DE2040133A1 - Sample injection in gas chromatography - Google Patents

Description

The invention relates to sample injection in gas chromatography.

The injection of samples to be analyzed into carrier gas streams in gas chromatography was previously carried out by means of a hypodermic syringe by injection through a septum or by using a variety of valves carried out that work by injection liquid or gas. If valves are used, there must be a large number of them working of temperatures so that the gas or the introduced liquid is at the correct temperature. This Requirement brings difficulties, especially where high temperatures are necessary, since the maximum temperature,

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in which the valve work satisfactorily kar.n, limited by the design and the material of the construction is. He has the use of a hypodermic syringe. Disadvantage that a trained operator is necessary, being the precision, rr.it of which a repeatable volur.en injected can be, is relatively bad. In addition, this method leads to leakage losses when used repeatedly on the septum and is for injecting samples from a continuously flowing liquid or gas stream not suitable.

According to the invention has a device for the delivery of a carrier gas flow to one or more chronatographic Columns and a port for injecting a sample into the stream as required, from which the chromatographic column is fed is a pressure or flow control member connected to a branch of the connection for feeding the connection with carrier gas is connected to a line for the transfer of a stream from a second pressure or flow control member a drain port, an unrestricted sample injection branch between the connector and the feed line the sample to the connection and a device for branching off a sample from the line through the sample injection branch for connection by creating a suitable pressure difference along the sample injection branch.

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The invention also provides a method for injecting a sample into a chromatographic column which is characterized in that a continuous stream of carrier gas is passed through the column that a separate Feeds a stream of a gas to be examined or a liquid to be examined and a part of this separate Gas or liquid flow through an unrestricted sample injection branch branches off into the carrier gas flow that one ^ the pressure differential across the branch varies.

According to one embodiment of the invention, a device for supplying a carrier gas stream to one or more chromatographic columns and for injecting a sample of your choice into the stream has a connection from which the chromatographic column or columns are fed, a device which a first pressure or Durchflu.isteuerglied for supplying the carrier gas to φ terminal via a carrier gas branch and a sample injection branch for the supply of the sample has to the terminal, wherein the branch coming from a conduit (a) with a means for gas access is to the conduit in a controlled Purchf lußrate · and (b) having a drain port is provided, which has a limiter for the gas stream and can be closed.

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BATH

According to a further embodiment of the invention, a device for supplying a carrier gas stream to one or more chromatographic columns and for injecting a sample of your choice into the stream has a connection from which the chromatographic column or columns are fed, a device, which comprises a first pressure or flow control member for supplying carrier gas to the connection via a carrier gas branch and a sample injection branch for supplying the sample to the connection, the branch extending from a conduit which (a) is provided with means for the Access of gas to the line with controlled pressure and (b) a drain opening is provided which has a restrictor for the gas flow, whereby either the drain opening or the carrier gas branch or both devices can be closed and in the event that only the drain opening can be closed , on the outlet side of the device for gas access to the Leit a limiter is provided for the gas flow. If the sample passes through the latter limiter for the gas flow, this is advantageously non-absorbent for the sample.

According to the invention, the device has for the supply of a carrier gas stream to one or more chromatographic ones Columns and a connection for the random injection of a sample into the stream, from which the chromatographieche

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Column or the chromatographic columns are fed, a first control member for pressure or flow for transfer carrier gas to the port and a sample injection branch for conveying the sample to the port, the injection branch emanating from a conduit which (a) is provided with a device for gas access to the conduit a controlled flow rate or means for gas access at controlled pressure; and (b) with a discharge flow opening is provided which has a gas flow limiter, the drain opening or (provided that the first control member is a pressure control member) the carrier gas branch or both can be closed and in the event that only the drain opening can be closed and (a) a device for gas access under controlled pressure, a Limiter for the gas flow is provided on the outlet side of (a). Unless a sample passes through the latter limiter it is advantageous for the sample not to be absorbent.

If the drainage opening can be closed, the device is operated in such a way that the material to be examined is in a continuous stream of gas coming from the means for gas access to the conduit leads to the discharge opening; is the device for gas access to the line Pressure control element, this is set so that it has a higher outlet pressure than the first pressure or flow control element works, setting the pressure in the sample injection branch to a value below that of the carrier gas,

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when the drain port is open; it is desirable to have a To inject the sample, close the drain opening or one narrows them further. The pressure in the sample injection branch rises above that of the carrier gas, with a Sample from the continuous gas flow goes into the connection.

