DE9013050U1 - Dosing device for analytical devices - Google Patents

Description

Utility model application

jSod eriseewerk Perkin -E lmer GmbH
Askaniaweg 4, D-7770 Überlingen

iö Dosing device for analytical devices

Technical area

The innovation concerns a oscillating device for analytical devices, in particular for liquid chromatography, containing

(a) a dosing loop,

(b) a switching valve with a stationary part and a part which is movable relative to the stationary part between a first and a second position, which has connecting channels and a sample inlet and which rests against the stationary part with a sealing body, wherein the switching valve

- in the first position, close the sample inlet with a

end of the dosing loop and the other end of the

Dosing loop connects to a waste connection and

- in the second position, one end of the dosing loop with a carrier fluid connection and the other end of the dosing loop with an analyzer connection

connection connects,
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(c) a dosing needle, which can be inserted by means of an adjusting mechanism with its front end once into a sample vessel and once sealingly into the sample inlet of the switching valve and

(d) a sample pump connected to the rear end of the dispensing needle and capable of sucking soft sample liquid from the sample vessel into the dispensing needle when the front

end of the dosing needle is in the sample vessel, and through which sample liquid can be pressed out of the dosing needle and transferred into the dosing loop when the dosing needle is in the sample inlet of the switching valve and since:

Changeover valve is in its first position.

The analysis device can therefore be a chromatographic separation column for liquid chromatograms with a downstream detector. The analysis device can also be, for example, an atomic absorption or atomic emission spectrophotometer using liquid chromatogram technology. The invention can be used wherever sample liquid is to be introduced into a dosing loop by means of a dosing needle.

Underlying state of the art

In a known dosing device, samples are arranged in sample vessels in a magazine. The sample vessels consist of sample bottles which are

septum. A sampling unit is mounted on a transport arm which can be programmed to move over each of the sample vials, over a rinsing vessel or over the sample inlet of a switching valve. The sampling unit contains a dosing needle which can be inserted into a sample vial, piercing the septum, into the sample inlet or into the rinsing vessel. ^The switching valve contains a stator and a rotor which can be rotated relative to the stator between a first and a second position. The rotor has the sample inlet. The rotor rests against the stator with a sealing body. In the first position, the switching valve connects the sample inlet to an end of a rinsing loop and the other end of the ^rotary loop to a waste connection. In the second position, the changeover valve connects one end ^of the dosing ^loop to a carrier liquid connection and the other end of the dosing loop to an analytical instrument connection, ^for example a connection that leads to a ^{chromatographic} separation column. The rear end of the dosing needle is connected via a capillary to a top pump and to a rinsing pump. The rinsing loop has check valves and sucks in carrier liquid, which can be released through the dosing needle into the rinsing vessel during a rinsing process. The dosing needle and the capillary are thus filled with carrier liquid up to the tip of the dosing needle. The capillary is also connected to a sample pump. This sucks in a volume of carrier liquid. As a result, carrier liquid is sucked back out of the dosing needle so that another medium, air or sample liquid, is sucked into the dosing needle from the tip.

During operation, the dosing needle is moved over a sample ^vial which is in a pre-programmed magazine position. The dosing needle initially only pierces the septum of the sample vial without dipping into the liquid. Then the dosing needle moves out of the sample vial again. After returning to the starting position, a small volume of air is added via the sample dump. This air volume serves as a separator between the carrier liquid and the sample liquid to be sucked in. After a waiting period, the dosing needle pierces the septum a second time and now ^dips into the sample liquid. The sample pump sucks a pre-programmed sample volume and a pre-programmed excess volume into the dosing needle and the dosing capillary. The dosing rod is then activated. The transport arm moves the dosing needle over the sample inlet of the changeover valve.

In the known dosing device, the switch valve is initially in the second position, in which the dosing loop is connected to a carrier liquid connection and an analysis device connection. In this position, part of the excess volume is pressed into the sample inlet in order to flush the sample inlet with sample liquid. This sample liquid used for flushing flows to a waste container. After a waiting time, the switch valve is turned to the first position &sfgr;. The sample pump presses the pre-programmed | sample volume into the dosing loop. The displaced § volume of carrier liquid flows out via a capillary §. After a further waiting time, the switch valve Ii is turned to the second position. The dosed sample I

9 volume is supplied by a carrier liquid stream, which is fed via the carrier liquid connection by a carrier liquid pump, to the analyzer, here |

a chromatographic separation column. The sample pump then presses the sample liquid and the sucked-in air into the sample inlet and via this to a waste flange. The rinsing pump then carries out a lifting cycle. This rinses the dosing needle and the sample inlet with carrier liquid. This rinsing liquid, which is pumped by ^the rinsing pump, also flows via the sample inlet to the waste flange. The dispensing needle is then raised. The transport arm moves the dosing needle into a rest position above the rinsing vessel.

