Preservation of Nuclear Spin Order by Precipitation

We demonstrate that non-equilibrium nuclear spin order survives precipitation from solution and redissolution. The effect is demonstrated on ¹³ C- and ² H-labeled sodium fumarate, with precipitation and dissolution achieved by altering the pH. The lifetime of the spin magnetization in the precipitate suspension is found to be much longer than in solution. Our preliminary results show an extension of the effective relaxation time T₁ for the metabolite fumarate by a factor of ≈6. We show that when the free radical agent TEMPO is present in the solution, it is not incorporated into the precipitate, suggesting that this procedure may provide a means to store and transport agents polarized by dynamic nuclear polarization. Although the relaxation time, T₁ , of the precipitate suspension is longer than that of the same molecules in solution, it is significantly shorter than that observed in the immobilized solid state.