JPH0989764A - Atomic absorption photometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an atomic absorption photometer which can shorten the time required for automatically setting an analytical condition. SOLUTION: A plurality of hollow cathode lamps 14 are held so as to be rotatable by a turret 12, and the turret 12 is turned by a motor 16. A sample to be analyzed is atomized by a burner 20 or a graphite furnace 30 as a sample atomization part. Light which is passed through the sample atomization furnace is separated into its spectral components by a spectroscope 50 so as to be detected by a photodetector 74. A μ-CPU 80 controls the motor 16, it scans the position of every hollow cathode lamp 14 in a prescribed range, and it checks the output of the photodetector 74 during the scanning operation of its light source. When the output exceeds a prescribed range, an applied voltage to the photodetector 74 is controlled so as to become the prescribed range. After the finish of the scanning operation, the position of the light source is moved to a position in which the intensity of light from the light source becomes maximum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an atomic absorption spectrophotometer, and more particularly to an atomic absorption spectrophotometer suitable for automatically setting analysis conditions.

[0002]

2. Description of the Related Art Recent atomic absorption spectrophotometers are equipped with a microcomputer as described in, for example, Japanese Patent Laid-Open No. 6-94606, and analysis conditions can be automatically set by designating measurement elements. Has become. The analysis conditions include the lamp current of the hollow cathode lamp as the light source, the measurement wavelength and slit width of the spectroscope, the type of burner and frame, and the type of flame of the sample atomization part when the sample atomization part is a burner. In the case of a furnace, the type of cuvette, the heating method, etc. are stored in advance in the microcomputer. Among these analysis conditions, the replacement of the burner and the replacement of the cuvette need to be replaced by the operator, but other conditions can be automatically set by the microcomputer.

Looking at the light source section, for example,
As described in Japanese Patent Application Laid-Open No. 2-311746, in the light source unit, a plurality of hollow cathode lamps are mounted on a rotatable turret, and the number of the turret holder and the number thereof are set in advance. By storing the type of the hollow cathode lamp, the desired hollow cathode lamp can be automatically selected by rotating the turret according to the measurement element. Further, regarding the spectroscope, the wavelength of the spectroscope can be automatically set by storing the measurement wavelength for each measurement element in advance.

However, the hollow cathode lamp installed on the turret may have its optical axis deviated from the peak of the emission spectrum emitted from the hollow cathode lamp due to the inclination at the time of mounting. Therefore, conventionally, the turret in which the hollow cathode lamp is installed is slightly rotated, the emission spectrum profile is measured, and then the turret position is controlled so that the peak position of the emission spectrum coincides with the optical axis. I have to.

[0005]

When measuring the profile of the emission spectrum, the applied voltage of the photomultiplier, which is a photodetector, is set to an arbitrary voltage, and the turret is rotated. If the applied voltage to the photomultiplier is not appropriate, the peak position of the emission spectrum of the hollow cathode lamp may not be detected because the output of the photomultiplier is too large or too small.

Therefore, after rotating the turret by a certain amount,
When the peak position could not be detected properly, it was necessary to repeat the operation of raising or lowering the applied voltage of the photomultiplier and then rotating the turret by a certain amount again. Therefore, there is a problem that it takes time to automatically set the analysis conditions to the optimum conditions. Incidentally, if the applied voltage of the photomultiplier is not appropriate, it may take about 2 minutes for this automatic setting.

An object of the present invention is to provide an atomic absorption photometer capable of shortening the time required for automatic setting of analysis conditions.

[0008]

In order to achieve the above object, the present invention provides a light source section in which a plurality of light sources are rotatably held, and a light source which moves the position of the light source held in the light source section. A position drive means, a sample atomization unit that atomizes the measurement sample and guides light emitted from a predetermined light source in the light source unit, and a predetermined amount of light that has passed through the sample atomization unit. In an atomic absorption photometer having a spectroscope for separating light of a wavelength and a photodetector for converting the light emitted from the spectroscope into an electric signal, the light source position driving means is controlled and held in the light source section. The position of the light source is scanned within a predetermined range, the output of the photodetector is checked during scanning of the light source, and if the output exceeds the predetermined range, the light is adjusted to fall within the predetermined range. Voltage applied to the detector A control means for controlling the position of the light source is provided at a position where the light intensity from the light source is maximized after the scanning is completed. The scanning of allows the position of the light source to be set to the optimum position.

In the atomic absorption spectrophotometer, preferably, the predetermined range includes a width obtained by adding a deviation amount of a light source position to a width of an emission spectrum emitted from the light source with the reference position of the light source as a center. With such a configuration, the scanning range can be minimized.

In the atomic absorption spectrophotometer, preferably, the control means further controls the spectroscope,
The spectroscope is scanned within a predetermined range, and the output of the photodetector is checked during wavelength scanning by the spectroscope. If the output exceeds the predetermined range, the photodetection is performed within the predetermined range. In addition to controlling the voltage applied to the spectroscope, after the scanning is completed, the movement is controlled to the wavelength position of the spectroscope at the position where the light intensity from the light source is maximized. As a result, the wavelength position of the spectroscope can be set to the optimum position with one scan.

In the atomic absorption spectrophotometer described above, preferably, the predetermined range is the center of the reference position of the spectroscope, and the deviation of the wavelength position of the spectroscope is added to the width of the optical spectrum emitted from the spectroscope. The scanning range can be minimized by adopting such a configuration.