If only the carrier gas branch can be closed, a sample is injected by allowing gas to enter the line and closes the carrier gas branch. If corrosive materials are to be investigated, this execution form is to be used the invention does not require a device for closing the drain opening, the device for the Closing the carrier gas branch does not have to come into contact with the sample. Since closing devices by corrosive Materials are easily damaged, this embodiment of the invention provides a significant advantage in this case. If necessary, the continuous gas flow, i.e. the sample flow normally consisting of carrier gas exist, and a sample to be analyzed can be introduced into the carrier gas by nan ζ. B. a hypodermic Syringe and a septum used. The closing and opening of the drain port or the carrier gas branch will then timed so that it occurs when the sample passes through the connector.

By closing the drain opening for a reproducible Time a reproducible sample can be introduced. The drainage opening is advantageous with the aid of a

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automatic timer opened and closed, which is in an appropriate interval after the sample is introduced into the continuous gas stream. The timer if necessary, is set manually to the time of introduction of the sample into the continuous gas flow or by closing electrical contacts on the hypodermic Syringe.

All limiters in the prescribed device can see chror.at ograf i along with all necessary Columns can be housed in an o'fen. The only one necessary The setting for injecting the sample consists in briefly opening the drain opening or the carrier gas branch or both close, this can be reached through taps on the outside of the stove,

Provided the carrier gas flow is programmed through the connection is, there is a variable loss of carrier gas through the drain opening, but if necessary, you can use it here Appropriate setting of the carrier gas pTEramr.s remedy this or alternatively by the fact that the second flow control member programmed by the same program as the first control element. If the carrier gas pressure is programmed and is used to feed the Line using a second pressure control member and a restrictor for the gas flow can achieve the same goal achieve that the second control element is programmed by the same program as the first.

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BATH ORIGINAL

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If it is desired to program the pressure of the carrier gas applied to the port, it may be desirable be to program the pressure applied by the second control member to ensure that it is always with a Pressure works higher than that of the first control member, although this is unnecessary when the pressure is set to a value so that it exceeds that of the first control member at any time when it is desired to test the sample to introduce.

If necessary, the sample injection branch or the line for transferring the sample flow with a a second drain port controlled only by a restrictor; this makes it possible for everyone to drain any portion of the sample stream. This ensures greater stability during the injection cycle. Unused samples can be returned in any way using a monitored process.

The invention is illustrated in the following with the aid of a schematic Drawings explained in more detail.

Pig. 1 shows schematically a first embodiment a device according to the invention;

Pig. 2 schematically shows a second embodiment the invention.

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A pressure control element 1 feeds a connection 2 which in turn feeds a chromatographic column which leads to a flame ionization detector k which is open to the atmosphere. A second branch 6 feeding connection 2 is provided with an inlet arm which comes via a liquid sample injection vaporizer 8 (ie a sample injection preheater) from a control member 7 for constant inflow or flow, with a septum for injecting the sample with the aid of a hypodermic syringe is provided, and also with a hot wire detector 9 »which is electrically connected to a pulse generator Io. An outlet arm 11 leads from a point between the connection 2 and the hot wire detector 9 through a needle valve 12 and a solenoid operated on / off cock 13, which is operated after a time delay by a timer Ik , which on receipt of a pulse from the pulse generator Io the valve 13 closes and opens in a predetermined period of time. The inlet arm and the outlet arm form the conduit for transferring the sample stream.

The device operates in the following manner.

The control member 1 for constant pressure and the control member 7 for constant inflow are connected to a carrier gas supply connected. The constant pressure control member 1 and the needle valve 12 are set to be attached to the port

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deliver a slightly higher pressure when tap 13 is open, than it results from the control member 7 for constant inflow. Under this condition the influx goes out of the Control member 7 for constant flow through the preheater S, the detector 9, the needle valve 12 and the tap 13 to The atmosphere. The carrier gas from the constant pressure control member 1 passes through the chromatographic column 3

If a sample is injected into the vaporizer 8 with the aid of a hypodermic syringe, a sample gas is sent to the hot wire detector 9; if the front of the Dar.pfmasse passes through the hot-wire detector, the resistance of the wire is changed, as the Wärneverlustrate in the i ^"3 rc he ο. atmosphere differs from that in the carrier gas atmosphere. The resistance change of the hot wire at the entrance of the sample into the detector generates a pulse in the pulse generator Io which causes the timer 14 to close the valve 13 after the sample has reached the Zv / eig 6. The pressure resulting in branch 6 rises as a result, and part of the sample is connected to the connection 2 and from there to the chromatographic column 3 · After a predetermined interval, the timer 14 opens the tap 13 so that the sample residue is drained off.

In this manner, a reproducible amount of sample is introduced into the column at any given flow rate of the constant flow controller.

