GB2213586A

GB2213586A - Fluid sample injection device

Info

Publication number: GB2213586A
Application number: GB8829979A
Authority: GB
Inventors: Klaus Kunzmann; Wolfgang Kopprasch
Original assignee: Medizin und Labortechnik Leipzig VEB
Current assignee: Medizin und Labortechnik Leipzig VEB
Priority date: 1987-12-29
Filing date: 1988-12-22
Publication date: 1989-08-16
Also published as: SE8803494D0; GB8829979D0; DE3833248A1; SE8803494L

Description

Fluid Sample Injection Device The invention relates to apparatus for introducing fluid samples into other fluids, in particular for introducing a defined volume of sample into a continuously flowing or static column of liquid.

It is necessary to introduce defined volumes of liquid samples into other liquids for the purposes of injection analysis and liquid chromatography. However, the apparatus currently available to do this is complex, expensive and not always reliable. The present invention seeks to overcome these problems.

According to the present invention there is provided a device for delivering a sample of a defined volume of fluid from a first fluid stream to a second fluid stream comprising; a sample holder, fluid diversion means and fluid connection means; wherein the fluid connection means first connects the sample holder to the first stream which is diverted to said sample holder by the fluid diversion means; and then connects the sample holder to the second stream which is diverted to said sample by the fluid diversion means; wherein the fluid diversion means and the fluid connection means both act on the same stream but never on both streams together.

In a preferred arrangement the sample holder is a section of pipe or conduit and the fluid connection means carry fluid from the fluid stream through the sample holder and back to the fluid stream. Preferably, the fluid diversion means is a member that blocks the fluid stream between sample holder inlet and outlet.

Preferably, the fluid connection and diversion means form part of a reciprocating member. In preference this is a grooved cylindrical rotor rotating in a chamber through which the fluid streams run.

In order that the invention and its various other features may be understood more easily, an embodiment thereof will now be described by way of example only, with reference to the drawings, wherein: Fig. 1 is a vertical cross section through the apparatus with the rotor in the "Filling" position; Fig. 2 is a vertical cross section through the apparatus with the rotor in the "injection" position; and Fig. 3 is a schematic diagram showing the operation of the apparatus.

The apparatus comprises a rotor 12 in a housing 11, piping 13-16 and a volumetric loop 4.

The rotor 12 is substantially cylindrical and on the surface of the rotor 12 are three transverse grooves 1,2,3. The grooves 1,2,3 all lie in the same vertical plane and are equally spaced around the circumference of the rotor 12.

The housing 11 is square in cross section and contains a cylindrical recess for the rotor 12. Six circular ducts 5-10 pass through the housing into the recess in the same vertical plane as the grooves 1,2,3. The ducts 510 are in three coaxial pairs. The upper 7,9 and lower 8,10 pairs of ducts are in positions such that the circumfential distances, around the wall- of+^the Stress, between the inside ends of each duct in the pairs equal to length of the grooves 1,2,3. The middle ducts 5,6 cross the housing at its diameter.

Connected to the upper 7,9 and lower ducts 8,10 are pipes 13-16 to take fluids to and from the apparatus.

The outside ends of the middle ducts 5,6, are connected together by a substantially "C" shaped volumetric loop 4 of piping, that runs around the outside of the housing 11.

In operation the apparatus injects a fixed volume of sample fluid taken from the lower ducts 8,10 into a carrier fluid in the upper ducts 7,9, via the volumetric loop 4.

To do this the rotor 12 of the apparatus reciprocates between two stationary positions. In the first filling position (Fig. 1) sample fluid from the lower ducts 8,10 fills the volumetric loop 4, the volumetric loop 4 being isolated from the upper ducts 7,9. To do this the rotor 12 is placed in a position where two of the grooves 2,3 extend between the inside ends of trie middle 5,6 and lower 8,10 ducts on the same side. This forms sample fluid flow path (Fig. 1) through the first lower duct 8, upward through the first transverse groove 2, through the first middle duct 5, through the volumetric loop 4, through the second middle duct 6, downward through the second transverse groove 3, and through the second lower duct 10.With the rotor 12 in the filling position the third transverse groove 1 extends between the first 7 and second 9 upper ducts, forming a carrier fluid flow path through the upper part of the apparatus.

