| Objectives Diphenyl ether herbicides（Des）are protoporphyrinogen oxidase inhibitors,which are commonly used to control broadleaf weeds in crops such as rice,soybean and corn.At present,such substances have been detected in water environment and related foods,so it is necessary to develop rapid and accurate analysis methods.Due to the complex matrix of food samples and the trace level of the target substances in water environment and food,it is the key to achieve effective enrichment and purification of the target substances before analysis and detection.In this study,Mn DUT-52 will be prepared by solvothermal method,combined with high performance liquid chromatography-ultraviolet detection（HPLC-UV）,to establish a rapid and economical method for the analysis of Des in water environment and soybean.Methods 1 Mn DUT-52 will be prepared by solvothermal method.The structure,morphology,element distribution,specific surface area and surface charge of the material will be characterized,respectively.2 Mn DUT-52 will be used as adsorbent for the dispersive solid phase extraction（DSPE）,and coupled with HPLC-UV,fast and economical analytical method for three Des in water environment will be established.The DSPE conditions such as adsorption conditions（amount of Mn DUT-52,adsorption time,p H and Na Cl concentration）and desorption conditions（desorption solvent and desorption volume）will be optimized.Under the optimal conditions,the method will be validated with linearity,limit of detection（LOD）,limit of quantification（LOQ）,accuracy and precision.The adsorption mechanism will be also discussed and the reusability of Mn DUT-52 will be investigated.3 In order to expand the application of adsorbent,the extraction effect of Mn DUT-52 on the three Des in soybean will be further investigated.On the basis of optimized conditions,an analytical method for three Des in soybean will be established.Results1 X-ray diffractometer and Fourier-transform infrared spectroscopy characterization results showed that Mn DUT-52 had the typical structure of DUT-52.The results of scanning electron microscopy showed that the crystal size of Mn DUT-52 did not change significantly compared with DUT-52.However,there were defects on the crystal surface,and some crystalline grains could not completely maintain the octahedral crystal structure.X-ray energy spectrum analysis found that Mn（II）was successfully doped into DUT-52.Compared with DUT-52,the specific surface area of Mn DUT-52 was reduced,but the Zeta potential could reach 43.2 m V,which was significantly higher than that of DUT-52（8.57 m V）.2 Mn DUT-52 was used as an adsorbent for DSPE of Des in water samples.The experimental results showed that 70 mg Mn DUT-52 could achieve complete adsorption within 20 min as the p H of the sample solution was 7 and there was no Na Cl concentration adjustment.The target could be eluted with 0.5 m L×2 acetone.Under the optimal conditions,the linear relationship of the method was good in the range of 0.2-300ng.m L-1.The LODs and LOQs were 0.06-0.10 ng.m L-1and 0.20-0.30 ng.m L-1,respectively.The recoveries of the method were 82.4%-102.5%at the three spiked levels.The relative standard deviations ranged from 2.7%to 10.2%,and the enrichment factors were 67.5-78.3.Mn DUT-52 could be reused for 6 times with the relative standard deviations of the target compound no more than 5.8%.It was found thatπ-πinteractions,hydrophobic interactions and electrostatic interactions played important roles in the adsorption.3 Mn DUT-52 was further used for the analysis of three Des in soybean.30 mg Mn DUT-52 was enough to complete the adsorption of the three Des in 0.5 g soybean sample within 15 min.The adsorbed Des could be eluted with 0.5 m L of acetone for 3 times.The method showed good linear relationship in the range of 1-150μg.kg-1（r≥0.9993）,and the LODs were lower than 0.4μg.kg-1.Under the three spiked levels,the recoveries of the method were81.7%-101.2%,the intra-day and inter-day precisions were lower than 6.2%and 10.2%,respectively.Conclusions 1 In this study,Mn DUT-52 was used as a DSPE adsorbent.Combined with HPLC-UV,the analytical method of the three Des in water environment was established.The LODs of the method were 0.06-0.10 ng.m L-1and only 70 mg of adsorbent could be needed for the adsorption in 20 min.The enrichment factor could reach 67.5-78.3.After the incorporation of Mn（II）,the adsorption capacity of the adsorbent for the three Des increased by 35%.And the adsorbent could be reused for at least 6 times.2 The prepared Mn DUT-52 was used for the analysis of the three Des in soybean.The LODs and LOQs of the method were 0.3-0.4μg.kg-1and 1.0-1.5μg.kg-1,respectively.Therefore,the method was fast and economical,and could meet the analysis requirements of the three Des in water and soybean samples.Figure 24;Table 13;Reference 171... |
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