US3385099A - Gas chromatograph with furnace - Google Patents

Description

May 28, 1968 P. DIEM ET AL GAS CHROMATOGRAPH WITH FURNACE 6 Sheets-Sheet 1 Filed Jan. 12, 1965 Fig 7 PAUL DIEM HANS GERLACH DIETRICH JENTZSCH EBERHARD KONIG IN VEN TOR.

May 28, 1968 DIEM ETAL 3,385,099

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May 28, 1968 P. D|EM ET AL 3,385,099.

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GAS CHROMATOGRAPH WITH FURNACE 6 Sheets-Sheet 5 May 28, 1968 Filed Jan. 12, 1965 INVENTOR.

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GAS CHROMATOGRAPH WI TH FURNACE Filed Jan. 12, 1965 6 Sheets-Shem e Fig 6 PAUL DIEM HANS GERLACH DI ETRICH JENTZSCH EBERHARD K'oms INVENTOR.

United States Patent 3,385,099 GAS CHROMATOGRAPH WITH FURNACE Paul Diem, Kornwestheim, Hans Gerlach, Sipplingen (Bodensee), and Dietrich Jentzsch and Eberhard Kiinig, Uberlingen (Bodensec), Germany, assignors to Bodenseewerk Perkin-Elmer & Co. G.rn.b.H., Uberlingen (Bodensee), Germany Filed Jan. 12, 1965, Ser. No. 424,992

Claims priority, application Germany, Jan. 15, 1964,

4 Claims. (Cl. 73-231) ABSTRACT OF THE DISCLOSURE A gas chromatograph, in which a main oven is used to program the column, has the sample injection block and the detector embeded in a thick insulating cover of the main oven. An auxiliary heater is utilized to heat the detector. Preferably this same auxiliary heater also is used to control the temperature of the sample injector. The ararngement allows maintaining the detector and injector at a different desired temperature from the programmed temperature of the column. It also minimizes the problem of effectively insulating the electrical leads to the detector, as well as heat losses in the various gas line connections.

The present invention relates to a gas chromatograph comprising a separating column, a sample injector at the entrance and a detector at the exit of the separating column and a furnace containing the separating column, said furnace being provided with insulating walls. It is the object to the present invention to provide a particularly advantageous arrangement of the detector and-in further modification of the invention-of the sample injector.

In such apparatus it is important to avoid condensation of the less voltatile mixture components and of the liquid separating substance carried along by the gas stream in the detector and the supply lines thereof. Thus, the detector together with its supply lines should preferably be maintained at a relatively high temperature. It is therefore advantageous to also arrange the detector, as is known as such, within the furnace. In doing so, however, electric insulation difliculties are encountered especially with high column temperatures, as an electric signal must be conducted from the detector. Some detectors, in particular ionization detectors, require fairly high voltage .(as is well-known) and it is difficult to insulate effectively such voltages in the presence of high temperatures.

It is further known 'to arrange the detector completely externally of the furnace and to heat the same separately. This, however, is disadvantageous in many respects. Not only must undesirably long supply lines be provided from the separating column to the detector, causing a disadvantageous dead volume, but these lines must be heated as well as the detector. This requires a relatively great additional heating on account of the quite considerable heat losses in this case or additional insulation.

It is the object of the present invention to avoid these difficulties of known arrangements.

According to the invention this object is attained by providing that the detector is at least partially arranged in the oven wall and provided with independent heating. By this means the supply lines leading from the column to the detector are located within the oven so that (without any special insulation or additional heating) a condensation of sample substance in the supply lines leading to the detector is avoided. Also the detetcor may (at least in regards to the parts thereof susceptible of condensation) still be protected by the oven insulation from undesired heat losses due to radiation. 0n the other hand, the elec- 3,385,099 Patented May 28, 1968 ice trio leads and the parts to be insulated electrically may be positioned in cooler areas and led outward so that no electric insulation difficulties arise. The invention is applicable with particular advantage if the detector is a flame ionization detector.

Advantageously, the sample injector in the form of an injection block is built into the oven wall together with the detector, and the separating column is arranged so as to be directly connected to the injection block and detector. In such case supply lines are avoided altogether. Problems similar to those encountered with the detector also arise with the injection block. The injection block must be kept at a relatively high temperature so as to cause the injected sample liquids to evaporate. On the other hand, the injection diaphragm must be kept cool. These problems are also solved by the arrangement according to the invention.

It particularly is expedient to heat the injection block and detector by a common elongated heating mandrel which is arranged in the vicinity of both parts in the oven wall.

Commonly, the detector and injection block are heated up to temperatures which are 50 to C. in excess of the oven temperature. This may be simply effected by means of the heating mandrel, without the temperature distribution in the oven itself being interfered with, as would be the case for instance if an auxiliary heated injection block were arranged within the oven itself.

An embodiment of the invention is presented in the drawings and described as follows:

FIG. 1 is a vertical section through a gas chromatograph of the invention;

FIG. 2 is a side elevation of a gas chromatograph in accordance with the invention, viewed in the direction of the arrow II in FIG. 1:

FIG. 3 is an enlarged side elevation of the assembly comprising detector and injection block of the gas chromatograph of the invention;

FIG. 4 is a top view thereof;

FIG. 5 is a section along line A-B in FIG. 3, and

FIG. 6 is a section along line C-D in FIG. 3.

