The Fabrication Of Novel Colorimetric Sensor Arrays And Their Applications In The Identification Of Pesticide Residues And Chinese Liquors

As we all know,agriculture is the national economy foundation of our country,and the important position of agricultural economics is highlighted increasingly with the increase in population.In order to improve crop yield and agricultural profit,pesticides are inevitably used in the agriculture production.However,the widespread and long-term usage of pesticides caused serious toxic hazard and 3R(Residue,Resistance,Resurgence)problems,which have attracted more and more attention,especially the food safety problems caused by pesticide residues.Therefore,it is of great importance to develop highly rapid,facile and sensitive technology for pesticide residues detection.The superior properties of colorimetric sensor array technique,i.e.,capable of rapid,efficient and simultaneous detection of multiple analytes,make it very suitable for discriminant analysis of pesticide residues.However,owing to less-reaction of most pesticides,indicators possessing strong chemical interactions and cross-reactivities are difficult to synthesize,which seriously hampered the wide application of colorimetric sensor array technique in discriminant analysis of pesticide residues.Consequently,based on colorimetric sensor array technique,this thesis focuses on converting less-reactive pesticides into the reactive analytes through designing and screening appropriate pretreatment methods,and then fabricate sensor array through a variety of indicators which could induce color changes of the reactive analytes,realizing indirect identification of organophosphates,carbamates and pyrethroids.The main contents of this thesis are as follows:In chapter 1,we firstly summarize the recent advances of multidimensional sensor devices,and particularly focus on their design strategies and applications in monitoring of biological active molecules,biomarkers,microbes,foods and beverages,etc.Then,some limitations of multidimensional sensors are discussed,and the significance of this thesis is proposed.In chapter 2,a colorimetric sensor array comprising five inexpensive and commercially available thiocholine and H₂O₂ sensitive indicators for the simultaneous detection and identification of organophosphates(OPs)and carbamates is developed.The sensing mechanism of this array is based on the irreversible inhibition capability of OPs and carbamates to the activity of acetylcholinesterase(ACh E),preventing production of thiocholine and H₂O₂ from S-acetylthiocholine and acetylcholine and thus resulting in decreased or no color reactions to thiocholine and H₂O₂ sensitive indicators.Through recognition patterns and standard statistical methods(i.e.,hierarchical clustering analysis and principal component analysis),the as-developed array demonstrates not only discrimination of OPs and carbamates from other kinds of pesticides but,more interestingly,identification of them exactly from each other.Moreover,this array is experimentally confirmed to have high selectivity and sensitivity,good anti-interference capability,and potential applications in real samples for OPs and carbamates.In chapter 3,based on the findings that N-methyl carbamate pesticides could be decomposed into reactive phenols in basic media,a novel strategy of strong base pre-treatment is developed and employed for the colorimetric sensor array detection and differentiation of the N-methyl carbamate pesticides in an indirect manner.With the use of five inexpensive and commercially available phenol responsive indicators,such a colorimetric sensor array can be facilely fabricated.Classification analysis(e.g.hierarchical clustering analysis(HCA)and principal component analysis(PCA))reveals that the as-fabricated sensor array has an extremely high dimensionality and,consequently,exhibits excellence in discriminating a variety of N-methyl carbamates from other types of pesticides and potential interferants,and further identifying them exactly from each other.Moreover,semi-quantitative detection could also be achieved through combining HCA/PCA,recognition patterns,and corresponding fitting curves.Overall,the as-developed method exhibits high selectivity and sensitivity,good anti-interference,simultaneous detection and identification capability for each of the N-methyl carbamate pesticides,and potential applicability in real samples.In chapter 4,a novel and simple colorimetric sensor array built on sulfuric acid assisted KMn O₄ fading strategy has been developed for pesticides detection and discrimination.This sensor array is facilely fabricated by KMn O₄ and sulfuric acid through simply adjusting their concentrations and ratios.HCA demonstrates that the as-fabricated colorimetric sensor array has a high dimensionality,and shows excellent capability to recognize common kinds of pesticides from potential interferants.Semi-quantitative detection was achieved through combining HCA and corresponding fitting curves.Moreover,the proposed sensor array was successfully applied to detect pesticide residues(e.g.carbaryl)in real samples.In chapter 5,we develop a new colorimetric sensor array for the discrimination of Chinese liquors.Six commercially available and inexpensive solvatochromic dyes are selected to construct the colorimetric sensor array.This sensor array has been demonstrated to discriminate more than twenty different liquors.To the best of our knowledge,this is the first example to realize the identification of Chinese liquors in the liquid phase by a simple array sensing technique without the aids of other analytical techniques.Finally,the successful distinction of Chinese liquors from water-added liquors by the fabricated sensor array is achieved as well.In the last section,we summarize the main conclusions of the above-mentioned work and prospect about the further research work.In this thesis,great contributions have been made for the detection of pesticide residues and the identification of Chinese liquor.And a more practical application field for the colorimetric sensor array technique is still to be explored to take full use of its potential.