Figure 2. Preserving hyperpolarization out of the polarizer.

(a) Procedure for lifting the sample above the polarizer and putting it back. In practice, the sample is lifted manually by 2 cm into a coil that provides a supplementary field of 40 mT, parallel to the B₀ field of the polarizer. In 5 s, the sample and the supplementary coil are then lifted together 90 cm above the centre of the main B₀ field. The sample is kept at room temperature for ∼30 s and is put back into the polarizer in ∼5 s. (b) ¹³C NMR spectra before and after lifting the solid powder out of the polarizer. ¹H decoupled ¹³C NMR of [¹³C₂, ¹⁵N]glycine, [¹³C₃, ¹⁵N]alanine, [1-¹³C]glucose and [1-¹³C]pyruvate measured with 0.5° nutation angle pulses after 10 min ¹H DNP followed by a single ¹H–¹³C cross-polarization contact, before (red line) and after (blue line) lifting the sample according to the procedure described in a, leading to polarization losses of ca. –8%, –13%, –15% and –70%, respectively, illustrated by the arrows.