Such arrangements are known from DE-C2-30 30 396 or DE-C2-30 37 014.

¹ ^ According to DE-C2-30 37 014, a volume of air is sucked into the dosing needle before the sample liquid is sucked in. To introduce the sample into the dosing loop, the dosing needle is inserted with its front end through a hole in the rotor and into a dosing hole in the stator . After the sample has been introduced into the dosing loop, the volume of air is pressed into the dosing loop. The dosing needle is then withdrawn before the changeover valve is switched. Due to the piston effect when the dosing needle is pulled out, only air is sucked back into the rotor, while the sample liquid remains completely in the stator.

For dosing devices of the type described,
In practice it has been shown that the dosed volume is difficult to reproduce, especially in the case of small samples. Considerable fluctuations in the dosed sample quantity occur.

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Revelation of innovation

The innovation is based on the issue of a dosing device of the type mentioned at the beginning ^, such that the dosed sample quantity can be easily reproduced at small concentrations.

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e) the movable part of the change-over valve is positioned at such an angle that when it is switched over; in the second position, a connection is established between the said other end of the dosing loop and the waste connection; ^before a connection is established between the sample and the said one end of the dosing loop.*; d.

The innovation is based on the knowledge ^that

2C observed poor retardation of the sample volumes: While the switch valve is switched from the second to the first position, the "inert ^" liquid in the dosing loop is under the slight pressure of the carrier liquid pump. When the dosing loop now comes into contact with the sample inlet, the sample liquid in the dosing needle is pushed back by the pressurized carrier liquid. As a result, part of the sample is missing during the subsequent sample discharge into the dosing loop. This is mixed with carrier liquid from the dosing loop in the front part of the dosing loop.

Embodiments of the innovation are the subject of protection claim 2.

An example of an embodiment of the innovation is explained in more detail below with reference to the accompanying drawings.

Short brushing of the drawings

Fig. 1 shows schematically a dosing device for liquid chromatography with a position of a switching valve in which a sample pump sucks in carrier liquid.

Fig. 2 shows the dosing device of Fig. 1 in the second position of the switching valve, in which the sample pump is connected to a dosing needle.
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Fig. 3 shows a changeover valve in the dosing device of Fig. 1 in a first position.

Fig. &■ shows the changeover valve in a second position. 20

Preferred implementation of the innovation

The dosing device according to Fig. 1 serves to direct sample liquid from sample vessels 10 to the inlet of a separation column 12 for liquid chromatography. The sample liquid is then transported through the separation column 12 by a carrier liquid, which is pumped by a pump 14. The substances emerging at the outlet of the separation column 12 are detected in a known manner by a detector 16. The outlet of the detector 16 is connected to a waste vessel 18. The sample vessels 10 are "seal bottles" which are closed by a septum. The sample bottles are arranged in a magazine in the usual way. To transfer a defined amount of sample liquid

A dosing needle 20, a sample loop 22 and a switching valve 24 are provided in the inlet of the separation column 12.

The changeover valve 24 contains a rotor 26 and a stator 28. The stator 28 has six connections ₃₀ , 31 , 32, 34 and 40. The connection 30 is connected to a first connection of the dosing loop 22. The connections 32 and 34 are connected in parallel via a line 42 to the waste container 18.

^iC ve, jiioen. The .~.:i3Chiuß 36 is connected to the second end of the dosing loop 22. The connection 38 is connected to the outlet side of the pump i4. The connection 40 is connected to the inlet of the separation column 12. The connections of the stator 28 are each at 60° to each other.