In the atomic absorption spectrophotometer, preferably, the control means further checks the output of the photodetector when the light source is set to the reference position, prior to the control by the light source position driving means. Then, when the output exceeds the predetermined range, the applied voltage to the photodetector is controlled so as to be within the predetermined range, and the control of the applied voltage to the photodetector is a control for lowering the applied voltage. By adopting such a configuration,
The control for increasing the applied voltage is eliminated, and the control can be performed in a short time.

In the atomic absorption spectrophotometer, preferably, the control means further sets the voltage applied to the photodetector to the maximum prior to the control by the light source position driving means, and The control of the applied voltage of the detector is such that the applied voltage is lowered, and with such a configuration, the control can be easily performed.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described.
This will be described with reference to FIGS. FIG. 1 is a block diagram of an atomic absorption spectrophotometer according to an embodiment of the present invention.

The light source unit 10 includes a disk-shaped turret 12 and
The turret is composed of a plurality of hollow cathode lamps 14 installed on the same circumference. The hollow cathode lamp 14 is attached by inserting its electrode terminal into a socket provided in the turret 12. Although four hollow cathode lamps 14 are illustrated, eight hollow cathode lamps 14 are mounted on the turret 12 at equal intervals, as will be described later.

The turret 12 can be rotated by a pulse motor 16 for driving the turret. A disk is fixed to the rotary shaft of the turret 12, and this disk has a size of 1
Slits are formed only at the portions, and photocouplers are provided at positions facing each other with the slits in between. Therefore, when the slit is located between the photocouplers, the output can be taken out from the photocoupler.
The reference position of the turret 12 can be detected. The relationship between the number of control pulses given to the pulse motor 16 and the rotation angle of the turret 12 rotated by the pulse motor 16 is designed so that the turret 12 rotates by 9 ° by 100 control pulses. The moving distance of the hollow cathode lamp 14 in the circumferential direction at this time is about 16 mm.

The pulse motor 16 is used for fine adjustment of the light source position.
Is controlled by the μ-CPU 80, the details of which will be described later.

Light emitted from the hollow cathode lamp 14 set at a predetermined position of the light source section 10 travels along the optical axis L and is guided to the sample atomizing section.

In the sample atomization section, a burner 20 and a graphite furnace 30 are provided as optical axes L as two types of sample atomization devices.
Are arranged in series. Below the burner 20, a chamber 22 and a nebulizer 24 are attached. The sample contained in the sample container 40 is sucked by the nebulizer 24, atomized and supplied into the chamber 22. In addition, the chamber 22 includes a gas control unit 26.
A combustible gas such as acetylene gas whose flow rate is controlled is supplied by the burner 20 together with the atomized sample.
Are combusted to form the flame 28. In the frame 28, the introduced sample is atomized.

Further, since it is an atomic absorption spectrophotometer utilizing the Zeeman effect, a pair of magnets 29 with the frame 28 interposed therebetween.
Are arranged facing each other. The magnetic field direction applied by the magnet 29 is a direction orthogonal to the optical axis L. This magnet 29
The absorption spectrum formed by the atomized sample by the magnetic field applied by is branched into a π component and a σ component having polarization directions orthogonal to each other.

The graphite furnace 30, which is another sample atomization device, has a cylindrical shape made of graphite, and is arranged so that the axis of the cylinder coincides with the optical axis L. The temperature of the graphite furnace 30 depends on the graphite atomizer (G
A) It is controlled by the power supply 32, and is heated to about 3000 ° C. through the temperature steps of drying, ashing and atomization. The measurement sample is introduced into the graphite furnace 30 through an opening formed in the upper portion of the graphite furnace 30,
It is atomized by heating to 000 ° C.

Further, since it is an atomic absorption photometer utilizing the Zeeman effect, a pair of magnets 34 are arranged to face each other with the graphite furnace 30 sandwiched therebetween. The magnetic field direction applied by the magnet 34 is a direction orthogonal to the optical axis L. Due to the magnetic field applied by the magnet 34, the absorption spectrum formed by the atomized sample is branched into a π component and a σ component having polarization directions orthogonal to each other.

In the sample atomization section, the light absorbed by the atomized sample is guided to the spectroscope 50. The spectroscope 50 has an entrance slit 52 on which light is incident and an exit slit 54 on which the dispersed light is emitted. Also,
Inside the spectroscope 50, a diffraction grating 56 for dispersing the incident light, a concave mirror 58 for collimating the light incident from the entrance slit 52, and the light dispersed by the diffraction grating 56 are collected. A concave mirror 59 is arranged. By the concave mirror 58, the diffraction grating 56, and the concave mirror 59,
It constitutes a Tzerny-Turner type spectrometer.

Therefore, the light from the hollow cathode lamp 14 absorbed in the sample atomization portion is guided to the spectroscope 50 and dispersed by the diffraction grating 56, and only the light of the target wavelength is extracted from the exit slit 54. Be done.

The widths of the slits 52 and 54 can be changed by a pulse motor 62 for controlling the slit width. Also,
The wavelength of the light split by the spectroscope 50 and extracted from the exit slit 54 is obtained by rotating the diffraction grating 56 by the pulse motor 64 for wavelength setting.
A feed screw mechanism (not shown) is provided between the diffraction grating 56 and the pulse motor 64.
The feed screw is rotated by, and the diffraction grating 56 is rotated by rotating the table holding the diffraction grating by the slider that linearly moves by the rotation of the feed screw.

