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EP0485410A1 - A detector for monitoring low molecular weight compounds - Google Patents

A detector for monitoring low molecular weight compounds

Info

Publication number
EP0485410A1
EP0485410A1 EP19900910797 EP90910797A EP0485410A1 EP 0485410 A1 EP0485410 A1 EP 0485410A1 EP 19900910797 EP19900910797 EP 19900910797 EP 90910797 A EP90910797 A EP 90910797A EP 0485410 A1 EP0485410 A1 EP 0485410A1
Authority
EP
European Patent Office
Prior art keywords
molecular weight
detector
low molecular
reagent
compounds
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP19900910797
Other languages
German (de)
French (fr)
Inventor
Stephen Clifford 65 Chetnole Close Woods
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
UK Secretary of State for Defence
Original Assignee
UK Secretary of State for Defence
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GB898915495A external-priority patent/GB8915495D0/en
Priority claimed from GB898916570A external-priority patent/GB8916570D0/en
Priority claimed from GB909005217A external-priority patent/GB9005217D0/en
Application filed by UK Secretary of State for Defence filed Critical UK Secretary of State for Defence
Publication of EP0485410A1 publication Critical patent/EP0485410A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • 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
    • G01N1/40—Concentrating samples
    • G01N1/405—Concentrating samples by adsorption or absorption
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
    • G01N31/22—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using chemical indicators
    • G01N31/223—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using chemical indicators for investigating presence of specific gases or aerosols
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
    • G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
    • G01N33/98—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving alcohol, e.g. ethanol in breath
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/02—Devices for withdrawing samples
    • G01N1/22—Devices for withdrawing samples in the gaseous state
    • G01N1/2202—Devices for withdrawing samples in the gaseous state involving separation of sample components during sampling
    • G01N1/2214—Devices for withdrawing samples in the gaseous state involving separation of sample components during sampling by sorption

Definitions

  • the invention relates to the detection of low molecular weight compoundsr especially ethanol andmethanol/ in the presence of highermolecularweight compounds and is particularly but not exclusively related to a methanol detector for atmosphere monitoring in closed environments.
  • Methanol (CH30H) is a toxicsubstanceandwhenpresentinclosedenvironments thereisaneedtoroutinelymonitortheair. Amoni ormustbeableto signal that the ambient level of methanol is less than a maximum permissible concentration.
  • a commercially availableDraeger detector tube Methanol 50/a
  • Methanol 50/a can be used tomonitor methanol in the range 50 to 3000 ppm.
  • Other tubes are available for themonitoringof other compounds.
  • the detector itself consists of a narrow bore tube containing a precleansing layer of drying agent followed by crystals impregnated with an orange Chromium (Cr(VI)) compound.
  • Cr(VI) Chromium
  • a sample of air of standard volume is drawn through the detector tube by means of a bellows pump.
  • the presence of methanol in that sample causes a colour change in the tube fromorange to black.
  • Thelength of theblack stain thendetermines the amount of methanol present in the sample for the given volume of air.
  • the detection process is illustrated by:
  • An object of the present invention is to provide a means to detect low molecular weight compounds when present in a sample with higher molecular weightcontaminants.
  • Afurtherobjectofthepresentinventionisto provide ameanstomonitormethanol inthepresenceofnoctane.
  • Ayetfurtherobject is to provide a means to detect ethanol in the presence of other organic species.
  • the invention provides a detector for monitoring low molecular weight compounds in the presence of higher molecular weight species comprising: a porous adsorber having relatively low retention for the low molecular weight co ⁇ pounds and relatively high retention for highermolecularweight species; and a reagent which undergoes a colour change on reaction with low molecular weight compounds; the arrangement being such that the adsorber and reagent are contained such that a sampleofair canbepassedthroughtheadsorberbeforepassingthrough the reagent, th amount of low molecular weight compound being calculable from the amount of reagent which changes colour.
  • lowmolecularweightcompound canbe referingtoeitherorganicor inorganic compounds.
  • the low molecular weight compounds are organic Compounds.
  • theorganiccompounds areeithermethanol or ethanol.
  • the lowmolecularweightcompound isanorganiccompound itpreferably contains between1 and5 carbonatomsandmaybe straightchainoroptionally branched.
  • the compounds may also be substituted. Typical groups of compounds would be Cj to C5 alkanes, alkenes, amines, alcohols, aldehydes, ketones organo-halides, such as vinyl chloride, etc.
  • SUBSTITUTE SHEET molecular weight compound is inorganic it will preferably comprise 2 to 4 atoms and typical examples could includeNCfc, S02, C02, NO, CO etc.
  • Higher molecularweight compounds referstocompoundscontainingmore than5 atoms. Thesevalues are thosewhichare generally applicable to theporous adsorber Tenax andwhere other adsorbers are used thetypesofcompoundsand retention on the adsorber on the basis ofmolecularweightmayvary.
  • the reagent isas specificaspossibletothecompoundsorclasses of compounds which require detection.
  • the reagent is a Chromium (VI) compound which changes colour from orange to black on reaction with methanol or ethanol.
  • the Chromium (VT) compound is impregnated on crystalscontainedwithinatubewithwiregauzesbeingprovidedtoretainthe crystals.
  • a drying agent may also be included in the tube to removewater from the air sample before passing over the reagent.
  • the adsorber is a porous powdered polymer, poly 2,6 diphe ⁇ l-p-phe ⁇ ylene oxide which may be retained by glass wool plugs.
  • the adsorber may be contained withinthesametubeasthereagentorinasecondtubewhichisconnectableto thereagenttube. Inapreferredarrangementthereagentandadsorbermaybe sealed before air sairpling and a pumpmeans is provided to draw a standard volume of air sample through the detector.
  • the reagent tube 10 available from Draeger, is a narrow-bore tube partly filled with orange Chromium (VI) compound 12, retained by plugs 13 ofwire.
  • VI Chromium
  • SUBSTITUTE SHEET show that Tenax selectively removes the n octane, thereby removing amajor cross sensitivity problem when detecting methanol.

