GB2160646A - Method for determining the concentration of a gas - Google Patents
Method for determining the concentration of a gas Download PDFInfo
- Publication number
- GB2160646A GB2160646A GB8412825A GB8412825A GB2160646A GB 2160646 A GB2160646 A GB 2160646A GB 8412825 A GB8412825 A GB 8412825A GB 8412825 A GB8412825 A GB 8412825A GB 2160646 A GB2160646 A GB 2160646A
- Authority
- GB
- United Kingdom
- Prior art keywords
- rubber
- gas
- infra
- liquid
- determined
- 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.)
- Granted
Links
- 238000000034 method Methods 0.000 title claims abstract description 16
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims abstract description 42
- 229920001971 elastomer Polymers 0.000 claims abstract description 34
- 239000005060 rubber Substances 0.000 claims abstract description 34
- 229910002092 carbon dioxide Inorganic materials 0.000 claims abstract description 21
- 239000001569 carbon dioxide Substances 0.000 claims abstract description 19
- 239000007788 liquid Substances 0.000 claims abstract description 17
- 230000005855 radiation Effects 0.000 claims abstract description 12
- 210000004369 blood Anatomy 0.000 claims abstract description 9
- 239000008280 blood Substances 0.000 claims abstract description 9
- 238000010521 absorption reaction Methods 0.000 claims abstract description 7
- 229920002379 silicone rubber Polymers 0.000 claims description 13
- 239000004945 silicone rubber Substances 0.000 claims description 11
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 4
- GQPLMRYTRLFLPF-UHFFFAOYSA-N Nitrous Oxide Chemical compound [O-][N+]#N GQPLMRYTRLFLPF-UHFFFAOYSA-N 0.000 claims description 4
- 238000005259 measurement Methods 0.000 claims description 3
- 235000019441 ethanol Nutrition 0.000 claims description 2
- 150000008282 halocarbons Chemical class 0.000 claims description 2
- 239000001272 nitrous oxide Substances 0.000 claims description 2
- 239000007789 gas Substances 0.000 description 21
- 230000003287 optical effect Effects 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 239000000463 material Substances 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-M Bicarbonate Chemical compound OC([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-M 0.000 description 1
- 244000043261 Hevea brasiliensis Species 0.000 description 1
- 239000005062 Polybutadiene Substances 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 238000000862 absorption spectrum Methods 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000004159 blood analysis Methods 0.000 description 1
- 210000000601 blood cell Anatomy 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-N carbonic acid Chemical compound OC(O)=O BVKZGUZCCUSVTD-UHFFFAOYSA-N 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000002848 electrochemical method Methods 0.000 description 1
- 238000004868 gas analysis Methods 0.000 description 1
- 239000007792 gaseous phase Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 229920003052 natural elastomer Polymers 0.000 description 1
- 229920001194 natural rubber Polymers 0.000 description 1
- 239000011236 particulate material Substances 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 229920002857 polybutadiene Polymers 0.000 description 1
- -1 polypropylene Polymers 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 229910000028 potassium bicarbonate Inorganic materials 0.000 description 1
- 235000015497 potassium bicarbonate Nutrition 0.000 description 1
- 239000011736 potassium bicarbonate Substances 0.000 description 1
- TYJJADVDDVDEDZ-UHFFFAOYSA-M potassium hydrogencarbonate Chemical compound [K+].OC([O-])=O TYJJADVDDVDEDZ-UHFFFAOYSA-M 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 239000000779 smoke Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229920003051 synthetic elastomer Polymers 0.000 description 1
- 239000005061 synthetic rubber Substances 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N21/3504—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing gases, e.g. multi-gas analysis
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
Landscapes
- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Or Analysing Biological Materials (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
A method is disclosed for determining the concentration of a gas in a liquid or gaseous medium, particularly carbon dioxide in blood, by contacting a rubber element with a gas or liquid containing the gas to be determined such that the rubber is in contact with the gas or liquid. The rubber is exposed to infra-red radiation and the infra-red absorption in the rubber of the gas is measured.
