JPH0763683A - Fluorescence analyzer - Google Patents

Abstract

(57) [Summary] [Purpose] The purpose is to obtain the fluorescence amount of only the gas to be analyzed from which the influence of interference components has been removed. [Composition] A fluorescence chamber (A) for introducing a sample gas containing a gas to be analyzed and a fluorescence chamber (B) for introducing the sample gas via a mechanism for removing only the gas to be analyzed are provided. The amount of fluorescence generated from only the gas to be analyzed is obtained by subtracting the amount of fluorescence detected from (1) from the amount of fluorescence detected from the fluorescence chamber (A).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultraviolet fluorescence analyzer used for measuring the concentration of SO ₂ (sulfur oxide) in a gas sample such as air or factory exhaust.

[0002]

2. Description of the Related Art A gas sample analyzer for SO ₂ or the like in the atmosphere or factory exhaust is an ultraviolet fluorescence analysis method, that is, when a gas sample is irradiated with ultraviolet rays and SO ₂ gas contained in the gas sample is caused to emit fluorescence. A method of measuring intensity is used.

However, in the gas sample as described above,
When the measurement target is SO ₂ gas, a gas having a property of emitting fluorescence similarly to SO ₂ gas (for example, nitrogen oxides such as nitric oxide and nitrogen dioxide and aromatic hydrocarbons such as ethylbenzene, xylene, naphthalene) is used. Often included. Therefore, when measuring, these gases contain S
It acts as an interference component with respect to the O ₂ gas, and the measurement accuracy is greatly reduced.

Therefore, conventionally, before the gas sample is introduced into the fluorescence chamber for SO ₂ gas analysis, the interference gas is previously removed from the sample gas by a catalyst that reacts with the interference gas component or a substance that adsorbs the interference gas component. A mechanism or a mechanism that inserts a narrow-band bandpass filter before irradiation of the excitation light source or at the input part of fluorescence detection to prevent the excitation of the interference component by the excitation light source or the detection of fluorescence emitted from the interference component. Was adopted.

[0005]

However, in the conventional interference gas removing mechanism, it is often the case that one catalyst or adsorbent can remove only a single interference component, and it is not possible to deal with a plurality of interference components. It made the device complicated and expensive. Moreover, since the adsorbent and the catalyst are consumable items, regular maintenance is required, resulting in an increase in cost.

The excitation of the interference component and the detection of the fluorescence by the bandpass filter are required to prevent the detection of the fluorescence, because the interference component is different from the excitation wavelength of the SO ₂ gas and the fluorescence emission wavelength range. In the case of an interference component in which either or both of the generated wavelength regions are the same, it is difficult to remove with a bandpass filter.

Therefore, an object of the present invention is to provide an apparatus capable of measuring only a gas to be analyzed by a novel mechanism that replaces the interference gas removing mechanism.

[0008]

In order to achieve the above object, the present invention uses a fluorescent chamber (A) for introducing a sample gas containing a gas to be analyzed and a mechanism for removing only the gas to be analyzed. A fluorescence chamber (B) for introducing a sample gas, a light source unit for irradiating both of them with ultraviolet rays, a detection unit for detecting the fluorescence of each of the fluorescence chambers A and B, and a fluorescence detected from the fluorescence chamber (A). And a calculation unit that calculates only the fluorescence amount of the analysis target gas by performing a calculation between the amount and the fluorescence amount detected from the fluorescence chamber (B).

The gas to be analyzed according to the present invention is, for example, S
O ₂ gas may be mentioned, but not limited thereto.
All gases that emit fluorescence upon irradiation with ultraviolet rays, for example, nitrogen oxides such as nitric oxide and nitrogen dioxide, and aromatic hydrocarbons such as ethylbenzene, xylene, and naphthalene can be measured.

The mechanism for removing only the gas to be analyzed may be, for example, an activated carbon packed column, but is not limited to this.

