WO2006008466A1

WO2006008466A1 - Liquid sampling

Info

Publication number: WO2006008466A1
Application number: PCT/GB2005/002750
Authority: WO
Inventors: Alastair Bewsher
Original assignee: The University Of Manchester
Priority date: 2004-07-15
Filing date: 2005-07-12
Publication date: 2006-01-26
Also published as: GB0415827D0

Abstract

A liquid sampling vessel (2) comprises a first inlet port (8) associated with a one-way valve (9) adapted to open to permit water flow into the vessel and being adapted to be closed by pressurisation of the interior of the vessel, and a second port (10) for connection to a source of pressurisation. A gas permeate e barrier membrane (11) is provided to allow pressurisation of the vessel (2) but prevent liquid passing out of the vessel (2) through the second port (10).

Description

LIQUID SAMPLING

The present invention relates to a liquid sampling vessel, a liquid sampling arrangement and also to the use of the arrangement for obtaining a sample of liquid. The invention is applicable particularly, but not exclusively, to the remote sampling of water.

It is often necessary to sample water for the purposes of inter alia monitoring pollution, contaminants and water quality. Water may be sampled, for example, from a river, lake, pond, borehole or other natural source.

A remote water sampling device as disclosed in WO-A-03098191 (The Victoria University of Manchester). The water sampling device in WO-A-03098191 comprises a generally cylindrical sampling vessel having a water inlet tube which extends from one end of the vessel substantially towards the opposite end thereof at which is provided an outlet. The outlet is connected to a vacuum source by a length of flexible tubing. The vessel is weighted so that, in water, the outlet is uppermost. To use the arrangement of WO-A-03098191, the vessel is introduced into water (so that, as described, the outlet is uppermost) and a vacuum is applied by means of the vacuum source. As a result, water is drawn up the inlet passage from which it exits into the vessel at a region adjacent the outlet. The water is thus collected in the vessel in the annular space between the outer surface of the water inlet tube and the inner surface of the vessel. However the use of such an inlet passage leads to a relatively complicated construction.

WO-A-0106230 (Zeneca Limited) discloses an apparatus for taking a liquid (e.g. water) sample of known volume. The apparatus comprises a chamber having a liquid inlet, a liquid outlet, a further port connected to a vacuum source. Associated with this latter port, is a gas permeable membrane across which sampled liquid cannot pass. In use, the liquid outlet of the chamber is initially closed, and a tube connects the liquid inlet to the liquid to be sampled. A vacuum is applied and the liquid is drawn into the chamber. The vacuum is continued to be applied until the liquid reaches the gas permeable membrane and gas bubbles present in the chamber have exited through the membrane. At this point, there is a known volume of liquid in the chamber. The outlet valve of the chamber may now be opened to collect the sample. WO-A-0106230 does mention the possibility of sampling water from a natural source but it is clear that the chamber would be located above ground and the water drawn therein by means of a tube extending downwardly into the water source.

According to a first aspect of the present invention there is provided a liquid sampling vessel comprising a first inlet port associated with a one-way valve adapted to open to permit water flow into the vessel and being adapted to be closed by pressurisation of the interior of the vessel, and a second port for connection to a source of pressurisation wherein a gas permeable barrier membrane is provided to allow pressurisation of the vessel but prevent liquid passing out of the vessel through the second port.

According to a second aspect of the present invention there is provided a liquid sampling arrangement comprising

(a) a liquid sampling vessel having a first inlet port associated with a one-way valve adapted to open to permit liquid flow into the vessel and being adapted to be closed by pressurisation of the interior of the vessel, and a second port for connection to a source of pressurisation,

(b) a source of pressurisation connected by a conduit (preferably flexible) to said second port, and

(c) valve means for relieving pressure in said vessel

wherein a gas permeable barrier membrane is provided to allow pressurisation of the vessel but prevent water passing into said conduit. The liquid sampling vessel employed in the arrangement of the second aspect of the invention may be a vessel as defined for the first aspect of the invention.

The first and second aspects of the invention are particularly suitable for use in obtaining a sample of water.

Conveniently the device is provided with weights (e.g. -adjacent to the lower end of the vessel) whose mass will determine the total depth to which the vessel is capable of sinking before water is sampled in accordance with the procedure described below.

