CA2084616A1 - Flow cell apparatus for use in headspace analysis - Google Patents
Flow cell apparatus for use in headspace analysisInfo
- Publication number
- CA2084616A1 CA2084616A1 CA002084616A CA2084616A CA2084616A1 CA 2084616 A1 CA2084616 A1 CA 2084616A1 CA 002084616 A CA002084616 A CA 002084616A CA 2084616 A CA2084616 A CA 2084616A CA 2084616 A1 CA2084616 A1 CA 2084616A1
- Authority
- CA
- Canada
- Prior art keywords
- cell
- collection zone
- fluid
- conduit
- outlet
- 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.)
- Abandoned
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
- G01N1/02—Devices for withdrawing samples
- G01N1/22—Devices for withdrawing samples in the gaseous state
- G01N1/2226—Sampling from a closed space, e.g. food package, head space
-
- 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
- G01N1/2226—Sampling from a closed space, e.g. food package, head space
- G01N2001/2229—Headspace sampling, i.e. vapour over liquid
Landscapes
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Biomedical Technology (AREA)
- Molecular Biology (AREA)
- Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Sampling And Sample Adjustment (AREA)
Abstract
ABSTRACT
A flow cell for sampling headspace of a dynamic fluid is disclosed. The cell includes a collection zone for receiving a headspace sample and a compensatory air line to admit gas into the cell during a sampling procedure.
A flow cell for sampling headspace of a dynamic fluid is disclosed. The cell includes a collection zone for receiving a headspace sample and a compensatory air line to admit gas into the cell during a sampling procedure.
Description
20846~
FLOW CBL~ APPAR~TU8 FOR U8B IN HBAD~PACE ANA~Y~IS
The present invention relates to a flow cell device for use in headspace analysis and more particularly, to a constant headspace volume cell permitting sampling in a dynamic condition.
Sampling of soils and industrial effluents for hazardous materials has always been of importance, however, with the advent of enhanced environmental concerns revolving around pollution, compliance with more stringent regulations has become important and required sophisticated analytical equipment.
The primary difficulty presently experienced by industry is the measurement of mixtures of volatile organic solvents, e.g.
benzene, toluene, xylene and perchloroethylene, CFC-113, etc.
Generally speaking, these substances, when dissolved in water in a flowing system, are difficult to sample and measure due to losses incurred by volatilization. In addition, most chlorinated solvents cannot be detected with flow through detectors, e.g. ultra-violet, fluorescence or conductivity HPLC
detectors since these compounds do not respond to such instrumentation.
Instruments which are capable of handling some organic compounds include, for example, gas chromatographs; a drawback still exists, however, since most organic solvents have a higher volatility than water making direct injection into gas chromatographs impractical.
Presently used methods for solvent collection include discrete sampling followed by analysis. Clearly, this procedure is labour intensive and is highly susceptible to partial losses 208~
of the volatiles.
Schnable et al., in LC-GC Vol. 9, number 12, describes a purge-and-trap sampling valve for use in the monitoring of small sample streams. This system does not provide a flow cell for sampling on-line and further lacks a compensatory fluid line for equalizing the pressure in the cell, such as that which is provided in the present invention.
Headspace analysis equipment which is known in the field is manufactured by Siemens. The Siemens apparatus is useful for on-line analysis, but does not provide a compensatory air-line or permit headspace analysis of low flow rate fluid streams.
U.S. Patent No. 5,050,425, discloses an apparatus for use in the analysis of headspace~ The valve employed in the apparatus is devoid of a compensatory air-line, and an over flow vent. In addition, there is no provision for a constant headspace volume in the valve. Further still, this sytem is not dynamic and only is useful for soil samples and not water samples.
Engelhardt et al., disclose in U.S. Patent No. 5,058,416, an apparatus for the determination of the partial pressure of gases dissolved in a fluid. There is no teaching of a constant volume flow cell for headspace analysis in this reference.
A continuous air monitoring apparatus is taught in U.S.
Patent No. 5,014,541. This document teaches the use of a solid sorbent material to concentrate airborne materials. The patentees do not discuss headspace analysis in an in-line system.
Other generally relevant references include U.S. Patent Nos.
208~616 4,617,828, 4,791,820 and 5,094,099.
