WO2012001979A1

WO2012001979A1 - Atomic absorption analyzer and method of atomic absorption analysis

Info

Publication number: WO2012001979A1
Application number: PCT/JP2011/003746
Authority: WO
Inventors: 勝堀; 加納　浩之
Original assignee: 国立大学法人名古屋大学; Ｎｕエコ・エンジニアリング株式会社
Priority date: 2010-06-30
Filing date: 2011-06-30
Publication date: 2012-01-05

Abstract

A novel atomic absorption analyzer in which self-absorption is utilized is rendered possible. The atomic absorption analyzer is configured of an atomizer (1), a mirror (2), and a spectroscope (3). The atomizer (1) generates a plasma (atomization plasma (5)) containing an atomized sample. The atomization plasma (5) is examined for emission intensity without the mirror (2) to determine the emission intensity (Ir1) of the resonance spectral line of a target element and the emission intensity (Iu1) of the excitation spectral line of Ar. The mirror (2) is disposed to generate a ghost (ghost plasma (6)) of the atomization plasma (5) by means of light reflection from the mirror (2), and the atomization plasma (5) in this state is examined for emission intensity to determine the emission intensity (Ir) of the resonance spectral line of the target element and the emission intensity (Iu) of the excitation spectral line of Ar. From the intensities (Ir1), (Iu1), (Ir), and (Iu), the absorption coefficient of the target element due to the self-absorption can be calculated.

Description

Atomic absorption spectrometer and atomic absorption spectrometry

The present invention relates to an atomic absorption analysis apparatus and an atomic absorption analysis method using self-absorption. Another invention relates to an atomic absorption analysis apparatus including an atomizer using atmospheric pressure plasma and a light source that emits a resonance line spectrum of a target element, and an atomic absorption analysis method.

An apparatus described in Patent Document 1 has been proposed as an atomic absorption spectrometer that can simultaneously analyze multiple elements. The atomic absorption spectrometer of Patent Document 1 uses a multi-micro hollow cathode light source that is a light source that emits emission spectrums of a plurality of elements to be analyzed. The multi-micro hollow cathode light source has a plurality of micro hollow pipes made of copper or copper alloy, and each micro hollow pipe is wound an appropriate number of times in the axial direction so that a plurality of metal wires penetrates the inside. Yes. The metal wire is a metal element to be analyzed or an alloy containing the metal element.

In atomic absorption analysis, a graphite furnace or the like is widely used as an apparatus (atomizer) for atomizing a sample. Further, as in Patent Document 2, an atomizer using atmospheric pressure plasma is also known and is described as being usable for absorption analysis. In the generation of atmospheric pressure plasma in the atomizer of Patent Document 2, it is described that the voltage of a commercial AC power source is boosted and applied to an electrode. Therefore, atmospheric pressure plasma is generated discretely.

In atomic absorption analysis, a hollow cathode lamp is used as a light source that emits a resonance line spectrum of a target element. The power source of the hollow cathode lamp is a DC power source. Here, since the atmospheric pressure plasma is generated discretely, the light source cannot be always turned on, and the light source needs to be turned on discretely within a period in which the atmospheric pressure plasma is generated. If atmospheric pressure plasma is not generated and the light source is lit, there is a state in which the light source does not absorb, and it is considered that the absorption rate is low, that is, the concentration of the target element is low. An error occurs in the measurement result. Therefore, the power source of the hollow cathode lamp needs to be synchronized with the power source of the atomizer by pulsing the DC power source.

Thus, in an atomic absorption spectrometer having an atomizer using atmospheric pressure plasma, an AC power source for the atomizer and a DC power source for the light source are prepared and used.

JP2007-257900A JP2008-241293

However, the multi-micro hollow cathode light source used in the atomic absorption spectrometer of Patent Document 1 needs to wind a metal wire many times around the micro hollow pipe in order to obtain sufficient emission intensity depending on the type of metal element. The number of times the metal wire can be wound is limited by the structure such as the diameter of the micro hollow pipe, and there is a limit to the improvement of the emission intensity. As a result, the measurable metal element is limited. Further, the multi-micro hollow cathode light source disclosed in Patent Document 1 cannot obtain a resonance line spectrum of an element other than a metal due to a configuration in which a metal element is wound around a micro hollow pipe. Therefore, elements other than metals such as B and P cannot be analyzed.

In addition, in the conventional atomic absorption spectrometer using atmospheric pressure plasma, it is necessary to prepare an AC power source for the atomizer and a DC power source for the light source as described above, and the DC power source for the light source is pulsed. It is necessary to synchronize with the AC power supply for the atomizer, and a circuit device for synchronization is required. If it is going to implement | achieve such a power supply device, the volume and weight of a power supply device will become large. For this reason, the atomic absorption spectrometer cannot be miniaturized and a portable type cannot be realized.

The inventors have intensively studied to solve the above problems, and have come up with the idea of using self-absorption. The present invention is based on this idea, and an object thereof is to realize an atomic absorption analysis apparatus and an element absorption analysis method capable of simultaneously analyzing multiple elements regardless of whether they are metallic elements or nonmetallic elements. .
Another object of the invention is to reduce the size of an atomic absorption spectrometer having an atomizer using atmospheric pressure plasma.