Landscapes

  • Life Sciences & Earth Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Immunology (AREA)
  • Engineering & Computer Science (AREA)
  • Molecular Biology (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Analytical Chemistry (AREA)
  • Pathology (AREA)
  • Physics & Mathematics (AREA)
  • Biochemistry (AREA)
  • Urology & Nephrology (AREA)
  • Hematology (AREA)
  • Biomedical Technology (AREA)
  • Cell Biology (AREA)
  • Microbiology (AREA)
  • Biotechnology (AREA)
  • Food Science & Technology (AREA)
  • Medicinal Chemistry (AREA)
  • Dispersion Chemistry (AREA)
  • Biophysics (AREA)
  • Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)

Abstract

Un détecteur permettant de contrôler des composés de faible poids moléculaire et tout particulièrement les alcools éthanol et méthanol dans des milieux où des contaminants de poids moléculaire supérieur peuvent également être présents. L'on fait passer des échantillons de gaz à travers un absorbant poreux qui présente une rétention relativement faible pour des composés tels que le méthanol et éthanol et une rétention relativement élevée pour des espèces de poids moléculaire plus élevé. L'on fait passer la partie de l'échantillon qui n'est pas retenue par l'absorbant à travers un réactif qui subit une variation de couleur due aux composés de faible poids moléculaire, le degré de variation de couleur étant caractéristique de la quantité de composé de faible poids moléculaire présente. L'invention s'applique en particulier au contrôle de la concentration d'alcools organiques de faible poids moléculaire tel que le méthanol et éthanol.A detector for monitoring low molecular weight compounds and especially ethanol and methanol alcohols in environments where contaminants of higher molecular weight may also be present. Gas samples are passed through a porous absorbent which exhibits relatively low retention for compounds such as methanol and ethanol and relatively high retention for higher molecular weight species. The part of the sample which is not retained by the absorbent is passed through a reagent which undergoes a color variation due to the compounds of low molecular weight, the degree of color variation being characteristic of the quantity. of low molecular weight compound present. The invention applies in particular to the control of the concentration of organic alcohols of low molecular weight such as methanol and ethanol.