Here, the wavelength selected by the spectroscope 50 is different from the set wavelength due to the secular change of the spectroscope itself, for example, the rattling of the feed screw mechanism and the effect of high temperature heat from the sample atomization section. Since an error may occur between the wavelengths actually extracted from the emission slit, in order to match the peak wavelength of the emission spectrum emitted from the hollow cathode lamp 14 of the light source unit 10 with the wavelength selected by the spectroscope 50, The diffraction grating 56 is rotated by a slight angle, and the spectroscope 5
The fine adjustment of the selected wavelength of 0 is performed by the μ-CPU 80, the details of which will be described later.

The light emitted from the exit slit 54 of the spectroscope 50 is guided to the polarizer 70. The polarizer 70 has the first polarization component and the σ component whose polarization directions are the same as the above-mentioned π component and the polarization direction in the emission spectrum from the hollow cathode lamp 14 which is absorbed by the absorption spectrum of the sample atomization part. The second polarized light component that matches is separated.

A chopper 72 that rotates to a position that blocks the light of the first and second polarized components separated by the polarizer 70.
Is arranged. A slit is formed in the chopper 72, and the slits are formed at a position where only the first polarized component is transmitted and a position where only the second polarized component is transmitted. By rotating the chopper 72,
The light of the first polarization component and the light of the second polarization component are alternately guided to the photodetector 74, converted into an electric signal, and the μ-CPU
It is taken into the μ-CPU 80 via the A / D converter built in the. As the photodetector 74, a photomultiplier whose gain can be changed by adjusting the applied voltage is used. The μ-CPU 80 controls the voltage applied to the photomultiplier.

Of the electric signals output from the photodetector 74, the difference between the electric signal for the light of the first polarization component and the electric signal for the light of the first polarization component is calculated by the μ-CPU 80 and the background is calculated. The corrected absorbance of can be determined.

The μ-CPU 80 can obtain the concentration of the measurement sample from the measured absorbance by obtaining the calibration curve from the standard sample in advance.

The waveform diagram of the measured absorbance signal and the data of the concentration value of the measurement sample are displayed on the CRT 82. Further, the concentration value data of the measurement sample, the analysis condition data, and the like can be printed out on the printer 84. In addition, μ-
A keyboard 86 is connected to the CPU 80 and is used for inputting analysis condition settings and the like.

Next, the principle of position adjustment of the light source will be described with reference to FIG. FIG. 2 is a diagram for explaining the displacement of the light source unit of the atomic absorption spectrophotometer according to the embodiment of the present invention.

When the disc-shaped turret 12 is viewed from the front side, the turret 12 has twelve hollow cathode lamps 14A, 14B, 14C, 14D, 14E, 14F and 1.
4G and 14I are attached on the same circumference at equal intervals. In the figure, the thick solid line represents the optical axis L, and the burner 20, the graphite furnace 30, the spectroscope 50, and the detector 74, which are the sample atomization parts, are arranged on this optical axis.

The rotating shaft 12a of the turret 12 has a disk 1
8 is attached. The disk 18 has a slit 18a formed in a part thereof in the outer peripheral direction. Slit 1
A photo coupler (not shown) is arranged at a position sandwiching 8a, and the reference position is detected by this photo coupler.

In the energized state of the hollow cathode lamp 14A, light is emitted from a black circle area E shown in the figure, and this area E is the effective range of light. Effective range diameter K1
Is, for example, 3 mm. The distance K2 from the rotation center 12a of the turret 12 to the center of the effective range is 100 mm, for example.

In the illustrated state, the reference position is detected by the slit 18a, and the center of the area E, which is the effective range of light, should normally be located on the optical axis L, but here, For example, since the hollow cathode lamp 14A is attached to the turret 12 while being inclined, the center of the area E, which is the effective range of light, is displaced from the optical axis L by a distance K3. The maximum value of this shift amount K3 is, for example, about ± 1.0 mm.

Therefore, the shift amount K is centered on the reference position.
By rotating the turret 12 over a range wider than the maximum value of 3 and examining the output of the photodetector 74 at that time, the profile of the light emitted from the hollow cathode lamp 14A can be measured, and the hollow from the reference position can be measured. It is possible to know the deviation amount K3 of the emission center of the cathode lamp.

Regarding the amount of deviation from the reference position,
It is possible to know not only the hollow cathode lamp 14A but also the hollow cathode lamp 14H, for example. That is, since eight hollow cathode lamps are arranged on the turret 12 at equal intervals, the angle between the hollow cathode lamps is 45 °. Therefore, slit 1
The position shifted by 45 ° from the position detected by 8a
If the reference position of the hollow cathode lamp 14H is used, the amount of deviation of the center of the effective range of the light emitted from the hollow cathode lamp 14H can be easily obtained. Here, the rotation of the turret 12 is configured to be controlled by the pulse motor 16 as described with reference to FIG. 1, and the turret is supplied by supplying 500 control pulses for driving to the pulse motor 16. 12 can be rotated 45 °.

The principle of measuring the profile of the light emitted from the light source section will be described with reference to FIG. FIG. 3 is a diagram illustrating a profile of an emission spectrum from the light source unit of the atomic absorption spectrophotometer according to the embodiment of the present invention.

The horizontal axis represents the rotational scanning range of the turret. The emission spectrum S with respect to the central reference position X0
The profile has a bilaterally symmetrical mountain shape as shown in the figure, and the distance K1 of the effective range of light is, for example, 3 mm. The peak of the emission spectrum S deviates from the reference position X0 by the distance K3. Here, the maximum value of the distance K3 is about 1.0 mm.

