
NMR Cryoporometry
NMR Cryoporometry is an
NMR method of measuring
Pore-Size Distributions
that is based on Thermodynamics.
NMR Cryoporometry Protocol
The protocol of an NMR Cryoporometry (NMRC) experiment involves absorbing a liquid into pores; freezing the liquid, and then warming the sample. The amplitude of the NMR echo amplitude is monitored using an NMR relaxation spectrometer, so as to determine the amount of liquid that has melted as a function of temperature. This gives a measure of the pore volume vs. melting temperature, and hence, via the Gibbs-Thomson equation, the pore size distribution.
Do you need to study the physical properties of your samples ?
Why not study your samples with time-domain NMR ?
Are you interested in the chemical structure of your samples ? - in which case you may be best with a high-frequency Fourier transform NMR spectrometer. The higher the frequency the better resolved the spectra.
Or are you interested in the physical properties of your samples ? - such as the viscosities, the mobility or stiffness of your samples - are they crystalline / amorphous / plastic / liquid ? - In which case you are often best to work in the time-domain, where the NMR relaxation times are better separated at lower frequencies.
Time-domain NMR to study the physical properties of your samples.
When to use Spectral and Time-Domain NMR
Studying Crystalline & Amorphous sample using Time-Domain NMR
NMR Cryoporometry
Theory and Protocol.
NMR Cryoporometry (NMRC) Theory
Thermodynamic pore-sizing methods are based on the Gibbs Equations :
Constant Temperature variant : the Kelvin Equation - hence gas adsorption pore-sizes.
Constant Pressure variant : the Gibbs-Thomson Equation - NMR Cryoporometry pore-size distributions : measurement range 1nm to 1um, or wider - Non-destructive.
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