# Lifetime of Parahydrogen in Aqueous Solutions and Human Blood.
> 水溶液およびヒト血液中におけるパラ水素の寿命に関する研究


## Abstract

Parahydrogen (pH₂), a nuclear spin isomer of molecular hydrogen, forms the basis of parahydrogen-induced polarization (PHIP), which can amplify NMR signals by several orders of magnitude. This study measured longitudinal relaxation times (T₁) and pH₂ spin-state lifetimes (τ) across multiple media, including methanol, water, oxygenated solutions, NaCl solutions, rhodium-catalyst-containing solutions, and human blood. T₁ values consistently fell within 1.4–2 s, while τ values ranged from approximately 10 to 300 minutes depending on the medium. A relaxation model incorporating both T₁ and τ was developed to enable more accurate theoretical predictions of hydrogen spin states in PHIP experiments. The relatively extended lifetimes observed across biological and aqueous environments suggest that in vivo PHIP-based NMR applications may be feasible.

### Mechanism

Parahydrogen spin order persists for 10–300 minutes in aqueous and biological media. A relaxation model combining longitudinal relaxation time T₁ (1.4–2 s) and spin-state lifetime τ enables theoretical prediction of nuclear spin states in PHIP experiments, supporting potential in vivo NMR signal enhancement.

## Bibliographic

- **Authors**: Schmidt AB, Wörner J, Pravdivtsev A, Knecht S, Scherer H, Weber S, et al.
- **Journal**: Chemphyschem
- **Year**: 2019 (2019-10-02)
- **PMID**: [31479580](https://pubmed.ncbi.nlm.nih.gov/31479580/)
- **DOI**: [10.1002/cphc.201900670](https://doi.org/10.1002/cphc.201900670)
- **PMC**: [PMC7687157](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7687157/)
- **Study type**: in vitro study
- **Delivery route**: in vitro
- **Effect reported**: not assessed

## Delivery context

This is basic research at the cellular or molecular level. For human application, inhalation is the most promising delivery route, but inhalation carries explosion risk and concentration matters (empirical LFL of 10%; high-concentration devices are not recommended).

## Safety notes

This is basic research at the cellular or molecular level. For human application, inhalation is the most promising delivery route, but inhalation carries explosion risk and concentration matters (empirical LFL of 10%; high-concentration devices are not recommended).

See also:
- [Inhalation concentration and LFL / UFL](https://h2-papers.org/en/safety-notes/inhalation-concentration)
- [Consumer Affairs Agency accident cases](https://h2-papers.org/en/safety-notes/accident-cases)
- [Inhalation safety threshold lineage](https://h2-papers.org/en/safety-notes/lineage)

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> **Cite as**: H2 Papers — PMID 31479580. https://h2-papers.org/en/papers/31479580
> **Source**: PubMed PMID [31479580](https://pubmed.ncbi.nlm.nih.gov/31479580/)