¹ S angle offset. The rotor 26 has two connecting channels 44 and 46. The two connecting channels are 60° apart from each other. A first connecting channel 44 extends over approximately 60°. The second connecting channel 46 extends over a much larger angle, approximately 90 ³ . A connection can thus be made between adjacent | connections of the stator 28 through the connecting channels 44 and 46. ^

The dispensing needle 20 is movable with a carrier in two j coordinates, as indicated by the double arrows 48 and ti

50. It can also be lowered and raised vertically relative to the support % as indicated by the double arrow 52.

With the carrier, the dosing needle 20 can be moved optionally over a programmed magazine position and thus over a "(■ sample vessel 10, over a rinsing vessel 54 or over a sample inlet 56 provided on the rotor 26 of the switching valve 24. The rinsing vessel 54 is designed as an overflow vessel I and is connected via a line 58 to the

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connected to line 42 leading to waste container 18.

The dosing needle 20 is connected to a switching valve 62 via a capillary 60. The switching valve 62 can be switched between two switching positions by a servomotor 64. In the switching position shown in Fig. 1, the switching valve 62 connects a sample pump 66 to a line 68 which leads to a carrier liquid vessel 70. The carrier liquid vessel /0 is also connected to the inlet of the pump 14 via a line 72. Zi; The sample pump 66 can be driven by a motor 74. The drive takes place because ^the piston of the sample pump 65 moves at a precisely defined stroke. In a second switching position, which is shown in Fig. 2, a connection is established between the sample pump 66 and the capillary 60 and thus the dosing needle LO via the switching valve 62.

In Fig. 2, the changeover valve 24 is in its first

position. In Fig. 1 the changeover valve is

24 in its second position. The two positions of the

The changeover valve is shown again in enlarged form in Fig. 3 and Fig. 4.

In the first position of the switching valve 24 shown in Fig. 3, a connection is established between the connections 38 and 40 via the connecting channel 44. The carrier liquid supplied by the pump 14 then flows via connection 38, channel 44 and connection 40 to the inlet of the separation column 12. In the first position of the switching valve 24, the sample inlet 56 is connected to the connection 30 and thus to one end of the dosing loop 22. The other end of the dosing loop 22 is connected to the waste vessel 18 via the connection 36, the connecting channel 46 and the connection 34.

In the second position (Fig. 4) of the changeover valve 24, the connection 38 is connected to the connection 36 via the connecting channel 46 and the connection 30 is connected to the connection 40 via the connecting channel 44. As can be seen from Fig. 4 &lgr;, in the second position the dosing

loop 22 is connected in series with the separation column 12. A stream of dehydrating liquid from the pump 14 flows via the port 38, the connecting channel 46 and the port 36 to the dosing loop 22 and from the other end of the dosing loop 22 via the port 30, the connecting channel 44 and the port 40 to the inlet of the separation column 12.

The described arrangement works as follows:
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In the position of the switching valve 62 shown in Fig. 1, the sample pump 66 sucks carrier liquid from the carrier liquid container 70 via line 68. After switching the switching valve 62 (Fig. Z) this is?

Carrier ^liquid , which serves here as washing liquid, is discharged via the capillary 60 around the dosing needle 20 into the rinsing vessel 54. The dosing needle 20 is now filled to the tip with carrier liquid. A small air vacuum is then sucked in via the sample pump 65, which is intended to separate the sample liquid and carrier liquid in the dosing needle 20. The sample pump 56 sucks in pure carrier liquid, and the carrier liquid in the dosing needle 20 and the capillary 60 sucked in via the switching valve 62 causes it to be sucked into the dosing needle 20. The dosing needle 20 is then moved with its carrier over a sample vessel 10, i.e. a sample vial. The dosing needle 20 is lowered and pierces the septum of the sample vial. The sample pump sucks a further volume of carrier liquid from the dosing needle 20 via the switching valve 62, whereby

Sample liquid is sucked from the sample vial into the dosing needle 20. The dosing needle 20 is then lifted again and removed from the sample vial

pulled out.
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As a next step, the dosing needle is moved over the sample inlet 1 a 3 56. The changeover valve 24 is in its first position in Fig. 2. The sample inlet 56 of the rotor 25 is connected to the connection 30 of the stator. The

The connection 30 is connected to an end of the dosing loop 22. The other end of the dosing loop 22 is connected to the waste container via connection 36, connecting channel 46 and connection 34. The sample pump 66 now makes a discharge stroke and thereby presses sample liquid into the sample inlet and into the sample loop 72. The carrier liquid still present in the sample loop 22 is displaced and flows to the waste container 18.

