pesticide residues in beans and cereals.In this work,the methods of SPE-HPLC and GPC-LC/MS/MS have been developed for simultaneous determination of six imidazolinone herbicides in beans and cereals.Method 1,A method was developed for simultaneous determination of six imidazolinone pesticides by Solid phase extraction and High Performance Liquid Chromatography.The analytes were extracted with NH₄HCO₃(0.1 mol/L,pH=5)-methanol (70:30,v/v).After concentration,the extract was partitioned with dichloromethane and cleaned up with Waters oasis MCX column.Separation were carried out on the Agilent XDB-C₁₈(250×4.6 mm i.d,5μm)with a binary gradient elution programme of acetonitrile-1%acetic acid in water at a flow-rate of 1.0 mL/min.Detection was performed by UV absorbance at 252 nm.The method of external standard was used for quantitative analysis.The calibration curves of imidazolinone herbicides showed good linearity in the range of 25～1000μg/L(imazaquin in 12.5～500μg/L)with correlation coefficients between 0.9998～0.9999.The limits of detection ranged from 0.002 mg/kg to 0.004 mg/kg(S/N=3).The average recoveries of six imidazolinone herbicides in the different samples ranged between 77.1%～102.2%(n=6).The relative standard deviations ranged between 2.5%～7.2%.Method 2,A method was developed for simultaneous determination of six imidazolinone pesticides by Gel permeation chromatography and Liquid chromatography with Electrospray ion trap mass spectrometry.The samples were extracted with NH₄HCO₃ (0.1 mol/L,pH=5)-methanol(70:30,v/v).After concentration,the extract was partitioned with dichloromethane and cleaned up with gel permeation chromatography.Separation was performed on Inertsil ODS-3(150×2.1mm i.d,5μm)by using the mobile phase gradient elution of methanol-1%acetic acid at a flow-rate of 0.3 mL/min.Indentificaton and quantification were performed by electrospray ion trap mass spectrometry in selected ion monitoring mode.The calibration curves of imidazolinone herbicides showed good linearity in the range of 5～200μg/L(imazaquin in 2.5～100μg/L)with correlation coefficients between 0.9987～0.9999.The limits of detection ranged from 0.0002 mg/kg to 0.0005 mg/kg(S/N=3).The average recoveries of six imidazolinone herbicides spiked ranged between 81.6%～103.3%(n=6)and the relative standard deviations were between 3.1%～8.3%.The two methods developed have been used for analyzing six kinds of imidazolinone herbicides simultaneously in beans and cereals with easy operation,good precision and linearity.The LODs of two methods are lower than MRLs that was established by G/SPS/N/USA/1229 and Positive list system.