A Mass Spectrometer Inlet System for Sampling Gases Dissolved in Liquid Phases

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A Mass Spectrometer Inlet System for Sampling Gases Dissolved

in Liquid Phases'


From RIAS, Baltimore, Maryland

Received November 23, 1962

.4 mass spectrometer inlet system has been devised which permits continuous sampling of gases dissolved in liquid phases. The principle is that of a semipermeable membrane which allows the dissolved gases, but not the liquid phases, to enter the mass spectrometer. The instrument permits rapid time response and high sensitivity. The application of this system to the study of reaction kinetics is described.


Biological systems consume or produce a variety of gases, among which are oxygen, carbon dioxide, nitrogen, hydrogen, nitrous oxide, nitrogen dioxide, methane, carbon monoxide, and others. The introduction of manometric methods to the study of the reactions in which a gas is either a product or a reactant has greatly facilitated the investigation of these processes. Measure- ment of pressure differences alone cannot, however, tell what gas (or gases) is changing concentration in a system. Separate methods must be employed to this end. Indeed, in a complex system, the usefulness of manom- etry is severely limited. The manometer is also an inherently slow instrument, chiefly because of the intrinsic nature of biological reactions, the reactions always occur in a liquid phase, while the instrument responds to changes in the gas phase. The liquid-air interface presents a diffusion barrier which makes the study of rapid alterations in the rate of gas concentration change difficult. Further complications exist in some sys- tems, for instance photosynthesis, in which the same gas is being simultaneously pro- duced and consumed by concomitant reac-

t This work described here was supported in part by the National Institutes of Health (RG- ci692) and the Air Force Office of Scient.ific Re-...