Therefore, in this embodiment, the reference position X0
Is detected by a slit, or is detected by a slit, and the turret is further rotated by an angle that is an integral multiple of 45 °, and then the turret is further rotated by a distance (-X1). Here, the distance X1 is, for example, 4.5 ° in terms of the turret rotation angle. This angle is about 8 mm when converted to a distance. The number of control pulses supplied to the pulse motor for rotating the turret is 50 pulses.

After the turret is rotated by the distance (-X1), the turret is rotated in the opposite direction by the distance (2X1) to rotate the turret by a predetermined angle to the left and right with the peak of the emission spectrum S as the center. By detecting the output of the photodetector at that time,
As a result, the profile of the emission spectrum S as shown in the figure can be detected.

Then, the distance K3 which is the difference between the detected peak position of the emission spectrum S and the reference position is obtained, the turret is rotationally moved, and the peak of the emission spectrum S is aligned on the optical axis. High analysis is possible.

Next, the principle of adjusting the set wavelength of the spectroscope will be described with reference to FIG. FIG. 4 is a diagram illustrating a profile of a spectrum of light extracted from the exit slit of the spectroscope of the atomic absorption spectrophotometer according to the embodiment of the present invention.

The horizontal axis represents the wavelength scanning range implemented by rotating the diffraction grating. The profile of the optical spectrum S'has a bilaterally symmetrical mountain shape as shown in the drawing, and the half-value width K4 at that time is, for example, 0.09 to
1.3 nm. The full width at half maximum depends on the exit slit width of the spectroscope. The peak of the optical spectrum S'is displaced from the reference position X0 by the distance K5. Here, the maximum value of the distance K5 is about 0.4 nm.

Here, the diffraction grating in the spectroscope is rotated by a slider that linearly moves according to the rotation of the feed screw, and the reference wavelength position of the diffraction grating is determined by detecting the position of the slider with a photocoupler. Can be detected. That is, when the slider is located at a predetermined position, the detection piece attached to the slider passes between the photocouplers and a signal is output from the photocoupler, whereby the reference wavelength position can be detected. The reference wavelength position is set to 190 nm, for example, and the number of control pulses supplied to the pulse motor for wavelength setting is 100, so that the wavelength scanning of 1 nm is possible. Lead (P
Since the measured wavelength in b) is 283.3 nm, if the reference motor is detected and then 9330 pulses are supplied to the pulse motor, it means that the diffraction grating can be set at the reference position X0 of 283.3 nm.

After setting the wavelength at the reference position in this way, the wavelength is further scanned by the wavelength (-X1 '). Here, the wavelength X1 is, for example, 0.45 nm. The reason for this is that the maximum value of the deviation K5 of the peak position of the optical spectrum from the reference position is about ± 0.4 nm. Therefore, the number of control pulses supplied to the pulse motor is 45 pulses.

After scanning the wavelength in the minus direction by the wavelength (-X1 '), the wavelength is scanned in the plus direction by the wavelength (2X1'), and at that time, the output of the photodetector is detected. , The profile of the optical spectrum S'as shown in the figure can be detected.

Then, the wavelength K5, which is the difference between the detected peak position of the optical spectrum S'and the reference position, is obtained, the wavelength is scanned, and the peak of the optical spectrum S'is aligned on the optical axis. Higher analysis is possible.

Next, a method of controlling the position adjustment of the light source unit and the wavelength adjustment of the spectroscope according to the embodiment of the present invention will be described with reference to FIGS. 1, 5, 6 and 7. FIG.
FIG. 6 is a flowchart for explaining the position adjustment of the light source unit and the wavelength adjustment of the spectroscope by the atomic absorption spectrophotometer according to the embodiment of the present invention, and FIG. 6 is the atomic absorption spectrophotometer according to the embodiment of the present invention. FIG. 7 is an operation explanatory diagram of applied voltage control to the photodetector, and FIG. 7 is an operation explanatory diagram at the time of adjusting the position of the light source unit and the wavelength adjustment of the spectroscope by the atomic absorption photometer according to the embodiment of the present invention. .

In FIG. 5, the control flow according to the present embodiment is basically based on the principle of “initial setting” in step 00, “adjusting applied voltage” in step 100, and FIGS. 2 and 3. It is composed of the four steps of the "light source position setting" of step 200 described above and the "spectrometer position setting" of step 300 whose principle has been described with reference to FIG. Therefore, the details of each step will be described below.

First, the initial setting in step 00 will be described.

In the memory circuit of the μ-CPU 80, standard measurement conditions for each measurement element and measurement conditions registered by the operator are stored in advance. For example, as an analytical element,
Taking copper (Cu) as an example, measurement wavelength: 324.8 nm,
Applied voltage of photomultiplier: 330 V, slit width of spectroscope: 1.30 nm, lamp current of hollow cathode lamp: 7.5 mA, turret holder No. The measurement conditions such as: 1 are stored in advance. In addition to the above, as the measurement conditions, the distinction between the burner and the graphite furnace used as the sample atomization unit, the type of combustion gas in each case, the gas flow rate, and the like are stored.

