Optimizing D2O/H2O Ratio for NMR pH Measurements
Department
Chemistry
Major
Chemistry
Research Advisor
Woelk, Klaus
Advisor's Department
Chemistry
Funding Source
Missouri S&T OURE Program
Abstract
Solvents with 2H isotopes (deuterium) are frequently used in NMR spectroscopy to avoid large solvent signals and to lock the external magnetic field of the spectrometer to the deuterium resonance frequency. In this research, deuterated water (D2O) was used in investigations of the NMR chemical-shift dependency on the pH of the solution. It was found that 2-fluoro-3-hydroxymethylpyridine shows a large 19F chemical-shift dependency on pH; however, in subsequent studies, we realized that the chemical shift of 2-fluoro-3-hydroxymethylpyridine also depends on the 2H/1H composition of the solvent water. Several D2O/H2O compositions were tested, and their influence on the relationship between 19F chemical-shift and pH was evaluated. While the chemical shift dependency is relatively small for aqueous solutions with high amounts of D2O (e.g., 90%), it increased substantially if the D2O portion in the solvent is reduced. The highest chemical-shift dependency was found for an about equal mixture of D2O and H2O.
Biography
Kaysi M. Lee is a sophomore of chemistry at Missouri S&T. She began her research career as a freshman in the 2018 FYRE program of the College of Arts, Science and Business (CASB). Her work included several poster presentations at regional and international conferences as well as a talk at the Missouri Academy of Science annual meeting and the Southeastern Undergraduate Research Conference (SURC 2019). Her passion for research was featured in October/November 2018 on the S&T web portal and portrayed in the newspaper St. Louis American. Kaysi continues her research on NMR pH measurements as an OURE student for Dr. Woelk working together with graduate student Ming Huang.
Research Category
Sciences
Presentation Type
Oral Presentation
Document Type
Presentation
Award
Sciences oral presentation, Second place
Location
Ozark Room
Presentation Date
16 Apr 2019, 11:00 am - 11:30 am
Optimizing D2O/H2O Ratio for NMR pH Measurements
Ozark Room
Solvents with 2H isotopes (deuterium) are frequently used in NMR spectroscopy to avoid large solvent signals and to lock the external magnetic field of the spectrometer to the deuterium resonance frequency. In this research, deuterated water (D2O) was used in investigations of the NMR chemical-shift dependency on the pH of the solution. It was found that 2-fluoro-3-hydroxymethylpyridine shows a large 19F chemical-shift dependency on pH; however, in subsequent studies, we realized that the chemical shift of 2-fluoro-3-hydroxymethylpyridine also depends on the 2H/1H composition of the solvent water. Several D2O/H2O compositions were tested, and their influence on the relationship between 19F chemical-shift and pH was evaluated. While the chemical shift dependency is relatively small for aqueous solutions with high amounts of D2O (e.g., 90%), it increased substantially if the D2O portion in the solvent is reduced. The highest chemical-shift dependency was found for an about equal mixture of D2O and H2O.
