GB2205943A

GB2205943A - Fluid sampling device

Info

Publication number: GB2205943A
Application number: GB08713876A
Authority: GB
Inventors: Alastair Sibbald
Original assignee: Thorn EMI PLC
Current assignee: Thorn EMI PLC
Priority date: 1987-06-13
Filing date: 1987-06-13
Publication date: 1988-12-21
Anticipated expiration: 2007-06-13
Also published as: GB8713876D0; GB2205943B

Abstract

A fluid sampling device is particularly suitable for transfer of blood for testing. A plunger disc 3 fits slidably into a sampling vessel 1. The disc 3 is provided with a fluid flow passage 4 so that when the disc 3 is moved the fluid 2 is transferred via the flow passage 4 and a coupled duct 5 from one site to another. One site or the duct 5 can include a sensor assembly 8. If the duct 5 includes the sensor assembly 8 the second site can be a waste fluid depot. <IMAGE>

Description

IMPROVEMENTS IN OR RELATING TO FLUID SAMPLING DEVICES This invention relates to fluid sampling devices and, in particular, to a device for transferring fluid from one site to another for the purpose of testing.

Fluid (e.g. blood) for analysis is usually transferred from a sampling tube (e.g. a hypodermic syringe) into an analyser by means of a peristaltic pump. This is effective, but the pump unit is expensive, bulky, heavy and requires circuitry for control and an electrical power source. Such factors prohibit the development of low cost, pocket-sized analyser units.

An alternative to this would be, for example, to use a unit containing a mechanical pumping system which could be activated manually and which would aspirate the samples from the sampling tube, through a sensor assembly to a waste depot. A mechanical pumping system would not require electronic control or an associated power source, but the unit would still be bulky and physically awkward to manipulate. Such an arrangement would also require a depot for waste fluid to be provided which may require frequent emptying and which would add significantly to the bulk of the analyser unit. It would also complicate the plumbing arrangements and restrict the portability of the device due to the possibility of spillage.

It is an object of the invention to alleviate the disadvantages of the prior art.

According to the invention there is provided a fluid sampling device for effecting transfer of fluid from one site to another, the device comprising a plunger-type disc for fitting slidably into a sampling vessel, the disc having a fluid flow passage extending through it from one side to the opposite side, and a duct coupled at one end to said fluid flow passage, the disc being displaceable in the sampling vessel to effect transfer of fluid from a fluid sample in said sampling vessel to said another site.

According to a further aspect of the invention there is provided a method of fluid sampling comprising providing a plunger-type disc which fits slidably into a sampling vessel, the disc having a fluid flow passage extending through it from one side to the opposite side, and displacing the disc in the sampling vessel to effect transfer of fluid from a fluid sample in the sampling vessel to another site.

According to another aspect of the invention there is provided a kit of parts suitable for assembling a fluid sampling device, the kit comprising a plunger-type disc, the disc having a fluid flow passage extending through it from one side to the opposite side, a duct suitable for coupling at one end to said fluid flow passage and one or more clip means suitable for holding respective lengths of the duct in fixed relative positions.

The kit of parts may also include a sensor.

In order that the invention may be clearly understood and readily carried into effect, it will be described by way of example, with reference to the accompanying drawings, of which: Figure 1 shows a fluid sampling device inserted into a sampling tube, and Figures 2, 3 and 4 show stages as the device is brought into contact with the fluid and further depressed.

Referring first to Figure 1, this shows a preferred embodiment of a fluid sampling device according to the invention. Sampling tube 1 contains an analyte 2 and the sampling device comprises a plunger-type disc 3 which fits slidably into the sampling tube. The disc has a fluid flow passage 4 which extends through it, and, in the embodiment illustrated, has a tube or duct 5 coupled to it, one end of which penetrates into the fluid flow channel. The tube has two substantially parallel limbs 6 and 7 and a sensor 8 is connected such that limb 6 has one end connected to the sensor inlet, and limb 7 has one end connected to the sensor outlet, its other end being the fluid outlet. The limbs of the tube may be clipped together or otherwise held in fixed relative position and may be attached to a rod or other means of physical support.Alternatively, the tubes may be essentially rigid and strong enough to be used to depress the disc in the sampling vessel.

Figures 1 to 4 show how the device may be operated. In Figure 1, the device is introduced into the upper region of the sampling vessel and is depressed towards the fluid. As the device is depressed downwards, air above the fluid is expelled through the sensor and out of the outlet tube. When the disc is brought into contact with the solution and is further depressed (as shown in Figure 2), the fluid is forced upwards and through the tubing and sensor, and, with the arrangement illustrated, passes back down into the sampling vessel. Figures 3 and 4 show how the fluid 9 which has passed through the device (the wusedw analyte) is partitioned from the virgin sample 2 by the plunger-type disc.