The changeover valve 24 is now switched to

2G the second position, which is shown in Fig. 4. During this switchover, the metering needle 20 remains in the sample inlet.^ 55. The metering needle 20 thus follows the rotary movement of the rotor 26. In the second position of the switchover valve 24 , the sample liquid introduced into the sample chamber 22 is transported by the carrier liquid stream into and through the separation column 12.

During this process, the sample pump 56 can press the remaining sample liquid from the dosing needle 20 and then carrier liquid for rinsing the sample vessel 56 into the sample inlet, whereby these liquids then flow out to the waste vessel 13 via the connection 32 of the switching valve 24. The dosing needle 2C is then pulled out of the sample inlet 56 and moved over the rinsing vessel 54. Here

if necessary, an additional flushing may be carried out. The switching valve 62 then switches back to the position shown in Fig. 1, in which the sample pump 66 can suck in carrier liquid from the carrier liquid container 70.

Because the second connecting channel 46 extends over an angle greater than 60°, namely approximately 90 ^° , when switching from the second position of the changeover valve 24 (Fig. 4) to the first position (Fig. 3), a connection is first established between the lower end of the dosing loop 22 in Fig. 4 via connection 36, connecting channel 46 and connection 34 and the waste connection 46 (Figs. 1 and 2) before the sample inlet 56 reaches the connection 30. The carrier liquid (eluent) in the desiccation loop 22 is therefore first released before a connection is established between the dosing loop 22 and the dosing needle 20. Therefore, no pressurized carrier liquid can "bounce back" onto the dosing needle and thus falsify the sample quantity by the sample liquid penetrating the tip of the dosing needle. It has been shown that a significantly better reproducibility can be achieved with a changeover valve 24 designed in the manner described than with an otherwise identical arrangement in which both connecting channels 44 and 46 each extend over 50°.

Claims (2)

• ■ t Protection claims 1. Dosing device for analytical instruments, in particular for liquid chromatography, containing I^ d)a dosing loop(22), b) a changeover valve (24) with a stationary part (28) and a part (26) movable relative to the stationary part (28) between a first and a second position, the connecting channels and a sample inlet (56) and ^which rests against the stationary part (23) with a sealing body (108), wherein Jas changeover valve f'24" 2C - in the first position the sample inlet (56) &tgr;&igr; i t one end of the dosing loop (22) and the other end of the dosing loop ^22) with a fax connection (42) and - in the second position an end of the dosing loop (22) with a carrier fluid connection and the other end of the dosing loop (22) with an analyzer connection, c) a dosing needle (20) which is connected by a Adjusting mechanism with its front end once in a sample vessel (10) and once sealingly into the Sample inlet (56) of the changeover valve (24) and d) a sample pump (66) which is connected to the rear end of the dosing needle (20) and which can suck sample liquid from the test vessel (10) into the dosing needle (20) when the front end of the dosing needle ( ²⁰ ) is in the sample vessel (10), and by which sample liquid can be pressed out of the dosing needle (23) and transferred into the ^dosing loop (21) when the dosing needle (20) is in the sample inlet; (56) the dosing pump (66) can suck sample liquid from the dosing needle (20 ) into the dosing needle (20) when the dosing needle ( 20 ) is in the sample inlet; and the changeover valve ·, Z -; : &eegr;its'" first Ste 1 i ¹ Jng is, characterized in that e) a connecting channel of the movable switching valve extends over such a width, except that when switching from the second to the first position a _connection is made between the said other end of the dosing valve and the first end A connection between the sample units is made. A connection is made between the sample units. A connection is made between the sample units. A connection is made between the sample units. A connection is made ^between the sample units ^. 2. Dosing device according to claim 1 , characterized in that a) the stationary part of the ümscha itvent: 1 s six j^i connections each offset by 60° from each other, of which - a first connection is connected to said one end of the dosing loop. - a second connection with a waste connection connected is, - a third connection is connected to the supply connection , - a fourth connection is connected to the other end of the dosing loop, - a fifth connection is connected to the carrier fluid connection and - a sixth connection is connected to an analyzer connection, b) the movable part has two connecting channels, one of which - a first connecting channel extends over approximately 60° and - a second connecting channel is provided opposite the first connecting channel at an angular distance of approximately 60° from the first connecting channel and extends over substantially more than 60°, and c) the sample inlet is arranged at an angular distance of 60° from the first connecting channel in the opposite direction.
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