US3545279A

US3545279A - Sample injection for gas chromatographs

Info

Publication number: US3545279A
Application number: US647744A
Authority: US
Inventors: Dietrich Jentzsch; Kurt Henker; Helmut Kruger
Original assignee: Bodenseewerk Perkin Elmer and Co GmbH
Current assignee: PE Manufacturing GmbH
Priority date: 1966-06-24
Filing date: 1967-06-21
Publication date: 1970-12-08
Anticipated expiration: 1987-12-08

Description

Dec. 8, 1970 n. JENTzscH ETAL 3,545,279

SAMPLE INJECTION FOR GAS CHROMATOGRAPHS Filed June 21, 1967 5 Sheets-Sheet 1 Dec. 8, 197() D. JENTzscH ET AL V3,545,279

SAMPLE INJECTION FOR GASTCHROMATOGRAPHS Filed June 21, 1967 5 Sheets-Sheet 2 Dec. 8', 1970 D, ,JENTZSCH ETALN 3,545,279

` SAMPLE INJECTION `FOR GAS `GHROlVITOCIRPI'IS Filed June 21, 1967 1 s sheets-sheet s fa, EK 52 Fig. 4"

DCC- 8, `1970 DQJENTzsc'H ETAL 3,545,279

` SAMPLE lNJECTIoNFoR GAS CHROMATOGRAPHS Filed June 21. 1967 5 Sheets-Sheet L Fig'.y 5

SAMPLE `INJECTION FOR GAS CHROMATOGRAPHS Filed June'zl, 1967 5 sheets-sheet 5 ///////v/////V///f/ United States Patent O 3,545,279 SAMPLE INJECTION FOR GAS CHROMATOGRAPHS Dietrich Jentzsch, Uberlingen (Bodensee), Kurt Henker, Muhlhofen, Baden, and Helmut Kruger, Uberlingen (Bodensee), Germany, assiguors to Bodenseewerk Perkin-Elmer & Co., G.m.b.H.,`Uberlingen (Bodensee), Germany, a corporation of Germany Filed June 21, 1967, Ser. No. 647,744 Claims priority, application Germany, June 24, 1966, 1,284,660 Int. Cl. G01n 1/00 ABSTRACT F THE DISCLOSURE A sample injection apparatus for a preparative gas chromatograph includes a vessel containing a sample and having a self-sealing closure member. Carrier gas flows from a source to an inlet of the chromatograph and a coupling line, extending into the vessel, couples the vessel to the inlet. A quick acting valve for alteringcarrier gas ow is positioned in the carrier gas line upstream from a point at which the vessel is coupled to the inlet. Means are provided for selectively causing the carrier gas to ilow through the coupling line to atmosphere for purging the line of residue sample material. Means are provided for restricting the ow of purging carrier gas to atmosphere thereby conserving carrier gas.

This invention relates to sample injection apparatus for use with gas chromatographic instruments. The invention relates more particularly to an improvedtsarnple injection apparatus employed with preparative gas chromatographic instruments.

A preparative gas chromatographic instrument is adapted for separating and collecting the constituents of a sample for various purposes, such as further analysis of the constituents. Various arrangements have been provided for introducing the sample into a separating column for effecting the separation. In one arrangement, pressure is established in a sample container and the sample is thereby forced into a gas stream and is carriedonto the column. In a particularly advantageous injection arrangement which is disclosed and claimed in U.S. Pat. No. 3,365,951 which is assigned to the assignee of the present invention, a throttling means or iiow impedance is positioned in the carrier gas line at a point relatively further `upstream from an inlet of the separating column than the connection thereto of an enclosed vessel containing the sample. This throttling means is bridged by a low flow impedance bypass line which may be selectively interrupted. The low impedance bypass provides for substantially unrestricted carrier gas flow to the chromatograph and the establishment of the upstream pressure in the enclosed vessel. Sample injection is accomplished by interrupting the bypass line. A dynamic pressure drop then occurs across the throttling means and an accompanying reduction in pressure at the inlet of the separating column occurs. The pressure previously established in the supply vessel then forces a sample onto the separating column. It is an object of this invention to provide an improved form of injection apparatus of the type referred to.

The form of sample injection apparatus described is adapted for the repeated introduction of a one and the same sample substance primarily for preparative purposes. When the sample vessel is removed such as when the` sample substances are being replaced or substituted, a relatively strong carrier gas stream discharges through the connection line, thereby leading to an undesired loss 3,545,279 Patented Dec. 8, 1970 ACC of carrier gas. It is desirable to limit this discharge of carrier gas to a certain extent, maintaining at the same time the necessary scavenging function.

It is another object of the present invention to provide an injection apparatus of the type decribed which is particularly suitable for the injection of diierent sample substances.

A further object of this invention is the provision of an injection apparatus of the type described. which is adapted for injecting samples of differing substances while substantially reducingthe possibility of contamination.

