JPH11183385A - Fluorescence analyzer meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluorescence analyzer water capable of measuring the content of sulfur dioxide without interfering with nitrogen monoxide even if nitrogen monoxide is contained in the measured gas. SOLUTION: The light from an exciting light source 2 in a light source chamber 1 passes through the gas filter 4 of an exciting wavelength selection section 3, the light near the wavelengths 214 nm and 226 nm is selectively absorbed j the nitrogen monoxide gas sealed in a gas filter 4, and the light of the wavelength 250 nm or above is absorbed by an optical filter 5. The sulfur dioxide in the sample gas is excited by this light and emits fluorescence, however the nitrogen monoxide emits no fluorescence because the light of the wavelengths 214 nm and 226 nm for excitation is lacking, only the fluorescence by the sulfur dioxide reaches a detector 10 in a detection section 9 as the light of the wavelength 300-400 nm through the optical filter 8 of a fluorescence wavelength selection section 7, and the fluorescence intensity of the sulfur dioxide is measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorescence spectrometer used for measuring the concentration of sulfur dioxide and the like in factory exhaust gas resulting from combustion of fuel containing sulfur compounds such as air and coal and petroleum.

[0002]

2. Description of the Related Art Among the methods for analyzing sulfur dioxide gas in the atmosphere and factory exhaust, there are light absorption analysis and fluorescence analysis as analysis using light. In the fluorescence analysis method, excitation light such as ultraviolet light is applied to a sample gas. And the intensity of fluorescence emitted when the sulfur dioxide molecules contained in the sample gas return from the excited state to the ground state is measured to measure the sulfur dioxide concentration.

[0003] Generally, molecules are brought into an excited state by absorption of light, and therefore, the wavelength of the exciting light to be irradiated coincides with the light absorption wavelength of the substance. The excitation light wavelength distribution for emitting this fluorescence is called an excitation spectrum, and the absorption wavelength due to the change in the electronic state of the molecule usually appears strongly in the ultraviolet region, so the excitation wavelength is selected from the ultraviolet region. Although the wavelength exhibiting the highest intensity of the excitation spectrum is the most efficient, various other conditions also need to be considered. On the other hand, the molecules in the excited state lose energy in a short time and return to the ground state, but this lost energy is emitted as light (fluorescence). This fluorescence is also distributed in a certain wavelength region, and the energy lost as a fluorescence spectrum is used for other than light emission (fluorescence), so the fluorescence spectrum has a wavelength longer than the excitation wavelength (small energy). .

As described above, in order to measure the fluorescence of a substance, a wavelength in the ultraviolet region is selected, the substance is irradiated as excitation light, and only the wavelength of a fluorescence spectrum region in a longer wavelength region different from the excitation light is detected. The fluorescence spectrum intensity of the substance is measured. Specifically, a fluorescence analyzer as shown in FIG. 2 is used, and a wavelength of 2 is used as an excitation wavelength for exciting sulfur dioxide molecules.
Ultraviolet light in the vicinity of 20 nm is selected, and as the excitation light source 2 therefor, for example, a zinc lamp, a deuterium lamp, a xenon lamp or the like is used. An excitation wavelength selector 3 is provided to extract light having a wavelength of 220 nm from these excitation light sources 2. When an emission line spectrum light source is used, a glass filter or an interference filter having a relatively large half width is used as the optical filter 5, In the case of a continuous spectrum light source, only a light of an excitation wavelength is irradiated on a sample using a narrow band interference filter.

The fluorescence spectrum of a sulfur dioxide molecule has a wavelength of 2
In the wavelength range of 50 nm to 400 nm, a fluorescence wavelength selector 7 is provided to detect the light wavelength in this region, and only a specific fluorescence spectrum region is detected using a glass filter and an interference filter as the optical filter 8.

[0006]

The conventional fluorescence spectrometer is constructed as described above, but the most important problem in performing fluorescence measurement is how to detect only the fluorescence spectrum of the substance to be measured. It is in.

[0007] Basically, although a fluorescence analysis method capable of making an excitation spectrum and a fluorescence spectrum different depending on a substance has higher selectivity (ability to measure only a target substance) than other analysis methods, a sample is measured. If the target substance is not a single substance,
When the excitation wavelength and the fluorescence spectrum are selected and measured by ordinary optical means (a filter, a spectroscope, or the like), there is a sufficient risk that fluorescence due to substances other than the substance to be measured is detected. It is naturally conceivable to install a device for removing these foreign substances as a pretreatment, but it is difficult to adopt it in view of the problems of compactness and cost of the device as a fluorescence analyzer. When measuring sulfur dioxide molecules in the gas using air or combustion gas as a sample gas, a wavelength around 220 nm is selected as the excitation light as described above, but when the sample gas contains nitric oxide, There is. This nitric oxide has a narrow spot-like absorption wavelength range around 214 nm and 226 nm, and is extremely close to the excitation light wavelength of 220 nm for sulfur dioxide. However, if they are so close together, it is difficult to separate them, and since the distribution of the fluorescence spectrum is originally broad, the fluorescence spectra of both overlap, so that the fluorescence of nitric oxide is also measured in the end. , And there is a problem that an interference effect is exerted on the measurement of sulfur dioxide as a target component, resulting in a measurement error.