Description
SPECIFICATION
Method for determining the concentration of a gas
This invention relates to a method for determining the concentration of a gas in a liquid or gaseous medium.
There are many instances when it is necessary to determine the concentration of a gas.
One example is the determination of carbon dioxide concentration in blood.
Carbon dioxide absorbs infra-red radiation at a wavelength of about 4.2 ,um and it is known to make use of this characteristic to measure the amount of carbon dioxide in a gaseous phase. However, this method cannot be applied directly to measure the carbon dioxide content of blood because the blood itself strongly absorbs the infra-red radiation.
In practice therefore, the carbon dioxide content of blood is generally determined indirectly by an electrochemical method (see for example, A.P. Adams and C. E. W. Hahn;
Principles and Practice of Blood-Gas Analysis;
General Diagnostics, Morris Plains, New Jersey, U.S.A.). A very thin layer of a solution of potassium bicarbonate is separated from the blood sample by a thin membrane which is permeable to carbon dioxide but not to water.
The carbon dioxide in the blood effects the pH of the bicarbonate solution by way of the equilibria: CO2 + H2O= H2CO3 = H+ + HCO3and the pH is determined by measuring the potential between a glass electrode and a suitable reference electrode.
While this method is widely used, it has the disadvantage that the measured potential difference does not depend directly on the concentration of carbon dioxide but on its logarithm. This means that the equipment cannot be properly equilibrated with zero concentration of carbon dioxide CO2 and has to be calibrated using two known concentrations.
We have now found a method of determining the concentration of a gas in a liquid or gaseous medium which comprises contacting a rubber with a gas or liquid containing the gas to be determined such that the rubber is in contact with the said gas or liquid, exposing the rubber to infra-red radiation and measuring the infra-red absorption in the rubber of the gas to be determined.
The method according to the invention may be used to determine the concentration of any gas or vapour provided that it is soluble in the rubber and has a suitable absorption spectrum in the rubber. Examples of suitable gases are carbon dioxide, nitrous oxide, halogenated hydrocarbons and ethyl alcohol.
According to the invention the concentration of the gas may be determined in any liquid or gaseous medium which may contain other gaseous, liquid and/or solid components.
The method according to the invention is particularly applicable to the measurement of carbon dioxide concentration in blood.
The rubber may be any transparent rubber such as those which are commercially available. The choice will depend, among other things, upon the nature of the gas since, in practice, a rubber is selected which does not absorb infra-red radiation at the same wavelength as the gas to be determined.
Suitable rubbers are transparent rubbers having a permeability to gases and vapours of at least 200 cc(STP)/cm2/mm/sec/cm HgxiO10 such as silicone rubbers, natural rubber and synthetic rubbers e.g. polybutadiene.
Silicone rubbers are preferred since they are particularly permeable to gases and vapours.
Moreover, a gas such as carbon dioxide dissolved in the rubber continues to absorb infra-red radiation as it does in the gas phase.
In consequence, using carbon dioxide as an example, if rubber is in contact with a surrounding gas or liquid that contains carbon dioxide, the infra-red absorption of the carbon dioxide can be measured in the rubber as though the carbon dioxide were in the gas phase. An advantage of measuring the infrared absorption in the rubber is that the rubber excludes many substances that would interfere with direct measurements. For example in blood analysis,the rubber excludes liquid water and the blood cells. In the analysis of gases, the rubber would exclude smoke and other particulate materials.
The method according to the invention can be implemented in a variety of forms to meet practical requirements.
For example, infra-red radiation can be shone through a piece of the selected rubber preferably silicone rubber that is in contact with the gaseous or liquid sample that is to be analysed. An arrangement for doing this is illustrated in Fig. 1.
A sample 1 is introduced into a tube 2.
