| Porous carbon nanomaterials are carbon nanomaterials with different porous structures.It has advantages of high specific surface area and good electrochemical performance.When the porous carbon is only modified on the electrode,it will bring a large error,which can be solved by loading a layer of polypyrrole.ZrO2 has a strong affinity for phosphate groups.ZrO2 was used as the recognition element to improve the specificity of the detection method.Glyphosate is a kind of the most popular herbicide.Excessive intake of glyphosate can cause symptoms of poisoning.In this study,porous carbons were prepared by chemical activation with corncobs（a kind of raw material of agricultural waste）as the carbon source.In order to develop a method for detecting glyphosate residues in food,an electrochemical sensor was assembled based on the role of porous carbon amplification of electrical signals and the affinity of ZrO2 for phosphate groups,and used to detect glyphosate residues in food.The main contents are as follows:1.Preparation and characterization of corn cob porous carbon（CCPC）:CCPC with high electrochemical performance was synthesized by using biomass corn cob as carbon source through activation method.The effects of reaction time,reaction temperature,ratio of pre-carbonized corn cob to K2CO3 addition and CCPC solution loading on electrochemical performance were investigated.Taking the difference of porous carbon peak current value of corn cob as the index,the optimal preparation conditions of CCPC were as follows:reaction time was 2 h,reaction temperature was 750°C,ratio of pre-carbonized corn cob to K2CO3 addition was 1:2,CCPC solution loading was 5μL.CCPC was characterized by SEM,XRD,BET,EDS,CV The results showed that the CCPC had good electrochemical properties and structural properties.The average pore size of CCPC was 4 nm.The nitrogen adsorption and desorption isotherm showd H2-type hysteresis loop,with a hierarchical pore structures of micropores,mesopores and macropores.2.Preparation and characterization of ZrO2/PPy@CCPC:On the basis of CCPC,PPy and ZrO2were modified.The effects of polymerization time,nitric acid concentration,and CTAB concentration on the electrochemical performance of PPy,and the effect of deposition time on the detection glyphosate performance of ZrO2/PPy@CCPC were studied.The optimal preparation conditions of PPy were obtained by taking the difference of PPy peak current value as the investigation index,:By polymerizing at concentration of 0.75 mol/L the nitric acid,0.01 mol/L CTAB,10 mol/L pyrrole for 275 s,and deposing ZrO2 for 960 s,the detection glyphosate performance of ZrO2/PPy@CCPC was the best.ZrO2/PPy@CCPC was characterized by SEM,EDS,CV and other means.And the effects of storage time,p H,and enrichment time on the glyphosate detection performance of ZrO2/PPy@CCPC were investigated.The results showed that ZrO2/PPy@CCPC had good electrochemical performance and could be used in the detection of glyphosate.The difference between the peak current value of the ZrO2/PPy@CCPC electrode could still be retained the original peak current value of 92%after stored at room temperature for90 days.3.ZrO2/PPy@CCPC detection of glyphosate:When ZrO2/PPy@CCPC was used to detect 9kinds of representative pesticides,the electrochemical performance of ZrO2/PPy@CCPC was only inhibited by glyphosate.The interference of common metal cations,anions and amino acid small molecules in food on the detection of glyphosate by ZrO2/PPy@CCPC was investigated.The results showed that ZrO2/PPy@CCPC had high selectivity and anti-interference ability for the detection of glyphosate.Based on the electrochemical inhibition of ZrO2/PPy@CCPC by glyphosate,a new method for detecting Gly was established.When the amount of glyphosate was added in the range of 0.1～1000μg/L,the degree of peak current value intensity inhibition of ZrO2/PPy@CCPC gradually increased with the increase of glyphosate concentration.The peak current value intensity of ZrO2/PPy@CCPC had a good linear relationship with glyphosate concentration of 0.1～10μg/L and 10-1000μg/L,and the detection limit of glyphosate was 24.4 ng/L.The recovery rate of glyphosate in actual samples was 90.37%～105.97%,and the RSD was less than 3.71%.The recovery rate of standard method SN/T4655-2016 for the detection of 0.1 mg/kg glyphosate rice spiked was 89%,and the electrochemical sensor prepared in this study had better recovery rate and better sensitivity,and experiments showed that ZrO2/PPy@CCPC could be applied to the detection of glyphosate in actual sample cereals. |