The gas chromatograph according to the invention comprises an oven having an inner shell 10, which is provided with the cupped edge 12 and is closed off by a screen plate 14. A heating grill 18 is secured to the shell 10 by means of insulating pieces 16. The inner shell 10 receives a helically wound separating column-not shown. It is encompassed by the spaced apart cup-shaped insulating casing 20 which is closed off at the top by a hinged insulating cover 22. Between the thermally insulating casing 20 and the inner shell 10 an annular space 24 is defined wherein the heating grill is centrally arranged. Below the screen plate 14 a centrifugal blower 26 and its driving motor 28 are positioned. The motor 28 is arranged in a separate casing 30 separated from the oven by a space 32, and the motor shaft 34 passes through the bottom of the insulating casing 20 and has secured to its upper end thereof the impeller 26. In the space 32 a further impeller 36 is arrange-d on the shaft 34. This impeller 36 produces a cooling-air current which flows from the lower casing 30* past the motor 28 and the end of the motor shaft 34 on the side of the motor and is then exhausted outwardly in the space 32. Thereby, the motor 28 is kept cool and is not influenced by the furnace temperature.

As can be seen from FIG. 2, the upper oven wall of the insulating casing 20 has arranged therein an assembly of an injection block 38 and a flame ionization detector 40. Reference numeral 42 designates the carrier gas supply line. The structure of this assembly will become more apparent from FIGS. 3 to 6.

In FIGS. 3, 4 and 5 reference numeral 4-8 designates a burner nozzle which is electrically insulated within a casing 50, comprising a cup-shaped bottom section 52 and an also cup-shaped top section 5-.- mounted thereupon. The bottom section 52 is partially embedded in the insulating casing 20. The burner nozzle communicates on one side with a burner gas supply line 58 and on the other side with a column connection 60 at the inner side of the insulating casing via a T 56 (see FIG. 5). ()n both sides of the burner nozzle are positioned electrodes 62 and 64, supported by means of insulating bodies 66 in the casing bottom section 52, which electrodes (62, 64) are connected with leads 68, '79 carried outwardly (see FIG. 4). Reference numeral 72 designates an ignition coil which is connected to a suitable power source by leads 74.

FIG. 6 shows the sample injection block 38 with an injection capillary 76 extending through the insulating casing 20 and protruding therefrom. On the protruding end of injection capillary 76 is mounted a block 78 into which the carrier gas supply line 42 terminates. Specifically, gas supply line 42 opens into an annular chamber 82 encompassing. the injection capillary 76 and being connected therewith by a radial opening 86. The injection capillary 76 is closed off at the end thereof by a selfsealing injection diaphragm 84. The diaphragm 84 is secured by means of a cap 86 screwed onto the block 78 and a supporting disk 88. Through a hole in the cap 36 and the supporting disk 88 an injector may pierce through the diaphragm 84 and enter into the capillary. By means of this injector a sample may be injected into the carrier gas stream, which flows from line 42 through the annular chamber 82 and the opening 80 into and through the capillary 76. This arrangement has (in a manner known as such) the advantage that the diaphragm is (among other parts) cooled by the carrier gas stream, and that no sample residues may reach and form deposits on the diaphragm. The diaphragm 84- is located externally of the oven. Inside the oven, at the inner (left in FIG. 6) end of the injection capillary '76, the second connector 90 for direct connection to the entrance end of the separating column is provided.

An elongated auxiliary heating mandrel 92 extends transversely across flame ionization detector 40 and injection block 38 whereby these two parts may be heated independently of the oven temperature.

In the arrangement as hereinbefore described the parts to be kept cool are arranged externally of the insulating casing. The parts to be kept warm are positioned within the insulating casing or in the oven interior. In such an arrangement, a minimum of connecting lines, insulation and heating power will be required.

We claim as our invention:

1. In a gas chromatograph of the type comprising a separating column, a sample injector connected to the entrance end thereof, a detector connected to the exit end of said column, and an oven containing said column and having walls of thermally insulating material, the improvement comprising:

said detector being at least partially embedded within an oven wall composed of said insulating material, said sample injector comprises an injection block,

which is also at least partially embedded in the insulating material of said same oven Wall; and an auxiliary heating means provided within said same oven wall in the vicinity of said detector and said sample injection block so as to heat at least parts of both said detector and said sample injection block independently of the heat supplied from said oven, whereby the temperature of at least parts of said detector and said sample injector may be maintained at a desired elevated temperature different from that of the column oven without causing undesirable thermal changes within said oven. 2. A gas chromatograph according to claim 1, in which:

said detector, sample injector and said column are so positioned that said detector is adjacent the exit end of said column and said sample injector is adjacent the entrance end of said column, whereby said detector and said sample injector are directly connected to said column, thereby avoiding dead volume, heat losses and insulation problems caused by long connecting lines. 3. A gas chromatograph according to claim 1, in which:

said auxiliary heating means is in the form of an elongated heating mandrel embedded in said same oven wall and passing close to both said detector and said injector, whereby said single mandrel will maintain the temperature of both said detector and injector at a desired elevated temperature. 4. A gas chromatograph according to claim 1, in which:

said detector is a flame ionization detector having electrodes; and the electrical leads from said electrodes extend directly therefrom to the outside of said oven wall, whereby the problem of electrically insulating such leads at high temperature is minimized.

References Cited UNITED STATES PATENTS 2,963,898 12/1960 Reynolds et al. 7323.l 3,026,712 3/1962 Atwood et al. 7323.1 3,124,952 3/1964 Johnson 7323.1 3,169,389 2/1965 Green, Jr. et al. 73-23.1

OTHER REFERENCES Ashbury, et al.: Analytical Chemistry, vol. 29, No. 6, June 1957, pp. 918-925.

Emery et al.: Analytical Chemistry, vol. 33, No. 4, April 1961, pp. 523-527.

RICHARD C. QUEISSER, Primary Examiner.

C. A. RUEHL, Assistant Examiner.

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