According to a first aspect of the present invention, there is provided an atomizer for generating an atomized plasma including an atomized sample, and an emission intensity of a resonance line spectrum of a target element and an emission intensity of an excitation line spectrum of a discharge gas in the emission spectrum of the atomized plasma. The emission intensity of the resonance line spectrum of the target element, and the discharge in the spectrum of the light in which the emission of the atomized plasma and the light emitted from the atomized plasma to the atomized plasma and transmitted through the atomized plasma are measured. It is an atomic absorption spectrometer characterized by having a measuring device which measures each luminescence intensity of the excitation line spectrum of gas.

Here, atomized plasma means plasma containing an atomized sample. Ar, He, nitrogen, oxygen, air, or the like can be used as a discharge gas for generating plasma. Any atomizer may be used as long as it is an apparatus that generates such atomized plasma. For example, it is an apparatus for generating atomized plasma by generating atmospheric pressure plasma, irradiating a sample containing a target element with atmospheric pressure plasma, and atomizing the sample. In addition, an ICP device or the like can be used as the atomizer of the present invention.

The measuring device measures the following four emission intensities.
(1) The emission intensity of the resonance line spectrum of the target element in the emission spectrum of atomized plasma.
(2) The emission intensity of the excitation line spectrum of the discharge gas in the emission spectrum of atomized plasma.
(3) The emission intensity of the resonance line spectrum of the target element in the light spectrum in which light emitted from the atomized plasma and irradiated with the atomized plasma and transmitted through the atomized plasma is added.
(4) The emission intensity of the excitation line spectrum of the discharge gas in the spectrum of the light emitted from the atomized plasma plus the light irradiated to the atomized plasma and transmitted through the atomized plasma.
You may measure the emitted light intensity of said (1) and (2) simultaneously. Moreover, you may measure the light emission intensity of said (3) and (4) simultaneously.

Of the emission intensities measured in the above (1) to (4), the emission intensity in (3) is self-absorbed by the target element in the atomized plasma, and the present invention provides (1) to (4) The absorptance due to self-absorption is calculated from the emission intensity, and the concentration of the target element in the sample is measured from the absorptance.

The means for irradiating the atomized plasma with light emitted from the atomized plasma is, for example, a means for reflecting using a mirror. At this time, the mirror preferably has a high reflectance at the wavelength of the resonance line spectrum of the target element and the wavelength of the excitation line spectrum of the discharge gas. As another means, there is a means that uses an optical fiber, receives light emitted from atomized plasma from one end of the optical fiber, guides it in a direction different from the light receiving direction, and irradiates it from the other end of the optical fiber.

The excitation line spectrum of the discharge gas preferably has a wavelength closest to the wavelength of the resonance line spectrum of the target element. This is to prevent the measurement accuracy from deteriorating due to the wavelength dependence of the measurement system. In particular, it is desirable to measure the excitation line spectrum of the discharge gas in which the difference from the wavelength of the resonance line spectrum of the target element is 150 nm or less.

A second invention is the atomic absorption spectrometer according to the first invention, wherein the measuring device has a mirror, and the light emitted from the atomized plasma is reflected by the mirror to irradiate the atomized plasma. .
According to a third aspect of the present invention, in the first or second aspect, the emission intensity of the excitation line spectrum of the discharge gas to be measured has the wavelength closest to the resonance line spectrum of the target element. Absorption spectrometer.

In a fourth aspect based on the first aspect to the third aspect, the atomizer generates the atmospheric pressure plasma, irradiates the sample containing the target element with the atmospheric pressure plasma, and atomizes the sample, whereby the atomized plasma is generated. Is an atomic absorption spectrometer characterized by the above.
According to a fifth aspect of the present invention, in the first to fourth aspects of the present invention, the atomizer has a rod-shaped first electrode and a tubular shape, and the first electrode extends from the inner wall of the tube around the axis of the first electrode in the tube. An insulating tube that holds the distal end portion of the first electrode so as to be spaced apart, and in which a discharge gas flows in the gap between the inner wall of the tube and the first electrode in the axial direction on the distal end side of the first electrode; A second electrode disposed at a certain distance from the tip of the electrode; and a sample holding portion made of an insulating material having a recess for holding the sample and exposing the second electrode on the bottom surface of the recess. And an atomic absorption spectrometer.

The sixth invention generates an atomized plasma including an atomized sample, and measures the emission intensity of the resonance line spectrum of the target element and the emission intensity of the excitation line spectrum of the discharge gas in the emission spectrum of the atomized plasma. In the spectrum of light in which the atomized plasma emission and the light emitted from the atomized plasma are irradiated to the atomized plasma and transmitted through the atomized plasma, the emission intensity of the resonance line spectrum of the target element and the discharge gas The atomic absorption spectrometry is characterized in that the emission intensity of the excitation line spectrum is measured.

The seventh invention is the atomic absorption analysis method according to the sixth invention, wherein the atomized plasma is irradiated with light emitted from the atomized plasma by being reflected by a mirror.

An eighth invention is characterized in that, in the sixth invention or the seventh invention, the emission intensity of the excitation line spectrum of the discharge gas to be measured is the one having the wavelength closest to the resonance line spectrum of the target element. Absorption spectrometry.

In a ninth aspect based on the sixth aspect to the eighth aspect, the atomized plasma generates atmospheric pressure plasma, irradiates the sample containing the target element with the atmospheric pressure plasma, atomizes the sample, and in the atmospheric pressure plasma. This is an atomic absorption analysis method characterized in that it is generated by mixing an atomized sample into the sample.

