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GB1591368A - Apparatus for analysis of samples by combustion - Google Patents

Apparatus for analysis of samples by combustion Download PDF

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Publication number
GB1591368A
GB1591368A GB3554776A GB3554776A GB1591368A GB 1591368 A GB1591368 A GB 1591368A GB 3554776 A GB3554776 A GB 3554776A GB 3554776 A GB3554776 A GB 3554776A GB 1591368 A GB1591368 A GB 1591368A
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United Kingdom
Prior art keywords
gas
combustion
sample
nitrogen
loop
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.)
Expired
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GB3554776A
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International Synthetic Rubber Co Ltd
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International Synthetic Rubber Co Ltd
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.)
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Publication date
Application filed by International Synthetic Rubber Co Ltd filed Critical International Synthetic Rubber Co Ltd
Priority to GB3554776A priority Critical patent/GB1591368A/en
Publication of GB1591368A publication Critical patent/GB1591368A/en
Expired legal-status Critical Current

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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N31/00Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
    • G01N31/12Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using combustion

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  • Health & Medical Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Combustion & Propulsion (AREA)
  • Molecular Biology (AREA)
  • Engineering & Computer Science (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)

Description

(54) APPARATUS FOR ANALYSIS OF SAMPLES BY. COMBUSTION (71) We, THE INTERNATIONAL SYN- THETIC RUBBER COMPANY LIMITED, a British Company, of Brunswick House, Brunswick Place, Southampton, Hampshire, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to an apparatus for use in the analysis of samples by combustion. In a particular embodiment it relates to an apparatus for the combustion of a solid or liquid material in the determination of its nitrogen, carbon or hydrogen content.
It is well known to determine the nitrogen, carbon or hydrogen content of a solid or liquid material by combustion of a weighed sample of the material in a combustion zone in a stream of oxygen and to determine the nitrogen, carbon or hydrogen content, as the case may be, of the combustion gas. In this specification the expression "combustion gas" is used to indicate the gas resulting from combustion of the sample. The combustion gas will, of course, comprise both the products of combustion and oxygen. One problem which occurs in such a method is the incomplete combustion of the sample leading to a result which is lower than the true figure. Further, in known apparatus a gas other than oxygen is used to flush the combustion gas from the combustion zone.
We have now found that these disadvantages may be obviated Iby recycling the combustion gas several times through the combustion zone using a closed loop system.
According to the present invention an apparatus for use in the analysis of a sample by combustion comprises a combustion'zone having an inlet and an outlet, a tubular loop linking the inlet to the outlet, a constant volume pump in the loop, a sample port for introducing the sample to be analysed into the combustion zone, a gas inlet to the loop ahead of the combustion zone and a gas sampling valve for extracting a measured volume of the gas circulated in the loop by the constant volume pump when the apparatus is in use.
One embodiment of the invention will now be described with reference to the drawing, filed with the Provisional Specification, which is a schematic diagram of the apparatus of this embodiment.
In this embodiment the apparatus comprises a combustion tube 1, a sample port 2, a gas inlet 3, a constant volume pump 4, and a gas sampling valve 5. In the case of nitrogen analysis, a carbon dioxide absorption tube 6, may be inserted in the loop or fitted to the outlet side of the gas sampling valve. However, the use of this tube is op tonal. The combustion tube 1, may be, for example, a straight tube approximately 60 cms. long of 2 to 2.5 cms. bore and may be made of fused quartz. The volume of the tube governs the volume of the apparatus and thus the size of sample required for a given sensitivity. The tube is loosely packed with a catalyst the function af which is to ensure combustion of the sample and conversion of the combustion product into nitrogen, carbon dioxide and/or water vapour.A suitable material is, for example, cupric oxide deposited on alumina or silica gel. Other oxygen donors may, of course, be used. If desired a layer of platinised pumice may be deposited on top of the catalyst to ensure immediate ignition. A cylinder of copper gauze may be inserted above the catalyst, ensuring good contact with the wall of the combustion tube so that in use the gauze oxidises to copper oxide assisting combus tibn of the vaporised sample. The constant volume pump is conveniently of the peri static type, a typical model b'eing the HR Flow Inducer Type MHRK, made by The Watson Mallow Air Pump Co. Desirably the loop, the sampling valve and the combustion tube are temperature controlled.This is especially important where the hydrogen content of a sample is to be determined since the system must be, maintained above the dew point of the circulating gases. If used in nitrogen analysis, the absorption tube, 6, removes carbon dioxide, hydrogen, sulphur oxides and possibly halogens. It may ibe packed with soda-asbestos mixed with pumice or other inert diluent. The diluent prevents clogging and ensures free passage of combustion gas through the absorption tube.