With the arrangement illustrated, with the end of the outlet tube being just above the upper surface of the disc, when the assembly is removed after the sensor output has been read or processed, a siphon effect occurs which causes the aspiration cycle to be reversed, back-flushing and cleaning the sensor cell. If the end of the outlet tube is close to the upper surface of the disc, substantially all the fluid can be flushed back through the device. A similar cycle using de-ionised water could be used to clean the device, or a reference solution, for example, may be used to calibrate the sensor.

If the sampled solution is transferred back into the sampling vessel, as described above, a fluid waste depot is not required and plumbing arrangements are relatively simple.

Although, in the specific embodiment illustrated, the device is arranged to transfer fluid from one site (below the plunger disc) to another (above the plunger disc, the plunger disc partitioning the fluid which has passed through the device from the virgin sample), a device according to the invention may be used to transfer fluid from one vessel to another, and it may be that it is not required to back-flush the cell by reversing the aspiration cycle.

Sensing means may be located at any position in the duct, or located in the fluid flow passage in the disc. The sensing means could be a flow through sensor and could be based on potentiometric sensors such as ion-sensitive electrodes (ISEs) and ion-selective field effect transistors (ISFETs), and other, similar, technologies for the measurement of dissolved gases, metabolites and antigens.

A suitable flow-through sensor for use in the invention is a flow-through cell such as that described in Analytica Chimica Acta, Vol. 159 (1984) pp. 47-52 (Sibbald, A., Whalley, P.D., and Covington, A.K.) or a chemical-sensitive semiconductor device of the type described in European Patent Application No. 86304836.9 (published on 25.03.87 under publication No. 0215546).

The invention is not restricted to electrochemical analysis techniques, but may have applications in other areas such as in optically based systems, using known fluorometric and photometric methods. If sensing means are not included, the device may simply be used for transferring fluid from one site to another.

Advantages of the fluid sampling device include that no electrical or mechanical pump is required, no valves are required and fluid waste depots are not required.

Back-flushing of the device provides intrinsic cleaning.

The device could be stored using a calibrant sample tube as a protective cover or bathing solution for the sensors.

Calibration sources could be supplied as ampoules, and could include, for example, dissolved gases.

Sampling vessels other than sampling tubes may also be used.

Sampling vessels could contain dry reagents, for example for precipitation of interfering species, and filters.

An enzyme column, for example, could be inserted into the aspiration tube section.

A fluid sampling device in accordance with the invention could be moulded as an integral part of a flow-through cell cap for a sensor device, such that each sensor has its own fluid-handling system. This could be advantageous from both a hygiene and from an ergonomic point of view. The unplugging and disposing operation is then simplified and reconnection of tubes to sensors is unnecessary.

Claims

1. A fluid sampling device for effecting transfer of fluid from one site to another, the device comprising a plunger-type disc for fitting slidably into a sampling vessel, the disc having a fluid flow passage extending through it from one side to the opposite side, and a duct coupled at one end to said fluid flow passage, the disc being displaceable in the sampling vessel to effect transfer of fluid from a fluid sample in said sampling vessel to said another site.

2. A fluid sampling device according to Claim 1 in which the other end of the duct is located close to the upper surface of the disc, whereby, on displacement of the disc in the sampling vessel, fluid is transferred from the original sample to a site within the vessel which is partitioned from the original sample by the plunger-type disc, and enabling substantially all the transferred fluid to be flushed back through the device by way of a siphon effect on withdrawal of the device from the vessel.

3. A fluid sampling device according to Claim 1 or Claim 2 in which the duct comprises two substantially parallel limbs.

4. A fluid sampling device according to any one of Claims 1 to 3 including means to hold the limbs in fixed relative position.

5. A fluid sampling device according to any one of the preceding claims in which a sensor is located in the fluid flow passage in the disc.

6. A fluid sampling device according to any one of the preceding claims in which a sensor is located in the duct.

7. A fluid sampling device according to Claim 5 or Claim 6 in which the sensor is a flow-through sensor.

8. A fluid sampling device according to any one of Claims 5 to 7 in which the sensor is an ion-selective field effect transistor (ISFET).

9. A fluid sampling device substantially as herein described with reference to the accompanying drawings.

10. A method of fluid sampling comprising providing a plunger-type disc which fits slidably into a sampling vessel, the disc having a fluid flow passage extending through it from one side to the opposite side, and displacing the disc in the sampling vessel to effect transfer of fluid from a fluid sample in the sampling vessel to another site.

11. A method of fluid sampling substantially as herein described.

12. A kit of parts suitable for assembling a fluid sampling device, the kit comprising a plunger-type disc, the disc having a fluid flow passage extending through it from one side to the opposite side, a duct suitable for coupling at one end to said fluid flow passage and one or more clip means suitable for holding respective lengths of the duct in fixed relative positions.

13. A kit of parts according to Claim 12 wherein the kit further includes a sensor.