JP2005201688A - Flame photometer for gas chromatograph - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cylindrical member in a fuel gas passage in the flame photometer of a gas chromatograph to make it possible to alter the combustion condition of a nozzle by altering the cylindrical member and to replace the cylindrical member simultaneously with the replacement of a column because the cylindrical member can be replaced from the interior of a column oven to simplify work. <P>SOLUTION: The cylindrical member is provided in a FPD fuel gas passage in the flame photometer of the gas chromatograph to be made replaceable from the side of the column oven. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a flame photometric detector used as a detector for a gas chromatograph.

  A flame photometric detector (hereinafter abbreviated as “FPD (= Flame Photometric Detector)”) is a gas chromatograph detector that has a particularly high sensitivity to sulfur and phosphorus compounds. FIG. 1 is a sectional view showing an example of the structure of a conventional FPD. (Patent Document 1) In FIG. 1, reference numerals 1 to 3 are gas chromatograph flow paths connected to the FPD. That is, the carrier gas adjusted to a constant pressure or a constant flow rate is introduced from the carrier gas introduction unit 1 and flows to the detector (FPD cell 4) through the sample inlet 2 and the column 3. The sample injected from the sample injection port 2 is separated into each component while passing through the column 3 on the carrier gas flow. Hereinafter, the carrier gas flowing out from the end of the column and the constituent gas of the separated sample component are referred to as column outflow gas.

Hydrogen as fuel gas and air as auxiliary combustion gas are introduced into the FPD cell 4 through conduits 51 and 61, respectively. The introduced fuel gas flows upward through the fuel gas passage 5 along the central axis of the cylindrical FPD cell. The upper end of the fuel gas passage 5 forms a nozzle 7 that opens toward the fuel chamber 42. The column end is inserted into the fuel gas passage 5 from the lower side of the FPD cell 4 and fixed by a nut 31 and a ferrule 32. The auxiliary combustion gas is blown out toward the combustion chamber 42 through the auxiliary combustion gas passage 62 provided so as to surround the fuel gas passage 5 and from the auxiliary combustion gas outlet 6 formed of a plurality of small holes arranged around the nozzle and opened in the vicinity of the nozzle. Is done. Note that the auxiliary combustion gas outlet 6 may be configured as a gap on a slit surrounding the nozzle in an annular shape. Although hydrogen and air are used as the fuel gas and the auxiliary combustion gas, other gas species may be used.

The combustion chamber 42 is a space above the nozzle 7 covered with the cell outer cylinder 41, where the fuel gas reacts with oxygen in the auxiliary combustion gas and burns to form a flame 8. The exhaust gas after combustion is discharged from the exhaust port 43 at the top of the cell outer cylinder.

The column outflow gas joins the fuel gas in the fuel gas passage 5 and is blown out from the nozzle 7 into the flame 8. If there is a component containing sulfur or phosphorus in the sample, light of a specific wavelength is emitted in the high-temperature flame 8. The light intensity of this light is measured by a photometric unit 10 provided on the side surface of the flame 8. At this time, the light emitted from the sample component in the flame 8 passes through the quartz window 13 and enters the photometry unit 10, and is further converted into an electric signal by the photon 12 through the interference filter 11 that passes only a specific wavelength, not shown. Output to an external measurement circuit.
JP 2002-22661

In gas chromatographs, analysis is performed under a variety of different conditions using a single device depending on the application. For example, the inner diameter of the analytical column, the carrier gas flow rate, the measurement component, and the like. When the analysis conditions, particularly the column type, are changed, the nozzle for the FPD detector must be changed to an appropriate one according to the conditions.
For example, when a packed column and a capillary column are used, the carrier gas flow rates are greatly different. Therefore, when the flame is formed at the nozzle tip, if the inner diameter of the nozzle tip is not an appropriate value corresponding to the gas flow rate, the flame is not formed well, and a fire may be lost. The distance from the tip of the nozzle to the light emission position of the sample varies depending on the conditions. Specifically, the higher the linear velocity of the gas introduced into the flame, the longer the distance from the nozzle tip to the light emission position, and the longer the distance to the light emission position when measuring a sample that takes time to emit light. Since there is a possibility that the light emission position changes due to a change in analysis conditions such as a longer length, it is necessary to change the height of the tip of the nozzle in order to improve the detection efficiency at the photomultiplier.

