US3699342A - Method and apparatus for detecting tracer gas - Google Patents

Method and apparatus for detecting tracer gas Download PDF

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Publication number
US3699342A
US3699342A US63571A US3699342DA US3699342A US 3699342 A US3699342 A US 3699342A US 63571 A US63571 A US 63571A US 3699342D A US3699342D A US 3699342DA US 3699342 A US3699342 A US 3699342A
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Prior art keywords
gas
tracer gas
electron capture
detector
membrane
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Expired - Lifetime
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US63571A
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English (en)
Inventor
Anthony Jenkins
Richard Charles Cornell
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Analytical Instruments Ltd
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Analytical Instruments Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
    • G01N15/06—Investigating concentration of particle suspensions
    • G01N15/0606—Investigating concentration of particle suspensions by collecting particles on a support
    • G01N15/0618—Investigating concentration of particle suspensions by collecting particles on a support of the filter type
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/62—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
    • G01N27/64—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode using wave or particle radiation to ionise a gas, e.g. in an ionisation chamber

Definitions

  • the apparatus comprises an electron capture detector and the en- 30 Foreign Application p i i D ta vironment to be sampled is first drawn through a membrane which has a greater permeability to the April qreat Bmam "20l80/70 tracergas than the remainder of the environment be- [521 U S 250/83 6 FT 55/16 250/43 5 FC fore being carried into the detector by a carrier gas.
  • the halogen detectors are not sufficiently sensitive for a number of applications.
  • detector for detecting the presence of the tracer gas.
  • An-electron capture detector generally comprises an ionization chamber containing a B particle emitter, such as tritium, as the primary source of ionizing radia tion.
  • a B particle emitter such as tritium
  • a carrier gas such as nitrogen possessing no affinity for electrons
  • recombination of positive ions and free electrons formed by the. ionizing radiation is unlikely to take place because of the free electrons high mobility.
  • a carrier gas such as nitrogen possessing no affinity for electrons
  • er gas contains a compound having an affinity for electrons, negative ion formation occurs which is accompanied by an observed decrease in current.
  • the present invention seeks to provide a method and apparatus which can be used to monitor atmospheric air or other gas samples for the presence and concentration of sulphur hexafluoride aNd other halogenated tracer gases.
  • Oxygen itself is capable of electron capture and it could therefore saturate the detector.
  • a method of detecting and monitoring the presence of halogenated tracer gas in a gas supply having as a major constituent thereof an electron capture material comprises selectively isolating said tracer gas from the remainder of the supply by diffusion through a membrane having a greater permeability to said tracer gas than to the remainder of thesupply, and thereafter conveying the tracer gas into an electron capture detector by means of a gas stream substantially inert to electron capture.
  • an apparatus for detecting an monitoring the presence of halogenated tracer gas supply comprises a probe carrying a membrane having a greater permeability to said halogenated tracer gas or gases than the remainder of the gas supply, means for conveying a carrier gas to the side of the membrane remote from the gas supply and an electron capture detector to receive said carrier gas containing the halogenated tracer gas whereby to detect the latter.
  • halogenated tracer gas When the halogenated tracer gas is present in the atmosphere it is necessary to separate the tracer gas from the oxygen of the atmosphere prior to introduction into the detector. Oxygen is itself an electron absorber and its presence would saturate the detector and effectively blanket the presence of the tracer gas. Sufficient amount of the tracer gas must be introduced into the detector to obtain a useful response of the detector and it is therefore necessary to separate the tracer gas from the atmospheric oxygen prior to its introduction into the detector.
  • the tracer gas can pass through the membrane and is then swept into the detector by a stream of inert gas i.e. inert to electron capture.
  • a suitable carrier gas is nitrogen.
  • a suitable membrane is formed from a silastomer.
  • FIG. 1 is a diagrammatic representation of an apparatus according to the invention.
  • FIG. 2 shows a modification of part of the apparatus in which a sampling probe is contained in an outer sheath.
  • a sampling probe 10 for introducing a gas to be analyzed into an electron capture detector is closed at one end by a membrane 12.
  • the membrane is preferably formed from a silastomer as this has a permeability to some halogenated tracer gases which is of the order of ten times greater than that to oxygen.
  • the opposite end of the probe is connected through a line 14 controlled by a valve 16 to a nitrogen supply, the nitrogen serving as a carrier gas to convey the gas to be analyzed into the electron capture detector 18 by way of a line 20.
  • the line 20 commences adjacent the membrane 12.
  • An amplifier 22 and a meter 24 are connected to the detector.
  • silastomer refers to a thin film or sheet of silicone rubber.
  • the sampling probe 10 is contained within an outer sheath 30.
  • the end of the sheath 30 adjacent the membrane 12 is open to the atmosphere while the other end of the sheath communicates through line 32 with a suction means, for example an air pump (not shown).
  • the pump draws air or gas to be sampled into the sheath and into contact with the membrane.
  • the exhaust from the detector 18 can be connected to the suction line 32. This provides a convenient method of determining flow from the detector.
  • the draft created by the suction makes the probe less directionally sensitive and it can pick up a tracer gas at greater distances from a leak than the apparatus of FIG. 1.
  • the apparatus can be used for detecting leaks in a gas system having a halogenated tracer gas.
  • tracer agents are sulphur hexafluoride SP and Freons (Registered Trade Mark) such as dichloroditluoromethane CC1 F and bromochlorodifluoromethane CBrC1F
  • Freons Registered Trade Mark
  • One particular use of the apparatus lies in the detection of leaks in containers such as aerosols. On account of its high sensitivity the apparatus can detect the presence of a very small leak and can be used to monitor such containers prior to their dispatch to consumers.
  • the apparatus is compact and readily transportable.
  • the apparatus is also sensitive to the presence of nitrmcompounds, such as nitroglycerine.
  • the apparatus can find use as a detector for of a gas stream substantially inert to electron capture.
  • An apparatus for detecting and monitoring the presence of an electron capture halogenated tracer gas in a gas supply which is itself, or includes as a con-' stituent, an electron capture material comprising a probe, a membrane at an end of said probe in which the membrane comprises a silastomer having a greater permeability to the halogenated tracer gas than the remainder of the gas supply, means for conveying a carrier gas to the side of the membrane remote from the gas supply and an electron capture detector to receive the carrier gas and tracer gas.
  • An apparatus including an outer sheath surrounding the probe and open to the atmosphere at one end, suction means being connected to the other end of the sheath whereby to draw in a sample into the vicinity of the membrane.