The present invention has been made in view of such circumstances, and provides a fluorescence spectrometer capable of measuring sulfur dioxide even when nitrogen monoxide is contained in a sample gas. With the goal.

[0009]

In order to achieve the above object, a fluorescence spectrometer according to the present invention is provided with an excitation wavelength selection section in an optical path between a light source chamber and a sample chamber, and the selection section includes a nitric oxide gas. Is provided with a gas filter in which is sealed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the fluorescence analyzer of the present invention will be described with reference to FIG.

In FIG. 1, reference numeral 1 denotes a light source chamber in which a xenon lamp is installed as an excitation light source 2. Excitation light source 2
Is not limited as long as it can excite the gas to be analyzed, and the type thereof is not limited, such as continuous light, pulsed light, or continuous light pulsed by a chopper. For example, a lamp (zinc, deuterium, or the like) that emits ultraviolet light or a laser can be used. Numeral 3 denotes an excitation wavelength selection unit, in which a gas filter 4 in which nitric oxide gas is sealed and an optical filter 5 are provided. As the optical filter 5, a long wavelength cut filter is used as a filter that transmits only the excitation wavelength and does not transmit the fluorescence spectrum. Alternatively, for example, wavelength 2
A narrow-band bandpass interference filter having a half width of about 6 nm centered at 20 nm is used.

Reference numeral 6 denotes a sample chamber, which is formed of, for example, a hollow cylindrical body, and has an opening provided at a place where it is connected to the excitation wavelength selecting section 3.
3 is inserted. The sample chamber 6 has a sample introduction section 11.
And a sample discharging unit 12. Reference numeral 7 denotes a fluorescence wavelength selection unit in which an optical filter 8 is installed. The optical filter 8 is, for example, a filter that transmits only the wavelength region of 300 to 400 nm. An opening is provided in the sample chamber 6 where the fluorescence wavelength selection unit 7 is connected. The fluorescent condenser lens 14 is fitted.

Reference numeral 9 denotes a detection unit formed of a hollow cylindrical body, and a photomultiplier tube as a detector 10 is installed therein.
The detector 10 may be anything that can detect the wavelength of the fluorescence spectrum, and for example, a phototube, a photoconductive cell, a photodiode, or the like can be used.

In this apparatus, the process of detecting fluorescence is performed as follows. A sample gas is sealed in the sample chamber 6 from the sample introduction unit 11. The light emitted from the xenon lamp used as the excitation light source 2 in the light source chamber 1 is white light including a wide wavelength of 200 nm or more. This light first passes through the gas filter 4 of the excitation wavelength selection unit 3, but has a wavelength of 2 due to nitric oxide gas sealed in the gas filter 4.
Light near 14 nm and 226 nm is selectively absorbed, and light with a wavelength of 250 nm or more is absorbed by the long wavelength cut filter used as the optical filter 5. Therefore, the wavelength range of the light applied to the sample gas in the sample chamber 6 is light having a wavelength of 200 to 250 nm and light lacking the wavelengths of 214 nm and 226 nm due to absorption of the nitric oxide gas.

This light excites sulfur dioxide in the sample gas and emits fluorescence, but nitric oxide does not emit fluorescence due to lack of excitable wavelengths of 214 nm and 226 nm, and emits fluorescence due to sulfur dioxide. Only the wavelengths of 300 to 400 are determined by the optical filter 8 of the fluorescence wavelength selection unit 7.
The light reaches the detector 10 in the detection unit 9 as light of nm, and the fluorescence intensity of sulfur dioxide is measured.

In the above embodiment, the gas filter 4 and the optical filter 5 are separated from each other. However, when the window material of the gas filter 4 is made of the material of the optical filter 5, or when the optical filter 5 is an interference filter, The gas filter 4 and the optical filter 5 can be integrated by giving the role of the optical filter 5 by performing a thin film treatment on the window plate of the gas filter 4 or the like.

In FIG. 1, the condenser lenses 13 and 1
Although the lens 4 is fitted into the opening of the sample chamber 6, these lenses satisfy the optical imaging relationship in the optical path between the excitation light source 2 and the sample chamber 6 and between the sample chamber 6 and the detector 10. Can be arranged at any position.

[0018]

The fluorescence spectrometer of the present invention is constructed as described above, and a gas filter containing nitrogen monoxide gas is installed in an excitation wavelength selection section for selecting an excitation wavelength, so that the monoxide is contained in the sample gas. Even if nitrogen is contained, it does not excite nitric oxide, so that only the fluorescence of sulfur dioxide can be measured.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of a fluorescence analyzer of the present invention.

FIG. 2 is a diagram showing a conventional fluorescence analyzer.

[Explanation of symbols]

 2 Excitation light source 3 Excitation wavelength selector 4 Gas filter 5 Optical filter 6 Sample chamber 7 Fluorescence wavelength selector 8 Optical filter 10 Detector

Claims (1)

[Claims] A sample chamber into which a sample gas is introduced, a light source chamber in which an excitation light source for irradiating the sample chamber with excitation light is provided, and a detection unit for detecting fluorescence emitted from the sample chamber. 1. A fluorescence spectrometer, comprising: an excitation wavelength selector provided in an optical path between a light source chamber and a sample chamber; and a gas filter filled with nitric oxide gas in the selector.