In view of the instruments which have been set forth in the art to date, there exists a need for an apparatus capable of collecting headspace material from a continuously flowing fluid sample without interrupting the flow of the fluid. The present invention addresses this need and provides a cell for sampling a stream containing volatile materials to be sampled comprising:
a sample receiving inlet; a sample discharging outlet; a collection zone intermediate said inlet and said outlet for collecting volatile material evolved from said fluid; outlet means for removing collected volatile material; and means for supplying make-up fluid proximate said collection zone.
The cell according to the present invention has been found to be particularly useful in on-line analysis procedures, since the cell is provided with a constant volume headspace collection zone, thus simplifying the analysis procedure. -In dynamic headspace analysis, the critical factor is to sample the headspace without disruptin~ the flow of material being sampled or draw it up the sampling tube. The present invention avoids this difficulty by including the compensatory or make-up air line to provide a stream of air above the air-water interface in the cell. In addition, the air-line flushes the volume above the water once the headspace sample has been taken. Accordingly, contamination of samples subsequently taken is avoided.
A further advantage attendant with the apparatus of the present invention is the provision of a vent to permit excess air to exit the cell and air to enter during a sampling procedure.
- ~.
208461~
A further aspect of the present invention is to provide a sampling cell for use in on-line analysis of continuous flow fluid streams, said cell comprising: a sample receiving inlet;
a sample discharging outlet; a collection zone intermediate said inlet and said outlet for collecting volatile material evolved from said fluid; a conduit in communication with said collection zone, said conduit for supplying a make-up gas to said collection zone; and vent means for venting excess make-up gas from said cell.
Yet another aspect of the present invention is to provide a flow cell for use in dynamic headspace analysis which facilitates direct and automatic analysis of the headspace constituents.
The flow cell, as a further feature, permits two phases, i.e. liquid and gas to be in contact and to equilibrate prior to sampling. Generally, some volatile compounds at equilibrium will be more highly concentrated in the headspace above the liquid than in the liquid itself. Accordingly, such a feature permits smaller volumes of liquid to be sampled effectively.
Having thus generally described the invention, reference will now be made to the accompanying drawings illustrating preferred embodiments and, in which:
Figure l is a cross-sectional view of the flow cell of the present invention; and Figure 2 is a schematic representation of the overall analysis system within which the flow cell is employed.
Referring now to the drawings, Figure 1 shows a cross-~. .. . ~, : - - -.. : -sectional view of the flow cell of the present invention generally represented by numeral 10.
The flow cell 10 includes a T-shaped body having communicating passageways therein. Contaminated fluid, for example water containing volatile organic compounds, enters the cell at inlet 12 and exits the cell at outlet 14. The cell is designed so that the inlet and outlet are in fluid communication to the extent that continuous flow is possible therethrough.
Fluid exiting at outlet 14 may be discarded, recirculated or recycled depending upon the constituents and their value. -As extension 16 is provided on the body of the cell 10 and is in fluid communication with the inlet and outlet and more importantly, the f~uid passing therethrough.
'~
Within the extension 16, a sufficiently sized collection area 18 is provided to capture volatile material evolving from the fluid stream. The collection area 18 is of constant volume and constitutes the headspace of the cell.
A juncture member 20 is connected to the T-shaped portion of the cell by a conduit 22 extending therebetween: conduit 22 may be clear to provide the possibility of visual inspection.
A plurality of additional communicating openings 24,26 and 32 are included. ;~
opening 24 comprises an outlet for the volatile materials collected in collection area 18. Various fittings, e.g. tubes, etc. may be connected at 24 to remove the volatiles for analysis by, for example, a gas chromatograph.
, "~
.. .. ~
~: .:: , .:
: - ,: ., :
- :
20~
Fluid conduit 30 extends within the cell via opening 26 in juncture 20 to the collection area 18.
The conduit 30 is releasably and sealingly engaged within juncture 20 with a septum 31. The septum may comprise silicone rubber, Teflon or other suitable materials.
Conduit 30 is positioned such that when fluid to be sampled is in the cell, the conduit 30 uses just above the fluid level.
When the headspace is sampled, there is a slight vacuum within the cell caused by negative pressure at outlet 24 and additionally, there is negative pressure included in collection zone 18 due to the flow of fluid from inlet 12 to outlet 14.