The light source section may be any as long as it can excite the gas to be analyzed, and the type of the excitation light source is not limited to continuous light, pulsed light, continuous pulsed light with a hopper. For example, a lamp that emits ultraviolet rays (xenon,
Zinc, deuterium, etc.) or laser can be used.

The operation unit typically calculates the fluorescence amount of the gas to be analyzed by subtracting the fluorescence amounts obtained from the two types of gas samples. Calculations such as division between fluorescence amounts and excitation light The calculation may be performed while adding the value obtained from the monitor unit and correcting the change in the light amount of the excitation light.

[0013]

According to the present invention, the amount of fluorescence detected from the fluorescent chamber (B) is the amount of fluorescence generated from the sample gas containing the interference component excluding the gas to be analyzed, which is calculated from the gas to be analyzed and the interference component. The amount of fluorescence generated from only the gas to be analyzed can be obtained by reducing the amount of fluorescence generated from the fluorescence chamber (A) containing the amount of fluorescence generated. The amount of fluorescence emitted from the fluorescent chambers (A) and (B) is switched simultaneously or in time series and measured by a single detection system or a plurality of detection systems with uniform characteristics, thereby depending on the interference component and the time change of the detection system. It is possible to obtain the fluorescence amount of the gas to be analyzed without using it.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the structure of an ultraviolet fluorescence analyzer for SO ₂ gas analysis. Reference numeral 1 denotes an excitation light source, which includes a lamp or laser that emits ultraviolet rays, a bandpass filter for selecting excitation light, a condenser lens, and the like.

Reference numeral 4 denotes a fluorescence detection section, which comprises a fluorescence selection bandpass filter, a condenser lens, a photodetector such as a photomultiplier tube or a photodiode, an electric signal conversion section, and an amplification section. The excitation light monitor unit 5 is mainly composed of a photodetector such as a photodiode or a photoelectric tube and an electric signal conversion / amplification unit, and monitors the electric and mechanical fluctuations of the light source. Reference numeral 13 denotes an arithmetic circuit, which calculates the concentration of SO ₂ gas from the electric signals obtained from the fluorescence detection unit 4 and the excitation light monitor unit 5 by arithmetic processing.

Reference numeral 2 denotes a fluorescent chamber (A), which comprises a sample gas introducing section 6, a sample gas discharging section 12, an excitation light source 1, a fluorescence detecting section 4,
It is connected to the excitation light monitor unit 5. 3 fluorescent chambers (B)
Are almost the same as the sample gas introduction part 9, the sample gas discharge part 10,
The excitation light source 1, the fluorescence detection unit 4, and the excitation light monitor unit 5 are connected, but the difference from the fluorescence chamber (A) is that the SO ₂ gas removal device 8 (for example, activated carbon) is always connected to the sample gas introduction unit 9. It is inserted in the route.

The fluorescent chamber (A) and the fluorescent chamber (B) have the same geometric shape. Further, 11-1 to 3 are optical path switching devices (for example, a method by changing the angle of a reflecting mirror), and 11-1 is an excitation light source and a fluorescent chamber (A).
And (B) and 11-2 switch the fluorescence detection unit 4 and the fluorescence chambers (A) and (B), and 11-3 switches the excitation light monitor unit and the fluorescence chambers (A) and (B), respectively. Note that 11-1 to 3 simultaneously switch to the fluorescent chamber (A) or (B).

The sample gas containing SO ₂ gas introduced into the fluorescent chamber (A) 2 from the gas introducing section 6 is irradiated with ultraviolet rays from the excitation light source 1 in the fluorescent chamber. Fluorescence is generated from the sample gas by the irradiation of ultraviolet rays. This is the target SO
_In addition to fluorescence due to the _two gases, that due to interference components is also included. The fluorescence is detected by the excitation light detector 4, and the detection signal is stored and held by the arithmetic circuit 13. This is a detection signal (A).

