US3916188A - Method of electrostatic filtration - Google Patents

Method of electrostatic filtration Download PDF

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Publication number
US3916188A
US3916188A US434695A US43469574A US3916188A US 3916188 A US3916188 A US 3916188A US 434695 A US434695 A US 434695A US 43469574 A US43469574 A US 43469574A US 3916188 A US3916188 A US 3916188A
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mass
ion
ions
primary
analyzer
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Expired - Lifetime
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US434695A
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English (en)
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Fernand Marcel Devienne
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Bpifrance Financement SA
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Agence National de Valorisation de la Recherche ANVAR
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/26—Mass spectrometers or separator tubes
    • H01J49/28—Static spectrometers
    • H01J49/284—Static spectrometers using electrostatic and magnetic sectors with simple focusing, e.g. with parallel fields such as Aston spectrometer
    • H01J49/286—Static spectrometers using electrostatic and magnetic sectors with simple focusing, e.g. with parallel fields such as Aston spectrometer with energy analysis, e.g. Castaing filter
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/02—Details
    • H01J49/10—Ion sources; Ion guns
    • H01J49/14—Ion sources; Ion guns using particle bombardment, e.g. ionisation chambers

Definitions

  • This invention relates to a method and a device for electrostatic filtration of secondary ions of mass m, said ions being in a given mass ratio with a primary ion of mass M which has formed said secondary ions by fission.
  • the invention has a large number of practical applications, especially in the field of accurate determination of the molecular mass of substances which have a high molecular mass, in the analysis of gas mixtures and in the separation of isotopes of a given chemical species.
  • the method according to the invention therefore makes it possible to measure the ratio M/m with a standard of accuracy of the same order of magnitude.
  • a number of applications can be contemplated such as, for example, the following:
  • the mass M of the primary ion is unknown, it will of interest especially if the mass M is of very high value and one of the products of dissociation of the primary ion M results in a well-known secondary ion of unit mass such as carbon C, for example, or one of the groups CH, N, CH OH, NH, 0, CH and so forth which are in that case readily identifiable by means of a low-resolution magnetic analyzer of the permanent magnet type.
  • the method according to the invention provides a simple means of achieving this aim by selecting a readily identifiable secondary ion of mass m from the secondary ions which can be formed in a predictable manner at the time of dissociation of a primary ion of mass M. Under these conditions, it is only necessary to regulate the different voltages V V and V" employed in the method in order to form an ion filter which will allow only the intended secondary ion of mass m to pass out at the exit end of the electrostatic analyzer.
  • the separation of isotopes of a given chemical substance can readily be carried out by means of the method according to the invention, starting from a compound of said substance.
  • molecules of said compound are ionized and if it is possible as a result of inelastic collision with neutral gas molecules to dissociate said ions in order that the isotope of mass m to be isolated may thus be caused to appear, it is then only necessary to adjust the voltages V V and V" in such a manner as to achieve filtration of said mass m of the isotope with respect to the molecular mass M of the starting compound.
  • the present invention is also directed to a device for the practical application of the method described in the foregoing.
  • Said device is mainly characterized in that it comprises in combination a source of ions of the substance of molecular mass M which are extracted at the voltage V,, a collision box containing molecules of gas and especially a rare gas and brought to a potential V an electrostatic analyzer for selecting the ions of energy eV", a retractable electrostatic detector for displaying the presence of secondary ions at the exit end of said analyzer.
  • the method according to the invention is performed very easily be means of equipment which is essentially of a conventional type.
  • the main feature of the device employed lies in the fact that it comprises a collision box which contains molecules of gas and preferably of rare gases at a very low pressure, said collision box being brought to a predetermined potential V It is in this very box that the vital phase of the process takes place, namely the dissociation of the primary ions of mass M, the creation of secondary ions of mass in and the transfer to said secondary ions of the portion m/M of the initial energy of the primary ions of mass M.
  • the detector which immediately follows the electrostatic analyzer meets two essential objectives: in the first place, it serves to check whether the ions of mass m have in fact been filtered and have passed through the system; in the second place, by measuring the peak height corresponding to the current of ions of mass m, the detector serves to determine the intensity of the filtered ion beam, which gives the value of the concentration of the ion M within the collision box.
  • Said detector is preferably intended to be removable in order that it can be withdrawn so as to permit inspection of the beam of ions of mass m in a magnetic analyzer.
  • a magnetic analyzer having low resolution since all the ions have already been filtered in energy by the device; this analyzer can be of a simple permanent-magnet type which is low in cost price.
