Development of analytical Fourier transform nuclear magnetic resonance spectroscopy for sensitivity enhancement and mixture analyses

Miscellaneous · Sun Jan 01 00:00:00 EST 1989

OSTI ID:7039117

Ha, Steven Tung-Kuen

FT-NMR has been explored with regard to its ability to analyze mixtures. The recycled-flow NMR method, which permits premagnetized nuclei to flow into the detector before acquisition, allows substantial sensitivity enhancement, especially for those nuclei with inefficient relaxation mechanisms. The enhancement factor of flow NMR over static NMR is between 3.5-5 for the slowly relaxing carbon nuclei. Similar enhancements have been observed in 1D spin-echo and 2D J-resolved experiments. A mathematical discussion of the potential enhancement in recycled-flow NMR indicates that this enhancement could be as large as 20. In addition, flow NMR also provides accurate quantitative {sup 13}C data in substantially less time. These dual advantages of recycled-flow NMR have been applied to analyze two mixtures and to determine the MW{sub n} of several polyethylene glycols. An on-line continuous-flow high performance liquid chromatography (HPLC)/{sup 1}H NMR system has been developed on a 400 MHz FT-NMR spectrometer. The detection limit of this system is estimated to be 30 {mu}g, using alanine and caffeine as test samples. For practical HPLC/NMR analyses, a 200 {mu}g quantity of material may be required. The eluent used in reversed-phase (RP)-HPLC, which interfaces with the proton signals of the eluates, is suppressed by the binomial and WATR (Water Attenuation by T{sub 2} Relaxation) pulse methods. RP-HPLC/{sup 1}H NMR is applied to the separation and identification of antimycin A, a class of antibiotics used in fishery management, and its degradation products, antimycin lactones. A method based on the long range J-resolved (LRJR) NMR experiment is developed to analyze mixtures. LRJR is used to select those carbons that are modulated due to the long range {sub 1}H-{sup 13}C coupling to a specific proton(s).

• Research Organization: California Univ., Riverside, CA (United States)
• OSTI ID: 7039117
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
MIXTURES
CHEMICAL ANALYSIS
NUCLEAR MAGNETIC RESONANCE
SENSITIVITY
CARBON 13
EXPERIMENTAL DATA
FOURIER TRANSFORM SPECTROMETERS
GLYCOLS
LIQUID COLUMN CHROMATOGRAPHY
MATHEMATICAL MODELS
QUANTITATIVE CHEMICAL ANALYSIS
ALCOHOLS
CARBON ISOTOPES
CHROMATOGRAPHY
DATA
DISPERSIONS
EVEN-ODD NUCLEI
HYDROXY COMPOUNDS
INFORMATION
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
MEASURING INSTRUMENTS
NUCLEI
NUMERICAL DATA
ORGANIC COMPOUNDS
RESONANCE
SEPARATION PROCESSES
SPECTROMETERS
STABLE ISOTOPES
400102* - Chemical & Spectral Procedures