Electrochemical Preparation And Application Of Dual Monomer Based Copolymer Coatings For Solid Phase Microextraction

Solid phase microextraction(SPME)is a new sample pretreatment technique.It has attracted much attention because of its high efficiency,low solvent consumption,and easy combination with other instruments.For SPME technique the key is coating,as it determines the stability,selectivity and extraction efficiency of SPME.Thus to exploit new coatings suitable for certain analyts is very important.The copolymerization of two monomers can combine their advantages such as good stability and easy control of the surface properties etc.Thus it can effectively overcome some shortcomings of single monomer based coatings,such as low thermal stability,poor film forming performance and low extraction capacity.Therefore,copolymerization is an important means to improve the comprehensive extraction performance of SPME fiber.In addition,some new functional materials:including ionic liquids/polymeric ionic liquids(ILs/PILs),carbonaceous materials(e.g.,graphene and carbon nanotubes(CNTs)),molecularly-imprinted polymers(MIPs),metal-organic frameworks(MOFs),are also used in constructing SPME coatings to achieve good extraction performance.In this dissertation,several copolymerization based coatings were prepared by electrochemical method,which concerned indole and 2,2-bithiophene.At the same time,they were combined with gas chromatography for the detection of some environmental pollutants.The details are as follows:(1)An ionic liquid-poly(indole-co-3-methylthiophene)composite coating was(P(In-3-MeT))electrodeposited on a stainless steel wire by cyclic voltammetry.The concentration of the two monomers,the kind and amount of ionic liquids were optimized.The coating showed porous structure and high thermal stability(>450 0C)and extraction efficiency in comparison with poly(indole)and poly(3-methylthiophene)coatings.The obtained fiber was combined with gas chromatography to detect six polycyclic aromatic hydrocarbons(i.e.,naphthalene,1-methylnaphthalene,biphenyl,acenaphthene,fuorene,phenanthrene).Under the optimized conditions,its extraction efficiency was 2-10 times that of poly(indole)and poly(3-methylthiophene)coatings.The linear range was 0.05—50?g·L-1,the detection limit was 6.25—25.2 ng·L-1(S/N = 3).The target analytes were successfully detected in cigarette extractant,industrial lubricant and mosquito-repellent incense samples.(2)Apoly(2,2-bithiophene-co-3-methylthiophene)-graphene(P(BT-3-MeT)/rGO)composite coating was prepared by electrochemical copolymerization.The coating was characterized by using electron microscopy and it presented cauliflower shape.It had high thermal stability(up to 375 ?)and could be used for at least 180 times of solid-phase microextraction without decrease in extraction performance.The obtained fiber was combined with gas chromatography to detect five benzenes(i.e.,bromobenzene,4-bromotoluene,2-nitrotoluene,3-nitrotoluene,1,2,4-trichlorobenzene).Under the optimized conditions,good linearity(correlation coefficients higher than 0.9946),wide linear range(0.01-50 ?g·L-1),and low limits of quantitation(17.5-41.7 ng·L-1)and limits of detection(5.25-12.5 ng·L-1)were achieved for these analytes.The fiber was successfully applied for the detection of the benzenes in nail polish,hair dye and correction fluid samples.(3)A poly(2,2-bithiophene-co-5-Methoxyindole)-oxide graphene P(BT-5-MIn)/GO composite coating was electrodeposited on the surface of a stainless steel wire.The concentration of the two monomers and the amount of oxide graphene(GO)were optimized.The coating was characterized with SEM,TG,FTIR etc,and the results showed that it was uniform,had high thermal stability(>400 ?),and was suitable for the extraction of antidepressants(i.e.,citalopram,fluoxetine,nortriptyline).The preparation and extraction conditions were optimized,good linearity(correlation coefficients higher than 0.9946),wide linear detection range(0.01-50 ?g·L-1),and low detection limit(4.25-6.25 ng-L-1(S/N = 3))were obtained.The proposed method was applied in the detection of these antidepressants in east lake,and-the recovery for standards added was 86.8-105%.