In accordance with a feature of the present invention, a carrier gas is supplied to a chromatograph through a carrier gas line.` An enclosed vesselcontaining a sample to be injected is coupled to the carrier gas line by a relatively narrow conduit. Valving means are provided in the carrier gas line upstream from a point of sample introduction for altering the carrier gas flow rate. The

sample vessel includes self sealing means for providing a gas seal and through which the relatively narrow conduit may be introduced and withdrawn for substituting sample j substances. Means are also providedfor purging sample ilow paths upon withdrawal of the narrow conduit from the vessel.

In a particularly advantageous scavening arrangement, a connection line for coupling the vessel to the gas ilow stream extends longitudinally through a piston about which is moveably positioned a cylinder having a throttling outlet. Means provide a gas seal between the cylinder and piston and the cylinder is provided with a selfsealing means on one face thereof. Means bias the piston and the cylinder respectively in a manner for maintaining the connection line with the cylinder.

In this particular scavening arrangement, as the sample is injected, the end of the capillary connection line is positioned internally of the cylinder :and the carrier gas is throttled to the atmosphere through a throttling outlet. When sample introduction is desired, a sample container having a self-sealing diaphragm is forced against the cylinder and forces the cylinder longitudinally against the action of the biasing means. In doing so, the capillary pierces the cylinder diaphragm, exits from the cylinder, and pierces the diaphragm of the sample vessel. The pressure will now build up in the sample vessel and when the carrier stream is interrupted, a quantity of the sample is forced from the vessel and onto the column. When carrier gas flow is re-established, the sample vessel is withautomatically moves over the capillary and encloses the sameas the capillary is drawn within the cylinder through the self-sealingi diaphragm. Thus, carrier gas flows to atmosphere through a iiow restrictive means.

In sample injectors of the type for injecting liquid samples, it is also advantageous to utilize heatable connecting lines for heating the couplinglines between the injection of different samples for the purposes of scavening and cleaning.

These and other objects and features of the present invention lwill become apparent with reference to the following specifications and drawings wherein:

FIG. l is a diagram of an apparatus constructed in accordance with the features of the present invention;

FIG. 2 is a diagram of a portion of the apparatus of FIG. 1 illustrating an alternative arrangement for injecting and scavenging;

IFIG. 3 illustrates a scavenging arrangement for use in the alternative arrangement of FIG. 2 and which limits the loss of carrier gas during the interval between sample insertions;

FIG. 4 illustrates an alternative injection and scavengof FIG. 2; and, i

FIGS. 5 and 6 illustrate the apparatus of FIG. 4 in different positions during the injection and scavenging modes.

In the embodied form according to FIG. 1 the carrier gas flows from a source 8 through a pressure-reducing valve 10, a filter l12., a precision pressure regulator 14 and a quick-acting gate valve 16. Valve 16 which comprises a magnet valve (i.e., solenoid actuated) is coupled to the inlet 18 of a gas chromatographic separating column. A sample to be injected is contained in a sample vessel 20 which is sealed at the top thereof by a selfsealing diaphragm 22. A relatively narrow conduit comprising a capillary connection line leads oif from the inlet 18 of the separating column, and which, in FIG. 1 includes two members. The first member 24 is coupled between the inlet 18 and change-over cock valve 26 and the second member 27 is coupled to the changeover cock 26 and terminates in a cannula 28. A line 32 including a throttle 34 branches off from the carrier gas line 30 and is coupled to the change-over cock 26. A fourth line 36 is also coupled to the change-over cock 26 and leads to the atmosphere via a ow restricting throttle 38. The cock valve 26 is formed with two opposing

grooves

40 and 42 extending across an angle of about 90. In one setting thereof line 24 is connected with line 36 via groove 40 and line 32 is connected with cannula 28 via groove 42 as shown in FIG. 1 during a scavenging mode of operation. In the other setting of the changeover cock an injection mode of operation is established and groove 42 connects line 24 with the cannula 28 and groove 40 connects line 32 with line 36.

The operation of the sample injector of FIG. 1 can be described as follows. Initially, the magnet valve 16 is opened and carrier gas will flow through line 30 to the inlet 18. The line 24 is connected with the throttled outlet line 36 via groove 40 of the change-over valve 26. The throttled line 32 is coupled to the exposed cannula 28 via the groove 42. Carrier gas ows to the atmosphere through both of these paths. This liow which is restricted by throttles 34 and 38 thereby cleans the

connection line

24, 28 and the

grooves

40, 42 from residues of the sample substance from the preceding sample injection.

The cannula 28 is then passed through the self-sealing diaphragm 22 of the sample vessel 20. It is possible to inject a gaseous or vaporous sample. When a liquid sample is injected, the cannula is positioned beneath the surface level of the liquid sample. Finally, the sample may also be taken from the saturated atmosphere above a sample liquid.