Description

A Detector for Monitoring Low Molecular Weight Compounds
The invention relates to the detection of low molecular weight compoundsr especially ethanol andmethanol/ in the presence of highermolecularweight compounds and is particularly but not exclusively related to a methanol detector for atmosphere monitoring in closed environments.
Methanol (CH30H) isa toxicsubstanceandwhenpresentinclosedenvironments thereisaneedtoroutinelymonitortheair. Amoni ormustbeableto signal that the ambient level of methanol is less than a maximum permissible concentration.
In one known detector arrangement a commercially availableDraeger detector tube, Methanol 50/a, can be used tomonitor methanol in the range 50 to 3000 ppm. Other tubes are available for themonitoringof other compounds. The detector itself consists of a narrow bore tube containing a precleansing layer of drying agent followed by crystals impregnated with an orange Chromium (Cr(VI)) compound. In order tomonitormethanol a sample of air of standard volume is drawn through the detector tube by means of a bellows pump. The presence of methanol in that sample causes a colour change in the tube fromorange to black. Thelength of theblack stain thendetermines the amount of methanol present in the sample for the given volume of air. The detection process is illustrated by:
CH30H + Cr6+ > Reaction products (black)
This monitoring arrangement, however, suffers from cross sensitivity to higher molecular weight alcohols and some other organic compounds, in particular n octane. According to the manufacturer, a concentration of500 ppm of n octane "impurity" gives an indication of approximate 2500 ppm of methanol. This makes the use of methanol Draeger tubes in closed environments impractical because many closed environments contain a large number of organic pollutants including octane which would interfere with methanol monitoring. The problem of cross sensitivity may also existwhen monitoring other low molecular weight organic compounds and possibly also with low molecular weight inorganic compounds.
SUBSTITUTE SHEET The inventorhasbeeninvolved indevelopmentof a samplingprocedureforthe quantitative collection of trace organic contaminants in air using a coπroerciallyavailableporouspolymerTenax. Tenaxhasdifferingretention characteristics for different chemical species and inparticular retention of methanol and ethanol are low compared with n octane. The breakthrough volumes formethanol, ethanol andnoctane sampledonTenaxare0.3 lg-1, 1.8 lg-1 and770 lg-1 respectivelyat20oc. Tenaxisavailablecommerciallyin two formsir TenaxTAandTenaxGC. For the invention inquestioneither form is suitable.
An object of the present invention is to provide a means to detect low molecular weight compounds when present in a sample with higher molecular weightcontaminants. Afurtherobjectofthepresentinventionistoprovide ameanstomonitormethanol inthepresenceofnoctane. Ayetfurtherobject is to provide a means to detect ethanol in the presence of other organic species.
The invention provides a detector for monitoring low molecular weight compounds in the presence of higher molecular weight species comprising: a porous adsorber having relatively low retention for the low molecular weight coπpounds and relatively high retention for highermolecularweight species; and a reagent which undergoes a colour change on reaction with low molecular weight compounds; the arrangement being such that the adsorber and reagent are contained such thata sampleofair canbepassedthroughtheadsorberbeforepassingthrough the reagent, th amount of low molecular weight compound being calculable from the amount of reagent which changes colour.
Theterm "lowmolecularweightcompound" canbe referingtoeitherorganicor inorganic compounds. Preferably the low molecular weight compounds are organic Compounds. Preferablytheorganiccompoundsareeithermethanol or ethanol.
Where the lowmolecularweightcompound isanorganiccompound itpreferably contains between1 and5 carbonatomsandmaybe straightchainoroptionally branched. The compounds may also be substituted. Typical groups of compounds would be Cj to C5 alkanes, alkenes, amines, alcohols, aldehydes, ketones organo-halides, such as vinyl chloride, etc. Where the low
