JP2002005832A - Method and apparatus for analysis of concentration - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a concentration analyzer, with which a component in a trace amount contained in water, is monitored directly and continuously. SOLUTION: An aqueous solution in a sample cell 1 is irradiated with an infrared pulse laser beam. Plasma light is generated in the aqueous solution. The plasma light is made incident on a spectroscope 40, whose central wavelength is set near the spectrum wavelength of an element to be analyzed. By the spectroscope 40, the plasma light is separated into the emission spectral line of the element to be analyzed and a spectrum in a wavelength range which does not contain the spectral line. By keeping the delay time from the irradiation time of a laser beam 3 through the use of an opening and shutting mechanism 7 arranged at the front of a light-intensity measuring device 8, the intensity of the emission spectral line of the element to be analyzed and a light intensity in the wavelength range which does not contain the spectral line are measured by the light-intensity measuring device 8 to be converted into an electrical signal. The signal intensity, which corresponds to the light intensity of the emission spectral line of the element to be analyzed, is divided by a signal intensity which corresponds to the light intensity, in the wavelength range which does not contain the spectral line of the element to be analyzed. On the basis of its divided value, the concentration of the element, to be analyzed, in the aqueous solution is found.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concentration analysis method and a concentration analysis apparatus for continuously measuring the elements contained in an aqueous solution in a non-contact manner. The present invention relates to a concentration analysis method and a concentration analysis device for continuously monitoring the concentration of Na as a seawater component for leak monitoring.

[0002]

2. Description of the Related Art Conventionally, in a power plant, a condensate salt detecting device for detecting a seawater leak from an acid conductivity of the condensate has been used for monitoring a seawater leak of a condenser.

[0003]

However, this device indirectly detects seawater leakage by acid conductivity.
It does not directly measure seawater components.

In addition, during inspections and during shutdowns, dirt during operation and carbon dioxide in the atmosphere dissolve into the condensate, producing the same anions as chloride ions. At present, the presence of seawater leaks is checked by manual analysis using an ion chromatograph every time.

Therefore, a method for directly and continuously monitoring a trace amount of seawater components leaking to the condensate has been required.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to respond to such a strong demand, and when a high-power laser is applied to a liquid, a part of the liquid becomes plasma and the contained components emit light. Is used to measure the Na concentration in the condensate from the intensity of the Na emission spectrum when the condensate flowing through the sample cell is irradiated with a laser from the outside and the emission intensity of the water.

According to a first aspect of the present invention, an aqueous solution in a sample cell is irradiated with a laser beam to generate plasma, and the spectrum of the plasma beam is analyzed to determine the concentration of an element to be analyzed in the aqueous solution. In the concentration analysis method, a spectroscope for dispersing the plasma light is set in advance to have a center wavelength near the spectral wavelength of the element to be analyzed, and the spectroscope analyzes the plasma light generated in the sample cell. The laser light is separated into an emission spectrum line of the target element and a spectrum in a wavelength range not including the spectrum line, and the intensity of the emission spectrum line of the analysis target element and the intensity in the wavelength range not including the spectrum line are determined by the laser light. After a delay time from the irradiation time, the light intensity of the emission spectrum line of the element to be analyzed is set to a range not including this spectrum line. And wherein the value obtained by dividing the light intensity to determine the concentration of the analyte element in the aqueous solution that.

According to a second aspect of the present invention, in the concentration analysis method of the first aspect, when measuring the light intensity of the spectrum, first, a noise signal for each wavelength of the light intensity measuring device in a state where the laser light is cut off. The intensity is measured by adding the number of times set in advance, and this is repeated the number of times set in advance to obtain the average value of the signal intensity for each wavelength, and the average value is calculated as the noise signal intensity at each wavelength. Then, irradiate a laser beam, add the signal intensity for each wavelength of the light intensity measuring instrument by the preset number of times, measure, repeat this for the preset number of times, and repeat for each wavelength. An average value of signal intensities is measured for each wavelength, and a value obtained by subtracting the noise signal intensity from the averaged signal intensity at this time is used as a light intensity signal value at each wavelength.

According to a third aspect of the present invention, in the concentration analysis method according to any one of the first and second aspects, when measuring the Na concentration, the light intensity of the sodium spectral line used for the concentration measurement is a sodium spectral line. 588.995 is
The signal intensity at 589.592 nm, which is a sodium spectrum line, is measured at the same time, and only the measured value when the relationship between the signal intensity at 588.995 nm and the signal intensity at 589.592 nm is close to 2: 1 is valid. It is characterized by data.

According to a fourth aspect of the present invention, an aqueous solution in a sample cell is irradiated with a laser beam to generate plasma in the aqueous solution, and a spectrum analysis of the plasma light is performed to analyze an element to be analyzed in the aqueous solution. In a concentration analyzer for analyzing the concentration of the sample, the center wavelength is set in advance in the vicinity of the spectral wavelength of the element to be analyzed, and the plasma light generated in the sample cell includes the emission spectral line of the element to be analyzed and this spectral line. A spectroscope that separates the spectrum into a spectrum having no wavelength range, and an optic that is disposed between the sample cell and the slit of the spectroscope where the plasma light is incident, and that blocks a higher-order spectral spectrum wavelength overlapping the vicinity of the emission spectrum wavelength. A filter, a light intensity measuring device for measuring the intensity of the plasma light separated by the spectroscope, and at least the light intensity measuring device An opening / closing mechanism arranged in front of a light receiving surface and controlling the passage of the plasma light, the intensity of the emission spectrum line of the element to be analyzed, with a delay time from the irradiation time of the laser light, and including the spectrum line And control means for controlling the opening / closing mechanism so as to measure the intensity in a wavelength range which does not exist.

According to a fifth aspect of the present invention, in the concentration analyzer of the fourth aspect, the slit for entering the plasma light into the spectroscope allows a change in the focal point of the laser light applied to the sample cell. As a result, the laser light optically extends in substantially the same direction as the optical axis of the laser light.

