US3398505A - Dual stage membrane gas separators with variable conductance means for varying their throughput - Google Patents

Dual stage membrane gas separators with variable conductance means for varying their throughput Download PDF

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Publication number
US3398505A
US3398505A US626194A US62619467A US3398505A US 3398505 A US3398505 A US 3398505A US 626194 A US626194 A US 626194A US 62619467 A US62619467 A US 62619467A US 3398505 A US3398505 A US 3398505A
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Prior art keywords
gas
membrane
throughput
separator
varying
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US626194A
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English (en)
Inventor
Peter M Llewellyn
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Varian Medical Systems Inc
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Varian Associates Inc
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Priority to US626194A priority Critical patent/US3398505A/en
Priority to DE19681773011 priority patent/DE1773011A1/de
Priority to GB04805/68A priority patent/GB1187417A/en
Priority to FR145583A priority patent/FR95043E/fr
Application granted granted Critical
Publication of US3398505A publication Critical patent/US3398505A/en
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
    • G01N30/02—Column chromatography
    • G01N30/62—Detectors specially adapted therefor
    • G01N30/72—Mass spectrometers
    • G01N30/7206—Mass spectrometers interfaced to gas chromatograph
    • G01N30/722—Mass spectrometers interfaced to gas chromatograph through a gas permeable barrier (membranes, porous layers)
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
    • G01N1/34—Purifying; Cleaning