The following method is used to collect a sample of water using the arrangement of the second aspect of the invention. This water may be a natural source such as a lake, river or borehole. Initially, the water sampling vessel is pressurised (by means of the source of pressurisation) to a desired level. This pressurisation will ensure that the one-way valve is closed and will not open (under the action of hydrostatic pressure) until the vessel has been lowered to a desired depth. The vessel is now lowered into the water to be sampled and the mass of the weights determines the total depth to which the vessel is capable of sinking. Once the vessel is at the desired depth, the pressure within the vessel may be relieved. This permits the one-way valve to open and allow water to enter the vessel. Water is permitted to rise in the vessel since air is displaced through the gas permeable barrier membrane. However water can only rise in the vessel to the level of the membrane which will not let water pass therethrough. The vessel may now be retrieved from the water.

The provision of the barrier membrane thus prevents water passing into the conduit connecting to the pressurisation means.

The sampling vessel may be a disposable unit and therefore used for a "one- off sampling operation. However the pressurisation source and conduit connecting this source to the vessel will be re-usable. The provision of the barrier membrane prevents water entering into the conduit and the pressurisation source (and possibly being a contaminant for a subsequent sampling operation). Given also that the pressurisation source has been maintained connected to the line during the sampling operation, then the pressurisation source is itself protected from the potential contaminant/deleterious effects of the sampled water.

The inlet port of the vessel may be removeably mounted theron, e.g. by means of a Luer fitting. The inlet port may thus be removed to retrieve the sampled water from the vessel and then replaced for a subsequent sampling operation. It is however more preferred that the vessel is a disposable unit, in which case the inlet port may be mounted on the main body of the vessel by means of a "snap-off connection (e.g. a line of weakness) whereby the port may be "broken-off to release the sampled liquid.

Preferably the barrier membrane is provided within or at an end of the second port. It is particularly preferred that the membrane is provided across that end of the second port which is adjacent the interior of the vessel. The port may, in fact, project a short distance into the interior of the vessel with the membrane being provided across the end of the port within the vessel.

The barrier membrane may be of a hydrophobic material, provided that the membrane is also permeable. Suitable hydrophobic materials include (but are not limited to) PTFE, FEP (Fluorinated Ethylene Propylene) or PDFM or derivatives thereof.

The means for relieving pressure in the vessel may, for example, may be a two-way or three-way valve. If the latter, then the valve will have a first position for use in pressurising the vessel, a second position for maintaining pressure in the vessel, and a third position for releasing the pressure. If a two-way valve is used, then it will have a first position for effecting pressurisation of the vessel and a second position for maintaining pressure in the vessel. In this case, the pressurisation source may be detached, pressurisation being maintained by virtue of the valve being in its second position and pressure subsequently being relieved by virtue of the valve being moved back to its first position.

The invention will be further described by way of example only with reference to accompanying Fig 1 which shows one embodiment of water sampling arrangement in accordance with the invention.

The illustrated water sampling arrangement 1 comprises a water sampling vessel 2 connected to a syringe 3 (providing a source of pressurisation) via a flexible hose 4.

Vessel 2 is generally cylindrical and is provided with lower and upper end caps 5 and 6 respectively. A weight 7 is provided adjacent the lower end of vessel 2. Lower end cap 5 is formed with a port 8 associated with a one-way valve 9. The port 8 (with its valve 9) may be removeably mounted on the vessel 2, e.g. by means of a Luer fitting. Valve 9 is configured to be closed by pressurisation of the vessel (as described more fully below) and to permit water to enter the vessel on release of the pressurisation. Upper end cap 6 is formed with a second port 10 which is provided (at its end within the vessel 2) with a gas permeable, hydrophobic barrier membrane 11, e.g. formed of PTFE.

The port 10 is attached to the hose 4 whereby the interior of vessel 2 is in communication with the syringe 3.

Syringe 3 is connected to hose 4 via a three-way valve 12. hi a first position of this valve 12, the interior of the vessel 2 communicates with the syringe 3. hi a second position of the valve, the interior of the vessel 2 vents to atmosphere, hi a third position of the valve, the interior of the vessel is "sealed" and does not communicate with either the atmosphere or the syringe 3.

The procedure for obtaining a sample of water using the illustrated arrangement 1 is as follows. Initially, the interior of vessel 2 is pressurised by means of the syringe 3 (for which purpose valve 12 is in its first position). Pressurisation of the vessel 3 ensures that valve 9 is closed.

