Study of liquid-liquid interfaces by an easily implemented localized NMR sequence

Area of Science:

• Analytical Chemistry
• Nuclear Chemistry
• Physical Chemistry

Background:

• Optimizing liquid-liquid extraction for heavy metals, especially from fission products, requires deeper understanding of underlying mechanisms.
• Current methods lack detailed spatial information near the critical liquid-liquid interface.

Purpose of the Study:

• To develop and validate a novel Nuclear Magnetic Resonance (NMR) technique for assessing concentration profiles of species in liquid-liquid extraction systems.
• To enable the study of chemical processes at the interface using standard NMR spectrometers.

Main Methods:

• Implementation of a localized NMR sequence (LOCSY) utilizing frequency-selective excitation pulses and pulsed field gradients for 1D spatial localization.
• Development of specialized data processing to generate 1D NMR spectra as a function of vertical position.
• Evaluation of the LOCSY sequence on three distinct systems: a phantom, a D(2)O/olive oil biphasic system, and saccharose dissolution in D(2)O.

Main Results:

• Demonstrated the capability of LOCSY to provide concentration profiles of chemical species.
• Successfully applied the technique to various liquid-liquid and dissolution systems.
• Highlighted the potential for studying diffusion phenomena.

Conclusions:

• The LOCSY sequence is a viable tool for studying concentration profiles near liquid-liquid interfaces.
• This NMR method can enhance the understanding and optimization of liquid-liquid extraction processes.
• Further development may expand its application to systems with broader dynamic ranges and sensitivities.