Research On Novel QuEChERS Purification Materials And Detection Methods For Pesticide Residues In Food

The QuEChERS is an analytical method of quick,easy,cheap,effective,rugged and safe for the detection of pesticide residues,and has been rapidly developed since 2003.The method can be simply classified as three steps of extraction,purification and detection,among which the purification step is of significant difference from the traditional methods.Therefore,the selection of clean-up materials is the main factor that determines the performance of the QuEChERS method.The traditional clean-up materials of QuEChERS have some limitations in the using process.It is urgent to develop the new high-performance clean-up materials to better develop QuEChERS method.Based on the requirement,several new QuEChERS clean-up materials have been developed,the clean-up performances have been evaluated,and several modified QuEChERS methods for detecting the pesticide residues in the foodstuffs have been established in this work.Chapter 1 IntroductionThe research background of this work is introduced firstly,and then several pretreatment methods of pesticide residues detection are outlined.The development of QuEChERS method and clean-up materials are reviewed.At last,the purpose and significance of this paper are illuminated.Chapter 2 A magnetic hyperbranched polyamide amine-based QuEChERS-GC-MS method for the detection of organophosphorus pesticide residues in orange juiceThe magnetic hyperbranched polyamide amine materials contain various types of amino and hyperbranched organic chains,so that the structure is similar to the structure characteristics of PSA and C18,and the magnetic property can make the operation process to be simpler and more efficient.Based on these considerations,the magnetic hyperbranched polyamide amine materials were successfully prepared and applied as a QuEChERS adsorbent to the gas chromatograph-mass spectrometer(GC-MS)detection of 11 organophosphorus pesticides in orange juice,recoveries ranged from 75.2 to 116.2%,with the relative standard deviation(RSD)of 4.1-18.9%and the limit of detection of 0.74-8.16 ?g/kg.Compared the performance with classical clean-up agents of PSA and C18,magnetic hyperbranched polyamide amine can remove most of the interfering substances in orange juice extract without the need to combine other clean-up materials.The results show that the method of using magnetic hyperbranched polyamide amine as adsorbent for QuEChERS sample preparation is an effective alternative with simplicity and rapidity.It is a potential commercial alternative adsorbent.This work is the first to apply hyperbranched materials to the purification process of QuEChERS,providing new ideas for the development of QuEChERS clean-up materials.Chapter 3 Magnetic tetraethylenepentamine modified multi-walled carbon nanotubes as matrix clean-up materials for organophosphorus pesticide residue analysis in cucumberIn order to better remove the interfering substances such as pigments in the vegetables,a type of tetraethylenepentamine modified multi-wall carbon nanotubes have been prepared.As-prepared materials contain amino-groups and organic chains,and magnetism is endowed by using physical blending method.Taking the magnetic tetraethylenepentamine modified multi-walled carbon nanotubes(M-TP-MWCNTs)as QuEChERS clean-up agents,a GC-MS method has been established for the detection of pesticide residues in cucumber.The recoveries of 10 pesticide targets were 73.5%-114.5%,and the RSD was between 4.9%and 18.6%,which can meet the requirements of food safety testing.Compared with the traditional clean-up materials,the prepared materials exhibit better clean-up performance while simplifying the pretreatment process.As a type of new materials for the purification of QuEChERS,the M-TP-MWCNTs are expected to be used in the purification of other samples with high pigment contents.Chapter 4 A magnetic fluorinated multi-walled carbon nanotubes-based QuEChERS-GC-MS method for organophosphorus pesticide residues analysis in lycium ruthenicum murrIn order to meet the requirements of pesticide residues' detection in complex matrix samples,a type of magnetic fluorinated multi-wall carbon nanotubes(M-F-MWCNTs)are prepared and used as new QuEChERS clean-up adsorbents.Fluorine is the most electronegative element and the fluorine groups make the prepared magnetic multi-wall carbon nanotubes higher surface polarity.Combined with GC-MS,an improved QuEChERS method for the detection of organophosphorus pesticide residues in lycium ruthenicum murr is successfully developed.The recoveries of 10 pesticide residues are from 74.9%to 113.5%,with the RSD of 3.9%-14.7%.The results show that the M-F-MWCNTs can effectively remove interfering substances from lycium ruthenicum murr samples extract and reduce the matrix effect.As new QuEChER clean-up materials for pesticide residues detection,the M-F-MWCNTs are expected to be used in other complex matrix sample purification processes to meet the increasing needs of food safety detection.Chapter 5 Solidification of a switchable solvent-based dispersible liquid-liquid microextraction QuEChERS method for the detection of pesticides in fruits and vegetablesThe purification processes of traditional QuEChERS method uses the dispersed solid phase extraction technique.Based on the solidification of a switchable solvent,a dispersed liquid-liquid microextraction QuEChERS method is developed using n-ocadecylamine as clean-up material,and the method is applied to detect a variety of pesticide residues in vegetables and fruits.At a higher temperature,the n-octadecylamine can be melted into a liquid status and combined with the matrix interferences in acetonitrile solution based on dispersive liquid-liquid microextraction;at a lower temperature,the n-octadecylamine carrying a large amount of the interfering substances of the matrix can rapidly solidify and easily separate from the acetonitrile solution.At the same time,the interfering substance is removed from the acetonitrile.Combined with gas chromatography and mass spectrometry,the method has been used for the determination of 16 pesticides such as organophosphorus,organochlorine,pyrethroids and amide herbicides in the cucumber.The results were also satisfactory for the detection of the 16 pesticides in pear,orange,apple,pepper,lettuce and tomato.This study opens up a new approach to the QuEChERS method,which is of great significance for the development of QuEChERS method.Chapter 6 ConclusionThe work of the full text is summarized,and the solutions are put forward for the existing problems.