Advancements and Applications of Ionic Conductivity Detection to Microcolumn and Microfluidic Separations Public Deposited

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  • March 19, 2019
  • Dennis, Patty Jorene
    • Affiliation: College of Arts and Sciences, Department of Chemistry
  • The research presented herein describes developments and applications of conductivity detection on both capillary and microfluidic platforms. Contactless conductivity detection is the foundation for this work and has been developed to provide an alternative means of universal detection from the traditionally used method of ultraviolet absorbance. Through the application of conductivity detection, a photothermal absorbance detector has also been developed. This detector provides a means of optical detection that is not subject to some of the limitations found in traditional absorbance methods, such as path length, and as such, has been applied to the small volume sampling regions found in microfluidics. Experimental investigations have been performed for the optimization of contactless conductivity detection, including an evaluation of electrical parameters and components, such as excitation frequency and voltage, capillary inner diameter, detector position, electrode length, and system parameters revolving around buffer ionic strength and composition. Through a thorough investigation of numerous buffer systems in an attempt to elucidate additional compositional sources of noise, a novel theory of ion movement under the confinement of the electrical fields and fluid flow in capillary electrophoresis systems has been developed. Experimental evidence has indicated the presence of an ion depletion region at the capillary inlet which indicates a unique interaction between these phenomena. Contact conductivity detection has been developed for use with microfluidic devices. A planar electrode configuration has been developed for conductivity detection on microchips. The decreased area inherent to planar electrodes necessitates a contact detection method. Proof of concept studies and investigation into electrode geometry and fabrication have been performed. Initial studies into the use of polyelectrolytic salt bridge electrodes have also been undertaken as an alternative to traditional metal electrode systems. Photothermal absorbance detection has been developed for use with microfluidic systems as an alternative to absorbance detection. Due to the path length dependence of traditional absorbance detection methods, it has been severely limited in practicality for small volume detection. Both theoretical and experimental investigations have shown an enhancement in the photothermal signal observed on a microfluidic platform. In addition, modifications to the photothermal system have also been made to enhance the stability and magnitude of the signal observed.
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  • In Copyright
  • Jorgenson, James
  • Open access

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