JPH11237340A - Flame photometric detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the quantity of light that reaches a photo detector. SOLUTION: A convex lens 23 is arranged between a hydrogen flame frame 21 and an interference filter 19, diffusion light being emitted from a combustion part 22 of a sample constituent in the frame 21 is collimated and is sent to the interference filter 19. Also, the frame 21 is put between the convex lens 23 and a concave mirror 24, and light being emitted in a direction opposite to a detection window 17 from the combustion part 22 is also reflected by the concave mirror 24 and is sent to the interference filter 19 via the convex lens 23, thus increasing the quantity of light being introduced to the interference filter 19, allowing the light to nearly vertically enter onto a filter surface, efficiently transmitting light with a desired wavelength for reaching a photomultiplier tube 20, and hence improving detection sensitivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flame photometric detector (hereinafter referred to as "FPD (= Flame Photometric Detector)") used as a detector of a gas chromatograph or the like.

[0002]

2. Description of the Related Art Various types of gas chromatograph detectors have been put into practical use.
Is a detector for selectively detecting a sulfur compound or a phosphorus compound. Therefore, it is used for a wide range of applications such as analysis of malodorous components such as hydrogen sulfide and methyl mercaptan, detection of trace sulfur content in chemicals, analysis of residual agricultural chemicals, and analysis of biochemical components.

FIG. 2 is a configuration diagram of a detection cell of a conventional general FPD. For example, a sample gas pipe 10, a hydrogen supply pipe 11, and an air (or oxygen) supply pipe 12 connected to a column outlet of a gas chromatograph are connected to a nozzle 13 having a gas outlet 14 above. A transparent quartz tube 15 is provided around the nozzle 13, and the entire quartz tube 15 is covered with a heat insulating block 16 made of metal. A heater and a temperature sensor (not shown) are embedded or provided in close contact with the heat retaining block 16 so that the heat retaining block 16 is maintained at a predetermined temperature. A detection window 17 is opened at a predetermined position of the heat retaining block 16,
An interference filter 19 is provided outside the detection window 17 through a cooling fin 18, and a photomultiplier tube 20 is further provided outside the detection filter 17 as detection means.

The operation principle of the above FPD is as follows.
The nozzle 1 supplies a carrier gas such as nitrogen supplied through a sample gas pipe 10, a hydrogen gas supplied through a hydrogen supply pipe 11, and air supplied through an air supply pipe 12.
The mixture is mixed at the three tips and burned to form a hydrogen flame frame 21. For example, when a sample component flowing out of a column of a gas chromatograph enters the flame, it burns and emits light having a wavelength unique to the component. In particular, in the reducing flame of perhydrogen, combustion of sulfur compounds and phosphorus compounds causes 39
It emits light with a wavelength of 4 μm, 526 μm. Light emitted from the combustion part 22 in the hydrogen flame frame 21 is a transparent quartz tube 15.
, And only light having the above specific wavelength is selectively transmitted by the interference filter 19 and reaches the photomultiplier tube 20. This makes it possible to detect components with extremely high selectivity. The quartz tube 15 is provided with an interference filter 1 made of water vapor or soot generated from the hydrogen flame frame 21.
9 is to prevent fogging.

[0005]

The transmittance of the interference filter 19 for the target wavelength light is most efficient when the light is incident vertically. Combustion part 2 in hydrogen flame frame 21
2 is diffused light (indicated by an arrow in FIG. 2), so that the farther the interference filter 19 is away from the hydrogen flame frame 21, the more light that reaches the interference filter 19 at an angle closer to the vertical (in FIG. 2). Light parallel to the optical axis c) decreases. To increase the efficiency, it is desirable to bring the interference filter 19 and the photomultiplier tube 20 close to the hydrogen flame frame 21. However, since both the interference filter 19 and the photomultiplier tube 20 have low heat-resistant temperatures, the interference filter 19 and the photomultiplier tube 20 must be close to each other. It is necessary to have a configuration in which the cooling fins 18 are arranged at a certain distance from each other and the cooling fins 18 are arranged on the way. For this reason, only a small part of the divergent light from the combustion section 22 reaches the photomultiplier tube 20, which is one of the causes of the deterioration of the detection sensitivity.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a flame light capable of improving sensitivity by efficiently introducing light into a photomultiplier tube. It is to provide a photometric detector.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. According to the present invention, a sample component is introduced into a hydrogen flame and burned, and light emitted from the burning portion has a specific wavelength. In a flame photometric detector to be introduced into the light detecting means via a selective transmitting means for transmitting light, a light condensing means is inserted between the hydrogen flame frame and the selective transmitting means.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a flame photometric detector according to the present invention, for example, a convex lens can be used as a light collecting means. When a convex lens is used, the approximate position of the convex lens is determined so that the combustion section is located at the focal position of the convex lens. According to this, the convex lens collimates the light emitted from the combustion part in the hydrogen flame frame, converts the light into light substantially perpendicular to the incident surface of the selective transmission means, and introduces the light into the selective transmission means. As a result, only light having a specific wavelength in the light is transmitted efficiently, that is, almost without attenuation, and reaches the light detecting means.