The tenth invention generates atmospheric pressure plasma, irradiates the sample with the atmospheric pressure plasma, atomizes the sample, emits the emission line spectrum of the target element in the sample, and irradiates the atomized sample A light source for analyzing the light from the light source transmitted through the atomized sample, and a power supply device for driving the atomizer and the light source. The power supply device includes an AC power source and an AC power source. A half-wave rectification circuit that rectifies a part of the output of the half-wave, supplies an output from an AC power source to the atomizer, and supplies an output from the half-wave rectification circuit to the light source And an atomic absorption spectrometer.

In an eleventh aspect based on the tenth aspect, the analyzer is configured to detect the first emission intensity of the light combining the light of the light source transmitted through the atomized sample and the emission of the atmospheric pressure plasma, and the atmospheric pressure plasma. Measuring the second emission intensity, which is only emission, and subtracting the second emission intensity from the first emission intensity to calculate the emission intensity of the light of the light source that has passed through the atomized sample. This is an atomic absorption spectrometer that is characterized.

In a twelfth aspect based on the tenth aspect or the eleventh aspect, the atomizer has a rod-shaped first electrode and a tubular shape, and the first electrode extends from the inner wall of the tube around the axis of the first electrode in the tube. An insulating tube that holds the distal end portion of the first electrode so as to be spaced apart, and in which a discharge gas flows in the gap between the inner wall of the tube and the first electrode in the axial direction on the distal end side of the first electrode; A second electrode disposed at a predetermined distance from the tip of the electrode, and a sample holding portion made of an insulating material having a recess for holding the sample and exposing the second electrode on the bottom surface of the recess. This is an atomic absorption spectrometer that is characterized.

Ar, He, nitrogen, oxygen, air, or the like can be used as the discharge gas.
As materials for the first electrode and the second electrode, SUS, copper, tungsten, or the like can be used. However, it is necessary not to use a material containing an element to be analyzed, or to coat the second electrode with a material that does not contain an element to be analyzed. This is to prevent the second electrode from being atomized and affecting the analysis.

The thirteenth invention generates atmospheric pressure plasma by applying an AC voltage, irradiates the sample with atmospheric pressure plasma, atomizes the sample, and applies a voltage obtained by half-wave rectifying the AC voltage. The emission of the emission line spectrum of the target element is generated, and the emitted light is irradiated and transmitted through the atomized sample. The first light of the light combining the emission of atmospheric pressure plasma and the light transmitted through the atomized sample is generated. And the second emission intensity that is only the emission of atmospheric pressure plasma, and the second emission intensity is subtracted from the first emission intensity, whereby the light of the light source that has passed through the atomized sample. This is an atomic absorption analysis method characterized in that the luminescence intensity is calculated.

Since the atomic absorption spectrometer or atomic absorption spectrometer of the present invention performs analysis using self-absorption, the resonance line spectrum of the target element required in the conventional atomic absorption spectrometer or atomic absorption spectrometer. A light source that emits light is not required. Therefore, the type and number of target elements are not limited by the light source, multiple elements can be analyzed simultaneously, and not only metallic elements but also nonmetallic elements can be analyzed. In addition, since no light source is required, the atomic absorption spectrometer can be reduced in size and cost.

Also, as in the second invention, the atomic absorption spectrometer of the present invention can be easily realized by using a mirror.

Further, according to the third invention, it is possible to suppress a decrease in measurement accuracy due to the wavelength dependence of the measurement system.

Also, as in the fourth invention, an atomizer using atmospheric pressure plasma can be used, and the atomic absorption analyzer can be reduced in size and cost.

Further, according to the fifth invention, the atomizer can be further downsized, and as a result, the atomic absorption spectrometer can be downsized.

Also, according to the atomic absorption analysis methods of the sixth to ninth inventions, multiple elements can be analyzed simultaneously irrespective of metallic elements and nonmetallic elements.

In the atomic absorption spectrometer and the thirteenth atomic absorption spectrometer of the tenth to twelfth inventions, the atomizer and the light source can be synchronized with a simple power supply configuration, and the power supply apparatus can be reduced in size and weight. Can do.

1 is a diagram illustrating a configuration of an atomic absorption analyzer of Example 1. FIG. 1 is a diagram showing a configuration of an atomizer 1 in an atomic absorption spectrometer of Example 1. FIG. The figure which showed the measurement principle by the atomic absorption analyzer of Example 1. FIG. FIG. 3 is a diagram showing a configuration of an atomic absorption analyzer of Example 2. FIG. 5 is a diagram showing the configuration of an atomizer 1 in the atomic absorption spectrometer of Example 2. The figure which showed the connection structure of the atomizer 1, the light source 7, and the power supply device 4 in the atomic absorption analyzer of Example 2. FIG. The figure which showed the response | compatibility with the applied voltage waveform in the atomic absorption analyzer of Example 2, and a light emission waveform. The figure which showed the time dependence of the emitted light intensity in the atomic absorption analyzer of Example 2. FIG. The figure which showed the time dependence of the emitted light intensity in the atomic absorption analyzer of Example 2. FIG. 6 is a graph showing the relationship between the absorption rate and the concentration in the atomic absorption spectrometer of Example 2.

Hereinafter, specific examples of the present invention will be described with reference to the drawings. However, the present invention is not limited to the examples.

