The Analysis Of Chiral Pesticides In Environmental Samples By Molecular Spectroscopy

Pesticides are chemicals,used to control the damage of insects,pests,weeds and others on agricultural products and crops,they can be synthetic compounds and also can be natural products.Everything has two sides,pesticides are benefit for agricultural productions and pest-control,but they could cause environmental pollution,may damage to the ecological environmental or human health.Countries around the world have introduced some environmental standards,have set the Maximum residue limit(MRL)or Acceptable daily intake(ADI)of pesticides.These indicated that people concern about the problems of pesticide pollution and effects of pesticides on human very much.Therefore.analysis the pesticide residue in the environment samples for health protection of ecological environment or human is very important and necessary.In this work,Molecular spectroscopy(resonance Rayleigh scattering and fluorescence spectroscopy)was used to analysis pesticide residues in environment samples.The chiral pesticides was about 40%of pesticides on the market,so the chiral pesticides malathion.quizalofop-p-ethyl and achiral pesticide glyphosate were used as research objects.We mainly investigated the interaction of research objects with probes(tryptophan,eosin Y,Pd(II),Cu(Ⅱ))by resonance Rayleigh scattering and fluorescence spectroscopy.The spectral characteristics,the optimum conditions and the influences factors of each system were discussed.Therefore,the resonance Rayleigh scattering method for determination of malathion or quizalofop-p-ethyl and the fluorescence spectroscopy for determination of quizalofop-p-ethyl or glyphosate were proposed.The reaction mechanisms and the reasons for scattering enhancement and fluorescence changes were discussed.The new methods could be applied to the determination in real samples with satisfactory results.Under the supports of two projects of National Science Foundation of China(No.21175015;No.21475014),the main research details are as follows:1.Resonance Rayleigh scattering and fluorescence spectra of Tryptophan-Pd(Ⅱ)-Malathion system and their analytical applications.A convenient method for determination of malathion(Mala)based on resonance Rayleigh scattering(RRS)enhancement of L-Tryptophan(L-Try)-Pd(Ⅱ)-Mala system was proposed in this paper.The interaction between L-Try,Pd(Ⅱ)and malathion in the system was investigated by fluorescence,RRS and UV-Vis absorption spectroscopy.In the optimum conditions,the RRS intensity of L-Try-Pd(Ⅱ)-Mala system had a remarkable enhancement because the hydrolysis products of malathion would interact with Pd(Ⅱ)and L-Try each other through electrostatic and hydrophobic interaction formed new complexes,which enhanced intensity was directly proportional to the malathion concentration within a certain range.The influence of coexisting substances on RRS was also investigated,and exhibited good anti-interference ability.So,the new analytical method could be applied to determine of malathion in real samples with satisfactory results.2.Resonance Rayleigh scattering,sceond order scattering and frequency doubling scattering spectra of interaction of palladium chloride with and quizalofop-p-ethyl their analytical applications.The interaction between palladium chloride(Pd(Ⅱ))and quizalofop-p-ethyl(Qpe)was investigated by UV-Vis absorption and resonance Rayleigh scattering(RRS)spectra,second-order scattering(SOS)spectra,frequency doubling(FDS)spectra in this paper.Based on the spectrum changes,found that Qpe could react with Pd(Ⅱ)to form a new Pd(Ⅱ)-Qpe complex,which induced the enhancement of RRS,SOS and FDS intensity significantly under optimum conditions.The increments of scattering intensity were directly proportional to the concentrations of Qpe in a certain range.The optimum conditions of RRS method and the influencing factors were investigated,and exhibited good anti-interference ability.Therefore,the RRS,SOS and FDS method for determination of Qpe could be developed.The detection limit of RRS method for determination of Qpe was 55.4 ng/mL and the quantitative determination range was 0.2-1.4 μg/mL.The reaction mechanism between Pd(Ⅱ)and Qpe was studied and the reasons for RRS enhancement were also discussed.The RRS method has a good selectivity and has been successfully applied for determination of Qpe in environmental samples with satisfactory results.3.Study on the eosin Y as fluorescence sensor for determination of quizalofop-p-ethyl and its application.A convenient fluorescence quenching method for determination of Quizalofop-p-ethyl(Qpe)was proposed in this paper.Eosin Y(EY)is a red dye with strong green fluorescence(λex/λem = 519/540 nm).The interaction between EY,Pd(Ⅱ)and Qpe was investigated by fluorescence spectroscopy,resonance Rayleigh scattering(RRS)and UV-Vis absorption.Based on changes in spectrum,Pd(Ⅱ)associated with Qpe giving a positively charged chelate firstly,then reacted with EY through electrostatic and hydrophobic interaction formed ternary chelate could be demonstrated.Under optimum conditions,the fluorescence intensity of EY could be quenched by Qpe in the presence of Pd(Ⅱ)and the RRS intensity had a remarkable enhancement,which was directly proportional to the Qpe concentration within a certain concentration range,respectively.Based on the fluorescence quenching of EY-Pd(Ⅱ)system by Qpe,a novel,convenient and specific method for Qpe determination was developed.The detection limit for Qpe was 20.3 ng/mL and the quantitative determination range was 0.04-1.0 μg/mL.The method was highly sensitive and had larger detection range compared to other methods.The influence of coexisting substances was investigated with good anti-interference ability.The new analytical method has been applied to determine of Qpe in real samples with satisfactory results.4.Study on the L-/D-Tryptophan as fluorescence "turn-off-on" sensor for determination of glyphosate and its application.The L-/D-Tryptophan(L-/D-Trp)have strong fluorescence with λex/λem = 279 nm/355 nm,the fluorescence could be quenched by Pd(Ⅱ)in pH 6.24 buffer solution while Cu(Ⅱ)at pH 8.67 but the fluorescence of the L-/D-Trp could be recovered by glyphosate(Gly).Comparison of L-/D-Trp-Pd(Ⅱ)system and L-/D-Trp-Cu(Ⅱ)system for detecting glyphosate,L-/D-Trp-Cu(Ⅱ)system have better sensitivity and accuracy,stronger anti-interference ability under the optimized experimental conditions.A detailed comparative study on the reaction mechanism and conditions of the system of L-/D-Trp-Pd(Ⅱ)and L-/D-Trp-Cu(Ⅱ)had be made in this paper,and a detailed discussion to the factors affecting the system for determination of glyphosate had be done.Thus,L-/D-Trp-Cu(Ⅱ)system are suitable for detecting Gly.L-/D-Trp-Cu(Ⅱ)system could be used to detect Gly at range from 0.025 to 1.0 μg/mL with the limit of detection was 8.6 ng/mL.The analytical results show that the method was more effectively applied to the determination of Gly in real samples.So,a simple and rapid methods for the determination of glyphosate based on fluorescence "turn-off-on" sensor was developed.