  • the ion source which serves to produce the primary ions of molecular mass M is itself constituted by a collision box of a type known per se which is brought to a potential V and in which the substance of molecular mass M in any desired form (solid, liquid or gaseous) is subjected directly to a molecular beam which is preferably a neutral gas and causes the desired ionization.
  • a collision box of a type known per se which is brought to a potential V and in which the substance of molecular mass M in any desired form (solid, liquid or gaseous) is subjected directly to a molecular beam which is preferably a neutral gas and causes the desired ionization.
  • the above-mentioned collision box is provided in addition to the aperture through which the molecular beam passes with one or a number of further lateral extraction apertures which serve to perform certain additional simultaneous analyses in regard to the characteristics of the formed ions of mass M.
  • the device aforesaid can comprise a plurality of collision boxes which are mounted in series and between each of which are placed an electrostatic analyzer and a removable detector.
  • This arrangement indeed proves to be advantageous when the primary ion of molecular mass M to be analyzed has a very high mass and when it is necessary to carry out a number of successive decompositions in order to obtain as an end result an ion of mass m which can readily 4 be analyzed.
  • the different successive collision boxes are brought to potentials V V V and the electrostatic analyzers are so adjusted as to filter the energies eV, eV eV.
  • the relations between mass ratios and voltages must clearly be written at each dissociation stage.
  • the voltages V V and V applied to the different components of the device aforesaid can be selected in accordance with a wide range of different modes ofoperation; said voltages may in particular be positive, negative or zero, constant or variable, depending on the particular problems to which the method of ion filtration in accordance with the invention is applied.
  • the method according to the invention offers a large number of decisive advantages and chief among these can be listed the following:
  • the separative power is independent of the peak ratio, that is to say of the relative concentrations of the substances which are present;
  • FIG. 1 illustrates a device for the electrostatic filtration of ions by means of a single collision box
  • FIG. 2 illustrates a device for the electrostatic filtration of ions which comprises two collision boxes.
  • FIG. 1 a first collision box 1 of known type which is brought to a potential V and is used for the production of primary ions of molecular mass M by bombardment of a target by means of the molecular beam 2.
  • the box 1 is fitted with means (not shown) for the introduction of the substance to be studied and comprises a device 3 consisting of plates for extracting ions of mass M which are formed within the box 1.
  • the ions of unit electric charge and of mass M produced within the box 1 are extracted from this latter with the kinetic energy eV;.
  • the collision box 1 further comprises a lateral exit 4 which is also provided with an extraction device 5.
  • Said device 5 serves to ob tain at 6 a beam of ions of mass M for experiments or analyses which it is desired to perform at the same time as the filtration of ions in accordance with the invention
  • Said second box is also filled with molecules of a rare gas (helium, argon, neon or krypton) at a very low pressure within the range of torr to 2 X l0 torr, for example.
  • the exit aperture 9 is provided with an extraction device 1 1 fitted in the same manner as the device 3 with a certain number of plates which are brought to different poten tials.
  • the device of FIG. 1 then comprises an electrostatic analyzer 12 in which the two circular cylindrical electrodes 13 and 14 are brought to potentials such that the complete assembly allows only those ions which have a kinetic energy eV" to be filtered along the circular median path 15.
  • the electrodes 13 and 14 are brought to symmetrical potentials with respect to ground in order to ensure that the path 15 itself is at ground potential and that the ions which follow said path are not subjected within the interior of the analyzer 12 to any exchange of energy with the field as this would have the effect of either accelerating the ions or of slowing them down.
  • the analyzer 12 can be of any known type and can in particular have any angular aperture which may be desired. In the example described, an angular aperture equal to 127 has been selected.
  • the detector 16 is mounted at the exit of the analyzer 12 and is retractable, with the result that it can be placed either in the position 16a shown in full lines in which case it intercepts the beam or in the withdrawn position 16b shown in chain-dotted lines in which case it does not intercept the beam.
  • FIG. 1 The device of FIG. 1 is finally completed by a lowresolution magnetic analyzer 17 of the permanent-magnet type equipped with its detector 18.
  • the magnetic analyzer 17 and the detector 18 of a type known per se are employed solely when it is desired to carry out accurate identification of the mass m and therefore of the chemical nature of the ions filtered by the electrostatic analyzer 12.
  • FIG. 1 the different elements are illustrated in a highly diagrammatic plan view seen from above; similarly it has been preferred for the sake of enhanced clarity of the drawings to omit from these latter all the systems for creating a vacuum within those parts of the installation which contribute to the circulation of the ions or the production of the molecular beam, arrangements of this type being in themselves sufficiently well-known to those versed in the art to dispense with any need to describe them.