As soon as the cannula 28 has pierced the diaphragm 22, the cock 26 is changed over. IGroove 42 no'w connects the sample with the inlet 18 of the separating column via the cannula 28, line 27, and line 24. The cannula 28, line 27, and line 24 comprise a connection line between the vessel 20 and column inlet 18. Since the magnet valve 16 is still open, the full carrier gas pressure becomes effective at the inlet 18 of the separating column. The carrier gas also enters into the sample vessel 20 'via the

connection line

24, 27 and 28 so that a pressure is built up in the vessel.

Sample injection is subsequently achieved by closing the magnet valve 1-6. The pressure at the inlet 18 of the separating column thereby decreases, since inlet 18 is coupled to the atmosphere via the separating column. A sample substance is then forced by virtue of this pressure dilerential from the sample vessel 20 to the column via the

connection line

24, 27 and 28.

In the scavenging mode, the magnet valve 16 is opened. The Ifull carrier gas pressure is again established at the inlet 18 of the separating column and the sample injection is interrupted. The valve 26 is changed over. A connection is now established via groove 40 between line 24 and the throttled outlet line 36 through which a carrier gas stream flows into the atmosphere. A carrier gas liows from the branch line 32 to the sample vessel 20 via groove 42, line 27, and cannula 28. The vessel 20 is now withdrawn so that this carrier gas stream also discharges into the atmosphere. These carrier gas streams are effective to scavenge the

line portions

24, 27, and 28 which have come into contact with sample substance and the grooves and 42 of the change-over valve. The sample injector is now ready yfor a new sample injection with another sample substance.

FIG. 2 illustrates an alternative embodiment of the invention during sample injection. The arrangement is similar to that of FIG. 1. However, the change-over cock 26 is omitted. The cannula 41 which herein comprises the connecting line leads directly to the inlet 18 of the separating column and is mounted at at 42. The cannula 4.1 is pierced through the diaphragm 22. When the magnet valve 16 is open and the full carrier gas pressure is present at the inlet 18 of the separating column, this pressure is transmitted to vessel 20 via cannula 41. As valve |16 is shut olf, the pressure at the inlet of the separating column decreases and sample substance is dralwn into the column inlet from vessel 20. This dosing action is stopped when valve 16 opens again. When the sample vessel 20 is Withdrawn from cannula 40, a strong carrier gas stream discharges through the cannula, Which effects cleaning thereof from residues of the sample substance.

Generally, this strong scavenging carrier gas stream would in the long run lead to an intolerable loss of carrier gas. For this reason in accordance 'with FIG. 3 there is provided a scavenging vessel 44 with a self-sealing diaphragm 46 and an outlet throttle 48. The cannula 40 is pierced through diaphragm 46 so that it terminates now in the scavenging vessel 44. Now only a carrier gas stream defined by throttle 48 can discharge.

The embodied form of the invention as illustrated in FIGS. 4, 5, and 6 is based on a similar principle. There too, the basic design is similar to that of FIG. 1 and FIGS. 2 and 3, respectively. The cannula 50 comprising the coupling line is centrally guided longitudinally through a piston 52. The piston 52 has sliding thereon a cylinder '54 and a gas tight seal is provided there between by means of an O-ring 56. The cylinder 54 is formed With a central aperture 58 in the lower face thereof. This aperture 58 is closed off by a self-sealing silicon rubber diaphragm 60. Diaphragm `60 is held by a cap 62 which is screwed onto the end of cylinder 54 and is formed with an aperture k64 in alignment with aperture '58. A screw cap 166 is screwed on at the upper end of the cylinder, which with the inner flange thereof abuts a shoulder 68 of piston 52 in a position of rest (FIG. 5) and limits the movement of cylinder 54 upwardly. A bias spring 70 forces cylinder 54 upwardly as illustrate din FIG. 5. In the position of FIG. 5, the end of the cannula l50 is located internally of cylinder 54, in alignment with the

apertures

58 and 64. 'Ihe interior of cylinder 54 is communicated with the atmosphere via an aperture 71 and a throttling capillary tube 72 which is helically wound about cylinder 54.

The arrangement of FIGS. 4, 5, and 6 operates as follows:

In the normal state the sample injector is in the position illustrated by FIG. 5. A carrier gas stream enters into the interior of cylinder 54 through cannula 50, is throttled via the capillary throttle 72, and flows to atmosphere. For sample injection, (FIG. 4) the sample vessel 20 is forced against cylinder 54 from below with the self-sealing diaphram 22 thereof and moves the same upwardly against the action of spring 70. In so doing, the cannula 50 passes through opening 58, pierces through the self-sealing diaphragm 60, passes through opening 64 and pierces through diaphragm 22 so as to protrude into the sample vessel with the end thereof. When the magnet valve 16 shuts olf now, as is shown in FIG. 4, sample substance is drawn into inlet 18 in the manned described hereinbefore until valve 16 opens again. Upon withdrawal of the sample vessel 20, cylinder 54 automatically moves again over the end of cannula 50 so that the carrier gas can discharge only ina throttled flow in the manner as described. It it is desired to have a stronger carrier gas stream temporarily for intensively scavenging cannula 50, cylinder 54 may be forced back so that the end of cannula 50 protrudes through diaphragm 60, as is illustrated in FIG. 6, and exhausts to the atmosphere.

