Research And Application Of Electric Stacking On Paper And Microfluidic Channels

Field amplification sample stacking（FASS）as a kind of online sample stacking method,is widely used in capillary electrophoresis.The research covers a wide range of areas,including DNA sequencing,analysis of natural products in foods and the clinical analysis of serum samples.Paper-based analytical device（PAD）shows good potential in on-site analysis due to its advantages of simple and portable,easy to operate and low cost,but the sensitivity of PAD is low.Therefore,the combination of nanoparticles（NPs）and PAD is introduced to improve the sensitivity,so as to realize on-site analysis.The first chapter introduced the principle of surface plasmon resonance（SPR）and the types and applications of SPR sensors.Subsequently,the common methods of electric stacking were introduced,including FASS,ion concentration polarization（ICP）,isotachophoresis（ITP）,sweeping and so on.Finally,the principle of FASS and its application were briefly explained in PAD and microfluidic channel.The second chapter mainly introduced a colorimetric sensing method that combined glutathione-modified silver nanoparticles（AgNPs-GSH）with PAD for environmental use to detect Pb²⁺.The Pb²⁺sensing mechanism in this study was based on the color change of AgNPs induced by SPR,which was related to the distance between adjacent AgNPs.Pb²⁺ in lake and river water could be detected by the color change of AgNPs on paper,which limited the time from sample extraction to sample analysis within 5 minutes.The results showed that the color reaction can not only perform in the paper-based fluidic channel,but also significantly enhance the concentration of the target components through FASS,which can improve the sensitivity of Pb²⁺ colorimetric detection based on mobile phone photography,and obtain better results than the spectrophotometer method.The method increased the signal intensity about four orders of magnitude by geometric field amplification,and the detection limit（LOD）of 86 nmol/L was obtained by colorimetric method based on mobile phone.It has potential application in on-site analysis to detect heavy metal ion in environmental water systems.The third chapter introduced a method combined FASS with reservoir injection in the selfmade microfluidic channel.The feasibility of the method was visualized by using the cation probe Rhodamine 6G and anion probe fluorescein sodium.The target components in hundreds of microliters of sample were deposited by the FASS effect onto the closed microfluidic channel to increase the sensitivity of optical detection,and it may break the limit of sample injection and improve the detection sensitivity of microfluidic chips.The results of this study provide an experimental basis for its possibility,and the stacked components can be recycled for offline or online mass spectrometry.