Freezing the Moment: Monitoring Freezing Processes Under MAS Conditions.

Area of Science:

• Physical Chemistry
• Materials Science
• Analytical Chemistry

Background:

• Studying the freezing of aqueous systems is crucial for understanding phase transitions in various materials.
• Traditional methods for analyzing liquid and solid states often require different experimental setups.
• Nuclear Magnetic Resonance (NMR) spectroscopy offers a powerful, non-invasive tool for molecular analysis.

Purpose of the Study:

• To investigate the freezing process of diverse aqueous systems using Magic Angle Spinning (MAS) NMR.
• To detail the prerequisites, challenges, limitations, and reproducibility of MAS NMR for freezing studies.
• To explore the application of MAS NMR for analyzing aqueous systems at sub-freezing temperatures.

Main Methods:

• Utilized Magic Angle Spinning (MAS) NMR spectroscopy without specialized equipment.
• Analyzed multiple NMR-active nuclei (¹H, ¹¹B, ¹³C, ²³Na, ⁷⁹Br) in various aqueous systems.
• Compared liquid and solid states of the same sample within a single experimental setup.

Main Results:

• Demonstrated the feasibility of studying aqueous solutions and gels across phase transitions using MAS NMR.
• Provided comprehensive insights into the practical aspects, including reproducibility and limitations, of the technique.
• Showcased the ability to analyze samples under sub-freezing conditions, expanding the scope of NMR applications.

Conclusions:

• MAS NMR is an accessible and versatile technique for investigating the freezing behavior of aqueous systems.
• The method allows for detailed characterization of phase transitions and provides additional information on sample properties.
• This approach facilitates the study of systems in both liquid and solid states, as well as at sub-freezing temperatures.