According to a sixth aspect of the present invention, in the concentration analyzer according to any one of the fourth and fifth aspects, a light receiver in which a light receiving element is arranged on an XY coordinate system is used as the light intensity measuring device. The X-axis direction light-receiving element array is set to detect the wavelength range of the spectrum of the spectroscope, and the Y-axis direction light-receiving element array is set so that the sum of the signals is measured for the signal intensity at each wavelength. Features.

In the above-described invention, in the concentration analysis method and apparatus, the emission spectrum signal intensities of several kinds of samples having known concentrations are measured in advance to obtain a calibration curve of the concentration and the signal intensity. The concentration may be calculated by measuring the emission spectrum signal intensity of the aqueous solution of the above.

In the above-mentioned concentration analysis method, the intensity of the emission spectrum line of the element to be analyzed and the intensity in the wavelength range not including the spectrum line are measured by a light intensity measuring instrument and converted into electric signals. The concentration of the element in the aqueous solution is determined by dividing the signal intensity corresponding to the light intensity of the emission spectrum line of the element to be analyzed by the signal intensity corresponding to the light intensity in the wavelength range not including the spectrum line of the element to be analyzed. Can be estimated using a linear expression or a quadratic expression.

In the above-described concentration analysis method and apparatus, the opening / closing mechanism disposed in front of the light intensity measuring device cuts off or passes light emission from the plasma, and waits several hundred nanoseconds after laser irradiation for several microseconds. The emission spectrum intensity of the plasma may be measured in the above time width.

In the above-described concentration analysis method and apparatus, the measurement of the emission spectrum intensity by laser irradiation may be performed after a predetermined time required for stabilizing laser oscillation elapses.

In the above-described concentration analysis method and apparatus, the center wavelength of the spectroscope is set near the wavelength of the emission spectrum line of the element to be analyzed, and the higher-order spectrum of plasma light incident on the spectroscope is cut off. An optical filter may be installed.

In the above-described method and apparatus for analyzing concentration, the sample cell and the lens are housed in a case made of a light-shielding member, and a part of the light-shielding member is provided with a hole for receiving laser light and a hole for taking out emission of plasma. An optical filter that selectively transmits laser light is provided in the entrance hole, and an optical filter that blocks laser light is provided in the plasma light extraction port. This is advantageous because intrusion of laser light and leakage of laser light to the outside can be prevented.

In the above-described concentration analysis method and apparatus, if the laser irradiation window of the sample cell, the laser condensing lens, and the laser light transmission filter are arranged at an angle of several degrees with respect to the laser optical axis, optical components can be used. The reflected laser light does not return to the laser oscillator.

In the above-described concentration analysis method and apparatus, when the inside of the sample cell is inclined upward, the sample is injected from below the sample cell and discharged from above the sample cell. At the laser focus point, the error decreases because the aqueous solution flows upward from below and no air bubbles stay in the sample cell.

In the above-described concentration analysis method and apparatus, if a bypass pipe and a flow path switching valve, each of which is provided with a filter for capturing a solid substance, are provided in the middle of the pipe in front of the sample inlet of the sample cell, the sample may be suspended. When a suspended substance is contained, the sample is injected into the sample cell through the filter, and the suspended substance can be removed.

In the above-described concentration analysis method and apparatus, the time interval for performing the analysis, the number of times of the analysis, the number of times of measuring the noise of the light intensity measuring device, the number of times of adding the emission spectrum intensity, the average number of times of the emission spectrum signal intensity, and By inputting the wavelength of the emission spectrum line of the element used for analysis, the wavelength range not including the spectrum of the target element, and the coefficient for obtaining the concentration from the signal intensity individually, the instrument can be optimized by specifying the element to be analyzed It is also possible to set conditions.

In the above-described concentration analysis method and apparatus, the analysis date and time, the measured spectrum distribution graph, the type and concentration of the element, and the time-dependent change of the past measured concentration value are displayed at necessary places, and the analysis date and time, the type and concentration of the element are displayed. Along with printing out, the analysis date and time, the measured spectrum distribution graph, the type and concentration of the element, the optimum analysis conditions and the signal intensity of the emission spectral line of the analysis target and the signal intensity of the wavelength range not including the spectral line of the analysis target If stored, a change in concentration over a long period of time can be observed, and data useful for estimating the cause can be obtained.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a concentration analyzer according to an embodiment of the present invention will be described with reference to the drawings. In addition,
In the description of the characteristics in the examples, description will be made mainly on the results of an experiment for measuring the concentration of Na. [(1) Apparatus configuration and settings] In FIG. 1, reference numeral 1 denotes a sample cell, 2 denotes a condensed water sample, 3 denotes a pulse laser beam, 4 denotes a lens for condensing a laser beam 3, and 5 denotes a plasma beam in an aqueous solution. A lens that emits light, 6 is a plasma light, 7 is an opening / closing mechanism, 8 is a light intensity measuring device, 9 is a laser transmission filter, 10 is a laser cutoff filter, 11 is an ultraviolet cutoff filter, 12 is a case,
Reference numerals 13 and 13 'denote flow switching valves, 14 a filter for trapping suspended substances, 15 a sample injection pipe, 16 a sample discharge pipe, 17 a connection pipe for introducing a sample, 18 a pulse generator, 19 and 20 A delay circuit, 21 is a personal computer with a monitor as a control device and an analyzing device, 22 is a printer, 23 to 27 are communication lines, and the sample cell 1 is made of tetrafluoroethylene. As shown in the vertical cross-sectional view of FIG. 2B, a sample passage 100 is formed inside. The sample passage 100 penetrates from the lower part of the sample cell 1 to the upper part, and the sample injection pipe 15
Is connected, and the sample discharge pipe 16 is connected to the upper opening. The sample cell 1 is arranged slightly inclined with respect to the optical axis when the laser light 3 is emitted.