Definitions

  • variable conductance device is connected in the exhaust tubulation through which the space between two successive membranes is evacuated.
  • the two stage gas separator with adjustable throughput is connected in line between a gas chromatograph and a mass spectrometer type gas analyzer.
  • the separator enriches the gas sample by discriminating against the carrier gases.
  • the variable conductance device permits adjusting the sample throughput to the mass spectrometer over a range from 80% to 2%.
  • the gas conductance of the exhaust tnbulation through which the space between successive memberane was evacuated was selected at a fixed value.
  • the membrane separator had a fixed percentage throughout to the mass spectrometer.
  • the problem with this arrangement at this the output of the gas chromatograph is characterized by a time sequence of gas bursts of the different constituents of the sample under analysis as charged to the gas chromatograph. These gas bursts or peaks are spaced in time by as little as a few seconds to as much as several minutes. Also the size of the gas burst or peak varies considerably.
  • the prior art separator passed a fixed percentage of the gas peaks to the mass spectrometer. Thus, the large peaks could overload the spectrometer with gas and prevent identification of the smaller peaks. If the selected percentage throughput was fixed at a sufliciently small percentage to avoid overloading the mass spectrometer, the small peaks could not be identified.
  • Another feature of the present invention is the same as as the preceding feature wherein the gas separator is included in-line between a gas chromatograph and a mass spectrometer, whereby the throughput of the gas separator may be readily controlled to prevent overloading of the mass spectrometer while monitoring relatively small gas peaks in sequence after relatively large peaks.
  • FIG. 1 is a schematic block diagram of a prior art system employing a gas chromatograph, dual stage membrane gas separator, and a mass spectrometer,
  • FIG. 3 is a chromatogram (graphical representation of an output of a gas chromatograph).
  • FIG. 1 there is shown a prior art gas analyzing system.
  • the system includes a gas chromatograph 1 into which is charged a sample to be analyzed.
  • the output gas flow of the gas chromatograph 1 comprises a time sequence of gas bursts or peaks carried along in a stream of inert carrier gas.
  • the difierent peaks represent different gaseous constituents of the sample under analysis.
  • the output gas stream is fed to a dual stage membrane type gas separator 2.
  • the separator 2 is more fully described below and in the aforecited patent application 563,235.
  • the gas separator 2 nearly eliminates the carrier gas thereby greatly enriching the percentage of the sample constituents in the gas flow output of the separator 2.
  • the output of the separator 2 is fed to a gas analyzer such as a mass spectrometer 3.
  • the spectrometer may be any of several types such as, for example,
  • a high vacuum pump pull-s the gaseous constit-' uents through the mass spectrometer.
  • the problem with the prior art system of FIG. 1 is that the output of the gas chromatograph 1 has peaks of greatly differing size as shown in FIG. 3.
  • the gas separator 2 has been set to pass a certain fixed percentage of the sample constitutents through to the mass spectrometer. This means that the sample flow rates into the mass spectrometer vary widely in accordance with the relative amplitudes of the peaks of FIG. 3.
  • the separator is set to pass a fixed percentage of the sample which is sufiicient for the mass spectrometer to identify the small peaks
  • the large peaks which pass into the spectrometer flood the spectrometer with sample material and prevent detection of small peaks occurring within the flooded time of the spectrometer which can be several minutes.
  • the fixed percentage flow rate of sample to the mass spectrometer is set sulficiently low to prevent flooding by the large peaks, the small peaks provide too little sample material to the spectrometer to be identified.
  • FIG. 2 there is' shown thegas handling and separating system of the present invention.
  • the apparatus is essentially identical to that of FIG. 1 except that .
  • a variable throttle valve 11 is provided for varying the percentage-of gas throughput of the gas separator 2.
  • a gas passageway 12, as of l" in inside diameter has an inlet pipe 13 at one end which is connected tothe output gas flow of the gas chromatograph 1.
  • a vent pipe 14 is connected to the conduit 12 opposite the inlet pipe 13.
  • a cap 15 closes off the input end of the gas passageway 12. Gas fiows into the passageway 12 via inlet pipe 13 at atmospheric pressure and is exhausted via vent pipe 14 at atmospheric pressure.
  • a pair of gas separating membranes 16 and 17 are sealed across the gas passageway 12 in spaced relation taken-in a direction along the gas passageway 12.
  • the membranes 16 and 17 each comprise, for example, a 1 mil, thick polysiloxane polymer membrane supported on a perforateddisk asof glass.
  • the membranes 16 and 17 are constructed from materials selected from the group consisting of polymers and stationary liquid phases. Stationary liquid phases are those liquid materialsemployed in chromatographic columns to partition materials to be separated. Comprehensive lists of such materials can be found in numerous publications, one being Gas Chromatography by Ernst Bayer, publishedby Elsevier Publishing Company, New York, 1961, Tables 2, 13 and 14.
  • a suitable reservoir supporting structure In those instances where stationary liquid phases form the membranes 16 and 17, a suitable reservoir supporting structure must be provided.
  • a reservoir constructed from a polymer or a fine screen mesh capable of supporting the liquid by surface tension would be suitable.
  • other materials will work if relative to gaseous state materials they are free of holes, and if the permanent gases will not enter into solution with the material.
