JPH10132741A - Technique and apparatus for measurement of trace component by using laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the concentration of a trace component existing in a substance by receiving a pulsed laser beam, a component in the substance into a plasma, and correcting a fluorescent intensity which is generated by exciting the laser beam with the component composition and plasma temperature existing in a plasma part. SOLUTION: A pulsed laser 1 for plasma is condensed, by using a lens 2, in a measuring field through a purge optical window, and a gas, a liquid and a solid substance which exist are changed into a plasma. In synchronization with the pulsed laser 1 for plasma, the output of a pulsed laser 3 for component excitation is incident on the plasma via a mirror 4, a beam combiner 5 and a lens 2. Fluorescence which is emitted by an excited component to be measured is condensed by a lens 7 via a mirror 6 so as to be divided into two directions by a beam splitter. Plasma light is incident on a spectroscope 9 so as to be detected by a CCD camera 10. Fluorescence which is emitted by the measured component to be measured is detected by a detector 11. A computer 12 corrects a fluroescent intensity on the basis of a component composition and a plasma temperature in the measuring field.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for measuring trace components using a laser and an apparatus therefor. More specifically, the present invention relates to measurement of trace components such as Na, Cl, and Mg contained in gases, liquids, and solid substances.

[0002]

2. Description of the Related Art A conventional trace component measuring apparatus is shown in FIG.
As shown in the figure, a solid sample in a measurement field is sampled by a sampler 01, and the sample is analyzed by an analyzer 02 (X
Components were analyzed with a line analyzer, a chemical analyzer, and the like.

As a method for detecting a trace component using a laser,
The following methods have been proposed. (1) A method in which laser light is focused on a gas, liquid, or solid substance, the components in the substance are turned into plasma, the plasma emission is detected, and the concentration of the trace component is measured (hereinafter, this method uses a laser. Conventional method 1).

(2) A method in which a laser beam having a wavelength corresponding to the electron energy difference of a component to be detected is incident, the intensity of fluorescence emitted from the excited component to be measured is detected, and the concentration of a trace component is measured (hereinafter, referred to as a method). This method is referred to as a conventional method 2 using a laser.)

(3) The first laser beam is focused on a gas, liquid, or solid substance, the target component in the substance is atomized (including plasma), and the electron energy of the component to be detected after a predetermined time A method in which a second laser beam having a wavelength corresponding to the difference is incident, the fluorescence intensity emitted from the excited measurement target component is detected, and the concentration of the trace component is measured (hereinafter, this method is referred to as a conventional method 3 using a laser). ).

[0006]

The conventional method shown in FIG. 2 requires the following steps. 1) Collect a sample from the measurement site. 2) Transport sample to component analyzer. 3) The sample is analyzed by the component analyzer 02.

For this reason, it takes a considerable time (10 to 120 minutes) until a sample is collected from the measurement field and the analysis result is obtained.
Need. In addition, in the sampling pipe, there is a problem that a detection component is mixed or a sampling substance stays in the sampling pipe and concentration of the detection component occurs.
There was a problem that instrument management and installation locations were severely restricted. In the case of automation, a transport device for sample samples, a transport pipe, a facility for installing the device, and the like are required, which has a disadvantage that the device becomes expensive.

Further, in the conventional measurement using a laser, there are a method using only a laser beam for plasma generation and a method using a laser beam having a wavelength corresponding to the electron energy difference of a component to be measured. ) The detection limit concentration cannot be reduced by the conventional method 1 using a laser. (2) In the conventional method 2 using a laser, the influence of the combined state of the components is large. Therefore, the laser wavelength must be changed for each combined state. In addition, the device becomes complicated, and the measurement may not be possible.

For example, when Na is detected, NaCl and NaSO ₄ change the energy level of Na due to chemical bonding, so that the excited wavelength changes, and it becomes impossible to excite simultaneously with a single wavelength. As an example, for Na, the excitation wavelengths are 330 nm, 568 nm, 589 nm,
While 233 nm and the like exist for Cl, 193 nm exists for NaCl.
nm or the like is the excitation wavelength.

[0010] Further, in this method, quantitative measurement becomes difficult. Generally, the fluorescence intensity I emitted by the laser-excited component
And its component concentration n have the following relationship. I = K · n / Q (1) where K is a proportionality constant and Q is a quenching speed.
Q is represented by the following equation as a function of the composition of the measurement field and the temperature.