The gas sampling valve 5, is used to extract a measured volume of gas and to inject this into a detector/analyser for determination of the desired content. A volume of 1 to 2 -cc. is normally adequate. A suit able-valve is that manufactured by Perkin Elmer for their gas chromatographs. The gas inlet 3, may be a simple diaphragm or similar valve and is used to supply oxygen at a fixed over-pressure to the loop. It is conveniently set at -t- or 1 psig.
In use the apparatus of the invention is connected to a, suitable detector/analyser.
One form of detector/analyser comprises a separating column packed with molecular sieve Grade 5A or 13 X and a katharometer detector. Alternatively a commercial gas liquid chromatograph (GLC) equipped with a helium carrier-gas line may be used. A suitable chromatograph is the Perkin Elmer Model 452.
To operate the apparatus of the invention the combustion tube 1, is heated to a suitable temperature, for example, 500"C to 1,000 C and oxygen is supplied to the apparatus through the gas inlet 3, at a pressure of, for example, 21 pslig. The gas sampling valve 5, lis closed and the constant volume pump 4, is started to circulate the oxygen. A weighed sample of the material to be analysed, weighing, for example, 10 to 40 mug., is introduced into the combustion tube 1, via sample port 2, which is promptly closed. Combustion of the sample occurs and the combustion gas is circulated around the loop.After a short interval, for example, 5 minutes to enable the system to equilibriate, a known volume sample of the circulating gas is extracted and passed to the detector/analyser for determination of the nitrogen, carbon or hydrogen content as the case may be. The apparatus is flushed with oxygen vented through sample port 2, and is ready for further use.
When nitrogen or carbon dioxide or water is released from the sample its partial pressure is determined by the quantity and the volume and temperature(s) of the loop. It is iindependent of the total gas pressure. The gas sampling valve supplies a measured volume of the atmosphere within the loop to an' analyser which measures the quantity of nitrogen or carbon or water in the sample.
The apparatus may be standardised using samples of known nitrogen, carbon or hydrogen content, for example, 8-hydroxyquinoline so that the detector/analyser may be calibrated and a direct reading of the re quired content obtained.
The apparatus of the invention is especially useful for the determination of the nitrogen content-of a wide variety of'samples and pro vides a cheap, speedy and reliable method for doing so. It is particularly applicable to the determination of the acrylonitr'ile'còn- tent of acrylonitrile butadiene styrene (ABS) plastics.
In the determination of all'three elements, carbon, hydrogen and nitrogen, the apparatus can be operated on the su;btractive principle. Carbon dioXide absorption tube 6, is omitted but may be replaced by a heated tube to remove the sulphur oxides and halogens, packed with absorbents such as lead chromate or silver. Oxygen is first removed by reaction with hot copper. The combustion gas containing carbon dioxide, water and nitrogen is passed in succession through first a katharometer cell, a water absorber such as anhydrone, a second katharometer, a carbon dioxide absorber such as sodaasbestos/anhydrone and finally a third katharometer. By matching the response factors of the detectors the amounts of carbon dioxide, hydrogen and nitrogen can readily be derived.Alternatively two sampling valves may be used to transmit samples to two columns in parallel. Carbon dioxide and water are removed from one sample and this is passed to a column which separates oxygen and nitrogen so that these will occur as two separate peaks. A second column separates oxygen/nitrogen, carbon dioxide and water so that these may be detected as separate peaks. Other ways of linking the apparatus of the invention to the detector/analyser may be envisaged such as the use of a second gas sampling valve linked to that employed in the apparatus to enable hydrogen carrier-gas to be used safely for the GLC analysis.
WHAT WE CLAIM IS: 1. Apparatus for use in the analysis of a sample by combustion comprising a combustion zone having an inlet and an outlet, a tubular loop linking the inlet to the outlet, a constant volume pump in the loop, a sample port for introducing the sample to be analysed into the combustion zone, a gas inlet to the loop ahead of the combustion zone and a gas sampling valve for extracting a measured volume of the gas circulated in the loop by the constant volume pump when the apparatus is in use.
2. Apparatus for use in the analysis for nitrogen content of a sample by combustion substantially as hereinbefore described with
