JP2004347394A - Fluorescence measurement device - Google Patents

Abstract

An object of the present invention is to provide a fluorescence measuring apparatus using a reflection-type spectroscopic mirror, which can reduce stray light and perform more accurate measurement.
An excitation light from an excitation light source (12) is reflected by the surfaces of spectroscopic mirrors (16a to 16d), and the reflected excitation light is applied to a sample gas, and the intensity of fluorescence (25) generated at that time is measured by a fluorescence detector. In the fluorescence measuring device for detecting light at 22, a material that absorbs light in the wavelength range detected by the fluorescence detector is used for the mirror base of the spectroscopic mirror. For example, in an SO ₂ measuring apparatus using a xenon flash lamp as an excitation light source, light having a wavelength of 220 nm is reflected on the surface of the spectroscopic mirror, and the mirror base material of the spectroscopic mirror absorbs light having a wavelength of 400 nm or less. .
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fluorescence measurement device that reflects excitation light from an excitation light source to a spectroscopic mirror, irradiates the sample gas with the reflected excitation light, and detects the intensity of fluorescence generated at that time with a fluorescence detector. . The fluorescence measurement device of the present invention can be suitably used, for example, as an ultraviolet fluorescence type SO ₂ (sulfur dioxide) measurement device.
[0002]
[Prior art]
As a dry measuring device for measuring the concentration of SO ₂ contained in the atmosphere or in the exhaust gas of a factory without using a reagent, there is a measuring device using an ultraviolet fluorescent method. This SO ₂ measuring apparatus utilizes the fact that when SO ₂ in a sample gas is irradiated with ultraviolet light having a wavelength of about 220 nm, the SO ₂ is excited to emit fluorescence having a wavelength of 300 to 400 nm. This is detected by a fluorescence detector such as a multiplier, and the SO ₂ concentration in the sample gas is determined from the detected value.
[0003]
In SO ₂ measuring apparatus using ultraviolet fluorescence method, as the excitation light source is generally used xenon flash lamp. However, since a xenon flash lamp is a light source having a continuous spectrum from the ultraviolet to the infrared region, it requires spectroscopy to obtain light of a desired excitation wavelength. At present, a dielectric multilayer mirror having a reflectance of near 100% for light having a wavelength around 220 nm and a reflectance of 10% or less for other wavelengths is used as a spectroscopic mirror, and light from a light source is used as the light for the above. In general, the light is reflected by the spectroscopic mirror a plurality of times to perform spectroscopy and irradiate only light having a wavelength of about 220 nm to the sample gas (for example, see Patent Document 1).
[0004]
FIG. 1 is a schematic view showing an example of a conventional SO ₂ measuring apparatus using an ultraviolet fluorescent method. In the apparatus shown in FIG. 1, reference numeral 2 denotes a light source cell, 4 denotes a spectral cell, 6 denotes a measurement cell, and 8 denotes a control unit. The light source cell 2 has a xenon flash lamp 12 installed inside a box 10. The spectroscopy cell 4 has four flat-plate-type reflection spectroscopy mirrors 16 a to 16 d disposed inside a box 14, and a cell entrance 19 and a cell exit 21 of the cell 4 are connected to the light source 12. And an exit lens 20 (both convex lenses) for converging the parallel light passing through the spectroscopic cell 4 in the measurement cell 6. In the drawing, reference numeral 17 denotes a fixing tool for fixing each reflection-type spectral mirror 16 in the cell 4.
[0005]
The reflection type spectroscopic mirrors 16a to 16d are arranged in a substantially rectangular frame shape such that the angle between adjacent filters is about 90 degrees. Then, the light from the light source 12 which has become substantially parallel rays through the entrance lens 18 is incident on the first reflection type spectroscopic mirror 16a at an incident angle of 45 degrees, and ultraviolet rays having a wavelength of about 220 nm in the mirror 16a. It reflects at a reflection angle of 45 degrees. Further, the ultraviolet rays are sequentially reflected on the second, third and fourth reflection type spectroscopic mirrors 16b, 16c and 16d, and then enter the measurement cell 6 through the exit lens 20. In this case, the angles of incidence and reflection of light on the filters 16b, 16c and 16d are all 45 degrees.
[0006]
The measurement cell 6 irradiates the sample gas introduced therein with ultraviolet rays emitted from the spectroscopic cell 4, and detects the intensity of the fluorescence 25 generated at that time by the fluorescence detector 22. In the measurement cell 6, 23 is a detector cell, 24 is a condenser lens provided in front of the detector 22 to collect fluorescence, 26 is an optical filter that selectively transmits ultraviolet light having a wavelength of 300 to 400 nm, 36 denotes a sample gas inlet, and 38 denotes a sample gas outlet. The control unit 8 obtains the SO ₂ concentration in the sample gas based on the fluorescence intensity detected by the fluorescence detector 22.
[0007]
[Patent Document 1]
JP-A-10-115584 [0008]
[Problems to be solved by the invention]
In the reflection type spectroscopic mirror composed of the dielectric multilayer mirror described above, light having a wavelength of about 220 nm is reflected on the mirror surface, but light of other wavelengths is transmitted through the mirror base material and is reflected on the back surface of the mirror base material. Reflected and scattered. Synthetic quartz or general optical glass is used for the mirror base material, and most of them have good transmittance of light having a wavelength of 300 to 400 nm. For this reason, although very weak, light having a wavelength of 300 to 400 nm reflected and scattered on the back surface of the mirror substrate is irradiated on the sample gas, which causes light (stray light) that interferes with the measurement. Was.