This tube 2 is made from a material that is reasonably transparent to infra-red, such as polypropylene. A bar of silicone rubber 3 is placed inside the tube so that it conducts infra-red radiation from a source 4 to a sensor 5, while at the same time being in contact with the sample 1. The absorption of infra-red in the rubber and the optical path can then be determined.
When the sample has a lower refractive index than the silicone rubber (e.g. air or water), light shone along thin pieces of the silicone rubber (in the form of threads or sheets) will be retained in the rubber by total internal reflections. The optical path is then determined by the length of thread or the width of the sheet, which can be adjusted from a few millimetres to several centimetres to provide the sensitivity required, while at the same time the rubber is kept sufficiently thin to reach equilibrium quickly.
According to another possibility, a sheet of rubber such as silicone rubber is attached to a transparent window and partially covered by a grid-form mirror.
This arrangement is illuistrated in the accompanying Fig. 2.
A sheet of suitable silicone rubber material 6 is attached by any suitable means to a transparent window 7. The sheet of silicone rubber 6 is partially covered at its face 8 remote from the window 7 by a mirror 9 in the form of a grid. A gaseous or liquid sample 10 containing the gas to be measured is placed at the face 8 of the silicone rubber 6, the grid-form mirror 9 allowing the sample 10 and silicone rubber 6 to be in contact. Infrared radiation 11 is shone through the window 7 and the absorption of it in the silicone rubber and the optical path can be determined.
Claims (6)
1. A method of determining the concentration of a gas in a liquid or gaseous medium which comprises contacting a rubber with a gas or liquid containing the gas to be determined such that the rubber is in contact with the said gas or liquid, exposing the rubber to infra-red radiation and measuring the infra-red absorption in the rubber of the gas to be determined.
2. A method according to claim 1, wherein the gas to be determined is carbon dioxide, nitrous oxide, a halogenated hydrocarbon or ethyl alcohol.
3. A method according to claim 1 or 2, wherein the rubber is a silicone rubber.
4. A method according to any of claims 1 to 3, which comprises shining infra-red radiation through a sheet of rubber which is in contact with a gaseous or liquid sample containing the gas to be determined.
5. A method according to any of claims 1 to 3, which comprises shining infra-red radiation through a transparent window in contact with a sheet of rubber which is partially covered at its face remote from the window by a mirror in the form of a grid.
6. A method according to any of claims 1 to 5 for the measurement of carbon dioxide concentration in blood.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8412825A GB2160646B (en) | 1984-05-18 | 1984-05-18 | Method for determining the concentration of a gas |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8412825A GB2160646B (en) | 1984-05-18 | 1984-05-18 | Method for determining the concentration of a gas |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8412825D0 GB8412825D0 (en) | 1984-06-27 |
| GB2160646A true GB2160646A (en) | 1985-12-24 |
| GB2160646B GB2160646B (en) | 1988-05-05 |
Family
ID=10561196
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8412825A Expired GB2160646B (en) | 1984-05-18 | 1984-05-18 | Method for determining the concentration of a gas |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2160646B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4800886A (en) * | 1986-07-14 | 1989-01-31 | C. R. Bard, Inc. | Sensor for measuring the concentration of a gaseous component in a fluid by absorption |
| US5371020A (en) * | 1991-09-19 | 1994-12-06 | Radiometer A/S | Method of photometric in vitro determination of the content of an analyte in a sample |
-
1984
- 1984-05-18 GB GB8412825A patent/GB2160646B/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4800886A (en) * | 1986-07-14 | 1989-01-31 | C. R. Bard, Inc. | Sensor for measuring the concentration of a gaseous component in a fluid by absorption |
| US5371020A (en) * | 1991-09-19 | 1994-12-06 | Radiometer A/S | Method of photometric in vitro determination of the content of an analyte in a sample |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2160646B (en) | 1988-05-05 |
| GB8412825D0 (en) | 1984-06-27 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19920518 |