SUBSTITUTE SHEET molecular weight compound is inorganic it will preferably comprise 2 to 4 atoms and typical examples could includeNCfc, S02, C02, NO, CO etc. Higher molecularweight compounds referstocompoundscontainingmore than5 atoms. Thesevalues are thosewhichare generally applicable to theporous adsorber Tenax andwhere other adsorbers are used thetypesofcompoundsand retention on the adsorber on the basis ofmolecularweightmayvary. These limitationsdonotrepresent clearboundariesforallcompoundswhichwillbe able to pass through the porous adsorber Tenax or be adsorbed by it but generallyit isfoundthat thelargerthemolecularweightofthemoleculethe more difficult it tends tobe for it topass through theporous adsorber and hence molecules containing 5 carbon atoms may take quite some time to pass through if they do at all. Furthermore where Tenax is theporous adsorber used polarity becomes a criteria in whether a compound will be adsorbed or not.. In this case there is a preference to adsorb polar compounds. To enable the invention to work it is necessary that the low molecular weight compound is in the vapour phase for passing through the porous adsorber.
Preferablythe reagent isas specificaspossibletothecompoundsorclasses of compounds which require detection. Where a detector for methanol or ethanol is required thenpreferably the reagent is a Chromium (VI) compound which changes colour from orange to black on reaction with methanol or ethanol. Advantageously the Chromium (VT) compound is impregnated on crystalscontainedwithinatubewithwiregauzesbeingprovidedtoretainthe crystals. A drying agent may also be included in the tube to removewater from the air sample before passing over the reagent. Advantageously the adsorber is a porous powdered polymer, poly 2,6 dipheιτl-p-pheιτylene oxide which may be retained by glass wool plugs. The adsorber may be contained withinthesametubeasthereagentorinasecondtubewhichisconnectableto thereagenttube. Inapreferredarrangementthereagentandadsorbermaybe sealed before air sairpling and a pumpmeans is provided to draw a standard volume of air sample through the detector.
The inventionwill nowbe described byway of example onlywith referenceto theaccompanyingFigurewhichshowsamethanoldetectorwithseparatereagent and adsorber tubes 10 and 11.
The reagent tube 10, available from Draeger, is a narrow-bore tube partly filled with orange Chromium (VI) compound 12, retained by plugs 13 ofwire.
SUBSTITUTE SHEET Onthe air inlet side14 ofthetube10 aporousdryingagent15 isprovidedand theoutlet16 isconnectabletoapumpfordrawingastandardisedvolumeofair through the reaction tube 10. Joined to the reaction tube inlet 14 by any knownmeansistheadsorbertube11whichcontains aporouspolymeradsorber, (poly-2,6-dipheϊψl-p-pheπylene oxide) TENAX (Trade Mark) 17 retained in position by porous glass wool plugs 18.
Thereagent tube10 andadsorber tube11 areinitiallysealedattheairinlet 21 totheadsorber tube11 andtheairoutlet16 fromthereagent tube10. In use, the seals arebroken, apump is connected to the reagent tube outlet16 and a standard volume of air is drawn through the tubes. The Tenax is effectivein adsorbing organicmolecules >C~- in a closed environmentwhile methanol isnot retained. Inparticular, theTenaxadsorbsnoctanewhichis present in the air. The amount of methanol in the sampled air is then proportional to the length of the chromium (VI) column which changes from orange to black.
Although the invention has beendescribedashavingtwoseparate reagentand adsorbertubes, itwill be apparent tothoseskilled intheartthatasingle tubecouldbeused, includingsuccessivequantitiesofadsorber, dryingagent andChromium(VI) reagent. TheChromium (VI) reagentwill alsoreactwiththe same sensitivity to ethanol. Tfous the invention could alsobe used for the detection of et-hanol where there is no methanol contamination. ThetableshowstheresultsofoperationoftheChrcmium (VI) Draegerreagent tube, with and -without a Tenax adsorber pre-cleanse tube in atmospheres containing known amounts of methanol and or n octane.
Each atmospherewas sampled by drawing 2500 ml of air through thedetector. This is five time the sampling volume for which the Draeger tube is calibrated. Thέobservedreadingsquotedaboveallowforthis. Theresults
SUBSTITUTE SHEET show that Tenax selectively removes the n octane, thereby removing amajor cross sensitivity problem when detecting methanol.
SUBSTITUTE SHEET