Conduit 30 alters this pressure difference by providing gas, typically air, nitrogen, helium or other suitable gases, to partially compensate for the difference. This prevents the fluid to be sampled from being drawn into the cell. In addition to this function, the conduit 30 is used to "sweep" or "flush" the collection zone of volatiles thus ensuring that carryover from a sample is removed before subsequent samples are taken.
The third opening 32 permits any pressure build up to be discharged from the cell. To this end, a vent 34 is positioned over the opening. The opening 32 further aids in supplementing gas entrance into the cell during sampling to prevent the sampling fluid from being drawn into the cell.
In terms of materials for constructing the cell, rugged inert materials are preferred, e.g. glass, with stainless steel being most desirable.
Figure 2 illustrates a schematic representation of the analysis system in which fell 10 would be employed.
20~4~B
A fluid sample 40 may be passed in conduit 42 to generator column 46 via pump 44.
The fluid sample enters cell 10 at 12, the headspace is sampled with the fluid sample passing into waste collection at 48. Volatiles evolved from the sampled headspace are passed on via sampling line 50 to, for example, a Photovac~M portable gas chromatograph. Data generated therefrom may be transferred to computer, etc.
Gas enters conduit 30 to purge the collection zone 18 (not shown) for subsequent sample collection.
Although embodiments of the invention have been described above, it is not limited thereto and it will be apparent to those skilled in the art that numerous modifications form part of the present invention insofar as they do not depart from the spirit, nature and scope of the claimed and described invention.
' ' ' .
.i' : ' ~' '-' `' ' ; , . ' " ~ ' . . '~
' . , ' ' ~ , ' ~ ' '
FLOW CBL~ APPAR~TU8 FOR U8B IN HBAD~PACE ANA~Y~IS
The present invention relates to a flow cell device for use in headspace analysis and more particularly, to a constant headspace volume cell permitting sampling in a dynamic condition.
Sampling of soils and industrial effluents for hazardous materials has always been of importance, however, with the advent of enhanced environmental concerns revolving around pollution, compliance with more stringent regulations has become important and required sophisticated analytical equipment.
The primary difficulty presently experienced by industry is the measurement of mixtures of volatile organic solvents, e.g.
benzene, toluene, xylene and perchloroethylene, CFC-113, etc.
Generally speaking, these substances, when dissolved in water in a flowing system, are difficult to sample and measure due to losses incurred by volatilization. In addition, most chlorinated solvents cannot be detected with flow through detectors, e.g. ultra-violet, fluorescence or conductivity HPLC
detectors since these compounds do not respond to such instrumentation.
Instruments which are capable of handling some organic compounds include, for example, gas chromatographs; a drawback still exists, however, since most organic solvents have a higher volatility than water making direct injection into gas chromatographs impractical.
Presently used methods for solvent collection include discrete sampling followed by analysis. Clearly, this procedure is labour intensive and is highly susceptible to partial losses 208~
of the volatiles.
Schnable et al., in LC-GC Vol. 9, number 12, describes a purge-and-trap sampling valve for use in the monitoring of small sample streams. This system does not provide a flow cell for sampling on-line and further lacks a compensatory fluid line for equalizing the pressure in the cell, such as that which is provided in the present invention.
Headspace analysis equipment which is known in the field is manufactured by Siemens. The Siemens apparatus is useful for on-line analysis, but does not provide a compensatory air-line or permit headspace analysis of low flow rate fluid streams.
U.S. Patent No. 5,050,425, discloses an apparatus for use in the analysis of headspace~ The valve employed in the apparatus is devoid of a compensatory air-line, and an over flow vent. In addition, there is no provision for a constant headspace volume in the valve. Further still, this sytem is not dynamic and only is useful for soil samples and not water samples.
Engelhardt et al., disclose in U.S. Patent No. 5,058,416, an apparatus for the determination of the partial pressure of gases dissolved in a fluid. There is no teaching of a constant volume flow cell for headspace analysis in this reference.
A continuous air monitoring apparatus is taught in U.S.
Patent No. 5,014,541. This document teaches the use of a solid sorbent material to concentrate airborne materials. The patentees do not discuss headspace analysis in an in-line system.
Other generally relevant references include U.S. Patent Nos.
208~616 4,617,828, 4,791,820 and 5,094,099.