[0009]
The present invention has been made in view of the above circumstances, and provides a fluorescence measurement device using a reflection-type spectroscopic mirror, which is capable of reducing stray light and performing more accurate measurement. The purpose is to:
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present invention reflects excitation light from an excitation light source on the surface of a spectroscopic mirror, irradiates the reflected excitation light to a sample gas, and reduces the intensity of fluorescence generated at that time. In a fluorescence measurement device that detects light with a detector, a mirror base material of the spectroscopic mirror absorbs light in a wavelength range that is detected by the fluorescence detector.
[0011]
According to the present invention, in a fluorescence measuring device using a reflection type spectroscopic mirror, a mirror base material of the spectroscopic mirror is made of a material that absorbs light in a wavelength range detected by a fluorescence detector. Thereby, generation of stray light due to reflection and scattering on the back surface of the mirror base material can be suppressed.
[0012]
In this case, in the present invention, as the mirror base material of the spectroscopic mirror, for example, an optical glass such as a UV cut glass, a long-pass filter (color glass filter), or a resin can be used.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in more detail. In the present invention, for example, a SO ₂ measurement apparatus fluorescence measuring device by ultraviolet fluorescence method, when the excitation light source is a xenon flash lamp, using those reflected wavelength 220nm light at the surface as a spectroscopic mirror, and, The base material of the spectroscopic mirror is made of a material that absorbs light having a wavelength of 400 nm or less, more preferably a material that absorbs light having a wavelength of 300 to 400 nm. Thereby, light of a wavelength 300~400nm with fluorescence detector sensitivity of SO ₂ measurement device is absorbed in the mirror base, the occurrence of stray light is suppressed by reflection and scattering at the rear surface of the mirror substrate.
[0014]
More specifically, in the present invention, the fluorescence measurement device is a SO ₂ measurement apparatus using ultraviolet fluorescence method, when the excitation light source is a xenon flash lamp, a spectral mirror, an optical glass available from Schott Corporation SF11 A dielectric multilayer mirror (reflection spectral mirror having a dielectric type high reflection coating on the surface) using (glass classification name) as a mirror substrate can be suitably used. In this dielectric multilayer mirror, light having a wavelength of 220 nm is reliably reflected on the mirror surface, and the mirror substrate (SF11) reliably absorbs light having a wavelength of 400 nm or less, particularly light having a wavelength of 300 to 400 nm. is there.
[0015]
Here, experimental results showing the effects of the present invention will be described. Use in SO ₂ measuring apparatus using ultraviolet fluorescence method, as a reflection-type spectral mirror, and if the mirror base material using a dielectric multilayer film mirror is synthetic quartz, the dielectric multilayer film mirror mirror substrate is SF11 Was compared. In the former, light having a wavelength of 300 to 400 nm is reflected and scattered on the back surface of the mirror base material. In the latter, light having a wavelength of 300 to 400 nm is absorbed by the mirror base material.・ No scattering.
[0016]
In this experiment, the amount of stray light of the SO ₂ measuring device was compared in terms of SO ₂ concentration. As a result, the amount of stray light is 11 μg / L (ppb) when synthetic quartz is used for the mirror base material and 3 μg / L when SF11 is used, and the present invention significantly reduces the disturbance due to stray light. Was confirmed. Conventionally, it has been proposed to use eight reflection-type spectroscopic mirrors to reduce stray light. However, by using a spectroscopic mirror based on SF11, four spectroscopic mirrors can be used with high sensitivity. It was confirmed that sufficient performance as a type of SO ₂ measuring device was obtained. Furthermore, SF11 is inexpensive as compared with synthetic quartz, and has also contributed to cost reduction.
[0017]
【The invention's effect】
As described above, according to the fluorescence measurement device of the present invention, it is possible to reduce stray light and perform more accurate measurement.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of a conventional SO ₂ measuring apparatus using an ultraviolet fluorescent method.
[Explanation of symbols]
2 light source cell 4 spectral cell 6 measuring cell 12 xenon flash lamps 16a to 16d reflective spectroscopic mirror 22 fluorescence detector 25 fluorescence

Claims (4)

In a fluorescence measuring device, which reflects the excitation light from the excitation light source on the surface of the spectroscopic mirror, irradiates the sample gas with the reflected excitation light, and detects the intensity of fluorescence generated at that time with a fluorescence detector, A fluorescence measuring device, wherein a mirror substrate of the spectroscopic mirror absorbs light in a wavelength range detected by the fluorescence detector. The fluorescence measuring device according to claim 1, wherein the mirror base material of the spectroscopic mirror is made of optical glass or resin. Fluorescence measuring apparatus is SO ₂ measurement apparatus using ultraviolet fluorescence method, the excitation light source is a xenon flash lamp, wavelength 220nm at the surface of the spectroscopic mirror light is reflected, the mirror substrate of spectroscopic mirror wavelengths below 400nm The fluorescence measurement device according to claim 1, wherein the fluorescence measurement device absorbs light. 4. The fluorescence measuring apparatus according to claim 3, wherein the spectroscopic mirror has a mirror type base material made of optical glass and a dielectric type high reflection coating applied to a surface thereof.

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