In the injection position (Fig. 2) the rotor 12 is positioned such that two of the transverse grooves 1,2 extend between the inside ends of the upper 7,9 and middle 5,6 ducts on the same side. This forms a carrier fluid flow path (Fig. 2) through the first upper duct 7, downward through the first transverse groove 2, through the first middle duct 5, through the volumetric loop 4, through the second middle duct 6, upward through the third transverse groove 1 and out through the second upper duct 9.

Thus, when the rotor 12 moves through 600 from the filling position to the injection position all of the sample fluid in the volumetric loop 4, the first middle duct 5 and the first transverse groove enter the carrier fluid stream. The change over time between the two positions is between O.ls and ls.

The sample fluid stream comes from a sample reservoir 22 and is pumped along pipes 14,16 and through the apparatus by a sample pump 19. The carrier fluid is carried by a carrier pump 18 along pipes 13,21, through the apparatus and into the detector system 21 of an analytical instrument (Fig. 4).

It is possible to use the apparatus in three modes. The carrier fluid stream may be stationary during the filling of the volumetric loop 4 with sample fluid, after which the sample fluid is also stopped. After the rotor 12 has moved from the filling to the injection position the carrier fluid stream is set in motion by the carrier pump 18 and the sample fluid is forced out of the volumetric loop 4 and into the detector system 21.

Alternatively, the carrier fluid stream can be kept moving during the filling and the injection stages of the operation as described for the first mode of operation. This mode is suitable for applications such as flow injection analysis where it is necessary to keep the carrier fluid stream flowing continuously.

A variation on the second mode of use is to make the carrier fluid stream part of a by-pass loop from the main body of the carrier fluid flow. The carrier fluid can then pass through the apparatus without the use of a carrier pump 18.

The configuration and mode of operation of the apparatus means that the fluid streams are relatively fluid tight.

This prevents leakage from the apparatus and internal leakage between the sample and carrier fluid streams.

The short change over time between the filling and injection positions of the apparatus reduces pressure build up during injection of a sample to a minimum.

The volume of sample injected into the carrier stream is governed by the volume of the volumetric loop 4. A number of interchangeable volumetric loops 4 of different sizes can be provided for the apparatus.

A number of units of the apparatus can be combined in a single housing 11 and rotor 12 wherein different single pieces of apparatus lie on different vertical planes along the length of the rotor 12.

Claims

1. A device for delivering a sample of a defined volume of fluid from a first fluid stream to a second fluid stream comprising; a sample holder, fluid diversion means and fluid connection means; wherein the fluid connection means first connects the sample holder to the first stream which is diverted to said sample holder by the fluid diversion means; and then connects the sample holder to the second stream which is diverted to said sample holder by the fluid diversion means; wherein the fluid diversion means and the fluid connection means both act on the same stream but never on both streams together.

2. The device according to claim 1 wherein the sample holder is a section of pipe or conduit.

3. The device according to claim 1 or 2 wherein the fluid connection means carry fluid from the fluid stream, through an inlet fluid connection, through the sample holder and out through an outlet fluid connection.

4. The device according to claim 3 wherein the fluid diversion means is a member that blocks the flow of the fluid stream between the inlet and outlet fluid connections.

5. The device according to any preceding claim wherein the connection means and the fluid diversion means form part of a reciprocating member that carries said connection means back and forth between the first and second fluid streams.

6. The device according to claim 5 wherein the reciprocating member is a generally cylindrical rotor that rotates back and forth within a cylindrical chamber to which the fluid streams and sample holder are connected; wherein the sections of the circumference of the rotor are elevated so that they seal with the inside of the chamber and form fluid diversion means, and other parts of the rotor are recessed and form fluid connection means.

7. The device according to claim 6 wherein the fluid connection means are a plurality of grooves in the rotor, all of the grooves being in a single plane that is normal to the axis of rotation of the rotor.

8. The device according to claim 7 wherein there are three grooves around the circumference of the rotor.

9. The device according to claim 8 wherein the rotor rotates through 600 per cycle.