Therefore, the μ-CPU 80 uses the keyboard 8
When the analysis element is selected via 6, the measurement conditions corresponding to the analysis element are read from the memory circuit in step 00, and the initial setting is performed. That is, when copper (Cu) is selected as the analysis element, a control signal is sent to the pulse motor 16 for driving the turret, the pulse motor 16 is driven to rotate the turret 12, and the turret No. Bring 1 to the optical axis. In FIG. 2, as described, the position where the output is obtained from the photocoupler provided at the position sandwiching the slit 18 provided in the disk 18 attached to the rotary shaft of the turret 12 is the reference position, and at this position,
Turret No. 1 is pre-positioned so as to be located on the optical axis.

Turret No. When the turret No. 1 is positioned in advance so as to be positioned on the optical axis. 1 is energized, and the lamp current at that time is controlled by the μ-CPU 80 to be 7.5 mA.

Further, the μ-CPU 80 outputs a control signal to the pulse motor 62 for controlling the slit width to control the slit width of the spectroscope 50 to be 1.30 nm.

At the same time, the μ-CPU 80 outputs a control signal to the pulse motor 64 for wavelength setting to set the selected wavelength of the spectroscope 50 to 324.8 nm.

Further, the μ-CPU 80 sets the applied voltage of the photomultiplier 74 to 330V in order to set the gain of the photodetector.

As described above, each part of the main body of the atomic absorption photometer is driven and controlled, and the initial setting is completed.

Next, in step 100, the applied voltage is set. The photomultiplier, which is a photodetector, can change its sensitivity by changing its applied voltage. Therefore, although the initial value of the applied voltage has been determined in advance for each measurement element, if the brightness of the hollow cathode lamp decreases due to aging, or the sensitivity of the photomultiplier deteriorates, the photomultiplier In such a case, it is necessary to increase the applied voltage because the output may decrease. Also, when the hollow cathode lamp is replaced with a new one, it is necessary to set the applied voltage higher.

Therefore, in step 100, the applied voltage is set. It should be noted that step 104 shown by a broken line in step 100 is a step of another embodiment, and thus the description thereof will be described later.

In step 101, the μ-CPU 80
Monitors the output of the photodetector 74 and determines whether it is within a predetermined range. Here, if the upper limit value of the monitor value is M1 and the lower limit value is M2, and the detected monitor value is less than or equal to the lower limit value M2, step 1
Go to 02. If the upper limit value M1 or more, the process proceeds to step 103.

In step 102, the μ-CPU 80
Controls the applied voltage of the photodetector 74 so as to raise the applied voltage by a predetermined voltage when the monitor value is equal to or lower than the lower limit value M2. That is, as shown by the broken line in FIG. 6, when the light source monitor value is lower than the lower limit value M2, the applied voltage is increased by the predetermined voltage V1. Then, the process returns to step 101 again, and when the monitor value is equal to or lower than the lower limit value M2, the applied voltage is increased again by the predetermined voltage V1. This step is repeated until the monitor value exceeds the lower limit value M2.

When the monitor value exceeds the upper limit value M1 in step 101, the flow proceeds to step 103, and the μ-CPU 80 applies the predetermined voltage to the applied voltage when the monitor value is equal to or higher than the upper limit value M1. The voltage applied to the photodetector 74 is controlled so as to lower it. That is, as indicated by the solid line in FIG. 6, when the light source monitor value is higher than the lower limit value M1, the applied voltage is lowered by the predetermined voltage V1. Then, the process returns to step 101 again, and when the monitor value is equal to or higher than the upper limit value M1, the applied voltage is again lowered by the predetermined voltage V1. Repeat this step until the monitor value reaches the lower limit M
It is repeated until it becomes 1 or less.

When the monitor value is within the predetermined range as described above, the process proceeds to the next step 200.

Step 200 is a step of setting the light source position. First, in step 201, the light source is moved to the scanning start position. The scanning start position referred to here is, as described in FIG. 3, a distance (−X
1) This is the position where the turret 12 is rotated. Here, the distance (−X1) is, for example, (−8 mm), which corresponds to 4.5 ° in the rotation angle of the turret, and therefore μ− for rotating the turret by 4.5 °. C
PU80 is 50 in the turret drive pulse motor 16
Outputs a pulse control signal. As a result, the turret 12 is rotated by 4.5 ° and moved to the scanning start position.

Then, in step 202, μ-
The CPU 80 moves the light source position, starts the search, and proceeds to step 203 until the search is completed. The light source position is moved by outputting a control signal for each pulse to the turret driving pulse motor 16.

In step 203, each time the light source position moves by one pulse, the μ-CPU 80 causes the photodetector 74 to move.
Take the output of and check if its value is within a predetermined range. Here, the predetermined range is the same as the upper limit value M1 and the lower limit value M2 described in FIG. If it is within the predetermined range, the operation proceeds to step 205, and the scanning position is changed. If it is not within the predetermined range, the operation proceeds to step 204, the applied voltage is lowered by a predetermined level, and then step 205
Proceed to and change the scan position.

The above control operation will be described with reference to FIG.

As shown in FIG. 7A, at the start of scanning, the monitor value of the light source, which is the output of the photodetector, is at a low level. Therefore, initially, by step 205,
Only the scan position is changed. When the effective range E of the light source shown in FIG. 2 approaches the optical axis, the monitor value of the light source starts to rise, exceeds the lower limit M2, and further rises to n.
At the th control pulse Pn, the monitor value is the upper limit value M1.
7B, the applied voltage to the photomultiplier is lowered from VA to VB by a predetermined voltage at step 204 at that timing, as shown in FIG. 7B.

