GB2122368A

GB2122368A - Fluid measurement cell

Info

Publication number: GB2122368A
Application number: GB08218107A
Authority: GB
Inventors: Alan Keith Hulme
Original assignee: STARNA Ltd; Optiglass Ltd
Current assignee: STARNA Ltd; Optiglass Ltd
Priority date: 1982-06-22
Filing date: 1982-06-22
Publication date: 1984-01-11
Also published as: DE3322488A1

Abstract

A fluid measurement cell, e.g. for a spectrophotometer, has threaded inlets and outlets 16,17 for fluid to be analysed and/or for fluid to be circulated in order to keep the cell at a constant temperature. The threads are preferably designed to fit standard fluid connectors. <IMAGE>

Description

SPECIFICATION Fluid measurement cells This invention relates to a cell, used as part of a device that measures a characteristic of a fluid by passing a beam of light through a sample of fluid held within the cell.

Such cells (hereinafter referred to as fluid measurement cells) are used in, for example, spectrophotometers, fluorimeters, colorimeters, absorptiometers, photometers and high pressure liquid chromatographs.

In some applications, it is necessary to connect a fluid measurement cell to fluid supply and discharge lines. This is required when, for example, a fluid that is being analysed is flowing continuously through an analysis chamber of the cell or when a fluid is flowing through an auxiliary passageway of the cell, to maintain the analysis chamber at a constant temperature.

Connections to such external apparatus have conventionally been made using tubing connected to a connection member that has been attached to the cell, the connection member being tubular, with an increased external diameter section which is gripped by the tubing, the tubing and connection member being clamped together in place.

A major problem with such "flow-through" fluid measurement cells, has been that the connections do not provide a highly effective seal, especially when the fluid pressure level within the cell is high, and this could result in leakage of possibly toxic or corrosive test fluid. Furthermore, the clamping of the tubing and connection member makes rapid disconnection of the cell from external apparatus impossible.

The fitting of the tubing over the connection member also leaves a "dead space", i.e. a volume at the top of the connection member but outside the main flow path of the fluid. This is a disadvantage when measuring the characteristics of different fluids, or fluids having different properties, because of the risk of contamination by previously-used fluid in the dead space.

One aspect of the invention consists in a fluid measurement cell having therein a fluid passageway having inlet and outlet ends, at least one of which is threaded for connection to an external conduit.

The use of a threaded connection excludes the need for clamping means associated with the connection, thus simplifying the apparatus and allowing rapid disconnection of the cell.

The invention has particular uses for devices incorporating a fluid measurement cell where high pressures are employed (e.g. for use in a high pressure liquid chromatograph) as the invention makes possible an inlet and/or outlet seal of very high integrity.

Standard fluid line couplings are available for laboratory use in order to connect together different pieces of apparatus. It is preferred that the cell of the invention be adapted for use with such couplings, for which purpose it is provided with a standardsized thread on its inlet and/or outlet end.

Standard fluid couplings are often designed to avoid dead spaces, and by designing the cell for use with use couplings the problems associated with dead spaces can be avoided.

Some standard couplings comprise hollow, internally-threaded sleeves into each end of which a threaded member at the end of a fluid line can be screwed. A cell according to a preferred embodiment of the invention has an end adapted so that one end of the sleeve can be screwed onto the end, instead of onto the fluid line.

Embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure I shows a flow-through fluid measurement cell according to the invention.

Figure 2 shows an alternative embodiment of the invention applied to a flow-through fluid measurement cell of the type shown in Figure 1.

Figure 3 shows an embodiment of the invention applied to a constant temperature fluid measurement cell.

With reference to Figure 1, a flow-through fluid measurement cell 1 has a main body portion 2 that is composed of two blocks of homogeneous and corrosion resistant material 3,4, usually glass or quartz, which have been fused together. The block 4 contains a black pigment and has channels or passageways 5, 6,7 formed therein. Passageways 5 and 7 are formed on the outside of the piece 4 and the passageway 6 is formed between them. The block 3 is transparent and has two passageways 8, 9 formed therein.

The various passageways can be formed by machining and/or ultrasonic drilling.

The two blocks 3 and 4 are fused together so that a flow path is defined between an opening 10 and an opening 11 in the upper surface of block 3 via passageways 8, 5, 6, 7 and 9. Two transparent plates 12, 13 are fused to the front and rear sides of the body portion 2 after the fusing together of the blocks 3, 4, and have polished optical surfaces.

Connection members 14, 15 are attached to the block 3 at the openings 10, 11 of the passageways 8, 9 to allow connection of the fluid measurement cell 1 to external apparatus. The connection members 14, 15 are manufactured from the same material as the body portion 2 and are attached thereto by fusing.