FIG. 1 is a diagram showing the configuration of the atomic absorption spectrometer of Example 1. The atomic absorption analyzer includes an atomizer 1, a mirror 2, and a spectrometer 3.

The atomizer 1 generates atmospheric pressure plasma, irradiates the sample with atomization, atomizes the sample, mixes the atomized sample in the atmospheric pressure plasma, and generates plasma (atomized plasma 5) including the atomized sample. .

A more detailed configuration of the atomizer 1 will be described with reference to FIG. As shown in FIG. 2, it has the rod-shaped electrode 10 (1st electrode of this invention) and the sample electrode 11 (2nd electrode of this invention). The rod-like electrode 10 is a Cu rod having a diameter of 1.2 mm, and the sample electrode 11 is a stainless steel tube having an outer diameter of 2 m and an inner diameter of 1 mm. The outer peripheral surface of the rod-shaped electrode 10 is covered with an insulator 102.

The rod-like electrode 10 can be made of stainless steel, molybdenum, tungsten, or the like in addition to Cu. In addition to stainless steel, Cu, molybdenum, tungsten, or the like can be used for the sample electrode 11. However, considering that the sample electrode 11 itself is atomized and affects analysis, the sample electrode 11 is made of a material that does not contain the target element, or is coated or plated with a material that does not contain the target element. Etc. need to be applied.

The tip portion 111 of the rod-shaped electrode 10 is accommodated in the tube 120 of the ceramic tube 12 so that the axial directions thereof coincide with each other. In the ceramic tube 12, the tip 121 facing the sample electrode 11 is narrowed by one step, and the rod-shaped electrode 10 extends to the position of the narrowed tip 121. A gap 101 is provided between the rod-shaped electrode 10 and the inner wall of the ceramic tube 12. A space around the axis of the rod-shaped electrode 10 becomes a flow path of Ar gas.

The ceramic tube 12 is connected to the insulating tube 13 at the root. The insulating tube 13 has a branch 13 a in a direction perpendicular to the axial direction, and the rod-like electrode 10 extending from the inside 120 of the ceramic tube 12 to the inside 130 of the insulating tube 13 is bent to be inside the branch 13 a of the insulating tube 13. Is inserted and exposed to the outside. An insulating material such as a fluororesin can be used for the insulating tube 13.

Furthermore, a short ceramic tube 14 having an outer diameter substantially coincident with the inner diameter of the ceramic tube 12 is fitted into the tip 121 of the ceramic tube 12 facing the sample electrode 11.

The insulating tube 13 is connected to a gas cylinder (not shown) filled with Ar as a discharge gas via a flow meter, a pressure reducing valve, and the like. Ar gas supplied from the gas cylinder is supplied in the axial direction from the inside 130 of the insulating tube 13 to the inside 120 of the ceramic tube 12, and the gap 101 between the rod-shaped electrode 10 and the inner wall of the ceramic tube 12 is disposed on the tip side of the rod-shaped electrode 10. The Ar gas is discharged from the tip 140 of the ceramic tube 14.

As the discharge gas, He, Ne, N, air, etc. can be used in addition to Ar.
The sample electrode 11 is covered with a ceramic tube 15 having an inner diameter of 2 mm and an outer diameter of 3 mm. The outer diameter of the tip 150 of the ceramic tube 15 is expanded, and a mortar-shaped recess 16 is formed on the end surface 151 of the ceramic tube 15. The sample electrode 11 is exposed on the bottom surface 152 of the recess 16. A sample to be atomized is held by the recess 16. In addition, by making the sample electrode 11 tubular, it is possible to supply a liquid sample to the recess 16 of the tip 150 of the ceramic tube 15 through the tube. The ceramic tube 15 is further covered with a fluororesin material 17. In addition, when holding a fixed amount of sample in a recessed part, the sample electrode 11 does not need to be tubular, and it is good also as a rod shape.

The rod-shaped electrode 10 and the sample electrode 11 are connected to a power source 18 and an AC voltage of 60 Hz is applied. By applying a voltage to the rod-shaped electrode 10 and the sample electrode 11 while flowing Ar gas in the gap 101 between the rod-shaped electrode 10 and the inner wall of the ceramic tube 12 in the axial direction on the distal end side of the rod-shaped electrode 10, Atmospheric pressure plasma is generated at the tip 111, and the atmospheric pressure plasma extends to the sample electrode 11. Then, the atmospheric pressure plasma is irradiated onto the sample held in the recess 16 and the sample is atomized. A part of the atomized sample is mixed with atmospheric pressure plasma to emit light.

The mirror 2 is disposed so as to face the spectrometer 3 with the atomized plasma 5 generated by the atomizer 1 interposed therebetween, and the direction perpendicular to the reflection surface of the mirror 2 coincides with the light receiving direction of the spectrometer 3. ing. With such an arrangement of the mirror 2, the emission of atomized plasma is reflected by the mirror 2 so that the spectroscopic measuring instrument 3 can receive the reflected light. It is also possible to remove the mirror 2 so as not to face the spectrometer 3 so that the light emitted from the atomized plasma 5 reflected by the mirror 2 is received by the spectrometer 3. You can also. The mirror 2 may be made not to face the spectroscopic instrument 3 by simply moving the mirror 2 or rotating it so that the side that is not on the reflecting surface is directed to the spectrophotometer 3 side.