Vessel 2 is pressurised such that valve 9 will not open (to permit water to enter the vessel) before the vessel has been submerged to a desired level in the water to be sampled. Once the vessel 2 has been pressurised to the required level, the valve 3 is moved to its third position to seal the vessel 2 to retain the pressure therein.

Vessel 2 is now lowered into a source of water from which a sample is to be taken. This source may, for example, be a river, lake, borehole or other natural water source.

Once vessel 2 has reached the required depth, valve 12 is moved to its second position so as to vent the pressure in vessel 2 to atmosphere.

Hydrostatic pressure now causes valve 9 to open and permit water to enter the vessel 2. Water can thus now rise within vessel 2 and this is of course permitted by virtue of air being displaced through the (air-permeable) membrane 11 into hose 4 and then to atmosphere. However water can only rise within vessel 2 to the level of membrane 11 which acts as a barrier to the passage of water.

In this way, water is prevented from entering the hose 4 and passing to syringe 3.

The vessel 2 may now be withdrawn from the water and the sample collected from vessel 2. This may be done by turning the Luer fitting and removing inlet port 8.

The fact that water is not able to pass beyond membrane 10 provides two advantages. Firstly, the syringe 3 is protected against ingress of water. Secondly, the fact that water has not entered hose 4 and syringe 3 (both of which are re-useable items) means there can be no possibility of cross-contamination of one sampling vessel with water from a previous sampling operation with a different vessel.

A number of modifications may be made to the illustrated arrangement. Thus, for example, although valve 12 has been described as a three-way valve, it could also be a two-way valve, m this case, once (the "first") position of the valve is used to allow pressurisation of the vessel 2 and the other ("second") position of the valve is used to maintain pressure in the vessel. In order to release pressure in the vessel, syringe 3 needs to be detached and valve 12 is moved to the first position.

Secondly, a pressurisation means other than a syringe may be used.

Thirdly, the vessel 2 may be constructed so that the inlet port 8 (with its associated valve 9) is attached to the main body of vessel via a region of weakness. As a result, the port 8 may be "snapped off to allow a water sample to be released from the vessel.

Claims

1. A liquid sampling vessel comprising a first inlet port associated with a one¬ way valve adapted to open to permit water flow into the vessel and being adapted to be closed by pressurisation of the interior of the vessel, and a second port for connection to a source of pressurisation wherein a gas permeable barrier membrane is provided to allow pressurisation of the vessel but prevent liquid passing out of the vessel through the second port.

2. A vessel as claimed in claim 1 wherein the body of the vessel is generally cylindrical and the first and second ports are provided at opposite ends of the vessel.

3. A vessel as claimed in claim 1 or 2 wherein the inlet port and the one-way valve are removeably and replaceably mounted on the vessel.

4. A vessel as claimed in claim 1 or 2 wherein the inlet port and the one-way valve are mounted on the vessel by means of a "snap-off connection.

5. A vessel as claimed in any one of claims 1 to 4 wherein the membrane is provided within or at an end of the second port.

6. A vessel as claimed in claim 5 wherein the membrane is provided across that end of the second port which is adjacent the interior of the vessel.

7. A vessel as claimed in any one of claims 1 to 6 wherein the barrier membrane is of a hydrophobic material.

8. A vessel as claimed in claim 7 wherein the barrier membrane is selected from PTFE, FEP, PDFM and derivatives thereof.

9. A vessel as claimed in any one of claims 1 to 8 wherein the vessel is provided with weights to enable the vessel to sink.

10. A vessel as claimed in claim 9 wherein the amount of the weight is proportional to the depth to which the vessel is intended to sink.

11. A liquid sampling arrangement comprising

(c) valve means for relieving pressure in said vessel

wherein a gas permeable barrier membrane is provided to allow pressurisation of the vessel but prevent water passing into said conduit.

12. An arrangement as claimed in claim 11 wherein the liquid sampling vessel is as claimed in any one of claims 1 to 10.

13. A method of collecting a sample of water using the arrangement as claimed in claim 11 or 12 comprising the steps of

(i) pressurising the sampling vessel by means of the source of pressurisation,

(ii) lowering the vessel into the water to be sampled. (iii) releasing the pressure in the vessel to permit the one-way valve to open and allow water to enter the vessel, and

(iv) retrieving the vessel from the water.