JPH0652241B2 - UV Fluorescence Analyzer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultraviolet fluorescence analyzer by an ultraviolet fluorescence analysis method used for measuring the concentration of SO ₂ (sulfur oxide) in the atmosphere, for example. It relates to improved technology.

[Conventional technology]

As an ultraviolet fluorescence analyzer by the above-mentioned ultraviolet fluorescence analysis method, inside the cells at positions corresponding to each other across the fluorescence chamber, an ultraviolet fluorescence irradiation light source and a light source light quantity detector for monitoring the light quantity of the light source, With the arrangement, further, in a direction orthogonal to the optical path from the light source to the light source light amount detector and at positions corresponding to each other across the fluorescent chamber, a fluorescent detector and a recess for stray light attenuation. Some are provided.

In such an ultraviolet fluorescence analyzer, while introducing a sample gas into the fluorescence chamber inside the cell, for example, when the ultraviolet irradiation light source is turned on so as to irradiate the fluorescence chamber with ultraviolet rays having a wavelength of around 215 nm, the The SO ₂ molecules in the sample gas are excited, and the excited SO ₂ molecules emit ultraviolet fluorescent light and return to the ground state repeatedly.

The intensity of the ultraviolet fluorescence emitted at this time depends on the excited SO ₂
Since it is proportional to the number of molecules, that is, the concentration of SO ₂ existing in the fluorescence chamber, it is possible to measure the concentration of SO ₂ in the sample gas based on the detection result of the ultraviolet fluorescence by the fluorescence detector. Of.

[Problems to be solved by the invention]

By the way, the above-mentioned ultraviolet fluorescence is generated in all directions of the fluorescence chamber, but in the conventional ultraviolet fluorescence analyzer, only a part of the ultraviolet fluorescence is detected by the fluorescence detector. However, the amount of the fluorescence signal incident on the fluorescence detector is small, and there is a problem in terms of measurement accuracy of the SO ₂ concentration.

Further, even if the light is simply collected by a mirror or the like, the increase in stray light is orders of magnitude greater than the increase in sensitivity, and thus it has not been put to practical use.

It is an object of the present invention to increase the amount of fluorescence signal incident on a fluorescence detector by adding a simple structure, and to enable SO ₂ concentration to be measured with high sensitivity.

[Means for solving problems]

In order to achieve the above object, the present invention is an ultraviolet fluorescence analyzer by the ultraviolet fluorescence method described at the beginning, in which the concave mirror that reflects the fluorescence emitted in the fluorescence chamber toward the fluorescence detector is concave. The feature is that it is provided in the entrance.

[Action]

According to the above characteristic configuration, among the ultraviolet fluorescent light generated in all directions, the fluorescent light toward the concave portion for stray light attenuation on the side opposite to the fluorescent light detector is reflected toward the fluorescent light detector. , The amount of fluorescent signal incident on the fluorescent detector increases.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a cross section of an ultraviolet fluorescence analyzer.
Is a cast cell made of aluminum whose inner surface is painted black by means of electro-deposition coating, and a straight cylindrical portion 2 having flanges 2a and 2b continuously provided at both ends, and an axial center P _{2 of which} is the cylindrical shape. Part 2
The first and second cylindrical bodies 3 and 4 which are concentric with each other and are orthogonal to the axis P ₁ of the are integrally connected, and the fluorescence chamber 5 is provided around the intersection P of the quantity axes P ₁ and P _2. The holder 7 of the condenser lens 6 which is formed and has its focal point located near the intersection P is formed into the cylindrical portion 2
On one end side and in the vicinity of the fluorescent chamber 5.

Reference numeral 8 denotes, for example, an ultraviolet irradiation light source that irradiates ultraviolet rays having a wavelength of about 215 nm. Rotated chopper
215 nm emitted from the ultraviolet irradiation light source 8 by the rotation of the chopper 10.
By intermittently irradiating the sample gas introduced into the fluorescence chamber 5 with ultraviolet light having a wavelength in the vicinity, the output from the detector can be converted into an alternating current and the background of the detector can be corrected.

