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Electrospun Nafion/Polyacrylonitirile Nanofibers As Ultrathin Layer Chromatography Stationary Phase THESIS Presented in Partial

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Electrospun Nafion/Polyacrylonitirile Nanofibers As Ultrathin Layer Chromatography Stationary Phase THESIS Presented in Partial Electrospun Nafion/Polyacrylonitirile Nanofibers as Ultrathin Layer Chromatography Stationary Phase THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Yanhui Wang Graduate Program in Chemistry The Ohio State University 2016 Master's Examination Committee: Dr. Susan Olesik, Advisor Dr. Philip Grandinetti Copyright by Yanhui Wang 2016 Abstract A method to separate charged molecules on ultrathin layer chromatographic (UTLC) plates using electrospun Nafion/Polyacrylonitrile (PAN) nanofibers as the stationary phase is described in this work. Sulfonate groups and the hydrophobic tetrafluoroethylene backbone on Nafion enable the UTLC plates to separate analytes based on charge and hydrophobicity. The addition of PAN with large molecular weight makes Nafion solution more compatible with the electrospinning process. Various compositions of Nafion and PAN in N, N-dimethylformamide were studied to create a bead-free nanofiber network. Nafion-PAN nanofibers as a stationary phase for UTLC were evaluated using the separations of amino acids and proteins, followed by visualizations using ninhydrin and fluorescamine, respectively. The electrospun Nafion- PAN plates showed high chemical stability in a wide range of buffer mobile phases with various organic modifiers. Mobile phase velocity decreased with the addition of Nafion into the electrospinning solutions. Contributions to band broadening of the spots were also investigated. The efficiency of separating amino acids was greatly improved compared to that determined on commercial ion exchange TLC. The separation of four proteins demonstrated the feasibility of Nafion-PAN UTLC for separating large biomolecules. ii Dedication This document is dedicated to my family. iii Acknowledgments First and foremost, I would like to express my sincere appreciation to my research advisor, Professor Susan Olesik for her encouragement and guidance throughout the past two years. I’m grateful to her for her great motivation and patience during all the difficult times in my research. Without her valuable ideas and expertise, the completion of this work would have not been possible. My thanks also go out to all of the members in Olesik group, especially Michael Beilke, Martin Beres, Jiayi Liu, Raffeal Bennett and Juan Bian, for providing a sounding board of ideas and the most pleasurable research environment. I may not have been able to solve problems over the duration of my project without their generous counsel and help. Also, I must recognize the National Science Foundation for providing the funding for this work. Additionally, I would like to express my gratitude to my beloved parents for their endless and unconditional support and love. No matter how hard life can get, they are always there like a safe harbor to get me recharged and keep me going. Without their moral and financial support, I would certainly not be here today. Last but certainly not least, I would like to give my thanks to my boyfriend Wey Jian Tan, who has always been there for me through my ups and downs for the past four iv years. He always encourages me to be patient and persistent on what I am doing. Thanks for all the positive thoughts, for reminding me not to give up and for having faith in me. v Vita 2013................................................................B.S. Chemistry, SUNY-Buffalo 2013 to present ..............................................Graduate Teaching Associate, Department of Chemistry and Biochemistry, The Ohio State University Publications Deuro, R. E.; Leiker, K. M.; Wang, Y.; Deuro, N. J.; Milillo, T. M; Bright, F.V. “Rapid, Nondestructive Denim Fiber Bundle Characterization Using Luminescence Hyperspectral Image Analysis,” Appl. Spectrosc. 2015, 69, 103-114. Fields of Study Major Field: Chemistry vi Table of Contents Abstract ............................................................................................................................... ii Dedication .......................................................................................................................... iii Acknowledgments.............................................................................................................. iv Vita ..................................................................................................................................... vi Publications ........................................................................................................................ vi Fields of Study ................................................................................................................... vi Table of Contents .............................................................................................................. vii List of Tables ...................................................................................................................... x List of Figures .................................................................................................................... xi Chapter 1: Introduction ....................................................................................................... 1 1.1 Thin Layer Chromatography ................................................................................ 1 1.2 Electrospinning..................................................................................................... 2 1.3 Ion Exchange Chromatography ............................................................................ 7 1.4 Nafion ................................................................................................................... 8 1.5 Nafion-Polyacrylonitrile Electrospun Ultrathin Layer Chromatography ........... 11 1.6 Research Focus ................................................................................................... 12 vii Chapter 2: Experimental ................................................................................................... 13 2.1 Materials ............................................................................................................. 13 2.2 Instrumentation................................................................................................... 14 2.3 Preparation of Nafion/PAN solution .................................................................. 14 2.4 Electrospinning................................................................................................... 15 2.5 Nanofiber and Mobile Phase Compatibility ....................................................... 15 2.6 Ultrathin Layer Chromatography ....................................................................... 15 2.7 Visualization....................................................................................................... 16 Chapter 3: Results and Discussion .................................................................................... 19 3.1 Optimization of electrospun Nafion/PAN nanofiber stationary phase ............... 19 3.1.1 Effect of polymer compositions on nanofiber structure ................................... 19 3.1.2 Effect of solution flow rate on nanofiber structure ........................................... 22 3.1.3 Effect of voltage on nanofiber structure ........................................................... 25 3.1.4 Effect of distance on nanofiber structure .......................................................... 28 3.1.5 Electrospun Nafion/PAN nanofibers ................................................................ 31 3.2 Nanofiber stability in mobile phases .................................................................. 34 3.3 Separation of amino acids .................................................................................. 36 3.3.1 Optimization of mobile phase........................................................................... 36 3.3.2 Comparison of Nafion/PAN UTLC and commercial ion exchange TLC ........ 41 viii 3.3.3 Mobile phase velocity ....................................................................................... 46 3.3.4 Band broadening ............................................................................................... 49 3.4 Separation of proteins......................................................................................... 52 3.4.1 Visualization Reagent ....................................................................................... 53 3.4.2 Buffer selection ................................................................................................. 54 3.4.3 Effect of buffer pH ........................................................................................... 60 3.4.4 Effect of salt concentration ............................................................................... 62 3.4.5 Effect of organic modifier concentration .......................................................... 65 Chapter 4 Conclusion ........................................................................................................ 69 References ......................................................................................................................... 71 ix List of Tables Table 1. Fluorescamine spray procedure. ......................................................................... 18 Table 2. Structures, pI values and charges in pH 4.0 of selected amino acids. ................ 43 Table 3. Retardation factors of amino acids separated on Nafion/PAN UTLC plate and on commercial
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