Application Of Functional Polymer Coated Capillary In Detection Of Trace Analyte

Capillary electrophoresis(CE)technique has received increasing attention in the field of sample analysis owing to rapid analysis,high efficiency,and small consumption of sample.But on account of the small sample injection volume and the short optical path of ultraviolet detector,the detection sensitivity and accuracy are limited,which is an apparent drawback for its application in the direct analysis of trace analytes.In order to solve this problem,on-line sample preconcentration method has been widely employed to enrich the analyte and amplify the detection signal,such as on-line sample preconcentration based on the coating of functional polymer.In this paper,poly(2methyl-2-oxazoline)(PMOXA)/poly(acrylic acid)(PAA)binary mixed brushes coated capillary with switchable behavior towards protein adsorption/desorption has been fabricated for on-line preconcentration and detection of lysozyme(Lyz)in egg white.However,due to the complex background matrix of real sample,the quantitative analysis of the target analyte in real samples was always interfered by other components existing in complex matrix.Therefore,molecularly imprinted technique was introduced to fabricate the molecularly imprinted polymer(MIP)coated capillary with specific recognition ability and on-line preconcentration ability by using sulfadiazine(SDZ)and lysozyme as template molecules,respectively.The post-modification with PMOXA further reduced the non-specific adsorption and improved the selective recognition performance.The main works in the dissertation are listed below.1.Polydopamine(PDA)/PMOXA/PAA coated capillary was prepared using PDA as an intermediate adhesive layer on account of its adhesion properties.The results of online preconcentration of Lyz in spiked simulated egg white and EOF mobility before and after the separation of proteins demonstrated that the ovalbumin,conalbumin,and ovomucoid,existing in hen egg white as main proteins,showed negligible interference on online preconcentration of Lyz.The value of limit of detection(LOD)for lysozyme could reach 0.02 ng/mL.The detection results of Lyz in real hen egg white demonstrated the on-line preconcentration method was accurate and the prepared PDA/PMOXA/PAA coated capillary was stable without being affected by complex matrix even after 75 consecutive runs.2.SDZ-MIP-PMOXA coated capillary was prepared based on self-polymerization of dopamine(DA)in the presence of template SDZ,and then PMOXA coating was further grafted onto PDA.The separation performance of SDZ-MIP-PMOXA coated capillary in three different matrixes confirmed the surface modification by grafting PMOXA coating onto non-imprinted regions can effectively inhibit the non-specific adsorption of sulfonamides.Compared with bare capillary,the peak area SEF value of SDZ-MIP-PMOXA coated capillary could reach 46.Besides,the prepared SDZ-MIPPMOXA coated capillary presented well specific adsorption,selectivity,and repeatability.The linear range of SDZ-MIP-PMOXA coated capillary was 5.0-100.0 ng/mL(R2=0.9988),with the LOD of 1.5 ng/mL.For spiked egg white and milk samples,satisfactory recoveries of SDZ ranged from 98.7-109.3%were obtained,while RSD values of concentration and migration time were lower than 7.4%and 3.8%.3.Lyz-MIP-PMOXA-EI coated capillary was prepared combining template immobilization strategy,surface imprinting technology and post-imprinting modification strategy,with Lyz as template molecule,DA as a functional monomer and PMOXA-EI as post-modification molecule.Under optimal on-line preconcentration condition,the peak area SEF value of SDZ-MIP-PMOXA coated capillary could reach 34,with LOD as low as 0.1 ng/mL.The imprinting factor of Lyz was much higher than that of ovalbumin,conalbumin,and ovomucoid,existing in hen egg white as main proteins,indicating satisfactory specific recognition of Lyz-MIP-PMOXA-EI coated capillary.Besides,Lyz-MIP-PMOXA-EI coated capillary presented good stability even after nine consecutive runs,and the recoveries of Lyz in spiked egg white samples were 96.0-98.7%,demonstrating the proposed on-line preconcentration method was accurate and reliable,and the molecularly imprinted coating capillary with specific recognition ability can suppress the influence of other components in complex matrix on analysis of the target molecules.