When a certain period of time has elapsed from the irradiation from the excitation light source 1 and the detection signal (A) is stored and held in the arithmetic circuit 13, the optical path switching devices 11-1 to 3-3 are simultaneously operated to generate the excitation light source 1, The connection between the fluorescence detection unit 4 and the excitation light monitor unit 5 is switched from the fluorescence chamber (A) to the fluorescence chamber (B).

By irradiating the inside of the fluorescent chamber (B) with ultraviolet rays, fluorescence is generated from the sample gas from which the SO ₂ gas has been removed by the SO ₂ gas removing device 8 introduced from the sample gas introducing section. From here, only fluorescence due to interference components is included. The fluorescence is detected by the excitation light detector 4, and the detection signal is stored and held by the arithmetic circuit 13. This is a detection signal (B).

By subtracting the value of the detection signal (B) from the value of the detection signal (A) in the arithmetic circuit 13, a signal due to fluorescence of only SO ₂ gas can be obtained, and the concentration of SO ₂ gas can be accurately measured. Becomes

(Other Embodiments) In the above embodiment, a single excitation / detection system was used by switching between two fluorescence chambers to perform measurement with the same excitation / detection system. Two excitations if the mechanical and electrical properties of the system are the same,
The detection system may correspond to two fluorescent chambers, and the electric signals obtained from the two fluorescent chambers may be compared by an arithmetic circuit.

Alternatively, the fluorescent chamber (A) 2, the SO ₂ removing device 8 and the fluorescent chamber (B) 3 are connected in series as shown in FIG.
Overall, the effects of the present invention can be obtained even if the introduction and discharge routes of the sample gas are combined. In FIG. 2, reference numeral 15 is a path for connecting fluorescent chambers, and the same parts as those in FIG. 1 are denoted by the same reference numerals.

Further, as shown in FIG. 3, a single fluorescent chamber is used, and a sample path 19 containing SO ₂ gas and an SO ₂ removing device 8 are provided.
The path 20 passing through may be connected to the gas sample introduction unit 18 and the fluorescent chamber 16 by the path switching mechanism 17. In this example, the gas sample in the fluorescent chamber 16 is forcibly exhausted from the gas sample exhaust unit 21, and then the path switching mechanism 17 is switched so that both the gas sample containing SO ₂ gas and the gas sample not containing SO ₂ gas are introduced into the fluorescent chamber 16. It is also possible to alternately introduce and store the fluorescence amount obtained from them in the arithmetic circuit 13 and perform the same arithmetic operation as in the above-mentioned embodiment. In the device of FIG. 3, it is easy to reduce the cost of the device and simplify the equipment.

In the case of continuous monitoring, the above operation may be repeated at regular intervals.

[0026]

According to the present invention, it is possible to obtain the fluorescence amount of only the gas to be analyzed from which the influence of the interference component is removed.

Further, since the concentration is measured while continuously comparing the fluorescence of the sample gas containing or not containing the gas to be analyzed, it is possible to prevent an error in the measurement value due to the interference component or the change over time of the excitation light source 1.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of a fluorometer according to an embodiment of the present invention.

FIG. 2 is a modified example of the present invention.

FIG. 3 is a modified example of the present invention.

[Explanation of symbols]

1 ... pumping light source 2,3,16 ... fluorescent chamber 8 ... SO ₂ removal unit 4 ... fluorescence detector 13 ... computing circuit

Claims (1)

[Claims] 1. A fluorescent chamber (A) for introducing a sample gas containing a gas to be analyzed, a fluorescent chamber (B) for introducing the sample gas via a mechanism for removing only the gas to be analyzed, and ultraviolet rays to both of them. Between a light source unit that irradiates the fluorescent chamber, a detection unit that detects the fluorescence of each of the fluorescent chambers A and B, and a fluorescent amount detected from the fluorescent chamber (A) and a fluorescent amount detected from the fluorescent chamber (B). And a calculation unit that calculates only the fluorescence amount of the gas to be analyzed.