The arrangement as hereinbefore described is a relatively simple and advantageous arrangement for handling and scavenging. It facilitates a quick and simple replacement of the silicon rubber diaphragm 60.

For sample injectors forliquid samples that is provided a heating by means of which the connection line is heatable up to a temperature above the temperature at which the least volatile sample componentvaporizes. By such a heating between the individual sample injections in connection with the scavenging streams, the sample residues are removed from the system. Thereafter the connection line may again be cooled down to its operating temperature, such as by means of a blower.

While a particular arrangement of the present invention have been described, various moditications may be made to the apparatus by those skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. Sample injection apparatus for a gas chromatograph having a separating column, said injection apparatus comprising:

an enclosed vessel containing a sample;

a quick-acting valve means having first and second selectable stable conditions;

iirst conduit means defining a first carrier gas passageway for conveying a carrier gas between a gas source and the inlet of said separating column through said valve means, the second condition of said valve means providing a flow impedance in said 'first passageway;

second conduit means deiining a second gas passageway between said sample vessel and said column inlet, said second conduit means having one end thereof coupled to said column inlet; means for selectively communicating the other end of said second conduit means with the interior of said sample vessel for establishing a pressure in said vessel when said Valve means exist in said first condition, and a iiow path for said sample between said vessel and said inlet when said valve means exists in said second condition, whereby said sample is caused to flow over said flow path by the pressure established in said vessel; and,

scavenging means for passing carrier gas through said second conduit means and exhaust to atmosphere when said other end of the second conduit is withdrawn from communication with the interior of said sample vessel, thereby cleansing said second conduit means of residue sample.

2. The apparatus of claim 1 where said means for selectively communicating includes a self-sealing diaphragm defining a wall portion of said sample vessel and said other end of the second conduit means is adapted for extending through said diaphragm into said vessel.

3. 'I'he apparatus of claim '1 wherein `said scavenging means includes means restricting the flow of carrier gas to atmosphere.

4. The apparatus of claim 1 wherein said second conduit menas includes a first member coupled to said column inlet and a second member selectively communicable with the interior of said sample vessel, and said scavenging means simultaneously passes carrier gas through a lirst gas flow path exhausting to atmosphere which includes said first member, and, through a second gas ow path exhausting to atmosphere which includes said second member.

5. The apparatus of claim 4 wherein said scavenging means includes a valve body having first, second, third, and fourth ports and means for providing gas iiow passageways between said rst and second ports and between said third and fourth ports during a scavenging mode of operation, and, gas dow passageways between said rst and fourth ports and Ebetween said second and third ports during a sample injection mode of operation,

means including a iiow restrictor for conveying a carrier gas from a source thereof to said third port, means including a flow restrictor for coupling said second port to atmosphere, and,

said irst` member is coupled to said first port, and

said second member is coupled to said fourth port.

6. The apparatus of claim 1 wherein said scavenging means includes an enclosure having an aperture;

a conduit penetrable self-sealing body positioned at said aperture, and,

said other end of the second conduit means selectively terminating within said enclosure or extending through the self-sealing body of said enclosure.

7. The apparatus of claim 6 wherein flow-restrictive means are coupled to said enclosure for exhausting said enclosure to atmosphere.

8. The apparatus of claim 7 wherein said enclosure includes a cylinder body with said aperture formed therein at one end thereof;

a piston body positioned coaxially within said cylinder;

said cylinder reciprocating motion with respect to said piston;

said second conduit means extending longitudinally through said piston with said other end thereof extending from said piston in alignment with said cylinder aperture; and, means biasing said piston away from said cylinder aperture.

References Cited UNITED STATES PATENTS 2,120,248 6/ 1938 Hinchman 222-5 2,496,258 2/ 1950 Alexander 222--83X 2,959,677 11/ 1960 Robinson et al 73-23.1X 2,593,552 4/ 1952 Folkman 222-5 3,238,784 3/ 1966 Dorsey 73-425 3,364,958 1/ 1968 Sartor 141--329X 3,383,923 5/ 1968 Conche ---s 73-421 FOREIGN PATIENTS 1,025,510 4/ 1966 Great Britain 73-23.1

`CHARLES A. RUBI-IL, Primary Examiner