Study On Adsorption Of Neonicotinoid And Phenoxy Acid Pesticide Residues By Metal-Organic Coordination Polymers

Objective: The purpose of this study was to synthesize novel metal-organic coordination polymers(MOCPs)with good adsorption properties and apply MOCPs to the sample pretreatment technology for the extraction of neonicotinoid insecticides and phenoxy acid herbicides.Highly sensitive detection methods for two pesticide residues in traditional Chinese medicine were established.Methods: Two spherical MOCPs of different sizes were successfully prepared by the Schiff base reaction between 4-(tert-butoxycarbonylamino)-aniline(NBPDA)and 2,6-pyridinedicarboxaldehyde(Dic Py)under the regulation of Co2+.The micronsized spherical MOCPs were applied to the solid phase microextraction(SPME)coating and then main parameters affecting the SPME efficiency were optimized.Finally,the SPME combined with high performance liquid chromatography(HPLC)method was successfully applied to analyze neonicotinoid insecticides in honey samples.The micronsized spherical MOCPs were used as the solid phase extraction(SPE)sorbent and parameters affecting the SPE procedure were examined.Under optimal conditions,high efficiency enrichment of phenoxy acid herbicides from complex samples was achieved.Results: The MOCPs controlled by Co2+ are regular spherical structure with good adsorption properties.The optimum extraction conditions for SPME were obtained as follows: sample salt concentration of 5%,sample p H value of 7.0,temperature of 40 oC,extraction time of 50 min,and then the neonicotinoid insecticides were eluted for 20 mins using 1 m L of trifluoroacetic acid/acetonitrile(4:96,v:v)solution.Four neonicotinoid insecticides(thiamethoxam,imidacloprid,acetamiprid,thiacloprid)showed good linearity(0.5~600 ?g·kg-1)and low limits of detection(0.05~0.15 ?g·kg-1),and the relatives recoveries from spiked honey samples ranged from 91.5% to 103.5% with the relative standard deviations(RSDs)of 3.8~6.3%.The optimum conditions for SPE were obtained as follows: the adsorption process was completed at a speed of 2 m L·min-1 when the p H value of sample was 6.0,and the elution process was completed at a speed of 1 m L·min-1 with 0.8 m L of methanol/formic acid(96:4,v:v)solution as desorption solvent.After analyzing with HPLC,six phenoxy acid herbicides(2-CPA,4-CPA,2,4-D,MCPA,2,4-DP,2,4,5-T)exhibited good linear relationships in the range of 0.5~500 ?g·kg-1 with limits of detection of 0.07~0.21 ?g·kg-1.In addition,the relative recoveries from spiked real samples are very good(84.2~104.8%)with RSDs of 3.6~8.7%.Conclusion: Highly sensitive detection methods for neonicotinoid insecticides and phenoxy acid herbicides was established based on the synthesis of novel MOCPs,and the accuracy was demonstrated by methodological investigation.This study provides reliable methods and experience for the detection of pesticide residues in traditional Chinese medicine such as honey and coicis semen.