In view of the instruments which have been set forth in the art to date, there exists a need for an apparatus capable of collecting headspace material from a continuously flowing fluid sample without interrupting the flow of the fluid. The present invention addresses this need and provides a cell for sampling a stream containing volatile materials to be sampled comprising:
a sample receiving inlet; a sample discharging outlet; a collection zone intermediate said inlet and said outlet for collecting volatile material evolved from said fluid; outlet means for removing collected volatile material; and means for supplying make-up fluid proximate said collection zone.
The cell according to the present invention has been found to be particularly useful in on-line analysis procedures, since the cell is provided with a constant volume headspace collection zone, thus simplifying the analysis procedure. -In dynamic headspace analysis, the critical factor is to sample the headspace without disruptin~ the flow of material being sampled or draw it up the sampling tube. The present invention avoids this difficulty by including the compensatory or make-up air line to provide a stream of air above the air-water interface in the cell. In addition, the air-line flushes the volume above the water once the headspace sample has been taken. Accordingly, contamination of samples subsequently taken is avoided.
A further advantage attendant with the apparatus of the present invention is the provision of a vent to permit excess air to exit the cell and air to enter during a sampling procedure.
- ~.
208461~
A further aspect of the present invention is to provide a sampling cell for use in on-line analysis of continuous flow fluid streams, said cell comprising: a sample receiving inlet;
a sample discharging outlet; a collection zone intermediate said inlet and said outlet for collecting volatile material evolved from said fluid; a conduit in communication with said collection zone, said conduit for supplying a make-up gas to said collection zone; and vent means for venting excess make-up gas from said cell.
Yet another aspect of the present invention is to provide a flow cell for use in dynamic headspace analysis which facilitates direct and automatic analysis of the headspace constituents.
The flow cell, as a further feature, permits two phases, i.e. liquid and gas to be in contact and to equilibrate prior to sampling. Generally, some volatile compounds at equilibrium will be more highly concentrated in the headspace above the liquid than in the liquid itself. Accordingly, such a feature permits smaller volumes of liquid to be sampled effectively.
Having thus generally described the invention, reference will now be made to the accompanying drawings illustrating preferred embodiments and, in which:
Figure l is a cross-sectional view of the flow cell of the present invention; and Figure 2 is a schematic representation of the overall analysis system within which the flow cell is employed.
Referring now to the drawings, Figure 1 shows a cross-~. .. . ~, : - - -.. : -sectional view of the flow cell of the present invention generally represented by numeral 10.
The flow cell 10 includes a T-shaped body having communicating passageways therein. Contaminated fluid, for example water containing volatile organic compounds, enters the cell at inlet 12 and exits the cell at outlet 14. The cell is designed so that the inlet and outlet are in fluid communication to the extent that continuous flow is possible therethrough.
Fluid exiting at outlet 14 may be discarded, recirculated or recycled depending upon the constituents and their value. -As extension 16 is provided on the body of the cell 10 and is in fluid communication with the inlet and outlet and more importantly, the f~uid passing therethrough.
'~
Within the extension 16, a sufficiently sized collection area 18 is provided to capture volatile material evolving from the fluid stream. The collection area 18 is of constant volume and constitutes the headspace of the cell.
A juncture member 20 is connected to the T-shaped portion of the cell by a conduit 22 extending therebetween: conduit 22 may be clear to provide the possibility of visual inspection.
A plurality of additional communicating openings 24,26 and 32 are included. ;~
opening 24 comprises an outlet for the volatile materials collected in collection area 18. Various fittings, e.g. tubes, etc. may be connected at 24 to remove the volatiles for analysis by, for example, a gas chromatograph.
, "~
.. .. ~
~: .:: , .:
: - ,: ., :
- :
20~
Fluid conduit 30 extends within the cell via opening 26 in juncture 20 to the collection area 18.
The conduit 30 is releasably and sealingly engaged within juncture 20 with a septum 31. The septum may comprise silicone rubber, Teflon or other suitable materials.
Conduit 30 is positioned such that when fluid to be sampled is in the cell, the conduit 30 uses just above the fluid level.
When the headspace is sampled, there is a slight vacuum within the cell caused by negative pressure at outlet 24 and additionally, there is negative pressure included in collection zone 18 due to the flow of fluid from inlet 12 to outlet 14.