Reference numeral 11 denotes a light source light amount detector composed of a photodiode or a photoelectric tube for monitoring the light amount of the light source 8. The holder 12 of the light source light amount detector 11 is attached to the flange 2b on the other end side of the tubular portion 2. There is.

Reference numeral 13 denotes a fluorescence detector, the holder 14 of which is attached to the flange 3a of the first cylindrical body 3, and an O-ring 15 is provided in the path from the fluorescence chamber 5 to the fluorescence detector 13. Is provided with a colored glass filter 16 and a condenser lens 17, and detects the amount of ultraviolet fluorescent light emitted from SO ₂ molecules in the fluorescent chamber 5, and based on the detected fluorescent amount. Then, the SO ₂ concentration in the sample gas is measured.

Reference numeral 18 denotes a lid that closes the opening of the second tubular body 4. The lid 13 and the second tubular body 4 form a concave portion A for attenuating stray light, and the lid 18 has Is provided with a concave mirror 19, and among the fluorescence generated in all directions in the fluorescence chamber 5, the fluorescence directed toward the concave portion A for stray light attenuation on the side opposite to the fluorescence detector 13 is It is designed so as to increase the amount of fluorescent signal which is reflected toward the fluorescent detector 13 and is incident on the fluorescent detector.

Reference numeral 20 denotes a light shield for preventing stray light from entering the fluorescence detector 13. The light shield 20 does not block the light beam emitted from the ultraviolet light irradiation source 8 and transmitted through the condenser lens 6 so as to prevent the light flux from being blocked. It is connected to the fluorescent light inlet 13b of the fluorescent chamber 5 to the fluorescent light detector 13.

Reference numeral 21 is a heater for heating the fluorescent chamber 5, 22 is a sample gas introduction hole, and 23 is a sample gas outlet hole.

In addition, except for the condenser lens 6, the light source light amount detector 11, the colored glass filter 16 and the concave mirror 19, the various holders 9,
Similar to the cell 1, all of the analyzer components such as 12, 14 and the lid 18 and the light shield 20, which are in contact with the sample gas, are painted black by means of electrodeposition coating.

According to the ultraviolet fluorescence analyzer having the above configuration, the light source slit a
Through the ultraviolet irradiation light source 8, ultraviolet rays are irradiated toward the fluorescence chamber 5, and the light amount of the light source 8 is monitored by the detector 11 to calibrate the light source light amount.

Then, the SO ₂ molecule in the sample gas excited by the irradiation of the ultraviolet rays returns to the ground state, at this time, the fluorescence is emitted from the SO ₂ molecule, and a part of the fluorescence is directly detected by the fluorescence detector.
The fluorescent light which is incident on the stray light 13 and is directed to the concave portion A for attenuating the stray light is reflected by the concave mirror 19 toward the fluorescent detector 13 side, that is, the amount of the fluorescent signal is increased and the fluorescent light is incident on the fluorescent detector 13. The fluorescent detector 13 is highly sensitive to SO ₂
The concentration is measured.

By the way, as described above, when a part of the fluorescent light is reflected by the concave mirror 9 toward the fluorescent detector 13, the amount of fluorescent signal increases, while the amount of stray light entering the fluorescent detector 13 also increases. .

However, the focal length and diameter of the concave mirror 19 and further the distance from the concave mirror 19 to the optical axis of the condenser lens 6 are optimally set, and the fluorescence is increased at a ratio larger than the increase ratio of the stray light. The SO ₂ concentration can be measured with high accuracy by increasing the signal amount.

Incidentally, when a concave mirror 19 having a focal length of 25 mm and a diameter of Φ60 mm was attached to the recess A for stray light attenuation and the SO ₂ concentration was measured, the results shown in FIG. 2 were obtained.

Here, 1 is the dimension of the condenser lens 6 from the optical axis to the concave mirror 19, and in the experiment, the dimension l is changed in units of 10 mm. Further, Z is an output from the fluorescence detector 13 based on stray light (background) when zero gas is introduced into the cell 1, and S is when sample gas containing SO ₂ component is introduced into the cell 1. The output from the fluorescence detector 13 based on the incident light of, and in the ultraviolet fluorescence analyzer used in this experiment, it is possible to separate the concave mirror 19 from the optical axis of the condenser lens 6 by 40 mm. It can be seen that the condition is favorable.

