Evaluation of benchtop NMR Diffusion Ordered Spectroscopy for small molecule mixture analysis

Area of Science:

• Analytical Chemistry
• Nuclear Magnetic Resonance (NMR) Spectroscopy

Background:

• Diffusion Ordered Spectroscopy (DOSY) separates liquid-state chemical mixtures by molecular weight.
• DOSY has potential applications in forensics, reaction analysis, quality control, and fraud detection, similar to LC-MS.
• Benchtop NMR instruments offer lower spectral dispersion and sensitivity, leading to spectral overlap issues in mixtures.

Purpose of the Study:

• To evaluate the performance of existing high-field DOSY pulse sequences and processing methods on a 43 MHz benchtop NMR instrument.
• To demonstrate the capability of benchtop DOSY for analyzing complex mixtures with overlapping spectra and varying diffusion coefficients.

Main Methods:

• Utilized existing high-field DOSY pulse sequences and processing techniques on a 43 MHz benchtop NMR spectrometer.
• Analyzed molecular mixtures with constituents exhibiting 20% and 50% differences in diffusion coefficients.
• Employed a bespoke spectral library for matching and identification of mixture components.

Main Results:

• Successful identification of mixture constituents with 20% diffusion coefficient differences and significant spectral overlap.
• Accurate identification of mixture components with severe spectral overlap and 50% diffusion coefficient differences.
• Demonstrated the effectiveness of benchtop NMR for DOSY analysis, overcoming limitations of lower field strength.

Conclusions:

• Existing high-field DOSY pulse sequences and processing methods perform effectively on benchtop NMR instruments at 43 MHz.
• Benchtop DOSY can accurately analyze complex mixtures, even with substantial spectral overlap and minor diffusion coefficient variations.
• The combination of benchtop NMR and modern DOSY techniques offers a promising, accessible solution for research and industrial chemistry laboratories.