  • entering into solution is defined as a process of condensation and then mixing of the gaseous state material in the surface layers of membranes 16 and 17. (See Physics and Chemistry of the Organic Solid State, edited by David Fox, Mortimer M. Labes and Arnold Weissberger, published by Interscience'Publishers, NewYork, 1965, vol. 2, p. 517.)
  • the membranes 16 and 17 operate as follows:
  • the carrier gas which is any one of a number of permanent gases such as N He, H Ar, etc. is not soluble-in the elastomer film membrane.
  • the organic vapor constituents of the sample, which are carried in the carrier gas are soluble in the elastomer film membrane. These organic vapors go into solution with the elastomer and diffuse through the membrane under a partial pressure differential thereacross and come -out'-of solution on the downstream side of the membrane. Since the organic vapor passes through the membrane and the carrier gas is largely excluded a substantial enrichment of the organic vapors in the carrier gas stream is obtained.
  • a vacuum pump 18 is connected into the region 19 of the conduit 12 between the two membranes 16 and 17 via an exhaust tubulation 21.
  • the throttle valve 11 is placed in the tubulation 21 to form a variable conductance in the gas passageway between the pump 18 and the chamber 19.
  • the vacuum pump 18 may be of the mechanical type to provide a base pressure, as of 10- torr. Varying the throttle valve setting varies the conductance of the pas sageway and, thus, the pressure in the chamber 19.
  • the throttle valve comprises a stainless steel slug 22 which has a permanent magnet 23 afiixed at one end.
  • the slug 22 is slidable in an arm 25 of a T fitting 24.
  • the outside of the T fitting arm 25 is threaded to receive the inside threads on a cylindrical magnet 26.
  • the magnet 26 is formed by two oppositely polarized semicylindrical magnets cemented together in slightly spaced relation to form a hollow cylindrical member which is then internally threaded. Turning the magnet 26 on the arm 25 causes the magnet 26 to move axially of the arm 25 and,
  • the gas throughput from the second membrane 17 is fed to the mass spectrometer 3 for analysis.
  • the high vacuum pump 5 maintains the gas pressure on thedownstream side of the second membrane 17 at a pressure of about 10- torr or' less.
  • the gas conductance to the mass spectrometer 3 is about 1 liter/sec. and the carrier gas flow for He is about 10- torr-liters] sec.
  • the organic vapor enrichment of the carrier gas flow is about 10 to 10
  • This range of variation is extremely useful in operation of the gas analyzing system as it permits the operator to examine and identify chromatograph peaks without flooding the spectrometer 3. More specifically, the operator can observe the ohromatogram' output recording of the gas chromatograph 1. When a large peak appears in the output of the chromatograph which'is likely to flood the spectrometer 3, the operator can change the setting of the throttle valve 11 to reduce the flow of the sample organic vapors into the spectrometer 3. Likewise, when a small peak occurs in the output of the gas chromatograph which it is desired to identify, the operator changes the setting of the throttle valve to pass more of the sample into the mass spectrometer 3.
  • the input charge to the gas chromatograph 1 is about 1 mg. This charge is spread out over a period of about 200 seconds in the output of the chromatograph 1 such that the output is about 5 g/ sec.
  • the separator 2 reduces the sample charge to the mass spectrometer 3 to about 0.1 g/sec.
  • the typical operating range for sample charge to the spectrometer is from 0.001 g/sec. to 0.1 ,ug./sec.
  • the throttle valve 11 permits economical use of sample material and, in addition, increases the operating range of the gas analyzing system.
  • a gas separator means forming a gas passageway, means forming first and second gas separating membranes sealed across said passageway in spaced relation taken along a direction of gas flow in said passageway, means for partially evacuating the region of said passageway between said spaced first and second membranes, said partial evacuating means including a second gas passageway in gas communication with the region between said spaced first and second membranes, the improvement comprising, throttle valve means for variably controlling the gas conductance of said second gas passageway, whereby the percentage gas throughput of the gas separator is variably controlled in response to changes in the gas conductance of said second gas passageway.
  • the apparatus of claim 1 including, means forming a vacuum pump connected to said second gas passageway for pulling gas from the region between said membranes through said variable conductance means and said gas passageway.
  • the apparatus of claim 1 including a gas chromatograph having its output gas peaks fed into said first gas passageway upstream of said first and second gas separating membranes, and a gas analyzer means connected in gas communication with said first gas passageway downstream or' said first and second gas separating membranes.
  • the method for analyzing the output gas flow of a gas chromatograph comprising the steps of, passing an output gas flow of the gas chromatograph having gas peaks of different sizes through a gas passageway having first and second gas separating membranes spaced apart along the gas passageway, partially evacuating the region of the gas passageway between the first and second membranes, passing at least a portion of the gas which has passed through the first and second separating membranes to a gas analyzer for analysis, and Varying the gas throughput of the second gas separating membrane in variable accordance with the size of certain ones of the gas peaks of the gas chromatograph to prevent excessive gas fiow to the gas analyzer.
  • step of varying the gas throughput of the second gas separating membrane comprises varying the gas pressure in the region of the gas passageway between the first and second gas separating membranes.
  • the method of claim 4 including the step of obtaining a mass spectrum of the gas fed to the gas analyzer.

