Table 1.

Measured spin–lattice relaxation times for ¹³C₁ and ¹³C₄ (S) in solutions of 20 mm [1,4-¹³C₂]fumarate dissolved in 90/10% H₂O/²H₂O or 100% ²H₂O at a magnetic field strength of 9.4 T (n = 6), 3.4 T (n = 3) and 1 mT (n = 3), and the predicted enhancement in the water signal with fumarate polarized [P(t_pol)] to 0.36 ± 0.02 at t_pol = 0. The spin–lattice relaxation time of the water protons (T_1,I) used for calculation of the predicted enhancement was 2.83 s ± 0.02 s, which was measured at 9.4 T (n = 6). Quoted errors are the standard deviation of the mean for T₁ s and the propagated errors for η_max

T1,S (in H2O) (s)	T1,S (in 2H2O) (s)	ηmax	B0 (T)
27.6 ± 0.3	30.8 ± 0.8	−0.020 ± 0.005	9.4
41.0 ± 1.3	66.6 ± 7.5	−0.14 ± 0.03	3.4
34.3 ± 5.5	49.5 ± 1.2	−450 ± 238	0.001