Each connection member 14, 15 has a threaded portion 16, 17 for connection to a standard fluid line coupling 30. The coupling 30 comprises a tubular connector 21 which is internally threaded and which can be screwed onto a threaded portion 16 or 17. The connector 21 has a hexagonal outer surface to facilitate gripping thereof. A fitting 32 is screwed into the other end of the connector 21. The fitting 32 comprises a threaded body 23 through which the end of a tube 22 extends. The tube terminates in a fitting 29 having a flat outer end 26 with a central aperture through which fluid flows.

The body portion 23 is screwed into the connector 21 so that the surface 26 abuts the upper end face 24 or 25 of a member 14 or 15. This avoids any dead space between the tube 22 and the inlet or outlet of the cell. The connection can be secured using a lock-nut 27 to minimise the possibility of leakage of often toxic or corrosive test fluid from the cell.

Suitable couplings 30 are manufactured under the Trade Mark OMNIFIT. The couplings 30 have standard threads of either 1/4 x 28 (Imperial) or 6 x 1 (Metric).

The connection members 14, 15 are preferably inclined from each other so that any respective connections made to the connection members 14, 15 do not interfere with one another.

In use, the fluid measurement cell 1 is placed in a device, such as a spectrophotometer, and the connection members 14, 15 are connected to supply and discharge lines for the test fluid. The fluid passes through the fluid measurement cell from the supply line attached to connection member 14 to the discharge line attached to connection member 15 via the passageway 6. The passageway 6 is an analysis chamber having precise dimensions, and through which light is transmitted during use of the cell to measure optical characteristics of a fluid in the cell.

Due to the use of the threaded portions 16, 17 of the connection members 14, 15, a much sounder connection can be made to any supply or discharge line than has previously been possible.

With reference to Figure 2, a flow-through fluid measurement cell has its openings 10, 11 formed in relatively inclined faces 18, 20 to which the connection members 14,15 are perpendicular so that they are inclined away from each other.

Figure 3 shows another embodiment of the invention, in which a fluid measurement cell 100 has a test fluid inlet 101 leading to an analysis chamber 102, that is surrounded on three sides 103,104,105 buy a fluid jacket 106. The jacket 106 has inlet and outlet openings communicating with connection members 114,115 through which fluid may pass so as to keep the test chamber 102 at a constant temperature. The connection members 114, 115 are formed from the same material as the fluid measurement cell 100 and are fused thereto. They are preferably inclined away from each other to facilitate easy connection to external apparatus. They have threaded portions 116, 177 that engage conventional threaded laboratory connectors (not shown).

Claims

1. Afluid measurement cell having therein a fluid passageway having inlet and outlet ends at least one of which is threaded for connection to an external conduit.

2. A cell as claimed in claim 1, wherein said inlet end is threaded for connection to an external conduit.

3. A cell as claimed in claim 1, wherein said outlet end is threaded for connection to an external conduit.

4. A cell as claimed in claim 1, wherein both said inlet and outlet ends are threaded for connection to respective external conduits.

5. A cell as claimed in any preceding claim, wherein said at least one threaded end is formed from a threaded portion which has been attached to a body portion of the cell.

6. A cell as claimed in claim 5, wherein the threaded portion has been fused to the body portion of the cell.

7. A cell as claimed in claim 5 or 6, wherein said threaded portion is externally threaded.

8. A cell as claimed in any one of claims 5,6 or 7, wherein the threaded portion and the body portion are made from the same material.

9. A cell as claimed in claim 8, wherein said material is quartq.

10. A cell as claimed in claim 8, wherein said material is glass.

11. A cell as claimed in any one of claims 5 to 10, when dependent on claim 4, having a threaded portion for each of the inlet and outlet ends, the portions being relatively inclined.

12. A cell as claimed in claim 11, wherein the portions have inclined ends which have been attached to a planar surface of the body portion.

13. A cell as claimed in any preceding claim, wherein the passageway includes an analysis chamber.

14. A cell as claimed in any one of claims 1 to 12, wherein the passageway is for conducting fluid around said cell to maintain the cell at a constant temperature.

15. A cell as claimed in claim 13, having a further passageway through which fluid can be conducted to maintain the cell at a constant temperature, the further passageway having inlet and outlet ends, at least one of which is threaded for connection to an external conduit.

16. Afluid measurement cell as hereinbefore described with reference to any of the accompanying drawings.

17. A combination of a conduit and a cell, the cell being as claimed in any preceding claim, the conduit having an end threadedly connected to the inlet or outlet of the fluid passageway.

18. A combination as claimed in claim 17, including a connection threadedly connected at one end to said inlet or outlet and at the other end to a threaded member at the end of said conduit.

19. A combination as claimed in claim 18, wherein said conduit has, at its end, a fitting with a flat abutment surface engaging a flat surface of said inlet or outlet to avoid a dead space between the conduit and the inlet or outlet.

20. A device for measuring a characteristic of a fluid by passing a beam of light therethrough, the device incorporating a cell as claimed in any one of claims 1 to 16.