For the mass spectrographic determination of impurities in helium, the impurities were collected from the flowing he sample by solidification in a trap and coil system cooled in a liquid he bath; the He sample is maintained above atmospheric pressure and at a flow rate sufficient to avoid its liquefaction. After evacuation, the trapping assembly is warmed to ambient temperature to vaporize the collected impurities for mass spectrographic determination. A dewar vessel containing the liquid he is maintained at a proper level with respect to the trap and coil assembly by an automatically controlled lift. A detection limit of 0.01 Ppm can be achieved.
U.S. Pat. 3,662,588; May 16, 1972; Chem. Abstr. 77:96,620R
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