JP2005201687A - Flame photometer for gas chromatograph - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the quantity of light arriving at a photomultiplier by emitting light at the optimum position by altering the position of a nozzle in a flame photometer (FPD detector) for a gas chromatograph to enhance detection sensitivity as a result. <P>SOLUTION: A nozzle center being a separate member is provided to the leading end part of the nozzle ejecting a mixture gas of a column outflow gas and a fuel gas in the flame photometer of the gas chromatograph to be made movable in a height direction so as to adjust the detection sensitivity in a photomultiplier. <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

The FPD nozzle 7 forms a flame 8, into which sample components from the column are introduced, burned, and emits light. The light emitted at this time is diffused light, and even if the intensity of emitted light is the same, the intensity of light entering the photomar is different if the relationship between the light emitting position and the height of the photomaru is different.
In FIG. 1, when the light emission position is at points a and b, the incidence efficiency is better when light is emitted at point b.

However, gas chromatographs perform analysis under various conditions depending on the application. For example, if the analysis conditions such as the inner diameter of the analysis column, the carrier gas flow rate, and the measurement component are different, the emission position of the sample is different even if the nozzle height is the same. Specifically, the higher the linear velocity of the gas introduced into the flame, the higher the emission position, and there is a possibility that the emission position will be higher when measuring a sample that takes time to emit light. .
As described above, the change in the analysis conditions may cause the light emission position to deviate from the optimum position, and the detection efficiency at the photomultiplier may deteriorate.

The present invention has been made in view of such circumstances, and in the FPD detector of a gas chromatograph, the sample component has a height suitable for the position of the photomultiplier even when the analysis conditions are changed without replacing the nozzle body. The purpose of this is to make it possible to emit light.

  In order to solve the above-mentioned problems, the present invention provides the following: “A mixture gas of a column outflow gas and a fuel gas is ejected from the tip of a nozzle, and the mixture gas and an auxiliary combustion gas are mixed and burned in a combustion chamber. In the flame photometer for gas chromatographs configured to detect the light of a specific wavelength emitted from the sample component in the column effluent gas in the flame caused by the nozzle, the nozzle center that can be fitted to the tip opening of the nozzle And a flame photometer detector for gas chromatograph which can change the height with respect to the optical axis of the nozzle center. That is, a nozzle center which is a separate member that can be fitted is provided at the tip of the nozzle that ejects the mixed gas of the column outflow gas and fuel gas inside the FPD detector of the gas chromatograph, and moves in the gas outflow direction. The height of the nozzle tip can be changed. Since the FPD detector often causes the gas to flow out vertically upward, in this specification, the gas outflow direction is defined as the height direction.

  Since the light emission position of the sample component changes 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.

According to the present invention, even when the analysis conditions are changed, the emission height of the sample component can be changed by changing the height of the nozzle center of the FPD detector so that the light can be emitted at the optimum height. . Therefore, the light entering the photomultiplier increases and the sensitivity of the FPD detector can be improved.

  One embodiment of the present invention is shown in FIG. 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. In FIG. 2, the column outflow gas merges with the fuel gas in the fuel gas passage 5, blows out from the nozzle, and burns to form a flame. On the other hand, the auxiliary combustion gas is blown from the auxiliary combustion gas outlet 6 through the auxiliary combustion gas passage 62, and the auxiliary combustion gas necessary for combustion is supplied to the flame.

This embodiment differs from the conventional nozzle in the structure near the tip. The tip 7 of the conventional nozzle is formed so as to narrow the upper end of the fuel gas passage, and the height is constant. The tip 70 of the nozzle of the present embodiment has a threaded portion formed on the inner periphery, and includes a nozzle center 72, which is a separate member, as shown in FIG. The nozzle center 72 has a threaded portion 71 on the outer periphery, and has a structure that can move in the gas outflow direction by fitting with a threaded portion on the inner periphery of the nozzle tip 70. The height of the nozzle center 72 can be changed by the tightening degree of the threaded portion (FIGS. 3A and 3B). As the nozzle center changes, the emission position of the sample component in the column effluent gas changes.

For example, when the inner diameter of the analytical column is different, the emission position of the sample component is greatly different because the linear velocity of the outflow gas is different. For example, when using a packed column, the screw part is not tightened so much, the nozzle center is raised (FIG. 3A), and the emission position of the sample component in the column outflow gas is raised. When a capillary column is used, the nozzle center can be lowered by tightening the screw to the back (FIG. 3B), and the light emission position can be lowered.

Thus, 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 or a configuration that can automatically move in the height direction. If nozzle centers having different inner diameters are provided, the height can be changed simultaneously with the present invention, and the inner diameter of the nozzle can also be changed. In addition, the nozzle center can be made of quartz to prevent sample adsorption.

Some FPD detectors for gas chromatographs have a structure as shown in FIG. 4, and the effect of the present invention is 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 photo through the flame, and the light reflected by the concave mirror 16 is also detected by the photo 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. In the past, the height of the nozzle tip was fixed, so when the analysis conditions were changed, the emission position of the sample component and this focal point shifted, and the arrival efficiency to the photomultiplier could deteriorate. 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. 5A is a diagram in which the nozzle center is lowered when the linear velocity is high, and FIG. 5C is a diagram in which the nozzle center is raised when the linear velocity is slow. By applying the present invention, by adjusting the position of the nozzle center so that the emission position of the sample component to be measured is as close as possible to the focal point according to the analysis conditions, the amount of light reaching the photomultiplier is increased and the detection sensitivity is increased. Can

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 a figure which shows the nozzle front-end | tip part 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 ... Conventional nozzle tip 70 ... Nozzle tip 71 of the present invention ... Screw part 72 ... Nozzle center 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 light having a specific wavelength, the nozzle center has a nozzle center that can be fitted into the tip opening of the nozzle, and the height of the nozzle center with respect to the optical axis is high. Changeable flame photometric detector for gas chromatograph

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