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. diluent prevents clogging and ensures free passage of combustion gas through the absorption tube. The gas sampling valve 5, is used to extract a measured volume of gas and to inject this into a detector/analyser for determination of the desired content. A volume of 1 to 2 -cc. is normally adequate. A suit able-valve is that manufactured by Perkin Elmer for their gas chromatographs. The gas inlet 3, may be a simple diaphragm or similar valve and is used to supply oxygen at a fixed over-pressure to the loop. It is conveniently set at -t- or 1 psig. In use the apparatus of the invention is connected to a, suitable detector/analyser. One form of detector/analyser comprises a separating column packed with molecular sieve Grade 5A or 13 X and a katharometer detector. Alternatively a commercial gas liquid chromatograph (GLC) equipped with a helium carrier-gas line may be used. A suitable chromatograph is the Perkin Elmer Model 452. To operate the apparatus of the invention the combustion tube 1, is heated to a suitable temperature, for example, 500"C to 1,000 C and oxygen is supplied to the apparatus through the gas inlet 3, at a pressure of, for example, 21 pslig. The gas sampling valve 5, lis closed and the constant volume pump 4, is started to circulate the oxygen. A weighed sample of the material to be analysed, weighing, for example, 10 to 40 mug., is introduced into the combustion tube 1, via sample port 2, which is promptly closed. Combustion of the sample occurs and the combustion gas is circulated around the loop.After a short interval, for example, 5 minutes to enable the system to equilibriate, a known volume sample of the circulating gas is extracted and passed to the detector/analyser for determination of the nitrogen, carbon or hydrogen content as the case may be. The apparatus is flushed with oxygen vented through sample port 2, and is ready for further use. When nitrogen or carbon dioxide or water is released from the sample its partial pressure is determined by the quantity and the volume and temperature(s) of the loop. It is iindependent of the total gas pressure. The gas sampling valve supplies a measured volume of the atmosphere within the loop to an' analyser which measures the quantity of nitrogen or carbon or water in the sample. The apparatus may be standardised using samples of known nitrogen, carbon or hydrogen content, for example, 8-hydroxyquinoline so that the detector/analyser may be calibrated and a direct reading of the re quired content obtained. The apparatus of the invention is especially useful for the determination of the nitrogen content-of a wide variety of'samples and pro vides a cheap, speedy and reliable method for doing so. It is particularly applicable to the determination of the acrylonitr'ile'còn- tent of acrylonitrile butadiene styrene (ABS) plastics. In the determination of all'three elements, carbon, hydrogen and nitrogen, the apparatus can be operated on the su;btractive principle. Carbon dioXide absorption tube 6, is omitted but may be replaced by a heated tube to remove the sulphur oxides and halogens, packed with absorbents such as lead chromate or silver. Oxygen is first removed by reaction with hot copper. The combustion gas containing carbon dioxide, water and nitrogen is passed in succession through first a katharometer cell, a water absorber such as anhydrone, a second katharometer, a carbon dioxide absorber such as sodaasbestos/anhydrone and finally a third katharometer. By matching the response factors of the detectors the amounts of carbon dioxide, hydrogen and nitrogen can readily be derived.Alternatively two sampling valves may be used to transmit samples to two columns in parallel. Carbon dioxide and water are removed from one sample and this is passed to a column which separates oxygen and nitrogen so that these will occur as two separate peaks. A second column separates oxygen/nitrogen, carbon dioxide and water so that these may be detected as separate peaks. Other ways of linking the apparatus of the invention to the detector/analyser may be envisaged such as the use of a second gas sampling valve linked to that employed in the apparatus to enable hydrogen carrier-gas to be used safely for the GLC analysis. WHAT WE CLAIM IS:
1. Apparatus for use in the analysis of a sample by combustion comprising a combustion zone having an inlet and an outlet, a tubular loop linking the inlet to the outlet, a constant volume pump in the loop, a sample port for introducing the sample to be analysed into the combustion zone, a gas inlet to the loop ahead of the combustion zone and a gas sampling valve for extracting a measured volume of the gas circulated in the loop by the constant volume pump when the apparatus is in use.
2. Apparatus for use in the analysis for nitrogen content of a sample by combustion substantially as hereinbefore described with
reference to and as shown in the drawing accompanying the Provisional Specification.
3. A method of analysis employing the apparatus of claim 1 or claim 2 substantially as hereinbefore described.
4. A method of analysis substantially as hereiitbefore described with reference to the Drawing accompanying the Provisional Specification.
GB3554776A 1977-11-28 1977-11-28 Apparatus for analysis of samples by combustion Expired GB1591368A (en)