[0011]

(Equation 1)

Where X _i is the concentration of the i component and σ _i (T) is i
The impact cross section of the component, which is a function of the temperature of the measurement field.
In order to obtain the component concentration n from the fluorescence intensity I emitted from the component to be measured from the formulas (1) and (2), information on the component composition and the temperature of the field to be measured is required. It is difficult, and it becomes difficult to quantify the components to be measured. In the conventional method 3 using a laser, as described in the method (2), the problem of the quenching speed occurs, and there are disadvantages such as difficulty in performing quantitative measurement.

[0013]

FIG. 4 is a schematic diagram of the means used in the present invention. First, as shown in FIG. 4A, the first pulsed laser light is focused on any one of a gas, a liquid, and a solid substance, the components in the substance are turned into plasma, and the substance in the plasma is turned into atoms. .

Next, as shown in FIG. 4B, after a certain period of time from the generation of the plasma, a second laser beam having a wavelength corresponding to the electron energy difference of the component to be detected,
A component to be detected is incident on the laser-induced plasma to excite the laser.

[0015] The plasma light generated by the first laser light irradiation is detected, the component composition and the plasma temperature existing in the plasma part are identified, and the intensity of the fluorescent light emitted by the measurement object excited by the second laser light irradiation is detected. Is detected using a photodetector. The concentration of the trace component present in a gas, liquid, or solid substance is measured by correcting the intensity of the fluorescence emitted from the component to be measured by the composition of the component present in the plasma part and the plasma temperature.

[Operation] In the conventional method, the collection of a sample, transportation to an analyzer, and the like have been a major obstacle to real-time measurement of trace components.
In addition to being able to perform situ measurement, it is not necessary to transport a sample sample, so that the cost of the apparatus can be reduced.

Further, in the present invention, since the sampling pipe is not used, there is no mixing of the detected component in the sampling pipe or the concentration of the detected component due to the stagnation of the sampling substance in the sampling pipe, and the disadvantages of the conventional method are eliminated. It is possible to do.

Also, there is a problem in the measurement using the conventional laser. (1) The detection limit concentration cannot be reduced by the conventional method 1 using the laser. (2) The conventional method 2 using the laser.
When the chemical bond changes, the excited wavelength changes, and it becomes impossible to excite at a single wavelength at the same time, and it is difficult to quantify. (3) It is difficult to quantify by the conventional method 3 using a laser. According to the present invention, first, since the temperature of a local place is raised to 10,000 to 20,000 ° C. by the plasma laser, almost all chemical species are in an atomic state, and the excitation wavelength does not change due to the bonding state.

Since a laser beam having a wavelength corresponding to the electron energy difference with respect to the measurement molecules converted into plasma is incident, the detection sensitivity can be greatly improved (about 3 to 5 digits) as compared with the case where a plasma laser is used. Becomes Also, by measuring the plasma emission, the component composition of the measurement field (plasma field) and the plasma temperature can be obtained. Therefore, the quenching rate can be calculated using the equation (2), and the measurement component can be calculated from the equation (1). Can be quantified.

FIG. 5 shows an example of plasma emission. The component composition (concentration) is calculated from the ratio of the emission intensity from each component. In addition, the ratio of the emission intensity of different wavelengths caused by the same component to the component in which the emission appears at a plurality of wavelengths (the emission of N in the diagram) has a temperature dependency (the emission in the diagram) The intensity of the plasma can be calculated from the ratio of the intensity of the light emission to the intensity of the light emission 2.

[0021]

FIG. 1 shows an apparatus according to a first embodiment of the present invention. As shown in FIG. 1, a pulse laser 1 for plasma is focused on a measurement field through a purge optical window using a lens 2, and a gas, a liquid, and a solid substance existing in the measurement field are turned into plasma. The pulse laser for plasma 1 is a laser for generating plasma induced by a laser in a measurement field.

In synchronization with the plasma pulse laser, the output of the component excitation pulse laser 3 enters the laser-induced plasma via the mirror 4, the beam combiner 5 and the lens 2. The component excitation pulse laser 3 is a laser that oscillates at a wavelength corresponding to the excitation wavelength of the measurement component in the substance.