The mirror 2 is, for example, a mirror in which Al is vapor-deposited on a glass substrate, and may have any high reflectivity in a resonance line spectrum of a target element described later and an excitation line spectrum of Ar as a discharge gas.

The spectrophotometer 3 receives the direct light emission of the atomized plasma 5 and the light emission of the atomized plasma 5 reflected by the mirror, and spectrally measures the light intensity for each wavelength. The light receiving angle of the spectrometer 3 is such that the angle formed by the surface perpendicular to the opposing direction of the rod electrode 10 and the sample electrode 11 with respect to the sample disposed in the atomizer 1 is 45 to 75 °. Is desirable. This is because the emission intensity of the atomized plasma 5 increases at such an angle. More preferred is 60 °.

Next, the principle of atomic absorption analysis by the atomic absorption analyzer of Example 1 will be described with reference to FIG.

In atomic absorption analysis, the emission intensity is measured in a state where the mirror 2 is removed as shown in FIG. 3A and in a state where the mirror 2 is arranged as shown in FIG. The measurement order in each state is not limited, and the measurement with the mirror 2 removed may be performed first, or the measurement with the mirror 2 disposed may be performed first.

First, the case where the emission intensity is measured with the mirror 2 removed will be described. In this state, when the sample is atomized by the atomizer 1 and the atomized plasma 5 is generated, the spectrophotometer 3 measures only the emission intensity of the atomized plasma 5. At this time, the light emitted from the atomized plasma 5 is spectrally separated by the spectrophotometer 3, and the emission intensity Ir1 of the resonance line spectrum (wavelength λr) of the target element in the sample and the excitation line spectrum (wavelength λu) of Ar as the discharge gas. The emission intensity Iu1 is measured. The excitation line spectrum of Ar to be measured has a wavelength λu closest to the wavelength λr of the resonance line spectrum of the target element. This is to prevent the measurement accuracy from being lowered due to the wavelength dependence of the measurement system. The difference between the wavelength λr and the wavelength λu is desirably 150 nm or less.

Next, a case where the emission intensity is measured with the mirror 2 disposed will be described. In this state, when the atomizer 1 atomizes the sample to generate the atomized plasma 5, the ghost (ghost plasma 6) of the atomized plasma 5 is generated by the reflection of light by the mirror 2. Therefore, the spectrophotometer 3 measures the intensity of light that combines the light emission of the atomized plasma 5 and the light emission of the ghost plasma 6 that has passed through the atomized plasma 5. Then, the received light is spectrally separated by the spectrophotometer 3, and the emission intensity Ir of the resonance line spectrum (wavelength λr) of the target element in the sample and the emission intensity Iu of the excitation line spectrum (wavelength λu) of Ar Measure each.

Here, since Ar as the discharge gas is in a highly excited state, it can be considered that there is no self-absorption. Therefore, if the emission intensity of the excitation line spectrum of Ar due to the emission of the ghost plasma 6 is Iu2, the emission intensity Iu of the excitation line spectrum of Ar with the mirror 2 disposed is Iu = Iu1 + Iu2.

On the other hand, the target element has self-absorption. That is, the light emission of the ghost plasma 6 partially absorbs light having a wavelength λr of the resonance line spectrum of the target element when passing through the atomized plasma 5. Therefore, if the emission intensity of the resonance line spectrum of the target element due to the emission of the ghost plasma 6 is Ir2, and the amount of absorption by the atomized plasma 5 is Δ, the emission intensity Ir of the resonance line spectrum of the target element with the mirror 2 disposed. Is
Ir = Ir1 + Ir2-Δ (1)
It is.

Further, the emission intensity of the ghost plasma 6 relative to the emission intensity of the atomized plasma 5 can be regarded as being constant. This is because the wavelength dependence of the mirror 2 can be ignored because the wavelength λr of the resonance line spectrum of the target element is close to the wavelength λu of the excitation line spectrum of Ar. Of course, the correction may be performed in consideration of the wavelength dependency of the mirror 2. Therefore, if the ratio of Iu to Iu1 (= Iu / Iu1) is f,
f = (Ir1 + Ir2) / Ir1 (2)
It is.

Further, the absorption rate A, which is the ratio of the light having the wavelength λr of the ghost plasma 6 absorbed by the atomized plasma 5, is A = Δ / Ir2. If the equations (1) and (2) are used, the absorption rate A is
A = (f * Ir1-Ir) / ((f-1) * Ir1) (3)
Can be expressed as

Therefore, by measuring the four light emission intensities Iu1, Ir1, Ir, and Ir depending on whether or not the mirror 2 is arranged, the absorptance A due to the self-absorption of the target element can be calculated by the equation (3). From the calculated absorption rate A, the concentration of the target element in the sample can be obtained.

Further, the atomic absorption spectrometer of Example 1 can also simultaneously analyze a plurality of target elements. For example, when the emission intensity is measured with the mirror 2 removed, the emission intensity Is1 of the resonance line spectrum of another target element is measured together with the measurement of Iu1 and Ir1, and the emission intensity with the mirror 2 disposed. When measuring the emission intensity Is of the resonance line spectrum of other target elements together with the measurement of Iu and Ir, A ′ = (f * Is1−Is) / ((f−1) * Is1 ) To calculate the absorption rate A ′ due to self-absorption of other target elements. Therefore, the absorption rate A of one target element and the absorption rate A ′ of the other target element can be measured simultaneously.

