A semipermeable membrane was utilized to separate the process gas helium from a continuous gas stream containing hyperpolarized $$$^{129}$$$Xe. By this the xenon partial pressure was increased by a factor of ten and the gross amount of helium was removed from the gas stream which was fed from the polarizer to a liquid probe within an NMR spectrometer. Using a sample of dissolved cryptophane-A cage allowed to separate the effects of up-concentration and polarization loss. The increase in xenon partial pressure was still a twofold higher than the polarization loss we have seen and improvements are obvious from the analysis.
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