Claims

£____ι
1. Adetectorformonitoringlowmolecularweightcompoundsinthepresence of higher molecular weight species comprising: a porous adsorber having relatively low retention for the low molecular weight compounds and relativelyhigh retention for highermolecularweight species; and a reagent which undergoes a colour change on reaction with low molecular weight compounds; the arrangement being such that theadsorberand reagentarecontainedsuch thatasampleofaircanbepassedthroughtheadsorberbeforepassingthrough the reagent, the amount of lowmolecular.weight compound beingcalculable from the amount of reagent which changes colour.
2. A detector as claimed in claim 1 wherein the low molecular weight compounds are organic compounds.
3. Adetectorasclaimedinclaim2whereintheorganiccompoundsareeither methanol or ethanol.
4. A detector as claimed in claim 2 or 3 wherein the organic compounds contain between 1 and 5 carbon atoms.
5. Adetectorasclaimedinclaim1whereinthelowmolecularweightcompound is inorganic and comprise 2 to 4 atoms.
6. Adetector as claimed in claim3 wherein the reagent isaChrcmium (VI) compoundwhichchangescolourfromorangetoblackonreactionwithmethanol or ethanol.
7. A detector as claimed in claim6 wherein theChromium (VI) compound is impregnatedimpregnatedoncrystalscontainedwithinatubewithwiregauzes being provided to retain the crystals.
8. Adetectorasclaimedinanyoneof thepreviousclaimswhereinadrying agent is included in the tube to remove water from the air sample before passing over the reagent.
SUBSTITUTE SHEET
9. A detector as claimed in any one of the previous claims wherein the adsorber is a porous powdered polymer, poly 2,6 dipheπyl-p-phenylene oxide optionally retained by glass wool plugs.
10. Adetectorasclaimedinanyoneofthepreviousclaimswhereinthereagent and adsorber are sealed before air sampling and a pumpmeans isprovided to draw a standard volume of air sample through the detector.
11. A detector substantially as herein described and with reference to the accαπpaηying drawings.
SUBSTITUTE SHEET
EP19900910797 1989-07-06 1990-07-04 A detector for monitoring low molecular weight compounds Withdrawn EP0485410A1 (en)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
GB898915495A GB8915495D0 (en) 1989-07-06 1989-07-06 Methanol monitor
GB8915495 1989-07-06
GB8916570 1989-07-20
GB898916570A GB8916570D0 (en) 1989-07-20 1989-07-20 Methanol monitor
GB9005217 1990-03-08
GB909005217A GB9005217D0 (en) 1990-03-08 1990-03-08 Compound detector

Publications (1)

Publication Number Publication Date
EP0485410A1 true EP0485410A1 (en) 1992-05-20

Family

ID=27264566

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19900910797 Withdrawn EP0485410A1 (en) 1989-07-06 1990-07-04 A detector for monitoring low molecular weight compounds

Country Status (2)

Country Link
EP (1) EP0485410A1 (en)
WO (1) WO1991001001A1 (en)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4215588A1 (en) * 1992-05-12 1993-11-18 Bayer Ag Biphenylmethyl-substituted pyridones
DE4215587A1 (en) * 1992-05-12 1993-11-18 Bayer Ag Sulfonylbenzyl-substituted benzo- and pyridopyridones
GB2283816B (en) * 1992-07-13 1996-05-29 Broken Hill Pty Co Ltd Sampling device for airborne particulate and vapour emissions
DE4319041A1 (en) * 1992-10-23 1994-04-28 Bayer Ag Trisubstituted biphenyls
ES2065268B1 (en) * 1993-05-04 1995-11-16 Univ Madrid Complutense LUMINISCENT OPTICAL SENSOR.
DE19830607C2 (en) 1998-07-09 2002-08-01 Hte Ag The High Throughput Exp Process for the detection of a product in the downstream of a catalytic material of a variety of catalytic materials

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2078128B (en) * 1980-06-24 1984-09-12 Nat Res Dev Monitoring gases
WO1987001204A1 (en) * 1985-08-15 1987-02-26 Global Geochemistry Corporation Chemical analysis by controlled sample modulation and detection correlation
DE3531650A1 (en) * 1985-09-05 1987-03-05 Draegerwerk Ag DIFFUSION SAMPLERS FOR GASEOUS MEDIA

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9101001A1 *

Also Published As

Publication number Publication date
WO1991001001A1 (en) 1991-01-24

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