Conventionally, however, replacement of the column is performed from the inside of the column oven, while adjustment of the nozzle has to be performed from the detector side, that is, from the outside of the column oven, which involves complicated operations such as removing the lid of the detector. It was.

The present invention has been made in view of such circumstances, and in the FPD detector of a gas chromatograph, a structure that can be changed to a nozzle inner diameter and a position suitable for analysis conditions without replacing the nozzle body. Objective. Since it is not necessary to remove the lid of the detector and the operation can be performed from the column oven side, the nozzle can be adjusted simultaneously with the replacement of the column.

In order to solve the above problems, the invention according to claim 1
“A mixed gas of column effluent gas and fuel gas is ejected from the tip of the nozzle, the mixed gas and auxiliary combustion gas are mixed and burned in the combustion chamber, and the sample in the column effluent gas in the flame caused by the combustion. In the flame photometric detector for gas chromatographs configured to detect light having a specific wavelength emitted by a component, a cylindrical member is provided inside the fuel gas passage, and the cylindrical member is removable from the column oven side. A flame photometric detector for gas chromatography is provided.
That is, by providing a cylindrical member inside the fuel gas passage inside the FPD detector of the gas chromatograph and replacing the cylindrical member, the inner diameter and height of the nozzle tip can be changed.

Since the light emission position of the sample component varies depending on the analysis conditions, the light intensity measured by the photomultiplier is different even when light emission of the same intensity occurs. Factors that change the light emission position are not limited to the inner diameter of the analytical column, and various factors such as changing the carrier gas flow rate and target components are conceivable.
By changing the inner diameter and length of the cylindrical member, if the detection sensitivity is considered to be improved by changing the inner diameter and height of the nozzle, such as when changing the analysis conditions, according to the present invention, By changing the inner diameter and the tip height of the nozzle of the FPD detector, the light emission height of the sample component can be emitted at an optimum height. Therefore, misfire is less likely to occur, the light entering the photomultiplier increases, and the sensitivity of the FPD detector can be improved. And since said operation | work can be performed from the column oven side, it can operate | work simultaneously with replacement | exchange of a column, and can attain labor saving of the whole operation | work.

  The nozzle part of this invention is shown to Fig.2 (a). FIG. 2B shows a conventionally used FPD nozzle. In FIG. 2, only the nozzles in the FPD detector and the periphery thereof are shown, and the portions not shown are the same as those in FIG.

This embodiment differs from the conventional nozzle in the structure near the tip. The tip 71 of the conventional nozzle is composed of one member, and the height of the tip is constant. In this embodiment, a cylindrical member 72, which is a separate member, is provided inside the nozzle, and the cylindrical member protrudes near the tip of the nozzle. An example of the cylindrical member 72 is shown in FIG. As shown in FIG. 3, the cylindrical member 72 has a threaded portion 74 and a groove 73 in the lower portion, and the cylindrical portion is preferably made of a material that hardly adsorbs measurement components such as quartz. In the present invention, a screw is also formed inside the nozzle and is screwed into the threaded portion 74 of the cylindrical member 72.

The groove 73 is formed to screw a screw with a screwdriver. The screwdriver 74 is inserted into the nozzle from the column oven side by placing the screwdriver into the groove 73, and the screw portion 74 is screwed with the screwdriver. It has come to be tightened. The cylindrical member 72 can be moved in the gas outflow direction and the height of the tip can be adjusted by the tightening degree of the screw portion 74. The end of the column is inserted directly under the threaded portion 74 or into the cylindrical member, and the outflow gas from the column passes through the cylindrical member 72 and is introduced into the combustion chamber. Emits light. At this time, the emission position of the sample component in the column effluent gas can be changed with the change in the height of the tip when the cylindrical member is screwed into the nozzle.