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  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Pathology (AREA)
  • General Health & Medical Sciences (AREA)
  • Immunology (AREA)
  • Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Physics & Mathematics (AREA)
  • Biomedical Technology (AREA)
  • Molecular Biology (AREA)
  • Engineering & Computer Science (AREA)
  • Sampling And Sample Adjustment (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)
US626194A 1965-12-06 1967-03-27 Dual stage membrane gas separators with variable conductance means for varying their throughput Expired - Lifetime US3398505A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US626194A US3398505A (en) 1965-12-06 1967-03-27 Dual stage membrane gas separators with variable conductance means for varying their throughput
DE19681773011 DE1773011A1 (de) 1965-12-06 1968-03-20 Verfahren zum Einlassen wenigstens eines Teils eines Gases in ein Gasanalysegeraet und zur Durchfuehrung des Verfahrens geeigneter Gasseparator
GB04805/68A GB1187417A (en) 1965-12-06 1968-03-27 Improvements in and relating to Gas-Separators
FR145583A FR95043E (fr) 1965-12-06 1968-03-27 Perfectionnements aux analyseurs de gaz.

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
US51175665A 1965-12-06 1965-12-06
US51179465A 1965-12-06 1965-12-06
US55561366A 1966-06-06 1966-06-06
US65323566A 1966-07-06 1966-07-06
US626194A US3398505A (en) 1965-12-06 1967-03-27 Dual stage membrane gas separators with variable conductance means for varying their throughput

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DE (1) DE1773011A1 (fr)
FR (1) FR95043E (fr)
GB (1) GB1187417A (fr)

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3649199A (en) * 1970-03-26 1972-03-14 Varian Associates Method for detecting trace quantities of an organic drug material in a living animal
US3724169A (en) * 1970-02-19 1973-04-03 Aero Vac Corp Delta t bar spectrometer
US3929003A (en) * 1969-06-16 1975-12-30 Varian Associates Method and apparatus for detecing materials in a liquid
US4089653A (en) * 1975-07-28 1978-05-16 General Electric Company Apparatus for the separation of hydrogen sulfide from gas mixture including carbon dioxide
US4201550A (en) * 1976-12-23 1980-05-06 Gyula Gaspar Process and apparatus for the determination of the total organic substance content of gases by a flame ionization detector
US4517461A (en) * 1982-11-29 1985-05-14 Phillips Petroleum Co Carbon isotope analysis of hydrocarbons
US4641541A (en) * 1986-02-11 1987-02-10 Daryl Sharp Internal mass spectrometer interface to a gas chromatograph
US4713963A (en) * 1986-06-26 1987-12-22 Daryl Sharp Method and device for vacuum chromatography
US4791292A (en) * 1986-04-24 1988-12-13 The Dow Chemical Company Capillary membrane interface for a mass spectrometer
US5469917A (en) * 1994-12-14 1995-11-28 Wolcott; Duane K. Use of capillary-membrane sampling device to monitor oil-drilling muds
US5479815A (en) * 1994-02-24 1996-01-02 Kraft Foods, Inc. Method and apparatus for measuring volatiles released from food products
US5703359A (en) * 1996-07-29 1997-12-30 Leybold Inficon, Inc. Composite membrane and support assembly
US7361206B1 (en) * 2004-09-07 2008-04-22 United States Of America As Represented By The Secretary Of The Navy Apparatus and method for water vapor removal in an ion mobility spectrometer
EP4320433A4 (fr) * 2021-04-08 2025-03-12 INFICON, Inc. Système d'étanchéité pour composants d'un analyseur de gaz

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3230335C2 (de) * 1982-03-05 1988-10-20 Friedel 4100 Duisburg Genender Verbolzung von Ausbaubögen zum Streckenausbau im Bergbau
DE4444524C2 (de) * 1994-11-30 1997-04-03 Inst Umwelttechnologien Gmbh Verfahren und Vorrichtung zum Nachweis von gasförmigen höhermolekularen Spuren in einem Trägergas für quasi real-time-Messungen in situ

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
None *

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3929003A (en) * 1969-06-16 1975-12-30 Varian Associates Method and apparatus for detecing materials in a liquid
US3724169A (en) * 1970-02-19 1973-04-03 Aero Vac Corp Delta t bar spectrometer
US3649199A (en) * 1970-03-26 1972-03-14 Varian Associates Method for detecting trace quantities of an organic drug material in a living animal
US4089653A (en) * 1975-07-28 1978-05-16 General Electric Company Apparatus for the separation of hydrogen sulfide from gas mixture including carbon dioxide
US4201550A (en) * 1976-12-23 1980-05-06 Gyula Gaspar Process and apparatus for the determination of the total organic substance content of gases by a flame ionization detector
US4517461A (en) * 1982-11-29 1985-05-14 Phillips Petroleum Co Carbon isotope analysis of hydrocarbons
US4641541A (en) * 1986-02-11 1987-02-10 Daryl Sharp Internal mass spectrometer interface to a gas chromatograph
US4791292A (en) * 1986-04-24 1988-12-13 The Dow Chemical Company Capillary membrane interface for a mass spectrometer
US4713963A (en) * 1986-06-26 1987-12-22 Daryl Sharp Method and device for vacuum chromatography
US5479815A (en) * 1994-02-24 1996-01-02 Kraft Foods, Inc. Method and apparatus for measuring volatiles released from food products
US5469917A (en) * 1994-12-14 1995-11-28 Wolcott; Duane K. Use of capillary-membrane sampling device to monitor oil-drilling muds
US5703359A (en) * 1996-07-29 1997-12-30 Leybold Inficon, Inc. Composite membrane and support assembly
US7361206B1 (en) * 2004-09-07 2008-04-22 United States Of America As Represented By The Secretary Of The Navy Apparatus and method for water vapor removal in an ion mobility spectrometer
EP4320433A4 (fr) * 2021-04-08 2025-03-12 INFICON, Inc. Système d'étanchéité pour composants d'un analyseur de gaz

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Publication number Publication date
DE1773011A1 (de) 1971-08-12
FR95043E (fr) 1970-03-27
GB1187417A (en) 1970-04-08

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