As described above, the atomic absorption spectrometer of Example 1 does not require a light source that emits the resonance line spectrum of the target element unlike the conventional atomic absorption spectrometer, and thus can analyze a plurality of elements simultaneously. It can be analyzed regardless of metallic elements and non-metallic elements. In addition, since no light source is required, the atomic absorption spectrometer can be reduced in size and cost.

In Example 1, self-absorption is used by reflecting using a mirror, but other methods can also be used. For example, the light emitted from the atomized plasma may be received by an optical fiber or the like, and the light that has been irradiated to the atomized plasma and transmitted through the atomized plasma may be received by a spectrophotometer.

Further, the atomizer is not limited to the one shown in the first embodiment, and any one that can generate atomized plasma can be used. For example, an ICP device or the like can be used.

Next, a specific second embodiment of the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiment.

FIG. 4 is a diagram showing the configuration of the atomic absorption spectrometer of Example 2. The atomic absorption analyzer includes an atomizer 1, a light source 7, an analyzer 30, and a power supply device 4. The atomizer 1 generates atmospheric pressure plasma by applying a voltage from the power supply device 4, and irradiates the sample with the atmospheric pressure plasma to atomize the sample.

A more detailed configuration of the atomizer 1 will be described with reference to FIG.
As shown in FIG. 5, it has the rod-shaped electrode 10 (1st electrode of this invention), and the sample electrode 11 (2nd electrode of this invention). The rod-like electrode 10 is a Cu rod having a diameter of 1.2 mm, and the sample electrode 11 is a stainless steel tube having an outer diameter of 2 m and an inner diameter of 1 mm.

The tip of the rod-shaped electrode 10 is accommodated in the tube 120 of the ceramic tube 12 so that the axial directions thereof coincide. In the ceramic tube 12, the tip 121 facing the sample electrode 11 is narrowed by one step, and the rod-shaped electrode 10 extends to the inside of the narrowed tip 121. A gap 101 is provided between the rod-shaped electrode 10 and the inner wall of the ceramic tube 12. A space around the axis of the rod-shaped electrode 10 becomes a flow path of Ar gas.

The ceramic tube 12 is connected to the insulating tube 13 at the root portion. The insulating tube 13 has a branch 13 a in a direction perpendicular to the axial direction, and the rod-like electrode 10 extending from the inside 120 of the ceramic tube 12 to the inside 130 of the insulating tube 13 is bent to be inside the branch 13 a of the insulating tube 13. Is inserted and exposed to the outside. An insulating material such as a fluororesin can be used for the insulating tube 13.

The insulating tube 13 is connected to a gas cylinder (not shown) filled with Ar as a discharge gas via a pressure reduction / flow rate controller or the like. Ar gas supplied from the gas cylinder is supplied in the axial direction from the inside 130 of the insulating tube 13 to the inside 120 of the ceramic tube 12, and the gap 101 between the rod-shaped electrode 10 and the inner wall of the ceramic tube 12 is disposed on the tip side of the rod-shaped electrode 10. The Ar gas is discharged from the tip 140 of the ceramic tube 14.

As the discharge gas, He, Ne, N, air, etc. can be used in addition to Ar.
The sample electrode 11 is covered with a ceramic tube 15 having an inner diameter of 2 mm and an outer diameter of 3 mm. The outer diameter of the tip 150 of the ceramic tube 15 is expanded, and a mortar-shaped recess 16 is formed on the end surface 151 of the ceramic tube 15. The sample electrode 11 is exposed on the bottom surface 152 of the recess 16. A sample to be atomized is held by the recess 16. In addition, since the sample electrode 11 is tubular, it is possible to supply a liquid sample to the recess 16 formed on the end face of the tip of the ceramic tube 15 through the tube. The ceramic tube 15 is further covered with a fluororesin material 17. In addition, when holding a fixed amount of sample in the recessed part 16, the sample electrode 11 does not need to be tubular shape, and it is good also as a rod shape.

The rod-shaped electrode 10 and the sample electrode 11 are connected to the power supply device 4, and an alternating voltage of 60 Hz is applied. By applying a voltage to the rod-shaped electrode 10 and the sample electrode 11 while flowing Ar gas in the gap 101 between the rod-shaped electrode 10 and the inner wall of the ceramic tube 12 in the axial direction on the distal end side of the rod-shaped electrode 10, Atmospheric pressure plasma is generated at the tip 111, and the atmospheric pressure plasma extends to the sample electrode 11. Then, the atmospheric pressure plasma is irradiated onto the sample held in the recess 16 and the sample is atomized. A part of the atomized sample is mixed with atmospheric pressure plasma to emit light.

The light source 7 emits a resonance line spectrum of the target element, and is a hollow cathode lamp, for example. The light from the light source 7 is applied to the sample atomized by the atomizer 1.

The analyzer 30 receives the light from the light source 7 that has passed through the atomized sample and separates it to measure the emission intensity.

As shown in FIG. 6, the power supply device 4 includes an AC power supply 8 and a half-wave rectifier circuit 9. The AC power source 8 is a power source obtained by boosting a commercial 60 Hz AC power source, the atomizer 1 and the AC power source 8 are directly connected, and the light source 7 is connected to the AC power source 8 via a half-wave rectifier circuit 9. A 60 Hz AC voltage from the AC power source 8 is applied to the atomizer 1 as it is. The half-wave rectification circuit 9 is a circuit using, for example, a diode, and half-wave rectifies and outputs an alternating voltage of 60 Hz. Then, the half-wave rectified voltage is applied to the light source 7.