An introduction hole 101 for introducing the laser beam 3 emitted from the laser device 30 is opened on one side surface of the sample passage 100 of the sample cell 1, and the introduction hole 101 is a part of the lens 4. A lens 113 is attached. The lens 4 includes a lens 113 and a nearby lens 114. A hole 102 through which plasma light generated in the sample by the laser light 3 passes is formed in a side surface at 90 degrees with the insertion hole 101 of the sample cell 1. Hole 1
A glass window 112 made of quartz glass is fixed to 02.

The case 12 is formed in a box shape by a light shielding plate, and has a hole 121 for introducing the laser light 3 and a hole 122 for taking out the plasma light 6, and a sample injection pipe 15.
And a sample discharge pipe 16 are attached. Hole 121
The laser device 30 is attached to the outside, and the laser transmission filter 9 is attached to the inside of the hole 121.
The above-described lens 114 is arranged between the laser transmission filter 9 and the sample cell 1. Since the sample cell 1 and the lenses 4 and 5 are stored in the case 12, the laser light transmission filter 9 is provided at the part where the laser light 3 is incident, and the laser light cutoff filter 10 is provided at the part where the plasma emission is taken out. Intrusion of disturbance light into a certain light intensity measuring device 8 and leakage of laser light to the outside are prevented.

The laser transmission filter 9 includes a laser device 30
The optical axes of the lenses 114 and 113 are not inclined at right angles to the optical axis of the laser light 3 emitted from the laser device 3, but are also inclined with respect to the optical axis of the laser light 3 emitted from the laser device 30. Accordingly, the optical component including the laser transmission filter 9 and the lenses 114 and 113 is inclined with respect to the laser light 3, so that the reflected laser light does not return to the laser transmitter of the laser device 30.

A slit 41 for introducing plasma light is opened in the plasma light introduction section of the spectroscope 40.
The slit 41 extends at right angles to the plasma light 6 and substantially along the optical axis of the laser light 3. When the plasma generation position of the sample 2 moves back and forth on the optical axis of the laser light 3, The position where the plasma is generated can be captured.

As shown in FIG. 1, a condensate sample 2 flowing through a sample cell 1 is provided with a Q switch-operated YAG laser device 3.
Pulse laser light 3 emitted from 0 (oscillation wavelength: 1064 nm, pulse width: about 7 nsec, oscillation repetition frequency: 10 Hz) is condensed by a laser condensing lens (focal length of a later-described lens system: about 30 mm) 4. And irradiate.

At this time, in the vicinity of the focal position of the condenser lens 4, the density of the laser beam 3 increases, and a part of the condensate sample 2 instantaneously becomes high temperature and is vaporized to be in a plasma state. Inside the plasma, the elements contained in the sample are excited and emit light having a wavelength unique to the element.

The light emission 6 from the plasma is collected by a lens 5 (focal length: 30 mm), and the spectroscope 40 (focal length: 5 mm) is used.
0cm, diffraction constant: 1800 lines / mm, decompose into spectral wavelengths, and measure light intensity (number of elements: CC of 1024 x 256)
D) The light intensity at each wavelength was measured at 8, and counted using a 16-bit A / D converter (not shown). This A /
The D converter is arranged as an interface board between the light intensity measuring device 8 and the serial port of the control analyzer 21.

The control analyzer 21 is constituted by a personal computer with a monitor and can start a concentration analysis program.

This concentration analysis program allows the spectroscope 40 to operate from the control analysis device 21 via the communication line 24 by designating the control analysis device 21 with Na as the element name to be analyzed. Has become. The spectroscope 40
The center wavelength can be set to a wavelength of 589 nm near the Na spectrum line. In front of the slit 41 of the spectroscope 40, an ultraviolet cut filter 11 for blocking a higher-order spectrum is installed. In this embodiment, an experiment was performed with the width of the slit 41 of the spectroscope 40 set to 150 μm. However, the width of the slit 41 can be changed depending on the measurement density range. The width of the slit 41 may be changed by exchanging a light shielding plate provided with a slit, or by forming a gap with a pair of light shielding plates and driving an actuator that moves the pair of light shielding plates by a concentration analysis program. Alternatively, the gap between the pair of light shielding plates may be changed. <Blocking of disturbance light> Sample cell 1, laser focusing lens 4,
The lens 5 is installed in an opaque case 12 made of a light shielding member, and the case 12 prevents intrusion of ambient disturbance light and foreign matter.

Since the laser device contains excitation light and light leaking from the surroundings, in addition to the laser light, an optical filter 9 that selectively transmits only the laser light is applied to the portion of the case 12 where the laser light enters from the laser device. Has been arranged. <Prevention of Laser Light Leakage> The case 12 prevents the laser light from leaking outside.

On the spectroscope side of the case 12, an infrared cut filter 10 for blocking laser light is arranged, and an ultraviolet cut filter 11 for blocking ultraviolet light contained in light emission from the plasma is passed through an ultraviolet cut filter 11 to cut off near the spectral wavelength of sodium. Only light is introduced into the spectrograph.

By disposing the spectroscope 40 and the laser device 30 in close contact with the case 12 or via an opaque beam guide, it is possible to completely block disturbance light and prevent laser light from leaking. With this configuration, when the apparatus is operating, the laser beam 3
Safety can be ensured. <Stable laser oscillation> When the reflected light of the laser beam 3 is fed back to the laser device 30, the laser oscillation becomes unstable. Therefore, optical components (optical filter 9, laser condenser lens 4, and sample cell 1 described later) on the optical axis of laser 3
Of the laser light 3) is attached at an angle of several degrees with respect to the optical axis so that the reflected light does not return to the laser device.