For example, when the inner diameters of the analysis columns are different, the emission positions of the sample components are greatly different because the linear velocity of the outflow gas is different. For example, when using a packed column, the cylindrical member is raised by tightening the screw all the way to raise the emission position of the sample component in the column outflow gas. When the capillary column is used, the light emitting position can be lowered by lowering the cylindrical member without tightening the threaded portion so much.

In this way, the light emission position of the sample component in the column effluent gas can be adjusted to an optimum height by tightening the screws. This adjustment method is not limited to the screw type, and may be a fitting type, a slidable configuration, or the like, or may be automated. Moreover, the cylindrical member can be made detachable, can be provided with cylindrical members having different lengths, and these can be exchanged. If cylindrical members having different inner diameters are provided, it is possible to change the inner diameter of the nozzle at the same time as changing the height according to the present invention. Further, since the cylindrical member can be adjusted from the column oven side, the adjustment work can be saved.

Some FPD detectors for gas chromatographs have a structure as shown in FIG. 4, and the effects of the present invention are more remarkable. Details of the FPD detector in FIG. 4 are disclosed in JP-A-11-237340. Briefly, a convex lens 15 is provided between the flame 8 and the photomultiplier 12, collimated diffused light emitted from the sample component in the flame is incident as light substantially perpendicular to the photomal entrance surface. Further, a concave mirror 16 is disposed on the opposite side of the photomask across the flame, and the light reflected by the concave mirror 16 is also detected by the photomal 12 as substantially vertical light by the convex lens 15. According to the FPD detector having such a structure, most of the light emitted in the flame reaches the photomal, but the convex lens and the concave lens are designed to form the focal point 17 at a certain point. Therefore, it is desirable to emit the strongest light at the focal position 17. Conventionally, since the height of the nozzle tip is fixed, when the analysis conditions are changed, the light emission position of the sample component is shifted from this focal point, and the arrival efficiency to the photomart may be deteriorated. By changing the nozzle position as shown in FIG. 5, the distance between the nozzle tip and the light emission position can be changed from (a) to (c), and the light emission position can be brought closer to the focal point 17. FIG. 5A is a diagram in which the cylindrical member is lowered when the linear velocity is high, and FIG. 5C is a diagram in which the cylindrical member is raised when the linear velocity is slow. . By applying the present invention, by adjusting the position of the cylindrical member so that the emission position of the sample component to be measured depending on the analysis conditions is as close as possible to the focal point, the amount of light reaching the photomultiplier is increased, and the detection sensitivity is increased. Can raise

It is a figure which shows the structural example of the conventional FPD. It is a figure which shows one Example of this invention, and the nozzle part of conventional FPD. It is the schematic of the cylindrical member of one Example of this invention. It is a figure which shows an example of a structure of the conventional FPD. FIG. 5 is a diagram illustrating an example in which the present invention is applied to an FPD having the configuration of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Carrier gas introduction part 2 ... Sample injection port 3 ... Column 31 ... Nut 32 ... Ferrule 4 ... FPD cell 41 ... Cell outer cylinder 42 ... Combustion chamber 43 ... Exhaust port 5 ... Fuel gas passage 51 ... Fuel gas conduit 6 ... Auxiliary combustion Gas outlet 61 ... auxiliary gas conduit 62 ... auxiliary gas passage 7 ... nozzle 71 ... conventional nozzle tip 72 ... cylindrical member 73 ... groove 74 ... screw part 8 ... flame 9 ... light shielding ring 10 ... photometric part 11 ... interference filter 12 ... Photomal 13 ... Quartz window 14 ... Quartz cylinder 15 ... Convex lens 16 ... Concave mirror 17 ... Focus on optical design

Claims (1)

The mixed gas of the column outflow gas and the fuel gas is ejected from the tip of the nozzle, the mixed gas and the auxiliary combustion gas are mixed and burned in the combustion chamber, and the sample components in the column outflow gas in the flame by the combustion In the flame photometric detector for gas chromatograph configured to detect the light having a specific wavelength emitted from the gas cylinder, a cylindrical member is provided inside the fuel gas passage, and the cylindrical member is detachable from the column oven side. Flame photometric detector for gas chromatography

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