FIG. 7 is a diagram showing the correspondence between the applied voltage waveform and the light emission waveform. 7A shows the voltage waveform applied to the light source 7 and the light emission waveform of the light source, FIG. 7B shows the voltage waveform applied to the atomizer 1 and the light emission waveform of atmospheric pressure plasma, and FIG. The light emission waveform after the light emission of the light source passes through the atomized sample and is absorbed by the sample is shown. As shown in FIG. 7B, the atomizer 1 is driven by an alternating voltage of 60 Hz. Therefore, the atmospheric pressure plasma is emitted periodically and discretely at 60 Hz, and the sample is atomized. Further, as shown in FIG. 7A, since the 60 Hz AC voltage is half-wave rectified and applied to the light source 7, the light source 7 is turned on in synchronization with the half of the light emission period of the atmospheric pressure plasma.

Here, when the light emission intensity is measured in a state where both the light source 7 and the atmospheric pressure plasma emit light in synchronization, light emission that combines both the state of FIG. 7B and the state of FIG. 7C. Strength KA is obtained. Therefore, the light emission intensity A is measured in a state where only the atmospheric pressure plasma is emitted (the state shown in FIG. 7B), and the light emission in the state shown in FIG. 7C is obtained by subtracting the light emission intensity A from the light emission intensity KA. The intensity, that is, the emission intensity KA-A of the light source after receiving absorption by the atomized sample can be calculated. Then, by comparing the light emission intensity (the light emission intensity of the light source 7) with the light emission intensity KA-A in the state of FIG. 7A, the absorptance can be found and the concentration of the target element in the sample can be measured. .

As described above, in the atomic absorption spectrometer of Example 2, the synchronization between the light emission of the atmospheric pressure plasma and the light emission of the light source 7 can be realized by the power supply device 4 having a simple configuration, and the power supply device 4 can be downsized. Weight reduction can be achieved. As a result, the atomic absorption analyzer itself can be reduced in size and weight.

FIG. 8 is a graph showing the results of measuring the time dependence of the emission intensity of the resonance line spectrum (wavelength 324 nm) of Cu using the atomic absorption analyzer of Example 2 with water containing 10 ppm of Cu as a sample. . 8A shows the emission intensity KA when both the light source 7 and the atmospheric pressure plasma emit light, and FIG. 8B shows the emission intensity A in the emission of only the atmospheric pressure plasma, FIG. 8C. Indicates the emission intensity KA-A obtained by subtracting the emission intensity A from the emission intensity KA. The light emission intensity KA and the light emission intensity A are plotted as values obtained by integrating the light emission intensities every 3 seconds. FIG. 8C shows the light intensity of the light source 7 that has absorbed the atomized Cu.

FIG. 8 (c) shows that the time when the emission intensity becomes the weakest, that is, the absorption peak due to Cu is seen approximately 3 seconds after the start of emission. Further, when about 15 seconds have passed, the change in the emission intensity is almost constant because all the sample is atomized and scattered and disappears. That is, the section where the light emission intensity is constant indicates the light intensity of the light source 7 itself. Therefore, the absorption rate is obtained by dividing the absorption amount at the peak of absorption by the emission intensity after 15 seconds (light intensity of the light source 7). In the case of FIG. 8C, the absorption rate is 100%.

FIG. 9 is a graph showing the results of measuring the time dependence of the emission intensity of the resonance line spectrum of Cu using the atomic absorption analyzer of Example 2 with the sample being water containing 0.1 ppm of Cu. FIG. 9A shows the emission intensity KA when both the light source 7 and the atmospheric pressure plasma are emitted, and FIG. 9B shows the emission intensity A in the emission of only the atmospheric pressure plasma, FIG. 9C. Indicates the emission intensity KA-A obtained by subtracting the emission intensity A from the emission intensity KA. The light emission intensity KA and the light emission intensity A are plotted as values obtained by integrating the respective light emission intensities per second. FIG. 9C shows the light intensity of the light source 7 that has absorbed the atomized Cu.

From FIG. 9C, when the absorption rate is obtained by the same method as in the case of FIG. 8C, it is about 70%. FIG. 10 is a graph showing the result of theoretical calculation of the relationship between the absorption rate and the concentration of Cu in the sample. The horizontal axis is the absorptance, and the vertical axis is the number of atoms per cm ³ . When 1 ppm of Cu is contained in water at normal temperature and 1 atmosphere, the number of Cu atoms per 1 cm ³ is 7.5 × 10 ¹² . It can be seen that the result of FIG. 9 that the Cu concentration is 0.1 ppm and the absorptance is 70% roughly matches the graph of FIG. Further, FIG. 10 suggests that the Cu concentration can be measured in the range of 0.001 to 1 ppm.

The atomic absorption analysis apparatus and atomic absorption analysis method of the present invention can simultaneously measure a plurality of elements, and can also measure nonmetallic elements such as P and B, which have been difficult to detect conventionally. The atomic absorption spectrometer of the present invention can be used for monitoring of sewage and the like.