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Application Number Priority Date Filing Date Title
GB3554776A GB1591368A (en) 1977-11-28 1977-11-28 Apparatus for analysis of samples by combustion

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB3554776A GB1591368A (en) 1977-11-28 1977-11-28 Apparatus for analysis of samples by combustion

Publications (1)

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GB1591368A true GB1591368A (en) 1981-06-17

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0964248A1 (en) * 1998-06-12 1999-12-15 Horiba, Ltd. System for analyzing elements in sample
GB2446824A (en) * 2007-02-26 2008-08-27 Thermo Fisher Scientific Inc Apparatus and method for detecting incomplete combustion in a combustion analyser
CN109459525A (en) * 2018-12-27 2019-03-12 山东宏业纺织股份有限公司 A kind of device and test method improving flame-retardant yarn flame retardant property testing precision
CN114965834A (en) * 2022-06-10 2022-08-30 长沙开元弘盛科技有限公司 A method and device for determining nitrogen content in non-gaseous samples

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0964248A1 (en) * 1998-06-12 1999-12-15 Horiba, Ltd. System for analyzing elements in sample
US6627155B1 (en) 1998-06-12 2003-09-30 Horiba, Ltd. Combustion furnace system for analyzing elements in a sample
GB2446824A (en) * 2007-02-26 2008-08-27 Thermo Fisher Scientific Inc Apparatus and method for detecting incomplete combustion in a combustion analyser
GB2446824B (en) * 2007-02-26 2009-06-17 Thermo Fisher Scientific Inc Apparatus and method for detecting incomplete combustion in a combustion analyser
CN109459525A (en) * 2018-12-27 2019-03-12 山东宏业纺织股份有限公司 A kind of device and test method improving flame-retardant yarn flame retardant property testing precision
CN109459525B (en) * 2018-12-27 2024-01-19 山东宏业纺织股份有限公司 Device for improving flame retardant property test accuracy of flame retardant yarns
CN114965834A (en) * 2022-06-10 2022-08-30 长沙开元弘盛科技有限公司 A method and device for determining nitrogen content in non-gaseous samples

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