Radiant energy – Ionic separation or analysis – Methods
Patent
1989-01-13
1990-12-04
Berman, Jack I.
Radiant energy
Ionic separation or analysis
Methods
250288, 250281, 436173, H01J 4914, H01J 4942
Patent
active
049755765
DESCRIPTION:
BRIEF SUMMARY
The invention is directed to a method for identifying the concentrations of individual types of molecules in gas mixtures, whereby the gas mixture to be examined is subjected to a selective pre-treatment and the product of this pre-treatment is then examined mass spectrometrically. The invention is also directed to an apparatus for the implementation of such a method.
Deriving as a direct problem in the mass-spectrometric examination of gas mixtures containing different types of molecule for the concentrations of individual types of molecule, is that different molecules having identical molecular mass cannot be separately recognized by the mass spectrometer due to the physical conditions on which the function thereof is based. For example, this applies to the combination of nitrogen monoxide (NO) and formaldehyde (CH.sub.2 O) each having 30 amu (atomic mass unit), to the combination of oxygen (O.sub.2) and methylalcohol (CH.sub.3 OH) each having 32 amu, and to the combination of CO with N.sub.2 and C.sub.2 H.sub.6 each of which has 28 amu.
Since measurement with a mass spectrometer is relatively simple to manipulate, and is precise and fast, efforts were undertaken to remedy this disadvantage. Methods and, respectively, apparatus of the species initially cited have been disclosed wherein the gas mixture to be examined is subjected to a selective pre-treatment in order to enable a pre-separation of the types of molecules of interest that have the same molecular mass.
Among the apparatus that have become known are those sold under the designation GCMS Systems. In the GCMS Systems apparatus a gas chromatograph is employed thereto, this enabling a chronologically graduated feed of the individual types of molecules to the mass spectrometer that carries out the actual measurement. The chronological graduated feed occurs as a result of the different transit times of the individual types of molecules and thus enables a separate identification--at least within limits--of the individual types of molecules or, respectively, of their concentration. For example, the molecules N.sub.2 O and CO.sub.2 that have the same molecular mass can thus be separately acquired, these having noticeably different transit times in the gas chromatograph.
In this context, however, there are already problems. For example, in the detection of different alcohols that have similar transit times in the gas chromatograph and that are fragmented in the mass spectrometer, the separate identification of individual types of molecules is impossible in practice. The extremely low response speed of these GCMS Systems is to be cited as a further disadvantage, this response speed, of course, being greatly restricted by the transit times of the gas mixtures being examined or, respectively, of the types of molecules to be detected in the gas chromatograph.
SUMMARY OF THE INVENTION
An object of the present invention is an improved method or, respectively, apparatus of the species initially cited such that the disadvantages of the known arrangements are avoided and such that, in particular, the concentration of individual types of molecules having the same molecular mass can be identified in a simple way in gas mixtures under examination without great delays caused by the measurement or by the preparation of the gas mixture for the measurement.
For separate identification of the concentration of molecules having the same molecular mass, this is inventively achieved in that the gas mixture to be examined is ionized with primary ions under single pulse conditions in hard vacuum, whereby the primary ions employed have an internal energy slightly above, preferably .ltoreq.2 eV above, that required for generating product ions representing the respective type of molecule of interest, and have a translational pulse energy of such an amount in the respective center-of-mass system that the kinetic effect on the ionization is negligible in comparison to the influence of the internal energy, preferably a pulse energy below 10 eV, and in that the mass-spectrometric
REFERENCES:
patent: 3555272 (1971-01-01), Munson et al.
patent: 4005291 (1977-01-01), Arsenault
patent: 4234791 (1980-11-01), Enke et al.
patent: 4378499 (1983-03-01), Spangler et al.
Kalinoski et al, Analytical Chemistry, vol. 58, No. 12, Oct. 1986, pp. 2421-2425.
Szabo, International Journal of Mass Spectrometry and Ion Processes, vol. 73, No. 3, Nov. 28, 1986, pp. 197-235.
Federer Werner
Villinger Johannes
Berman Jack I.
V & F Analyse- und Messtechnik GmbH
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