The fluorescence emitted from the measurement component excited by the plasma emission and the component excitation pulse laser beam is condensed by the lens 7 via the mirror 6. Each light is split in two directions by a beam splitter 8. The plasma light enters the spectroscope 9 and is detected by the CCD camera 10. Fluorescence emitted by the measurement component is detected by the photodetector 11.

Each signal is transferred to the computer 12 and is measured from a plasma emission signal based on a plasma emission signal.
And the plasma temperature are obtained, the fluorescence intensity is corrected based on the information, and the concentration of the trace component present in the measurement field is calculated. Oscillation of pulse laser 1 for plasma and pulse laser 3 for component excitation, CCD camera 10, photodetector 11
Are synchronized by the synchronization line 13.

Examples of the wavelengths of the plasma laser and the component excitation laser are shown below. For example, as a plasma laser wavelength example, 1064 nm (basic wave of YAG laser), 5
32 nm (second harmonic of YAG laser), 355 nm
(Third harmonic of YAG laser), as an example of the component excitation laser wavelength,
Either 8 nm or 589 nm;
nm. By changing the wavelengths of the pulse laser for plasma and the pulse laser for component excitation depending on the measurement object, it is possible to measure a wide range of objects and components.

FIG. 3 shows an apparatus according to a second embodiment of the present invention.
Shown in The present embodiment is characterized in that plasma emission and fluorescence emitted by a measurement component are detected by the same CCD camera 10. Other configurations are the same as those of the above-described first embodiment, and provide similar effects.

[0027]

As described above in detail with reference to the embodiments, according to the present invention, in-situ measurement of trace components such as Na, Cl and Mg contained in gas, liquid and solid substance. It is possible to perform safe operation of various plants and estimate the remaining life by automation and high accuracy of measurement.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a trace component measuring device of an embodiment according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a trace component measuring device using a conventional method.

FIG. 3 is a configuration diagram of a second embodiment of the present invention using one detection device for plasma emission and fluorescence of a measurement component.

FIG. 4 is a graph showing the temperature dependence of a plasma emission spectrum and an emission intensity ratio.

FIG. 5 is a schematic diagram of the measurement principle of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pulse laser for plasma 2 Lens 3 Pulse laser for component excitation 4 Mirror 5 Beam combiner 6 Mirror 7 Lens 8 Beam splitter 9 Spectroscope 10 CCD camera 11 Photodetector 12 Computer 13 Synchronization line 01 Sampler 02 Analyzer (X-ray analyzer , Chemical analyzer, etc.)

Claims (2)

[Claims] When detecting a trace component contained in a gas, liquid, or solid substance, a first laser beam is focused on the gas, liquid, or solid substance, and the components in the substance are turned into plasma. A second laser beam having a wavelength corresponding to the electron energy difference of the component to be detected is incident on the plasma induced a certain time after generation, and the component to be detected present in the plasma is laser-excited. Detecting the plasma light generated by the first laser light irradiation, identifying the component composition and the plasma temperature present in the plasma portion, and detecting the fluorescence intensity emitted by the measurement target component excited by the second laser light irradiation. By detecting with a detector and correcting the fluorescence intensity emitted by the component to be measured with the component composition and plasma temperature present in the plasma section, gas, liquid,
A trace component measurement method using a laser, which comprises measuring the concentration of a trace component present in a solid substance. 2. A measuring device for detecting a trace component contained in a gas, a liquid, or a solid substance, wherein the plasma laser outputs a first laser beam for converting the gas, liquid, or solid substance into a plasma. A light source and an optical system for condensing the laser light on the substance; and a second laser light having a wavelength corresponding to the electron energy difference of the component to be detected and laser-exciting the component to be detected present in the plasma. A laser light source for component excitation that is output after a certain time from generation and an optical system that causes the laser light to enter the induced plasma, and detects plasma light generated by the first laser light irradiation,
Means for identifying the component composition and the plasma temperature present in the plasma portion, and detecting the fluorescence intensity emitted by the measurement target component excited by the second laser beam irradiation using a photodetector,
Means for correcting the fluorescence intensity emitted by the component to be measured with the component composition and the plasma temperature present in the plasma portion, and measuring the concentration of a trace component present in a gas, liquid, or solid substance. Trace component measurement device using