Schmidt, Andreas B., Jakob Wörner, Andrey Pravdivtsev, Stephan Knecht, Harald Scherer, Stefan Weber, Jürgen Hennig, Dominik Elverfeldt, and Jan‐Bernd Hövener. “Lifetime of Para-Hydrogen in Aqueous Solutions and Human Blood.” ChemPhysChem 20, no. 19 (October 2, 2019): 2408–12.
Molecular hydrogen has unique nuclear spin properties. Its nuclear spin isomer, parahydrogen (pH2), was instrumental in the early days of quantum mechanics and allows to boost the NMR signal by several orders of magnitude. pH2-induced polarization (PHIP) is based on the survival of pH2 spin order in solution, yet its lifetime has not been investigated in aqueous or biological media required for in vivo applications. Herein, we report longitudinal relaxation times (T1) and lifetimes of pH2 ( tPOC) in methanol and water, with or without O2, NaCl, rhodiumcatalyst or human blood. Furthermore, we present a relaxation model that uses T1 and tPOC for more precise theoretical predictions of the H2 spin state in PHIP experiments. All measured T1 values were in the range of 1.4–2 s and tPOC values were of the order of 10–300 minutes. These relatively long lifetimes hold great promise for emerging in vivo implementations and applications of PHIP.