Laser oscillation is required only during analysis, and the laser apparatus used in this embodiment required a time of 10 seconds or more for laser oscillation to stabilize. It was set to perform the spectrum measurement after that. <Sample supply> The condensate sample 2 is supplied from the pipe 17 and is injected into the sample cell 1 from the sample injection pipe 15 connected to the lower part of the sample cell 1 via the valve 13 'and the valve 13. The sample is discharged to the outside from a sample discharge pipe 16 connected to the upper part of the sample. The valves 13 and 13 'are provided with a bypass pipe and a filter 14 for capturing solid matter is provided.
When analyzing a sample containing a suspended substance, the sample is injected into the sample cell 1 from the pipe 17 via the flow path of the valve 13 ′, the filter 14, the valve 13, and the pipe 15. Teflon or stainless steel from which Na does not elute is used for the piping, valves and filters. <Structure of Sample Cell> FIGS. 2A and 2B show the internal structure of a sample cell 1 made of Teflon (trade name of tetrafluoroethylene). Inside the housing 111 of the sample cell 1,
As shown in the vertical cross-sectional view of FIG. 2B, a hole is formed from the bottom to the top so that the condensate sample 2 is injected from below, and passes upward and is discharged. The upper portion 114 of the inner wall of the sample cell 1 is inclined, and bubbles generated in the condensed sample at the time of laser beam irradiation do not stay in the sample discharge portion 16.
It is structured to be quickly discharged from

The irradiation window 101 for the laser beam 3 of the sample cell 1 is provided with a quartz lens 113 for focusing the laser beam (focal length: 50 m).
m) is fixed by a ring-shaped jig not shown in the drawing. The quartz lens 113 and the laser condensing lens 114 (focal length: 60 mm) shown in FIG. 1 constitute a combined lens system 4 (focal length: about 30 mm) having a short focal length, and enhance the condensing property of the laser light 3. are doing.

Window 102 for taking out light emission 6 from plasma
Quartz plate with a ring-shaped jig not shown in the drawing
112 is fixed.

The quartz glass used for the lens 113 and the quartz plate 112 is made of a synthetic quartz material that does not contain Na.
It is fixed to the housing 111 via a ring. <Disposition of spectroscope slit and light intensity measuring device> Sample cell 1
The refractive index of the sample 2 supplied to the sample varies depending on the type and concentration of the substance. This change in the refractive index causes a change in the condensing position of the laser light 3, resulting in a change in the light emitting position of the plasma, and appears as a change in the image forming position by the lens 5 on the slit 41 of the spectroscope 40.

This movement of the light emitting position occurs along the optical axis of the laser 3. For this reason, the longitudinal direction of the slit 41 of the spectroscope 40 (the direction perpendicular to the wavelength axis of the spectroscope) is arranged so as to match the moving direction of the imaging position of the lens 5.
The slit extends substantially parallel to the optical axis of the laser light 3 so that the plasma light can pass through the spectroscope 40 regardless of the position of the plasma on the optical axis of the lens 5 before and after the plasma generation position.

In the embodiment, the light intensity measuring device 8 has a CCD
Element (wavelength direction: 1024 elements, wavelength vertical 256 elements)
Is used, light from the plasma can be received even when the optical axis moves in the direction perpendicular to the wavelength, and the effect of fluctuations in the light emission position is mitigated.

When there is a restriction on the arrangement of the spectroscope 40, the moving direction of the image can be made to follow the longitudinal direction of the slit 41 of the spectroscope 40 by using two mirrors or prisms. FIG. 3 illustrates this.

As shown in FIG. 3, the imaging position 20 of the lens 5
3 moves on the virtual optical axis 205. This optical axis 205 is parallel to the laser beam 3. The mirror 201 and the mirror 202 are arranged as shown in the figure, and the light 6 from the plasma is reflected from the arrow 206 to the arrow 207 and further to the arrow 208, so that the light 6 can enter the slit 204 of the spectroscope in parallel. This optical system is inserted between the lens 5 and the spectroscope.

As another method of alleviating the fluctuation of the light emission position, the light from the plasma is incident by arranging the entrance surfaces of the plurality of optical fibers uniaxially in the moving direction of the image formation position by the lens 5. It is also possible to adopt a structure in which the opposite surface of the optical fiber is arranged along the aperture of the spectroscope slit.

When the type and concentration contained in the sample to be analyzed are limited and the change in the refractive index can be ignored,
The above-mentioned consideration is unnecessary, and the slit 41 of the spectroscope 40 is unnecessary.
Can be arranged freely. Further, a one-dimensional linear sensor can be used for the light intensity measuring device 8.

In the embodiment, the longitudinal direction of the CCD of the light intensity measuring device 8 is arranged in the wavelength direction, and the wavelength measuring area is set to 0 to 1024.
The signal intensity of each channel is obtained by adding the amount of light received to 256 elements orthogonal to the wavelength direction as channels. <Timing of Laser Irradiation and Plasma Emission Observation> In the embodiment, the image intensifier 7 is disposed in front of the light receiving surface of the light intensity measuring device 8, and the voltage applied to the image intensifier 7 is controlled by the delay circuit 19. Then, the light emission 6 from the plasma is incident on the light intensity measuring device 8 within a time width of several microseconds or more after several hundred nanoseconds have elapsed from the laser irradiation.

In order to accurately control the timing of laser irradiation and spectrum measurement by the light intensity measuring device 8, a reference signal is generated by a pulse oscillator 18 and a delay circuit 19
The signal is supplied to the light receiving system via the delay circuit 20, and to the oscillation signal input system of the laser device via the delay circuit 20, respectively.

The generation timing of the reference signal is determined by the signal transmission system 24.
The signal of the light intensity measuring device 8 is fetched through a signal transmission system 23, and these are controlled by a control analyzer 21 such as a personal computer. <Necessity of Timing Control> FIG. 4 shows the intensity of Na spectral lines (measured wavelength: 588.995 nm) and the emission of water when plasma is generated in an aqueous solution containing Na by pulse laser irradiation. Wavelength: 586 to emit light over a wide wavelength
The time course of intensity (measured in nm) is shown.

Immediately after the laser irradiation, the luminescence intensity of water and the luminescence intensity of Na are almost the same, and the intensity of the Na spectral line cannot be specified. However, as the time elapses, the luminescence of water rapidly decreases, while the luminescence of Na decreases slowly. And the ratio ((emission intensity of Na) / (emission intensity of water))
Increases with time, reaches a maximum at 2 μsec, and then decreases.

