| Nowadays,more and more the starting crudes,such as wheat,soybean,vegetables,fruit and tea,are recklessly abused organophosphorus pesticides during the planting process.Organophosphorus pesticides have high toxicity,which easily make the central nervous system poison.Therefore,the rapid efficient method should be established and realizing the detection for the organophosphorus pesticides possesses very important significance.Functional nucleic acids are achieved by SELEX,which embrace widely targets,high specificity and affinity.In this paper,functional nucleic acids was used as functional molecule.We researched the application for organophosphorus pesticides detection based on Hemin and AuNPs.A series of rapidly,sensitively and specifically new methods was developed and the detection of organophosphorus pesticides for the starting crudeprovidedguarantee.The main jobs of this article are as follows:(1)The method for isocarbophos detection aggregating hemin based on ssDNA was researched.Free hemin molecules have a strong absorption peak at Soret band in polar organic solvents,and they can assemble into few small particles with random ssDNAs via their special π-π stacking interaction.However,the subsequent addition of isocarbophos into above sensing system can aggregate hemin molecules to form many larger particles,which result in a great decrease in absorbance value of sensing solution.Therefore,the detection of isocarbophos by aggregating hemin based on ssDNA was realized.UV/Vis absorption spectra and scanning probe microscope(SPM)were used to characterize hemin aggregation.Under the optimal conditions,the present assay platform has a detection limit as low as 0.2 μg/L,a dynamic range of 0.5-500 μg/L,and high selectivity over other competitive pesticides.Moreover,the assay platform also displays excellent stability and accuracy in the detection of spiked real samples and the spiked recoveries for isocarbophos by current method were in the range of 97% and 113%.The reliability of current method was further verified by GC.(2)A simple colorimetric method for detection of isocarbophos was developed based on the enhanced peroxidase-like activity of hemin.Hemin could catalyze the oxidation of peroxidase substrate 3,3’,5,5’-tetramethylbenzidine(TMB)by H2O2,which made TMB to lose one electron and caused reaction solution color changing from initial transparent to blue-green.Adding isocarbophos improved hemin affinity to substrates,which enhanced peroxidase-like activity of hemin and made TMB to lose two electrons.The color of TMB solution was further changed from blue-green to yellow,and the degree of color change was proportional to the concentration of isocarbophos.Under the optimal conditions,the present analytical method for isocarbophos detection had a dynamic range from 2 μg/L to 100 μg/L with a detection limit of 1.2 μg/L.The selectivity assay demonstrated that other organophosphorus pesticides exhibited negligible interferences for isocarbophos detection.The application of the proposed method in the practical samples showed that the mean recovery of isocarbophos was in the range of 93%-113.0%.Then,using ssDNA further regulates peroxidase-like activity of hemin based on the above research,and a simple colorimetric method for detection of isocarbophos was developed based on the ssDNA and target enhancing peroxidase-like activity of hemin.ssDNA could cover the surface of hemin by π-π interaction,which restrained peroxidase-like activity of hemin to substrates.Hemin could catalyze the oxidation of peroxidase substrate 3,3’,5,5’-tetramethylbenzidine(TMB)by H2O2,which made TMB to lose one electron and caused reaction solution color changing from initial transparent to blue.Adding isocarbophos improved hemin affinity to substrates based on ssDNA,which further enhanced peroxidase-like activity of hemin and rapidly made TMB to lose two electrons.The color of TMB solution was further changed from blue to yellow,and the degree of color change was proportional to the concentration of isocarbophos.Under the optimal conditions,the present analytical method for isocarbophos detection had a dynamic range from 2 μg/L to 100 μg/L with a detection limit of 0.6 μg/L.The selectivity assay demonstrated that other organophosphorus pesticides exhibited negligible interferences for isocarbophos detection.The application of the proposed method in the practical samples showed that the mean recovery of isocarbophos was in the range of 91.6%-116.8%.The introduction of functional nucleic acids on the one hand restrained peroxidase-like activity of hemin,on the other hand significantly enhanced peroxidase-like activity of hemin with together interaction of isocarbophos,further improving the sensitivity of isocarbophos detection and accelerating the process of whole detection.(3)A simple colorimetric method for detection of dimethoate was developed based on the ssDNA and target regulating peroxidase-like activity of AuNPs.The ssDNA could adsorb on the surface of AuNPs.AuNPs could catalyze the oxidation of peroxidase substrate o-Phenylenediamine(OPD)by H2O2,which caused reaction solution color becoming tenne.Adding dimethoate restrained peroxidase-like activity of AuNPs,which made the color of OPD solution change,and the degree of color change was proportional to the concentration of dimethoate.Under the optimal conditions,the present analytical method for dimethoate detection had a dynamic range from 10 μg/L to 1500 μg/L with a detection limit of 7.1 μg/L.The selectivity assay demonstrated that other organophosphorus pesticides exhibited negligible interferences for dimethoate detection.The application of the proposed method in the practical samples showed that the mean recovery of dimethoate was in the range of 88.5%-110.3%.In conclusion,single chain deoxyribonucleic acid was used as functional molecule in this paper,using hemin and AuNPs as sensor output carrier,and thus a series of sensitive,fast,specific and legible to the naked eye method detecting the organophosphorus pesticides was established.In this paper,these methods establishing were simple and reliable,and didn’tneed complex molecular modification and expensive instrument,which could be applied to the detection of the organophosphorus pesticides in the starting crude. |
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