Preparation Of Composite Nanomaterials And Their Applications In Detection Of Herbicide Residues In Cereal

In modern agricultural production,the application of herbicide has become one of the indispensable measures to prevent grasses and increase crop yields.However,excessive usage of herbicide may cause persistent herbicide residues in cereal,which poses a serious threat to human health.Nanomaterials have become excellent candidates for adsorption media due to their unique structure and surface characteristics and strong adsorption capacity for pollutants.Nanomaterial-based sample pretreatment technology has become one of the main research directions in the field of analysis and detection.In this study,two composite nanomaterials adsorbents were designed and synthesized,and used as adsorbents for dispersive solid phase extraction and solid phase extraction techniques,and applied to the detection of herbicide residues in rice and corn.The specific research content is as follows:?1?Gold nanoparticles modified halloysite nanotubes?Au/HNTs?were synthesized by the co-precipitation method,their morphology and structures of this composite were characterized by fourier transform infrared spectrometer?FI-TR?,transmission electron microscopy?TEM?,surface area and microporous analyzer,as well as inductively coupled plasma source mass spectrometer?ICP-MS?.Then,it was used as an adsorbent of dispersive solid-phase extraction to extract the triazine herbicides of the n-hexane extracted solution.Several parameters that may affect the extraction efficiencies,including type and volume of extraction solvent,times of ultrasonic extraction and adsorption,amount of Au/HNTs,volume and flow rate of the elution solvent were optimized.Under the optimum conditions,Au/HNTs has good purification,selectivity and adsorption properties for the target analytes in the complex matrix sample.Good linearities in the range of 5²00 ng g^-1 for five triazines were found with the correlation coefficients r>0.995.The limit of detection?LOD?and limit of quantification?LOQ?were 0.06¹.32 ng g^-1 and 0.18⁴.40 ng g^-1 respectively,and the relative standard deviations?RSD?were<13.5%.The intra-day relative standard deviation?RSD?is less than 9.6%.The established method was applied to the detection of triazine herbicides in rice,and the recovery was between 70.2¹07.6%.This method broadens the scope of application of nanomaterials and provides an alternative way for the detection of triazine herbicides.?2?Based on the availability and structural porosity of melamine sponges,the carboxylized multiwalled carbon nanotubes?MWCNTs?doped metal organic skeleton MIL-101?Cr?was successfully loaded onto the skeleton of melamine sponge,and their appearance of related materials was characterized by scanning electron microscopy?SEM?.The functionalized melamine sponge was used as an adsorbent of solid-phase extraction to extract the triazine herbicides of the n-hexane extracted solution.The eluate was quantitatively analyzed with high performance liquid chromatography-tandem mass spectrometry?HPLC-MS/MS?.Several parameters that may affect the extraction efficiencies,including type of adsorbent,amount of coating adsorbent,type and volume of extraction solvent,times of ultrasonic extraction etc.,were optimized.The experimental results show that under the optimal conditions,the recovery and spiked concentration of six triazine herbicides have good linearity in the range of0.50⁵0.00 ng g^-1 with the correlation coefficients r>0.992.The LOD and LOQ of methods were 0.01⁰.04 ng g^-1 and 0.05⁰.14 ng g^-1,respectively.This method improves the dispersibility of the adsorbent to a certain extent,reduces the aggregation of the adsorbent,improves the extraction efficiency,and can be applied to the trace detection of triazine herbicides in complex samples.