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  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Pathology (AREA)
  • General Health & Medical Sciences (AREA)
  • Immunology (AREA)
  • Physics & Mathematics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Toxicology (AREA)
  • Dispersion Chemistry (AREA)
  • Examining Or Testing Airtightness (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
  • Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)
  • Sampling And Sample Adjustment (AREA)
US63571A 1970-04-27 1970-08-13 Method and apparatus for detecting tracer gas Expired - Lifetime US3699342A (en)

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GB2018070 1970-04-27

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4304752A (en) * 1979-03-23 1981-12-08 Anthony Jenkins Detection of tracer materials in the atmosphere
EP0046699A3 (en) * 1980-08-21 1982-03-10 The Bendix Corporation Ion mobility detector provided with a membrane interface
US4424067A (en) 1982-07-29 1984-01-03 Allied Corporation Purification of anhydrous hydrogen fluoride
US4433982A (en) 1980-03-10 1984-02-28 Bruker-Franzen Analytik Gmbh Input head of a measuring or identification system for chemical agents
US4793830A (en) * 1987-12-28 1988-12-27 Murphy Milton K Process for producing high quality gas for instrumentation application using gas separation membranes
US20100251803A1 (en) * 2003-11-13 2010-10-07 E. I. Du Pont De Nemours And Company Detectable refrigerant compositions and uses thereof

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3361908A (en) * 1964-01-03 1968-01-02 Barber Colman Co Method and apparatus for electron attachment detection
US3545931A (en) * 1968-08-28 1970-12-08 Monsanto Co Ammonia analysis system

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3361908A (en) * 1964-01-03 1968-01-02 Barber Colman Co Method and apparatus for electron attachment detection
US3545931A (en) * 1968-08-28 1970-12-08 Monsanto Co Ammonia analysis system

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4304752A (en) * 1979-03-23 1981-12-08 Anthony Jenkins Detection of tracer materials in the atmosphere
US4433982A (en) 1980-03-10 1984-02-28 Bruker-Franzen Analytik Gmbh Input head of a measuring or identification system for chemical agents
EP0046699A3 (en) * 1980-08-21 1982-03-10 The Bendix Corporation Ion mobility detector provided with a membrane interface
US4424067A (en) 1982-07-29 1984-01-03 Allied Corporation Purification of anhydrous hydrogen fluoride
US4793830A (en) * 1987-12-28 1988-12-27 Murphy Milton K Process for producing high quality gas for instrumentation application using gas separation membranes
US20100251803A1 (en) * 2003-11-13 2010-10-07 E. I. Du Pont De Nemours And Company Detectable refrigerant compositions and uses thereof

Also Published As

Publication number Publication date
GB1266832A (enrdf_load_stackoverflow) 1972-03-15
USRE28417E (en) 1975-05-06

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