  • the operation of the device of FIG. 1 is as follows: under the action of the impact of the molecular beam 2, ions of mass M are detached from the substance to be studied which has previously been introduced into the box 1 and are extracted with the kinetic energy eV from the collision box 1 along the path 19. Said ions in turn penetrate at 8 into the collision box 7 which is on the one hand brought to the potential V and on the other hand filled with a gas which is preferably a rare gas in order to prevent any possible chemical reactions between the molecules of said gas and the ions of molecular mass M. Within the collision box 7 a certain number of primary ions of mass M are caused to dissociate under the action of collisions which they are liable to undergo with the molecules of neutral gas.
  • Said secondary ion of mass m is then extracted by the plate device 11 at the voltage V which imparts to said ion a complementary kinetic energy eV Among all the possible secondary ions which are derived from the dissociation of the primary ion of mass M within the collision box 7, the electrostatic analyzer 12 makes it possible to select those which possess a given kinetic energy equal to eV".
  • the detection and analysis of these secondary ions of mass m are then carried out according to the different potential applications by the retractable detector 16 and the magnetic analyzer 17.
  • any case lies in the fact that, by simply measuring a ratio of two voltages, said device makes it possible to determine with a very high degree of accuracy the ratio of the masses M and m corresponding respectively to the primary ion under study and to one of the secondary ions derived from its dissociation as a result of impact on the molecules contained in the collision box 7.
  • the device is identical with the device of FIG. 1 as far as the analyzer 16 but then has a second stage which is identical with the first.
  • This second stage is made up of a second collision box 20 which is brought to a potential V by means 21 known per se.
  • the collision box 20 is fitted with a device 22 for the extraction of formed ions and is filled internally with a rare gas at low pressure in the same manner as the box 7.
  • the box 20 is followed by a second electrostatic analyzer 23 which is similar to the analyzer 12; the electrostatic analyzer 23 is in turn completed by a retractable detector 24 and if necessary by a low-resolution magnetic analyzer 25 of the permanent-magnet type which is in turn followed by its detector 26.
  • V has a constant value equal to 10,000 volts
  • V has a constant value equal to 100 volts
  • V is chosen so as to be variable and positive, in order to obtain carbon having a mass m 12.
  • a voltage V 59.7609 volts must be applied to the collision box 7. It is deduced therefrom that Third example of measurement of molecular mass.
  • One of the applications of the method according to the invention which is of particular interest consists in determining the existence of a compound, even in the state of traces, in a predetermined mixture of substances. It is even more especially worthy of note that the invention meets a real need in the determination of atmospheric air pollution in cities and surrounding areas or industrial centers by permitting simple and immediate determination of polluting compounds even if they are present in the atmosphere in the state of traces.
  • one method of determination of nitric oxide NO in atmospheric air will be described hereinafter. It will first be recalled that this determination cannot readily be performed by conventional methods of mass spectrometry if the concentrations are of a low order and especially within the range of 10 to 10' for example.
  • the peaks of nitrogen and oxygen in this case are of such high value that it is impossible to separate the peak of nitric oxide NO when the sensitivity is considerably increased as is clearly necessary at this very low level of concentration (the method is also made more difficult by the fact that the peak of carbon monoxide CO, the peak of nitric oxide NO and the peak of molecular nitrogen N practically coincide).
  • the air is introduced into the box 1 and the molecules contained therein are ionized.
  • the analyzed air in fact contains molecules of oxide NO, they are converted to NO ions which are then dissociated into atomic ions N+ and 0+; the problem is thus very readily solved since it is impossible to confuse the atomic ion N+ derived from the dissociation of nitric oxide NO with the nitrogen ion N+ derived from the decomposition of the molecule of nitrogen N
  • the precise atomic mass of nitric oxide NO is 29.9979. If the filtration of an atomic ion of nitrogen is achieved in the device of FIG.
  • the ratio m/M is equal to: l4.003074/29.9979 0.4668 when said nitrogen is derived from the dissociation of nitric oxide NO whereas, on the contrary, a ratio of 0.5 is obtained when the dissociation of a molecular ion N of free nitrogen is involved.
  • the device of FIG. 1 is employed by adopting a constant negative value equal to 500 volts in the case of V and a value of 50 volts in the case of V whereas V is variable. Under these conditions, if the characteristic peak of nitrogen is in fact detected in the magnetic analyzer 17, two cases can accordingly arise:
  • Atomic nitrogen N+ derived from the decomposition of a molecular ion N in thiscase the ratio where V 600 V.
  • a method according to claim 1 wherein, in order to filter very high molecular masses, a number of successive fragmentations in series of the primary ion of mass M are carried out at potentials V V V,,, each fragmentation being followed by a filtration of energy eV", eV' eV" in an electrostatic analyzer.
  • a device wherein provision is additionally made for a low-resolution magnetic analyzer of the permanent magnet type.
  • a device wherein the ion source is constituted by a collision box containing the substance of molecular mass M and brought to a potential V,, a molecular beam being applied to the entrance aperture of said collision box.
  • a device wherein the collision box is further provided with one or a number of lateral extraction apertures so as to permit one or a number of additional simultaneous analyses.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
  • Electron Tubes For Measurement (AREA)
US434695A 1973-01-26 1974-01-18 Method of electrostatic filtration Expired - Lifetime US3916188A (en)