In this embodiment, since the emission spectrum is observed with a delay of several hundred nanoseconds or more from the laser irradiation, the emission spectrum of Na mixed with the emission of water can be measured as a large signal.

According to the embodiment, as shown in FIG. 5, the intensity of the emission spectrum of the Na aqueous solution having the same concentration decreases with the lapse of time from the laser irradiation to the observation of the emission spectrum. 589.6nm).

The change with time is represented by the signal ratio ((Na emission intensity)
/ (Emission intensity of water)), as shown in FIG. 6, the signal ratio increases with the delay time from the laser irradiation. However, the coefficient of variation (standard deviation / average value) in the ten measurements also increases at the same time, and the analysis accuracy decreases.

This means that the analysis accuracy and the signal ratio can be adjusted by controlling the timing of the laser irradiation and the observation time of the emission spectrum. That is,
By increasing the delay time, a large signal ratio can be obtained in an extremely low concentration region at the expense of analysis accuracy. Also,
When a sufficient signal ratio can be obtained, the delay time can be shortened to improve the analysis accuracy.

In the present embodiment, the analysis accuracy required for seawater leak monitoring is set to a variation coefficient of 10% or less, and the delay time from laser irradiation to emission spectrum observation is set to 1.4 μs. <(2) Measurement procedure> Next, in the measurement procedure, Na is specified as the element name of the element to be analyzed in the control analysis device 21.
The spectrometer 40 is operated from the control analyzer 21 via the communication line 24, and the center wavelength of the spectrometer 40 is set to 589 nm near the Na spectrum line. The ultraviolet cut filter 11 (see FIG. 1) is provided before the slit 41 of the spectroscope 40.

In the analysis, a calibration curve is obtained using an aqueous solution of Na having a known concentration, and thereafter, a sample having an unknown concentration is measured.

FIG. 7A shows a time chart from laser irradiation to spectrum measurement.

First, after setting the parameters for the measurement shown in FIG. 7B, a series of measurements is started by the synchronization signal from the control analyzer 21.

First, from the control analyzer 21 to the pulse oscillator 18
To send a measurement start signal A. Next, a signal having a delay time and a measurement gate width set with reference to the pulse signal is applied from the delay circuit 19 to the image intensifier 7,
The noise signal B of the light intensity measuring device 8 is measured for each channel. In the measurement of the noise intensity, the preset addition n times are performed m times, and the signal intensity of the average value is used as the noise level value of the detector.

Next, the measurement of the emission spectrum is started. In the measurement of the emission spectrum, the laser device 30 includes a delay circuit.
A signal is output from 20 and a laser is oscillated as shown by a waveform C in FIG. 7A, and laser irradiation on the sample 2 of the sample cell 1 is started.

When the time during which the oscillation intensity stabilizes after the start of laser oscillation, a synchronization signal is input from the control analyzer 21 to the light intensity measuring device 8 (see waveform D in FIG. 7A).
The spectrum intensity is measured, A / D converted, and taken into the control analyzer 21 as data. For the measurement of the spectrum intensity, the preset addition n times are performed k times, and the average value is defined as the signal intensity.

After the emission spectrum intensity is taken into the control analyzer 21, the stop signal of the pulse generation is transmitted from the control analyzer 21 to the pulse oscillator 18 (falling of the waveform C).
Laser oscillation and data capture (falling of waveform D) end.

After the measurement of the emission spectrum, analysis and output of the result are performed. In the analysis, the control analyzer 21 calculates the emission spectrum intensity by laser irradiation by subtracting the noise component of the light intensity measuring device from the spectrum intensity of each channel, and calculates the Na concentration by comparing with the signal intensity of the calibration curve. . The result, the analysis conditions and the data of the spectrum intensity are stored in a recording device such as a floppy (registered trademark) disk or a hard disk, and the Na concentration in the sample is displayed on a screen. If a value equal to or higher than the concentration set in advance is detected, an alarm is output to the display unit 28.

This series of measurements is performed a set number of times at set analysis time intervals. In addition, in the analysis standby state, the processing can be ended by the interruption command.

In this embodiment, n = 100, m
= 2, n = 100 and k = 5 during spectrum measurement. In this setting, the Na concentration is 0.1 ppb to 60
It was experimentally confirmed that 0 ppb can be measured with a variation coefficient of 10% or less. Further, it was experimentally confirmed that when the concentration was high, the analysis time could be shortened by reducing n. <(2) Analysis method> Signal ratio Fig. 8 shows a laser (energy: 80mJ) and an aqueous solution (Na concentration: 3).
ppb), and an observation example of the intensity of the emission spectrum (wavelength: 585 to 593 nm) obtained 1.4 μsec after the laser irradiation. The emission spectrum intensity is the emission intensity obtained by subtracting the noise component of the light intensity measuring device from the spectrum intensity of each channel.

In FIG. 8, two peaks 31 (wavelength: 588.995 nm) and 32 (wavelength: 589.592 nm) of the emission spectrum are the emission spectrum lines of Na, and the short wavelength side 33 away from these peaks and the long wavelength The spectrum on side 34 is the emission of water.

In the embodiment, the emission spectrum intensity S of Na
Is used as the signal intensity S1 of the peak 31. The light emission intensity of water is used as the background intensity BG.

However, as shown in FIG. 8, since the emission intensity of water fluctuates depending on the wavelength, the average value of the signal intensity from 585 nm to 587 nm on the short wavelength side of the Na spectrum line and the signal intensity from 591 nm to 593 nm on the long wavelength side are changed. The average value of the intensity is obtained, and the average value of these two values is treated as the background intensity BG. (These wavelength ranges are input and set in advance in the control analyzer 21.) The advantages of handling the signal ratio will be described below.

It is assumed that, when the sample of the target element is irradiated with the laser of intensity I, the emission intensity of the target element at the emission wavelength λ0 is i0 and the emission intensity at the surrounding wavelength λ1 is i1. By selecting a wavelength that is not affected by the spectral line of the target element as λ1, the emission intensity of the solvent (Planck sample) can be estimated. This intensity is defined as the background intensity BG.