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BATH ORIGINAL

Instead of the hot wire detector 9 and the Ir.pulsgenerators Io can set the timer, for example, by closing contacts on a hypodermic syringe during injection the sample can be activated, in addition, the time delay can be incorporated into the gas system if necessary be that one in the preheater to a detector "vora 8 leading line, omitting the detector 9, provides a branch and selects the dimensions so that the sample reaches the detector immediately after arriving at branch 6.

In the embodiment of the invention according to FIG. 2, differential pressure control members 2o and 21 supply carrier gas to the device at fixed, coordinated pressures. The control element 2o feeds a liquid sample injection vaporizer 22, which in turn supplies line 23 from which a sample injection branch 2 ¹ I leads to a connection 25. The line 23 is vented to the atmosphere via a fixed limiter 26. The control member 21 feeds a carrier gas inlet 27 to the connection 25, to be precise via an on / off valve 28 which, after a time delay, is activated by means of a timer 29. A line 30 leads from the connection 25 to a chromatographic column 31 ', the outlet of which goes to an elamraionization detector 32 which is vented to the atmosphere.

BATH

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A hypodermic syringe (not shown) of conventional design is electrically connected to the timing element 29 in order to supply a signal by closing contacts on the syringe when a sample is injected through the syringe.

The device works in the following way:

The differential pressure control members 2o and 21 are fed with carrier gas and are adjusted in pressure to each other so that the pressure in the line 23 is approximately the same or slightly lower than that at the connection 25 when the valve 28 is open. With the aid of the hypodermic syringe, a sample is injected into the sample injection vaporizer 22, which supplies a signal to the timer 29 which is set so that it closes the on / off valve 28 when the vaporized sample on branch 2 ¹ J is passed while the tap 28 is opened again as soon as a predetermined time interval has elapsed. If the cock 28 is closed, the pressure at connection 25 drops below that in line 23, with part of the sample going along branch 2h and then into column 31. If the tap 28 is opened again, no further sample flow follows along the branch 2h , the sample being determined by the column 31 and the outflow in the flame ionization detector 32.

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Claims (9)

2 O A ü 1 3 3 Claims 1 / Device for the delivery of a carrier gas stream to one or more chromatographic columns and to injection a sample as required in the stream, characterized by a connection (2.25) from which the chromatographic Column or the · chromatographic columns (3 »31) fed be a pressure or flow control member (l, 2o) for the supply of carrier gas for connection to a branch of the connection is connected by a line that carries a flow from a second pressure or flow control member (7,21) to a drain (13,28 leads through one between the connector and the conduit for feeding a sample to the connector located unrestricted sample injection branch (11; 24) and by a device (9 »29) for branching off a Sample from the line through the sample injection branch for connection by creating a suitable pressure differential • above, the sample injection branch. 2) Device according to claim 1, characterized in that the line is fed by a flow control member (7,21) and the device for branching off a sample from the line through the sample injection branch to the connection in the outflow from the line a limiter for the gas flow, wherein the drain can be closed. 109809/1508 -in- 2 ^ 1 3 3 3, device according to claim 1, wherein the line is fed by a pressure control member, thereby C '-' ^ - inze Leh that the facility for branching off a Prol-o a; .. the Line through the sample injection branch to the connection has a gas flow limiter in the outlet of the line, wherein either the drain or the carrier gas branch or both can be closed and in the event that only tier Ab is lockable, on the exit side of the device the gas access to the line a lockable tar.atr is provided. 4) Device according to one of the preceding claims, characterized in that means (8,22) are provided for converting the sample into a continuous gas stream introduce that goes through the line before it reaches the terminal (2.25). 5) Device according to claim 4, characterized in that that a device (lo, 22) is provided to a sample in a predetermined time after the retraction of the Prot.e to lead the sample injection branch. ' 6) Device according to claim 5 »characterized in that the time control element holds the sample for a predetermined time span injected. 1 09809 / 1S08 _BAD original 7) Device according to one of the preceding claims, characterized in that all limiters are incorporated into an oven that has the chromatic graphical columns, wherein taps (131,28), the drain or the carrier gas branch or both close, outside of the: Oven located siftd. 8) Device according to one of the preceding claims, characterized in that both control elements (1> 7ί 20.21) Pressure control members are and are connected to a common facility for controlling their pressure setting. 9) Device according to one of the preceding claims, characterized in that the line with a second Drain is provided, which is only controlled by a limiter iat. lo) Procedure for injecting a sample ir. a chromatographic column, characterized by: ·. · leaning, because you ο inen continuous stream of carrier gas through cVio oiiule, there? " one a separate stream of a to be examined "asos or a liquid to be examined that one Part of the separate stream through an unlimited tone sample injection pipe into the Tr / icercasstrom abzv / eisi., 'r.der. a pressure difference across the branch is varied. 109809 / 1S08 BATH