In order to more efficiently collect light, a concave mirror is disposed on the opposite side of the hydrogen flame frame from the light collecting means, and the light reflected by the concave mirror is sent to the light collecting means. Is preferred. According to this configuration, not only the light directly sent from the combustion part of the hydrogen flame frame to the light collecting means, but also the light which has not been used conventionally and which is emitted from the combustion part and travels in the opposite direction to the selective transmission means is reflected by the concave mirror. The light is reflected and sent to the light collecting means. Therefore, the amount of light incident on the selective transmission unit increases. If the concave surface of the concave mirror is a spherical surface and the concave mirror is arranged so that the combustion part of the hydrogen flame frame is at the center of the spherical surface, the light reflected by the concave mirror passes through the vicinity of the combustion part and reaches the light collecting means. The reflected light is also bent into substantially parallel light by the condensing means. For this reason, more light reaches the light detecting means.

[0010]

As described above, according to the flame photometric detector of the present invention, since more light is incident on the interference filter and almost perpendicularly to the filter surface, light of a specific wavelength determined by the interference filter is obtained. Is efficiently transmitted and introduced into the light detecting means. For this reason, the signal level of the light detecting means is increased, and as a result, the detection sensitivity is improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a flame photometric detector according to the present invention will be described with reference to FIG. FIG. 1 shows an FPD according to the present embodiment.
And the same or corresponding parts as those in the conventional FPD of FIG. 2 are denoted by the same reference numerals.

As shown in FIG. 1, in the FPD of the present embodiment, between the hydrogen flame frame 21 and the interference filter 19,
The convex lens 23 is provided so that the combustion part 22 becomes a focal point. Since the convex lens 23 is placed at a position relatively close to the hydrogen flame frame 21, it is preferable to form the convex lens 23 from, for example, quartz or the like in order to have heat resistance. Further, the heat retaining block 16 on the opposite side of the convex lens 23 with the hydrogen flame frame 21 interposed therebetween.
On the inner wall, a spherical concave mirror 24 centering on the combustion portion 22 is provided.
Are arranged. The concave mirror 24 may be formed, for example, by forming the inner wall surface of the heat retaining block 16 into a spherical shape and forming a mirror surface by depositing a metal or the like having a reflective effect on the inner wall surface by vapor deposition or the like.

In the FPD of this embodiment, the hydrogen flame 2
When a sample component is introduced into the sample 1, the sample component is burned in the vicinity of the combustion section 22, and light having a wavelength specific to the component is emitted. This light is diffused in all directions around the combustion portion 22, but the light that travels rightward in FIG. 1 and reaches the convex lens 23 is collimated by the convex lens 23 and changed to a direction parallel to the optical axis c. . Then, the light enters the filter surface of the interference filter 19 almost perpendicularly, and only light having a specific wavelength according to the characteristics of the interference filter 19 is transmitted and reaches the light receiving surface of the photomultiplier tube 20.

On the other hand, as shown in FIG.
Is reflected by the concave mirror 24 in a direction substantially opposite to the incident direction. Therefore, the reflected light is transmitted to the combustion section 22.
The light passes through the vicinity and reaches the convex lens 23. For this reason, in addition to the light that directly reaches the convex lens 23 from the combustion section 22 as described above, the reflected light is also collimated by the convex lens 23 and becomes light substantially parallel to the optical axis c, so that the interference filter 19
Sent to Therefore, in addition to the effect of condensing light by the convex lens 23, the effect of increasing the amount of light by the concave mirror 24 can be obtained.

As described above, in the FPD of the above embodiment, both the convex lens 23 and the concave mirror 24 make the conventional FPD
A much larger amount of emitted light reaches the interference filter 19 as parallel light, and only the light of a desired wavelength is extracted by the interference filter 19 and reaches the photomultiplier tube 20. Therefore, the detection sensitivity is improved, and a smaller amount of sample components can be measured.

The above embodiment is merely an example, and it is apparent that changes and modifications can be made within the spirit of the present invention.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of a flame photometric detector according to the present invention.

FIG. 2 is a configuration diagram of a conventional flame photometric detector.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Sample gas pipe 11 ... Hydrogen supply pipe 12 ... Air supply pipe 13 ... Nozzle 14 ... Gas ejection port 15 ... Quartz cylinder 16 ... Heat insulation block 17 ... Detection window 18 ... Cooling fin 19 ... Interference filter (selective transmission means) 20 ... Photomultiplier tube (light detecting means) 21 ... hydrogen flame frame 22 ... burning part 23 ... convex lens (light collecting means) 24 ... concave mirror

Claims (1)

[Claims] 1. A flame photometric type in which a sample component is introduced into a hydrogen flame and burned, and light emitted from the combustion section is introduced into light detection means via selective transmission means for transmitting light of a specific wavelength. A flame photometric detector, wherein a light collector is inserted between the hydrogen flame frame and the selective transmission means in the detector.