In order to determine the concentration of the target element, the difference in emission intensity (S-BG) and the ratio of emission intensity (S / BG) will be considered.

Assuming that the luminous efficiency of the target element and the solvent by laser irradiation is α and β, respectively, i0 = αI and i1 = βI.

Subtracting the emission spectrum intensity of the solvent from the emission spectrum intensity of the target element means finding i0−i1 = αI−βI = (α−β) I. Assuming that the laser irradiation intensity has changed by ΔI due to fluctuations in the output of the laser oscillator, contamination of the laser irradiation window, etc., the difference between the emission spectrum intensities is (i0 + Δi0) − (i1 + Δi1) = α (I + ΔI) −β (I
+ ΔI) = (α−β) (I + ΔI), and is directly affected by the change in the laser irradiation intensity.

If the transmittance between the observation window and the sample is γ, the detectable signal intensities are S = γi0 and BG = γi1. The difference in signal strength is given by S-BG = γ (i0−i1). If the change in transmittance due to contamination of the observation window or turbidity of the sample is Δγ, then S-BG = (γ + Δγ) (i0-i1), where the signal intensity is also affected by the contamination of the observation window and the turbidity of the sample. Will be directly received.

On the other hand, focusing on the ratio between the emission spectrum intensity of the target element and the emission spectrum intensity of the periphery, the intensity ratio is expressed as i0 / i1 = αI / βI = α / β (constant). Is changed, (i0 + Δi0) / (i1 + Δi1) = α (I + ΔI) / β (I + Δ
I) = α / β (constant), and is not affected by the laser intensity.

Even if the transmittance of the observation window changes, the signal ratio between the emission intensity S of the target element and the emission intensity BG of the solvent is S / BG = (γ + Δγ) i0 / (γ + Δγ ) i1 = i0 / i1 = αI / βI =
α / β (constant), and there is no change in transmittance or laser intensity. The relationship between the above-mentioned signal intensity (S / BG) measured using the emission intensity S of Na, the background intensity BG, and the Na concentration was determined experimentally. FIG. 9 shows the results. The relationship between the signal ratio and the Na concentration is a straight line.
The Na concentration can be determined using the following equation. Even if a sample containing a suspended substance (iron oxide) is flowed into the sample cell to forcibly cause dirt on the quartz lens 113 of the laser irradiation window 101 and the quartz plate 112 of the plasma emission window 102, Na It was experimentally confirmed that the relationship between the concentration and the signal ratio was maintained.

In the embodiment, the Na concentration C is determined by C = 1.24R-1.27 [ppb], where R is the signal ratio. As shown in FIG. 10, the linearity has been confirmed up to the Na concentration of 600 ppb. This is a sufficient measurement range for the condenser salt detector. Linearity According to FIG. 10, when the Na concentration is 600 ppb or more, the signal ratio tends to be saturated. This is due to the loss of linearity between the light intensity and the output signal intensity due to an excessive amount of light incident on the light intensity measuring device 8. Therefore, the slit 4 of the spectroscope 40
It has been experimentally confirmed that when an optical attenuator is arranged before the number 1 to reduce the amount of light, linearity can be ensured even at a higher density. FIG. 11 shows a use case of the optical attenuator. Na Spectral Intensity As described above, considering the case where a strong light is incident on the light intensity measuring device 8 and the signal is saturated, in the case of this embodiment, when the emission of Na becomes strong, the dynamic range of the CCD (16 bits: 65536) Count). In other words, even if the signal S1 of 588.955 nm having strong light emission is saturated, the BG signal (S3, S4, etc.) is counted without being saturated. As a result, the signal ratio (S / BG) is observed to be smaller than it should be, and an incorrect Na concentration is calculated.

Here, the emission spectrum line of the Na atom is
See the two wavelengths of light 588.995nm and 589.592nm
And the lower level of the two spectral lines is the ground state, 58
The upper level of 8.995nm is energy 16973cm^-1Excited state
589.592nm upper level is 16959cm ^-1In the excited state. Encouragement
The transition probabilities from the starting state to the ground state are each 1.8 × 10⁸/ s
ec and 0.9 × 10⁸/ sec, emission at 588.995nm and 589.592nm
The intensity ratio is theoretically 2: 1.

Focusing on this fact, 588.95 with strong light emission
Even if the 5 nm signal S1 is saturated, the 589.592 nm signal S2
Are counted until saturation. As a result, as shown in FIG. 11A, the signal intensity S1 of 588.955 nm is 589.592n.
The signal strength S2 of m is observed to be stronger than 1/2 of the theoretical value. Therefore, the saturation phenomenon of the light intensity measuring device 8 can be known by monitoring the intensity ratio between the two Na emission spectrum lines.

If S2 / S1 is observed to be somewhat larger than 1/2 (FIG. 11 (a)), such as when a high concentration of Na instantaneously passes through the sample cell, this measured data is invalidated. By performing re-measurement, erroneous measurement can be avoided. When S2 / S1 is continuously observed to be somewhat larger than 1/2, an optical attenuator is automatically inserted in front of the slit of the spectroscope to reduce the light amount (FIG. 11B). (3) Analytical performance As a result of testing this example at a power plant, the effects of pH adjusters (ammonia, hydrazine, ethanolamine) and anions (sulfate, chloride, carbonate, and phosphate) contained in the condensate water. 0.1ppb to 60 without receiving
It was verified that a sodium concentration of about 0 ppb can be measured. In addition, it was found that the sample having a large amount of the suspended substance had an effect on the Na concentration measurement, and the influence of the suspended substance was determined by using a filter having a pore size of 7 μm or less as the filter 14 in this embodiment. It was confirmed that it could be avoided.

As a result of applying the concentration analysis method of the above embodiment to monitoring of seawater leakage from a condenser, the following was experimentally confirmed.

A continuous and automatic analysis of 0.1 to 600 ppb of Na concentration can be performed without contact and without contact.