Applications Claiming Priority (1)

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FR7302771A FR2215874A5 (enrdf_load_stackoverflow) 1973-01-26 1973-01-26

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US (1) US3916188A (enrdf_load_stackoverflow)
JP (1) JPS5820102B2 (enrdf_load_stackoverflow)
CH (1) CH577684A5 (enrdf_load_stackoverflow)
DE (1) DE2403575A1 (enrdf_load_stackoverflow)
FR (1) FR2215874A5 (enrdf_load_stackoverflow)
GB (1) GB1410315A (enrdf_load_stackoverflow)
NL (1) NL182523C (enrdf_load_stackoverflow)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4861987A (en) * 1987-11-03 1989-08-29 Devienne Fernand Marcel Process for the detection of a chemical substance of known mass M
US4952803A (en) * 1988-02-23 1990-08-28 Jeol Ltd. Mass Spectrometry/mass spectrometry instrument having a double focusing mass analyzer
US5097124A (en) * 1989-11-24 1992-03-17 Devienne Fernand Marcel Apparatus and process for the detection in an atmosphere to be monitored of a chemical substance of known mass m and whereof the dissociation fragments are known
US5466933A (en) * 1992-11-23 1995-11-14 Surface Interface, Inc. Dual electron analyzer

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3238474C2 (de) * 1982-10-16 1987-01-08 Finnigan MAT GmbH, 2800 Bremen Hybrid-Massenspektrometer
DE3905631A1 (de) * 1989-02-23 1990-08-30 Finnigan Mat Gmbh Verfahren zur massenspektroskopischen untersuchung von isotopen sowie isotopenmassenspektrometer
DE4019005C2 (de) * 1990-06-13 2000-03-09 Finnigan Mat Gmbh Vorrichtungen zur Analyse von Ionen hoher Masse
DE19544808C2 (de) * 1995-12-01 2000-05-11 Bruker Daltonik Gmbh Verfahren zur Untersuchung der Struktur von Ionen in einem Flugzeitmassenspektrometer
JP6647224B2 (ja) * 2014-06-13 2020-02-14 ディーエイチ テクノロジーズ デベロップメント プライベート リミテッド 質量分析を用いる脂質の分析のための方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3610921A (en) * 1968-05-01 1971-10-05 Perkin Elmer Corp Metastable mass analysis
US3673404A (en) * 1970-05-15 1972-06-27 Perkin Elmer Corp Ion kinetic energy analysis
US3769513A (en) * 1972-12-14 1973-10-30 Perkin Elmer Corp Ion kinetic energy spectrometer

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3610921A (en) * 1968-05-01 1971-10-05 Perkin Elmer Corp Metastable mass analysis
US3673404A (en) * 1970-05-15 1972-06-27 Perkin Elmer Corp Ion kinetic energy analysis
US3769513A (en) * 1972-12-14 1973-10-30 Perkin Elmer Corp Ion kinetic energy spectrometer

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4861987A (en) * 1987-11-03 1989-08-29 Devienne Fernand Marcel Process for the detection of a chemical substance of known mass M
US4952803A (en) * 1988-02-23 1990-08-28 Jeol Ltd. Mass Spectrometry/mass spectrometry instrument having a double focusing mass analyzer
US5097124A (en) * 1989-11-24 1992-03-17 Devienne Fernand Marcel Apparatus and process for the detection in an atmosphere to be monitored of a chemical substance of known mass m and whereof the dissociation fragments are known
US5466933A (en) * 1992-11-23 1995-11-14 Surface Interface, Inc. Dual electron analyzer

Also Published As

Publication number Publication date
NL182523C (nl) 1988-03-16
NL182523B (nl) 1987-10-16
JPS5820102B2 (ja) 1983-04-21
JPS49111691A (enrdf_load_stackoverflow) 1974-10-24
GB1410315A (en) 1975-10-15
CH577684A5 (enrdf_load_stackoverflow) 1976-07-15
FR2215874A5 (enrdf_load_stackoverflow) 1974-08-23
NL7401050A (enrdf_load_stackoverflow) 1974-07-30
DE2403575A1 (de) 1974-08-08

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