1: Atomizer 2: Mirror 3: Spectrometer 4: Power supply device 5: Atomized plasma 6: Ghost plasma 7: Light source 8: AC power supply 9: Half-wave rectifier circuit 10: Rod electrode 11:

Sample electrode

12, 14, 15: Ceramic tube 13: Insulating tube 16: Recessed portion 17: Fluorine resin material 18: Power supply 30: Analyzer

Claims

An atomizer for generating an atomized plasma containing an atomized sample;
In the emission spectrum of the atomized plasma, the emission intensity of the resonance line spectrum of the target element and the emission intensity of the excitation line spectrum of the discharge gas are respectively measured, and the emission of the atomized plasma and the emission from the atomized plasma are measured with the atomization. A measuring device that measures the emission intensity of the resonance line spectrum of the target element and the emission intensity of the excitation line spectrum of the discharge gas in the spectrum of the light that is irradiated with the plasma and transmitted through the atomized plasma. ,
An atomic absorption spectrometer characterized by comprising:
The atomic absorption spectrometer according to claim 1, wherein the measuring device includes a mirror, and the mirror plasma reflects light emitted from the atomized plasma to irradiate the atomized plasma.
3. The atomic absorption spectrometer according to claim 1, wherein the emission intensity of the excitation line spectrum of the discharge gas to be measured has a wavelength closest to the resonance line spectrum of the target element.
The atomizer generates the atmospheric pressure plasma, irradiates the sample containing the target element with the atmospheric pressure plasma, and atomizes the sample to generate atomized plasma. Item 4. The atomic absorption spectrometer according to any one of items 3 to 4.
The atomizer is
A rod-shaped first electrode;
A tip of the first electrode is held in the tube so that the first electrode is separated from the tube inner wall around the axis of the first electrode, and the tube inner wall and the first electrode are held in the tube. An insulating tube through which discharge gas flows in the axial direction on the tip end side of the first electrode,
A second electrode disposed at a certain distance from the tip of the first electrode;
A sample holding portion made of an insulating material having a concave portion for holding the sample, and the second electrode exposed on the bottom surface of the concave portion;
The atomic absorption spectrometer according to claim 1, wherein the atomic absorption analyzer is provided.
Generate atomized plasma containing atomized sample,
In the emission spectrum of the atomized plasma, the emission intensity of the resonance line spectrum of the target element and the emission intensity of the excitation line spectrum of the discharge gas are respectively measured.
In the spectrum of light in which the light emitted from the atomized plasma and the light that is emitted from the atomized plasma to the atomized plasma and transmitted through the atomized plasma are added, the emission intensity of the resonance line spectrum of the target element, and the discharge Measure the emission intensity of the excitation line spectrum of the gas,
Atomic absorption spectrometry characterized by that.
The atomic absorption analysis method according to claim 6, wherein the atomized plasma is irradiated with light emitted from the atomized plasma by being reflected by a mirror.
The atomic absorption analysis method according to claim 6 or 7, wherein the emission intensity of the excitation line spectrum of the discharge gas to be measured has a wavelength closest to the resonance line spectrum of the target element.
Atomized plasma is generated by generating atmospheric pressure plasma, irradiating the sample containing the target element with the atmospheric pressure plasma, atomizing the sample, and mixing the atomized sample into the atmospheric pressure plasma. The atomic absorption analysis method according to any one of claims 6 to 8, wherein:
An atomizer that generates atmospheric pressure plasma, irradiates the sample with the atmospheric pressure plasma, and atomizes the sample;
A light source that emits an emission line spectrum of a target element in the sample and irradiates the atomized sample;
An analyzer for receiving and analyzing light from the light source that has passed through the atomized sample;
A power supply device for driving the atomizer and the light source;
Have
The power supply device includes an AC power supply and a half-wave rectification circuit that rectifies a part of the output from the AC power supply, and supplies the output from the AC power supply to the atomizer. Supplies the output from the half-wave rectifier circuit,
An atomic absorption spectrometer characterized by that.
The analyzer is
A first emission intensity of the light combining the light of the light source transmitted through the atomized sample and the emission of the atmospheric pressure plasma, and a second emission intensity that is only emission of the atmospheric pressure plasma; ,
By subtracting the second emission intensity from the first emission intensity, the emission intensity of the light from the light source that has passed through the atomized sample is calculated.
The atomic absorption spectrometer according to claim 10.
The atomizer is
A rod-shaped first electrode;
A tip of the first electrode is held in the tube so that the first electrode is separated from the tube inner wall around the axis of the first electrode, and the tube inner wall and the first electrode are held in the tube. An insulating tube through which discharge gas flows in the axial direction on the tip end side of the first electrode,
A second electrode disposed at a certain distance from the tip of the first electrode;
A sample holding portion made of an insulating material having a concave portion for holding the sample, and the second electrode exposed on the bottom surface of the concave portion;
The atomic absorption spectrometer according to claim 10 or 11, characterized by comprising:
An atmospheric pressure plasma is generated by applying an alternating voltage, the sample is irradiated with the atmospheric pressure plasma, the sample is atomized,
By applying a voltage obtained by half-wave rectification of the AC voltage, emission of the emission line spectrum of the target element in the sample is generated, and the emitted sample is irradiated and transmitted through the atomized sample.
Measuring the first emission intensity of the light combining the emission of the atmospheric pressure plasma and the light transmitted through the atomized sample, and the second emission intensity that is only emission of the atmospheric pressure plasma;
By subtracting the second emission intensity from the first emission intensity, the emission intensity of the light from the light source that has passed through the atomized sample is calculated.
Atomic absorption spectrometry characterized by that.