Further, even at the (n + 1) th control pulse Pn + 1, if the monitor value exceeds the upper limit value M1, at that timing, as shown in FIG.
In, the applied voltage to the photomultiplier is lowered from VB to VC by a predetermined voltage. From now on,
Since the monitor value does not exceed the upper limit value M1, the applied voltage is Vc constant.

In this way, when the applied voltage is not changed, the monitor value of the light source changes as shown by the dotted line in FIG. 7 (A) and reaches the peak value at the timing of Pn + 2.
The monitor value of the light source is saturated at a certain level as shown by the broken line, and the peak value cannot be detected.

On the other hand, by changing the applied voltage based on the monitor value of the light source, the monitor value of the light source changes as shown by the solid line, so that the monitor after the applied voltage reaches the minimum level is displayed. The peak position can be easily detected by detecting the maximum value.

As described above, the movement of the light source position is repeated to perform the search, and the μ-CPU 80 outputs the control signal of 100 pulses to complete the search.
To step 206.

In step 206, the μ-CPU 80
Since the peak position can be detected in the search so far, the center of the light source can be aligned with the optical axis by moving the light source to the position where the peak value is detected.

Here, conventionally, since the light source position is moved while the applied voltage to the photomultiplier is constant, the monitor value is saturated as shown by the broken line in FIG. 7 (A). The peak position could not be found by moving the entire range once, and the optimum light source position was detected because the applied voltage was lowered again and the light source position was repeatedly moved in the same range. It took time to do. This time may take up to 2 minutes at maximum, but when the upper limit is exceeded while monitoring the light source as in the present embodiment, the voltage applied to the photomultiplier is lowered. By doing so, the peak position can be detected by moving the light source position only once, and the time required for this can be about 5 seconds.

When the setting of the light source position is completed as described above, next, in step 300, the spectroscope position is set.

Step 300 is a step of setting the spectroscope position. First, in step 301, the selected wavelength of the spectroscope is moved and set to the scanning start position. The scanning start position mentioned here is the position where the diffraction grating 56 is rotated by the pulse motor 64 by the wavelength (-X1 ') from the reference position, as described in FIG. Here, the wavelength (−X1 ′) is, for example, (−0.45 nm), and therefore the μ-CPU 80 outputs a 45 pulse control signal to the diffraction grating driving pulse motor 64.
As a result, the diffraction grating 56 rotates and moves to the scanning start position.

Then, in step 302, μ-
The CPU 80 scans the wavelength, starts the search, and proceeds to step 303 until the search is completed. The wavelength scanning is performed by outputting a control signal for each pulse to the diffraction grating driving pulse motor 64.

In step 303, each time the wavelength shifts by one pulse, the μ-CPU 80 takes in the output of the photodetector 74 and checks whether the value is within a predetermined range. Here, the predetermined range is the same as the upper limit value M1 and the lower limit value M2 described in FIG. If it is within the predetermined range, the operation proceeds to step 305, the scanning position is changed, and if it is not within the predetermined range, the operation proceeds to step 304,
After lowering the applied voltage by a predetermined level, the process proceeds to step 305 to change the scanning position.

The above control operation will be described with reference to FIG.

As shown in FIG. 7A, at the start of scanning, the monitor value of the light source, which is the output of the photodetector, is at a low level. Therefore, initially, by step 305,
Only the scan position is changed. When the spectrum shown in FIG. 4 approaches the optical axis, the monitor value of the light source starts to rise, exceeds the lower limit value M2, and further rises, and at the nth control pulse Pn, the monitor value becomes the upper limit. When the value exceeds the value M1, at that timing, as shown in FIG. 7B, in step 304, the applied voltage to the photomultiplier is decreased from VA to VB by a predetermined voltage.

Further, even at the (n + 1) th control pulse Pn + 1, when the monitor value exceeds the upper limit value M1, at that timing, as shown in FIG.
In, the applied voltage to the photomultiplier is lowered from VB to VC by a predetermined voltage. From now on,
Since the monitor value does not exceed the upper limit value M1, the applied voltage is Vc constant.

In this way, when the applied voltage is not changed, the monitor value of the light source changes as shown by the dotted line in FIG. 7 (A) and reaches the peak value at the timing of Pn + 2.
The monitor value of the light source is saturated at a certain level as shown by the broken line, and the peak value cannot be detected.

On the other hand, by changing the applied voltage based on the monitor value of the light source, the monitor value of the light source changes as shown by the solid line. Therefore, the monitor after the applied voltage reaches the lowest level The peak position can be easily detected by detecting the maximum value.

As described above, the wavelength scanning is sequentially performed to perform the search, and when the μ-CPU 80 outputs the 90-pulse control signal to complete the search, the process proceeds from step 302 to step 306.

In step 306, the μ-CPU 80
Has detected the peak position in the search so far, so by moving the spectroscope to the position where the peak value was detected, the wavelength selected by the spectroscope should match the center wavelength of the emission spectrum of the light source. You can

Here, conventionally, since the wavelength scanning was performed while the applied voltage to the photomultiplier was kept constant,
As indicated by the broken line in FIG. 7A, the monitor value is saturated, and the peak position cannot be found by only scanning the entire range once. Since the wavelength scanning of the range was repeated, it took time to detect the optimum spectroscope position. This time may take up to 2 minutes at maximum, but when the upper limit is exceeded while monitoring the light source as in the present embodiment, the voltage applied to the photomultiplier is lowered. By doing so, the peak position can be detected by only one wavelength scan, and the time required for this can be about 5 seconds.

