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The Development of Nanomaterials and "Green" Methods for Separation Science

Beilke, Michael C
http://rave.ohiolink.edu/etdc/view?acc_num=osu1448475540

Abstract Details

2015, Doctor of Philosophy, Ohio State University, Chemistry.
A primary focus of current separations research is directed toward the reduction of both the diameter and particle size distribution of the material utilized as a stationary phase. The work reported herein follows a common theme. Research is focused on novel approaches for the application of electrospun nanomaterials or the search for improved efficiency in separation science. Electrospinning is a cost-effective and simple technique that relies on repulsive electrostatic forces to generate nanofibers from a conductive polymeric solution. Electrospun nanofibers have proven to be an effective stationary phase in ultra-thin layer chromatography (UTLC), giving more efficient separations in shorter analysis time than traditional particle-based stationary phases. This technology was further enhanced by aligning the nanofibrous mats in a single direction. Aligned electrospun UTLC (AE-UTLC) devices showed improved performance relative to non-aligned electrospun (E-UTLC) phases, demonstrating higher separation efficiency and reduced time of analysis. A major disadvantage of conventional TLC analysis is that the mobile phase velocity decreases with increasing separation distance. Here, the chromatographic performance of electrospun (UTLC) stationary phases were explored with induced forced-flow of mobile phase across the stationary phase with applied potential. This type of forced-flow is used in planar electrochromatography (PEC). Compared to UTLC, improved efficiency resulted from analytes with greater migration distance. Utilization of nanofibers to provide a co-reactant electrochemiluminescent determination for nucleobases was examined. Nafion, a cation-exchange polymer becomes electrospun with the aid of a second polymer, poly(acrylic) acid (PAA). Good linear agreement between concentration and the evolution of electrochemiluminescent signal for guanine solutions are demonstrated. A “green” hydrophilic interaction chromatography (HILIC), a liquid-liquid partition mechanism, method for separating mixtures with broad ranges in polarities is explored using enhanced-fluidity mobile phases. Under HILIC conditions, analytes elute with increasing polarity. Enhanced-fluidity liquid chromatography (EFLC) involves the addition of liquefied gas to conventional liquid mobile phases. The liquefied gas provides greater diffusivity and lower viscosity character to the mobile phase. The impact of carbon dioxide addition to a methanol:water mobile phase was studied to optimize HILIC conditions. Additionally, the buffer type, pH, and ionic strength were adjusted to achieve optimal chromatographic performance. For the first time a separation of 16 ribonucleic acid (RNA) nucleosides/nucleotides was achieved in 16 minutes with greater than 1.3 resolution for all analyte pairs. An optimized separation using carbon dioxide:methanol:water mobile phase was compared to methanol:water and acetonitrile:water mobile phases. Based on chromatographic performance parameters (efficiency, resolution, and speed of analysis) and the environmental impact of the mobile phase mixtures, carbon dioxide:methanol:water mixtures are preferred over acetonitrile:water or methanol:water mobile phases for the separation of mixtures of nucleosides and nucleotides. The separation of 16 nucleosides and nucleotides, representing a large group of compounds with wide ranging polarities, is taken as an example to assess the usefulness of EFL-HILIC. Addition of gradient elution conditions were also explored to provide reduced analysis time for the wide ranging polar mixture.
Susan Olesik (Advisor)
Heather Allen (Committee Member)
Vicki Wysocki (Committee Member)
Abigail Shoben (Committee Member)
226 p.
Chemistry
HILIC; EFLC; Electrospinning; PEC; UTLC

Recommended Citations

Citations

  • Beilke, M. C. (2015). The Development of Nanomaterials and "Green" Methods for Separation Science [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1448475540

    APA Style (7th edition)

  • Beilke, Michael. The Development of Nanomaterials and "Green" Methods for Separation Science. 2015. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1448475540.

    MLA Style (8th edition)

  • Beilke, Michael. "The Development of Nanomaterials and "Green" Methods for Separation Science." Doctoral dissertation, Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1448475540

    Chicago Manual of Style (17th edition)

osu1448475540
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This open access ETD is published by The Ohio State University and OhioLINK.