Hi Jason,

Not sure if you can directly "read" the value of the chemical potential from NMR data (e.g. T1 relaxation time), but from data shown in this paper by Weber and Kimmich it is clear that T1 relaxation time will respond to changes in the chemical potential of a polymer.

Fig 1C. shows plots of T1 vs larmor frequency (strength of magnetic field) at different concentrations of a polymer. Since concentration is a "component" of chemical potential quantity there very well may be some correlation. Still, I think it would be worthwhile to run a series of control experiments where you know the (chemical potential) and can measure T1, to prove the concept and maybe "calibrate" your measurement.

The data obtained in the paper used a specially built relaxometer where strength of the magnet could be adjusted. If you only have access to a standard NMR instrument with a fixed field - you'll benefit most from a low-field instrument (an old school non-superconducting electromagnet NMR may work better) as changes in T1 are more sensitive to various sample parameters at lower field.

T1 relaxation process is inherent in a sytem and to measure the relaxation time, the spin system is prepared in a higher energy non(thermal)equilibrium state. Thus the energy is released to the surrounding and if it is not dissipated to the lattice, it would possibly be availed for a useful work.

Thus this makes it possible to relate (conceptually) the chemical potential [partial molal free energy] to NMR.

The build up of magnetization with the T1 relaxation time requires that the spin system get to a higher energy state to attain a thermal equilibrium with the External Field perturbation. This if one considers as a work done on the spin system to increase its energy, then can this energy of magnetic field interaction with the spin be transformed into Chemically amenable energy? For example, magnetic field effects on the chemical reactions which can be monitored by a concomitant CIDINP, does it translate itself into description in terms of Chemical Potential? Only by considering the pro and con of these would conceptually clarify the stand on Chemical Potential and its relation to NMR parameters.

The experimental requirements to measure the chemical potential can thus be further thought about.

Aravamudhan

It is not obvious whether the previous posting has been read or not. The term Chemical Potential is used whever a chemical enrgy is transformed into other forms of energy available for usefully extracting work. For example the magnetization build up does not any chemical energy getting transformed or briging about chemical changes. If the spin system energy is changed it is not obviuosly a Chemical Bond forming/breaking energies or even Chenge of state from Solid to liquid to gases which would involve intermolcular interactions. Since the number of spins available per mole of a chemical substance dpendes on the number of specified proton in the molecule there need not be always the same spin energy related to per mole of all substances. Thus trying to relate "concentration" dependence as the only criterion for depenedences of chemical potential in the case of spin system may not be all the time valid. Given the same strength of the Magnetization built up (eneregy of the spin system) the relaxation time may vary. Thus the relaxation time may be a measure of power deriverable rather than simply the total amount of energy available. Unless the relaxation time is related to its cause as a chemical transformation and that chemical transformation may relate to chemical potential and in favourable cases it may be possible to correlate the relaxation rates withy the chemical potentials. And, in this sense the caution expressed by evgeny is in place; that the chemical potential may not be directly readout from relaxation data. As far as Transverse relaxation time T2 is concerned, it is a change in the spin system ordering/aligning and no change energy is suppopsed to be associated with it. Then, changes in order a mere redistribution for the most probable state without energy changes corresponds to entropy change and the entropy change part is subtracted from the heat changes while calaculating Free energy which is related to Chemical potential.

Aravamudhan