According to the present embodiment, the voltage applied to the photodetector is controlled so that the output of the photodetector is within a certain range while the position scanning of the light source is performed, and the position where the light intensity is maximum is obtained. By moving the position of the light source, the position of the light source can be set to the optimum position only once by scanning the position of the light source.

While scanning the position of the spectroscope, the applied voltage of the photodetector is controlled so that the output of the photodetector is within a certain range, and the position of the spectroscope is set to the position where the light intensity is maximum. By moving the, it is possible to set the wavelength to the optimum position of the spectroscope only by scanning the wavelength of the spectroscope only once.

With the light source set to the reference position,
Since the applied voltage of the photodetector is controlled so that the output of the photodetector is within a certain range, the applied voltage of the photodetector is controlled during the subsequent scanning of the light source position and scanning of the wavelength of the spectroscope. Is
Since it only needs to be lowered, control becomes easier and faster.

As a result of the above, the time for setting the conditions of the light source and the spectroscope can be shortened.

Next, another embodiment of the present invention will be described with reference to FIGS. 1, 5 and 8.

FIG. 8 is an operation explanatory diagram when the position of the light source unit and the wavelength of the spectroscope are adjusted by the atomic absorption photometer according to another embodiment of the present invention.

A feature of this embodiment is that step 104 is used in place of steps 101, 102 and 103 in the applied voltage setting of step 100 in the flowchart shown in FIG.

That is, after the initial setting is completed in step 00, in the applied voltage setting in step 100,
In step 104, the applied voltage is set to the maximum value. As described with reference to FIG. 6, in the first embodiment,
The applied voltage was raised or lowered so that the monitor value of the light source was within the predetermined range.
It takes some time. Therefore, the next step 20
0, in step 300, the applied voltage is set to the maximum value in view of the fact that the applied voltage is only in the decreasing direction.

Therefore, although the flow of the light source position setting in step 200 and the flow of the spectrometer position setting in step 300 are the same as those in the first embodiment, the control operation is slightly different.

Therefore, with reference to FIGS. 5 and 8, the light source position setting flow in step 200 and step 30
The control operation based on the spectroscope position setting flow at 0 will be described.

Step 200 is a step of setting the light source position. First, in step 201, the μ-CPU
Reference numeral 80 controls the pulse motor 16 to move the light source to the scanning start position.

Next, in step 202, μ-CP
U80 moves the light source position, starts the search, and proceeds to step 203 until the search is completed. The movement of the light source position is
This is performed by outputting a control signal for each pulse to the turret driving pulse motor 16.

In step 203, each time the light source position moves by one pulse, the μ-CPU 80 causes the photodetector 74 to move.
Take the output of and check if its value is within a predetermined range. Here, the predetermined range is the same as the upper limit value M1 and the lower limit value M2 described in FIG. If it is within the predetermined range, the process proceeds to step 205, and the scanning position is changed. If it is not within the predetermined range, the process proceeds to step 204, the applied voltage is lowered by a predetermined level, and then the step 205 is performed.
Proceed to and change the scan position.

As shown in FIG. 8A, at the start of scanning, the monitor value of the light source, which is the output of the photodetector, is at a low level. Therefore, initially, by step 205,
Only the scan position is changed. When the effective range E of the light source shown in FIG. 2 approaches the optical axis, the monitor value of the light source starts to increase, exceeds the lower limit M2, and further increases, and the monitor value exceeds the upper limit M1. At that timing, as shown in FIG. 8B, in step 204, the applied voltage V to the photomultiplier is decreased by a predetermined voltage.

Since the applied voltage to the photomultiplier is set to the maximum value, the applied voltage is repeatedly lowered thereafter, the applied voltage is lowered by the m-th control pulse Pm, and then the light source is output at the next timing Pm + 1. It is repeated until the monitor value of 1 does not exceed the upper limit value M1, and thereafter, the applied voltage becomes constant.

As described above, the movement of the light source position is repeated to perform the search, and the μ-CPU 80 outputs a 100-pulse control signal to complete the search.
To step 206.

At step 206, the μ-CPU 80
Since the peak position can be detected in the search so far, the center of the light source can be aligned with the optical axis by moving the light source to the position where the peak value is detected.

Here, conventionally, the position of the light source was moved while the applied voltage to the photomultiplier was kept constant, so the peak position could not be found by moving the entire range once. Since the applied voltage was lowered again and the light source position was repeatedly moved within the same range, it took time to detect the optimum light source position. This time may take up to 2 minutes at maximum, but when the upper limit is exceeded while monitoring the light source as in the present embodiment, the voltage applied to the photomultiplier is lowered. By doing so, the peak position can be detected by only moving the light source position once, and therefore the time required for that can be shortened compared to the conventional case. In the present embodiment, compared to the first embodiment, although it takes a little time to adjust the light source position, looking at the control of the applied voltage,
The control is easy because only the control for lowering the applied voltage is required.

Further, in the above description, the adjustment of the light source position has been described, but the wavelength position is adjusted in the same manner.

According to the present embodiment, while the position of the light source is being scanned, the voltage applied to the photodetector is controlled so that the output of the photodetector is within a fixed range, and the position where the light intensity is maximized is controlled. By moving the position of the light source, the position of the light source can be set to the optimum position only once by scanning the position of the light source.