An accurate concentration can be obtained even in the presence of a pH adjuster or an anion.

By arranging the optical attenuator before the slit of the spectroscope, high density measurement can be performed.

The time required for an analysis of about 1 ppb is less than 3 minutes, and the time can be greatly reduced as compared with the conventional analysis method.

Since the lower limit of the required concentration of sodium analysis for monitoring the seawater leak of the condenser may be on the order of several ppb to several hundred ppb, it has been experimentally confirmed that the present invention can sufficiently cope with this requirement. It can be said that it was done.

The above-described concentration analysis method can be applied not only to condensate but also to Na analysis of any aqueous solution sample. Also, an example in which the concentrations of K and Ca were measured by the above-described concentration analysis method is shown in FIG.
This is shown in FIG. 12 and FIG. For the measurement of K, the K spectrum intensity of 766.5 nm and the intensity of 667.5 to 568.5 nm as BG are used. For the measurement of Ca, a Ca spectrum intensity of 422.7 nm and an intensity of 421 to 422 nm as BG are used. As a result, it was found that the method can be applied to the analysis of K and Ca of the aqueous solution sample.

[0087]

As described above, according to the concentration analysis method of the present invention and the concentration analyzer of the present invention, the plasma emission of water and the plasma emission of an element to be analyzed can be performed in a short time. After the water emission of the water is completed in a short time, the spectral intensity of the analyte can be measured, so that the concentration of the analyte can be accurately measured. That is, the emission spectrum intensity of the plasma is measured in a time width of several microseconds or more after several hundred nanoseconds or more from the laser irradiation, and the light intensity of the emission spectrum line of the element to be analyzed is in a range not including this spectrum line. Since the concentration of the element to be analyzed in the aqueous solution is obtained from the value obtained by dividing the light intensity, the emission component of water during plasma generation and the spectrum of the substance to be monitored can be separated, and the spectrum of the component becomes clear and accurate. Analysis.

According to the concentration analysis method of the present invention, when measuring the light intensity of the spectrum, first, the laser light is shielded, and the average value of the noise signal intensity for each wavelength of the light intensity measuring device is calculated for each wavelength. Measure the average value of the signal intensity for each wavelength of the light intensity measuring device by irradiating laser light with the noise signal intensity, and subtract the average value of the noise signal intensity from the average value of the signal intensity at each wavelength. Since it is the light intensity signal value,
Since the spectral light intensity for each wavelength can be accurately measured in a wide concentration range and errors can be reduced, the concentration of the element to be analyzed in the sample can be measured more accurately.

According to the concentration analysis method of the third aspect of the present invention, the saturation phenomenon of the light intensity measuring instrument can be known by monitoring the intensity ratio of the two Na emission spectrum lines.
For example, when a momentarily high concentration of Na passes through the sample cell,
If S2 / S1 is observed to be somewhat larger than 1/2, the measurement data is invalidated and re-measurement can be performed to avoid erroneous measurement. Also, S2 /
If S1 is observed to be somewhat larger than 1/2,
An optical attenuator can be automatically inserted before the spectroscope slit to reduce the amount of light.

According to the concentration analyzer of the fifth aspect of the present invention, the longitudinal direction of the entrance slit of the spectroscope coincides with the moving direction of the luminous image of the plasma condensed by the lens. Observation is possible.

According to the concentration analyzer of the sixth aspect of the present invention, a light intensity measuring device using a light receiving device in which a light receiving device is arranged on an XY coordinate system is used, and a light receiving device array in the X-axis direction is converted into a wavelength of a spectral spectrum. Direction, and the sum of the signals of the light receiving element rows arranged in the Y-axis direction is two-dimensionally captured as the signal intensity at each wavelength. Therefore, each wavelength included in the spectrum and its intensity are converted into electric signals and monitored. The target component and concentration can be measured in a short time.

In addition to the above, in the concentration analysis method and the concentration analyzer according to the first to sixth aspects of the present invention, Na, K, C
The target component can be directly measured in an aqueous solution such as a, the trace amount of seawater component leaking to the condensate can be monitored directly and continuously, and the analysis time and process time can be significantly reduced. , A wide range of concentration analysis becomes possible.

Further, even when the conductivity increases due to contamination during inspection, at rest, or during operation, and when carbon dioxide in the atmosphere dissolves in the condensate and generates the same anion as chloride ion, the ion chromatograph is not changed each time. It is not necessary to confirm the presence or absence of seawater leak by manual analysis with the device, and the accurate concentration of the target component in the sample can be obtained.

Further, for example, when used for monitoring seawater leak of a condenser of a power plant, the lower limit of the required concentration of Na analysis is several
Since the order of ppb to several hundred ppb is sufficient, the invention of claim 1 can sufficiently cope with this demand.

Further, the concentration analysis method of the present invention can be applied not only to the condensing of power plants, but also to the analysis of components of a wide range of aqueous samples, such as the measurement of the concentration of substances contained in water.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a concentration analyzer according to an embodiment of the present invention.

2A is a horizontal sectional view of the sample cell of FIG. 1, and FIG. 2B is a vertical sectional view of the sample cell.

FIG. 3 is an explanatory view of a method of changing an optical axis in the case of FIG. 1;

FIG. 4 is a measurement diagram of a change over time in luminescence intensity in the concentration analyzer of FIG. 1;

FIG. 5 is a measurement diagram of a temporal change of an observed spectrum according to the embodiment of FIG. 1;

FIG. 6 is an explanatory diagram showing a relationship between a delay time from laser irradiation, a signal ratio, and a coefficient of variation.

FIG. 7A is a timing chart of a noise measurement portion and an emission spectrum measurement portion of the light intensity measuring device;
(B) is a flowchart from the noise measurement of the light intensity measuring device to the emission spectrum measurement.

FIG. 8 is an explanatory diagram of an observed spectrum according to the example.

FIG. 9 shows the results of a calibration curve measurement experiment according to the example of the present invention.