Conduit 30 alters this pressure difference by providing gas, typically air, nitrogen, helium or other suitable gases, to partially compensate for the difference. This prevents the fluid to be sampled from being drawn into the cell. In addition to this function, the conduit 30 is used to "sweep" or "flush" the collection zone of volatiles thus ensuring that carryover from a sample is removed before subsequent samples are taken.
The third opening 32 permits any pressure build up to be discharged from the cell. To this end, a vent 34 is positioned over the opening. The opening 32 further aids in supplementing gas entrance into the cell during sampling to prevent the sampling fluid from being drawn into the cell.
In terms of materials for constructing the cell, rugged inert materials are preferred, e.g. glass, with stainless steel being most desirable.
Figure 2 illustrates a schematic representation of the analysis system in which fell 10 would be employed.
20~4~B
A fluid sample 40 may be passed in conduit 42 to generator column 46 via pump 44.
The fluid sample enters cell 10 at 12, the headspace is sampled with the fluid sample passing into waste collection at 48. Volatiles evolved from the sampled headspace are passed on via sampling line 50 to, for example, a Photovac~M portable gas chromatograph. Data generated therefrom may be transferred to computer, etc.
Gas enters conduit 30 to purge the collection zone 18 (not shown) for subsequent sample collection.
Although embodiments of the invention have been described above, it is not limited thereto and it will be apparent to those skilled in the art that numerous modifications form part of the present invention insofar as they do not depart from the spirit, nature and scope of the claimed and described invention.
' ' ' .
.i' : ' ~' '-' `' ' ; , . ' " ~ ' . . '~
' . , ' ' ~ , ' ~ ' '
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A cell for sampling a fluid stream containing volatile materials to be sampled comprising:
a sample receiving inlet;
a sample discharging outlet;
a collection zone intermediate said inlet and said outlet for collecting volatile material evolved from said fluid;
outlet means for removing collected volatile material; and means for supplying make-up fluid proximate said collection zone.
a sample receiving inlet;
a sample discharging outlet;
a collection zone intermediate said inlet and said outlet for collecting volatile material evolved from said fluid;
outlet means for removing collected volatile material; and means for supplying make-up fluid proximate said collection zone.
2. The cell as set forth in claim 1, wherein said collection zone is a constant volume collection zone.
3. The cell as set forth in claim 1, wherein said means for supplying make-up fluid comprises a conduit.
4. The cell as set forth in claim 3, wherein said conduit extends within said cell and in operative association with said collection zone.
5. A sampling cell for use in on-line analysis of continuous flow fluid streams, said cell comprising:
a sample receiving inlet;
a sample discharging outlet;
a collection zone intermediate said inlet and said outlet for collecting volatile material evolved from said fluid;
a conduit in communication with said collection zone, said conduit for supplying a make-up gas to said collection zone; and vent means for venting excess make-up gas from said cell.
a sample receiving inlet;
a sample discharging outlet;
a collection zone intermediate said inlet and said outlet for collecting volatile material evolved from said fluid;
a conduit in communication with said collection zone, said conduit for supplying a make-up gas to said collection zone; and vent means for venting excess make-up gas from said cell.
6. The cell as set forth in claim 1 or 5, wherein said conduit is positioned within said collection zone for sweeping volatile materials from said zone.
7. The cell as set forth in claim 1 or 5, wherein said outlet means comprises an extension of said cell adapted for connection with gaseous analysis means.
8. The cell as set forth in claim 1 or 5, in combination with gaseous analysis means.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002084616A CA2084616A1 (en) | 1992-12-04 | 1992-12-04 | Flow cell apparatus for use in headspace analysis |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002084616A CA2084616A1 (en) | 1992-12-04 | 1992-12-04 | Flow cell apparatus for use in headspace analysis |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2084616A1 true CA2084616A1 (en) | 1994-06-05 |
Family
ID=4150802
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002084616A Abandoned CA2084616A1 (en) | 1992-12-04 | 1992-12-04 | Flow cell apparatus for use in headspace analysis |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2084616A1 (en) |
-
1992
- 1992-12-04 CA CA002084616A patent/CA2084616A1/en not_active Abandoned
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued | ||
| FZDE | Discontinued |
Effective date: 19960604 |