Microfluidic Preconcentration System Based On Accelerated Evaporation In Capillary With High Concentration Factors

The advantages of microfluidic analysis make itself successfully adapt to the main trend of miniaturization, automation, time-saving and integration for recent analytical techniques. However, the ability to manipulate small volumes of fluid is one of its strengths but also a weakness because nanoliters to microliters chambers put constraints on the detection of analytes of interest, especially when one moves towards trace amount analytes. The very nature of microfluidic devices makes sample concentration a necessary task in almost any application. So in this work, a novel and efficient microfluidic preconcentration system in capillary based on accelerated evaporation was proposed to conquer the difficulty.In the first chapter, several conventional preconcentration techniques including extraction, evaporation and electrokinetic-based method were introduced. Their advantages and disadvantages, as well as development in miniaturization were discussed in detail.In the second chapter, it put great emphasis on the applications of evaporation in analytical chemistry, such as evaporation induced pump, concentration and the formation of nanomaterials.In the third chapter, a high fold microfluidic preconcentration system in capillary based on accelerated evaporation was proposed. A stable gas-liquid phase interface between nitrogen and sample solution filled in the capillary was formed at the tip of the capillary based on capillary effect. When the nitrogen with a certain rate and temperature flew through the tip of the capillary, analyte in the sample solution was concentrated in a narrow zone near the phase interface based on accelerated evaporation. The performance of the present system was demonstrated with low concentration brilliant blue (BB) solution. The present system was also applied in determination of Fe²⁺ and FITC-labeled BSA. A highest enrichment factor of 110,000 fold for BB was obtained at the capillary tip within 15min. The present approach has the advantages of high enrichment factor, low sample consumption, simple device and fast concentration speed, which could be coupledwith many analytical systems to serve as a powerful tool for sample preconcentration.