FIG. 10 shows the results of an experiment for measuring the linearity of this example.

FIG. 11 is a signal saturation countermeasure example of the present embodiment.

FIG. 12 is an application example of the present invention, and FIG.
(A) shows the spectrum distribution, and FIG. 12 (b) shows the results of the calibration curve measurement.

FIG. 13 is an application example 2 of the present invention, and FIG.
(A) is the spectrum distribution, and FIG. 13 (b) is the result of the calibration curve measurement.

[Explanation of symbols]

 1 sample cell, 2 sample, 3 laser light, 4 laser focusing lens, 5 lens, 6 light from plasma, 7 opening and closing mechanism, 8 light intensity measuring instrument, 9 infrared transmission filter, 10 infrared cut filter, 11 ultraviolet cut filter , 12 cases, 13, 13 'flow path switching valve, 14 filter, 15 sample injection pipe to sample cell, 16 sample discharge pipe from sample cell, 17 pipe, 18 pulse oscillator, 19, 20 delay circuit, 21 control Analysis device, 22 printer, 23-27 communication line, 28 display unit 30 laser device 31 Na spectrum line (wavelength: 588.995 nm), 32 Na spectrum line (wavelength: 589.592 nm), short wavelength side of 33 Na spectrum line , 34 Long wavelength side of Na spectrum line, 40 Spectrometer 41 Slit 111 Sample cell case, 112 Quartz plate of emission observation window, 113 Laser irradiation window and laser focusing stone Lens, 114 Inclined part for discharging air bubbles above sample cell, 201, 202 Reflector, 203 Image position, 204 Slit aperture of spectroscope, 205 Virtual optical axis, 206-208 Direction of plasma emission, S1 Na spectrum line (Wavelength: 588.995 nm), intensity of S2Na spectrum line (wavelength: 589.592 nm), intensity of short wavelength side of S3Na spectrum line, intensity of long wavelength side of S4Na spectrum line.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shiro Kikuchi 2-5 Marunouchi, Takamatsu City, Kagawa Prefecture F-term in Shikoku Electric Power Company (reference) 2G020 AA04 BA02 CA01 2G043 AA01 CA03 DA05 FA03 GA02 GA08 GB03 GB21 HA01 JA03 KA02 KA05 KA08 KA09 LA03 MA01 MA04 MA11 NA01

Claims (6)

[Claims] 1. A concentration analysis method for irradiating an aqueous solution in a sample cell with laser light to generate plasma, and performing spectrum analysis of the plasma light to analyze the concentration of an element to be analyzed in the aqueous solution. A spectroscope for splitting light is set in advance so that the center wavelength is in the vicinity of the spectral wavelength of the element to be analyzed, and the spectrometer converts the plasma light generated in the sample cell into an emission spectrum line of the element to be analyzed. The intensity of the emission spectrum line of the element to be analyzed and the intensity of the wavelength range not including the spectral line are separated from the spectrum of the wavelength range not including the spectral line by the delay time from the laser light irradiation time. From the value obtained by dividing the light intensity of the emission spectrum line of the element to be analyzed by the light intensity in a range not including this spectrum line. Concentration analysis method characterized by determining the concentration of the analyte element in the serial solution. 2. The concentration analysis method according to claim 1, wherein in measuring the light intensity of the spectrum, first, a noise signal intensity for each wavelength of a light intensity measuring device is set in advance in a state where laser light is cut off. The measurement is performed by adding a number of times, and this is repeated a predetermined number of times to obtain an average value of the signal intensity for each wavelength, and the average value is set as a noise signal intensity at each wavelength. Then, add and measure the signal strength of each wavelength of the optical power meter for the preset number of times, repeat this for the preset number of times, and calculate the average value of the signal strength for each wavelength. A concentration analysis method characterized by measuring and subtracting the noise signal intensity from the averaged signal intensity at this time as a light intensity signal value at each wavelength. 3. The concentration analysis method according to claim 1, wherein in measuring the Na concentration, the light intensity of the sodium spectral line used for the concentration measurement is a signal intensity at 588.995 nm which is the sodium spectral line. At the same time, the signal intensity at 589.592 nm, which is a sodium spectral line, was measured, and the signal intensity at 588.995 nm and 589.592 n were measured.
A concentration analysis method characterized in that only measured values when the relationship between signal intensities at m is close to 2: 1 are used as valid data. 4. A concentration analyzer for irradiating an aqueous solution in a sample cell with laser light to generate plasma in the aqueous solution, and performing spectrum analysis of the plasma light to analyze the concentration of an element to be analyzed in the aqueous solution. In the method, the center wavelength is set in advance in the vicinity of the spectral wavelength of the element to be analyzed, and the plasma light generated in the sample cell is separated into an emission spectral line of the element to be analyzed and a spectrum in a wavelength range not including the spectral line. A spectroscope, an optical filter disposed between the sample cell and the slit of the spectroscope to which the plasma light is incident, and blocking a higher-order spectrum spectrum wavelength overlapping the emission spectrum wavelength, and separated by the spectroscope. A light intensity measuring device for measuring the intensity of the plasma light that has been emitted; and An opening / closing mechanism for controlling the passage of the plasma light; and, after a delay time from the irradiation time of the laser light, the intensity of the emission spectral line of the element to be analyzed and the intensity of the wavelength range not including the spectral line. , To measure,
Control means for controlling the opening and closing mechanism. 5. The concentration analyzer according to claim 4, wherein the slit for inputting the plasma light to the spectroscope allows the focal point of the laser light applied to the sample cell to fluctuate. A concentration analyzer which extends optically substantially in the same direction as an optical axis. 6. The concentration analyzer according to claim 4, wherein a light-receiving element having a light-receiving element arranged on an XY coordinate system is used as the light intensity measuring device, and a light-receiving element array in the X-axis direction is used. A concentration analyzer wherein a wavelength range of a spectrum of the spectroscope is set to be detected, and a light receiving element array in a Y-axis direction is set so that a sum of signals is measured for a signal intensity at each wavelength.