By the way, the measurement result of SO ₂ concentration performed under the same conditions as the above experiment by removing the concave mirror 19 from the ultraviolet fluorescence analyzer used in this experiment, was compared with the experimental result when the concave mirror 19 was attached. Then, assuming that each of Z and S-Z and (S-Z) / Z when the concave mirror 19 is not attached is 1.00, when the concave mirror 19 is attached, Z is 0.
88, S-Z is 2.49, and (S-Z) / Z is 2.83, and it is easy to see how the attachment of the concave mirror 19 is excellent in terms of measurement.

From the result that Z is 0.88, it seems that the addition of the concave mirror 19 leads to the reduction of the incident amount of stray light. This is because the light from the ultraviolet irradiation light source 8 is directly In order to prevent the fluorescent detector 13 from entering the fluorescent detector 13 as stray light, conventionally, the L-shaped plate is the entrance of the fluorescent light to the fluorescent detector 13 and the light source 8 side with respect to the fluorescent chamber 5. In contrast to the conventional light-shielding member, it is provided in the configuration of the present invention as the cylindrical light-shielding member 20 at the fluorescence inlet portion b to the fluorescence detector 13. is there.

That is, in the stairs before the concave mirror 19 is attached, the light shield 20 which has been L-shaped in the past is changed to a cylindrical one, and SO
_{2 When the} concentration measurement experiment was conducted, the result that the output of Z decreased was obtained, and the output of Z when the concave mirror 19 was attached was larger than the output of Z at this time. Therefore, in the ultraviolet fluorescence analyzer with a concave mirror used in the above experiment, if the cylindrical light shield 20 is an L-shaped light shield as in the conventional case, the output of Z is larger than that without the concave mirror 19. Is supposed to be 1.00 or more.

However, when the concave mirror 19 is attached, the amount of fluorescent signal is increased at a ratio larger than the increase ratio of stray light, so it should be attached regardless of whether the light shield 20 is cylindrical or L-shaped. Considering the focal length, diameter, etc. of the concave mirror 19, the concave mirror is located near the maximum output value of (S−Z) / Z.
By providing 19, it is possible to greatly improve the measurement accuracy of the SO ₂ concentration.

〔The invention's effect〕

As described above, the present invention is a concave mirror that reflects the fluorescence emitted by SO ₂ molecules toward the fluorescence detector in the fluorescence chamber,
By providing in the recess for stray light attenuation at a position corresponding to the fluorescence detector across the fluorescence chamber, among the ultraviolet fluorescence generated in all directions, conventionally it was wasted. , Fluorescence directed toward the recess for stray light attenuation on the side opposite to the fluorescence detector can also be made incident on the fluorescence detector, and is then made incident on the fluorescence detector. The increase in the amount of fluorescent signal has made it possible to measure the SO ₂ concentration with high accuracy.

[Brief description of drawings]

FIG. 1 is a sectional view of an ultraviolet fluorescence analyzer showing an embodiment of the present invention, and FIG. 2 is a graph of experimental results. DESCRIPTION OF SYMBOLS 1 ... Cell, 5 ... Fluorescence chamber, 8 ... Ultraviolet irradiation light source, 11 ... Light source light intensity detector, 13 ... Fluorescence detector, 19 ... Concave mirror, A ... Recessed part for attenuating stray light.

Claims (1)

[Claims] 1. An ultraviolet irradiation light source and a light source light amount detector for monitoring the light amount of the light source are arranged inside the cells at positions corresponding to each other across the fluorescent chamber, and further, from the light source to the light source. In a UV fluorescence analyzer comprising a fluorescence detector and a recessed portion for stray light attenuation, provided at positions corresponding to each other across the fluorescence chamber in a direction orthogonal to the optical path leading to the light amount detector, An ultraviolet fluorescence analyzer, characterized in that a concave mirror for reflecting fluorescence emitted from a fluorescence chamber toward a fluorescence detector is provided in the concave portion.