Further, while scanning the position of the spectroscope, the applied voltage of the photodetector is controlled so that the output of the photodetector is within a certain range, and the position of the spectroscope is adjusted to the position where the light intensity is maximum. By moving the, it is possible to set the wavelength to the optimum position of the spectroscope only by scanning the wavelength of the spectroscope only once.

With the light source set to the reference position,
Since the applied voltage of the photodetector is set to the maximum value, the control of the applied voltage of the photodetector can be performed only in the lowering direction during subsequent light source position scanning and scanning of the wavelength of the spectroscope. It will be easy.

As a result of the above, the time for setting the conditions of the light source and the spectroscope can be shortened.

[0112]

According to the present invention, the time required for automatic setting of analysis conditions in an atomic absorption spectrophotometer can be shortened.

[0113]

[Brief description of drawings]

FIG. 1 is a block diagram of an atomic absorption spectrophotometer according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a positional shift of a light source unit of an atomic absorption spectrophotometer according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating a profile of an emission spectrum from a light source unit of the atomic absorption photometer according to the embodiment of the present invention.

FIG. 4 is a diagram illustrating a profile of a spectrum of light extracted from an exit slit of a spectroscope of an atomic absorption photometer according to an embodiment of the present invention.

FIG. 5 is a flowchart illustrating position adjustment of a light source unit of an atomic absorption spectrophotometer and wavelength adjustment of a spectroscope according to an embodiment of the present invention.

FIG. 6 is an operation explanatory diagram of voltage application to a photodetector by the atomic absorption photometer according to the embodiment of the present invention.

FIG. 7 is an operation explanatory diagram when the position of the light source unit of the atomic absorption spectrophotometer and the wavelength of the spectroscope are adjusted according to the embodiment of the present invention.

FIG. 8 is an operation explanatory diagram when the position of the light source unit of the atomic absorption spectrophotometer and the wavelength of the spectroscope are adjusted according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Light source part 12 ... Turret 14 ... Hollow cathode lamp 16, 62, 64 ... Pulse motor 20 ... Burner 22 ... Chamber 24 ... Nebulizer 26 ... Gas control part 29, 34 ... Magnet 30 ... Graphite furnace 32 ... Graphit atomizer power supply 40 ... sample container 50 ... spectroscope 52 ... entrance slit 54 ... exit slit 56 ... diffraction grating 70 ... polarizer 74 ... detector 80 ... .mu.-CPU 82 ... CRT display 84 ... printer 86 ... keyboard

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Tomita 882 Ichige Ichi, Hitachinaka City, Ibaraki Prefecture Stock Company, Hitachi, Ltd. Measuring Instruments Division (72) Hayato Tobe 882 Ichige Ichiga, Hitachinaka City, Ibaraki Prefecture Hitachi Ltd. Measuring Instruments Division (72) Inventor Mikitaro Maruoka 882 Ichimo Ichi, Hitachinaka City, Ibaraki Stock Company Hitachi Ltd. Measuring Instruments Division (72) Ryuji Saito 832 Nagakubo, Horiguchi, Hitachinaka City, Ibaraki Prefecture Engineering Co., Ltd.

Claims (6)

[Claims] 1. A light source section in which a plurality of light sources are rotatably held, a light source position driving means for moving the position of the light source held in the light source section, an atomization of a measurement sample, and the light source section. Sample atomization part to which the light emitted from the specified light source is guided; In an atomic absorption spectrophotometer having a photodetector for converting light into an electric signal, the light source position driving means is controlled to scan the position of the light source held by the light source unit within a predetermined range, and Check the output of the photodetector during scanning, and if the output exceeds a predetermined range, control the voltage applied to the photodetector so that it is within the predetermined range, and after the end of the scanning. , The above light source An atomic absorption spectrophotometer comprising a control means for moving the position of the light source to a position where the light intensity is maximum. 2. The atomic absorption spectrophotometer according to claim 1, wherein the predetermined range is a width obtained by adding a deviation amount of a light source position to a width of an emission spectrum emitted from the light source with the reference position of the light source as a center. Atomic absorption spectrophotometer, characterized in that the range includes. 3. The atomic absorption spectrophotometer according to claim 2, wherein the control means further controls the spectroscope to scan the spectroscope in a predetermined range and to perform the wavelength scanning by the spectroscope. The output of the photodetector is checked, and when the output exceeds the predetermined range, the voltage applied to the photodetector is controlled so that it is within the predetermined range, and after the scanning is completed, Atomic absorption spectrophotometer, wherein movement is controlled to a wavelength position of the above spectroscope at a position where the light intensity of the above is maximum. 4. The atomic absorption spectrophotometer according to claim 3, wherein the predetermined range is centered on a reference position of the spectroscope.
An atomic absorption spectrophotometer, which is a range including a width obtained by adding a deviation amount of a wavelength position of a spectroscope to a width of an optical spectrum emitted from the spectroscope. 5. The atomic absorption spectrophotometer according to claim 1, wherein the control means further sets the light source at a reference position prior to the control by the light source position driving means.
The output of the photodetector is checked, and when the output exceeds a predetermined range, the voltage applied to the photodetector is controlled so that the output falls within the predetermined range, and the voltage applied to the photodetector is controlled. Is an atomic absorption spectrophotometer, characterized in that the applied voltage is controlled to be lowered. 6. The atomic absorption spectrophotometer according to claim 1, wherein the control means further sets the voltage applied to the photodetector to a maximum prior to the control by the light source position driving means. The atomic absorption spectrophotometer, wherein the control of the applied voltage of the photodetector is a control of lowering the applied voltage.