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APPLICATION OF POLARITY MODELS TO CHARACTERIZING THE REVERSED-PHASE LIQUID CHROMATOGRAPHY SEPARATION OF CHIRAL STEROID ISOMER PAIRS EMPLOYING VARIOUS TERNARY MOBILE PHASES

Kipruto, Eric Wekesa
http://rave.ohiolink.edu/etdc/view?acc_num=csu1631533233544729

Abstract Details

2021, Doctor of Philosophy in Clinical-Bioanalytical Chemistry, Cleveland State University, College of Sciences and Health Professions.
Three models of mobile phase polarity were investigated for fitting to selectivity data in the C18 HPLC separation of steroid enantiomers. Models examined were Snyder’s Solvent Selectivity Triangle, and the solvatochromatic ET(30) and normalized ETN scale. Each consists of polarity components that add up to a composite polarity (P’). The polarity components are: acidity, basicity and dipolarity/polarizbility. The fractional contribution of each polarity component to the P’ is derived from gas-liquid partition coefficients for solutes done by Rohrschneider’s, incorporated into Snyder’s Solvent Selectivity Triangle, and Kamlet-Taft’s solvatochromatic parameters, incorporated into ET(30) and ETN. The models were tested by employing ternary mobile phases of two organic modifiers (different binary combinations of methanol, acetonitrile, isopropanol, dioxane, tetrahydrofuran) and water, in which polarity of the mobile phase was changed by varying the ratio of organic modifiers while keeping the strength constant by varying water percentage. Previous published studies employ binary mobile phases of one organic modifier in water, varying polarity by changing organic modifier concentration, while also changing mobile phase strength. In the present work, effects of polarity components on selectivity factor alone were investigated, keeping mobile phase strength constant. The steroid pairs separated were: 3-keto-5β-abiraterone and 3-keto-5α-abiraterone; 3β-OH-5β-abiraterone and 3α-OH-5β-abiraterone; 3β-OH-5α-abiraterone and 3α-OH-5α-abiraterone, 17α-estradiol and 17β-estradiol and 11α-hydroxyprogesterone and 11β-hydroxyprogesterone. Selectivity factor data was best fitted by the ET(30) model for non-acetonitrile containing mobile phase, correlating with dipolarity/polarizbility π* component for all the enantiomer pairs, except for the 3β-OH-5α-abiraterone and 3α-OH-5α-abiraterone’s pair. Summing π* and β components of these steroid pairs resulted in better fit. The exception (3β-OH-5α- and 3α-OH-5α-abiraterone’s pair) correlated with the acidity (α) and α+π* component(s). For all non-ACN mobile phases, there was mostly a linear relationship of selectivity factor versus the value of the above-mentioned polarity components when plotted together, independent of the organic modifiers employed. Depending on the enantiomer pair, peak separation either increases or decreases with increasing polarity of the particular polarity component(s). Computational studies were done to solve for 3D structures of the enantiomer pairs, including calculations of magnitudes and directions of the dipole moments. How these factors related to their chromatography are discussed.
David Anderson, Professor (Advisor)
Aimin Zhou, Professor (Committee Member)
Nolan Holland, Professor (Committee Member)
Baochuan Guo, Professor (Committee Member)
Yana Sandlers, Assiatant Professor (Committee Member)
Analytical Chemistry; Chemistry

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Citations

  • Kipruto, E. W. (2021). APPLICATION OF POLARITY MODELS TO CHARACTERIZING THE REVERSED-PHASE LIQUID CHROMATOGRAPHY SEPARATION OF CHIRAL STEROID ISOMER PAIRS EMPLOYING VARIOUS TERNARY MOBILE PHASES [Doctoral dissertation, Cleveland State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=csu1631533233544729

    APA Style (7th edition)

  • Kipruto, Eric. APPLICATION OF POLARITY MODELS TO CHARACTERIZING THE REVERSED-PHASE LIQUID CHROMATOGRAPHY SEPARATION OF CHIRAL STEROID ISOMER PAIRS EMPLOYING VARIOUS TERNARY MOBILE PHASES. 2021. Cleveland State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=csu1631533233544729.

    MLA Style (8th edition)

  • Kipruto, Eric. "APPLICATION OF POLARITY MODELS TO CHARACTERIZING THE REVERSED-PHASE LIQUID CHROMATOGRAPHY SEPARATION OF CHIRAL STEROID ISOMER PAIRS EMPLOYING VARIOUS TERNARY MOBILE PHASES." Doctoral dissertation, Cleveland State University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=csu1631533233544729

    Chicago Manual of Style (17th edition)

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