Study On Pretreatment Methods Of Pyrethroid Pesticide Residues Detection In Complex Matrix

Pyrethroid pesticides have gradually replaced organophosphorus,organochlorine and other pesticides as the most commonly used pesticides,leading to increasingly serious pesticide exposure in the environment and the human body.Therefore,it is extremely urgent to establish a set of efficient,fast and accurate analysis approaches.In this paper,the residues of pyrethroid pesticides in traditional Chinese medicine oral liquid preparations were determined by optimized QuEChERS method combined with high-performance liquid chromatography（HPLC-UV）.The magnetic molecular imprinted polymers（MMIP）were synthesized and used as magnetic solid phase extraction adsorbent for the determination of type Ⅱ pyrethroids residues in human plasma combined with gas chromatography mass spectrometry（GC-MS）.Polypyrrole nanowires were synthesized as solid phase extraction adsorbent,combined with GC-MS detection to determine the trace residues of pyrethroid pesticides in human plasma.This study is mainly divided into the following parts:（1）The extraction conditions of QuEChERS method（including types of extraction solvent,the amount of extraction solvent,type of purification agent and type of added salt）were studied and optimized,and then combined with high performance liquid chromatography（HPLC-UV）to determine pyrethroid pesticides in traditional Chinese medicine oral liquids.The matrix effect was estimated in the organic solvent and the actual samples by comparing the slopes of calibration curves,and the results showed that the matrix effect is not significant when using the modified QuEChERS method.The pyrethroid pesticides could be completely separated in 30 min.The linear correlation coefficients were more than 0.999,and the recoveries of all the pyrethroid pesticides ranged from 83.9%to 104.8%.Moreover,the limits of quantitation were in the range of0.022-0.057 ng mL^-1.（2）This study details an efficient method employing magnetic molecularly imprinted polymers（MMIP）as a magnetic solid-phase extraction adsorbent followed by gas chromatography-mass spectrometry（GC-MS）for the determination of type Ⅱ pyrethroids in human plasma.Molecular simulations were used to screen a suitable monomer and ratio of monomer to template molecule.A series of functional nanoparticles were synthesized,and characterized by vibrating sample magnetometer（VSM）,Fourier transform infrared spectroscopy（FT-IR）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,and thermogravimetric analysis.Then,binding experiment was employed to evaluate the adsorption properties,and the SPE conditions were investigated,including eluent type and MMIP amount.The chromatographic separation of type Ⅱ pyrethroids in human plasma was carried out by GC-MS;The linearity was within the range of 0.2-50 ng mL^-1,and the correlation coefficients for the four pyrethroids were higher than 0.995.The enrichment factor of this method is between 48.2 and 49.2.（3）Polypyrrole nanowires were synthesized as solid phase extraction materials,and corresponding characterized experiments were employed.Molecular dynamics simulation was used to study the adsorption mechanism of polypyrrole and pyrethroid compounds.Based on the density analysis,molecular recognition analysis and binding energy,the van der Waals force was an important driving force for adsorption.Extraction conditions including eluent type,time of extraction,volume of eluent and the amount of ppy nanowires were optimized to obtain the best recoveries.The linearity was within the range of 0.5-50 ng mL^-1,and the correlation coefficients for the six pyrethroids were higher than0.995.The intra-day precisions（n=6）were 2.12-5.09%,and the inter-day precisions（n=6）were 0.66-2.11%.