JPH0968493A - Atomic absorptiometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent lowering of absorption sensitivity and production of contamination by shielding a magnet from radiation heat and conduction heat emitted from a graphite tube thereby blocking the corrosive gas produced through evaporation of acids from a sample contained in the graphite tube. SOLUTION: A gas control section 14 supplies a carrier gas 16 to the inside of a graphite tube 1 and a sheath gas 17 to the outside of graphite tube 1 and into a shield tube 4. When an electrode 3 is fed with a current, the graphite tube 1 is heated through the resistance and thereby a sample 5 is heated to produce atomic vapor. A light subjected to atomic absorption through the atomic vapor is passed through a spectrometer 8 and only the measuring light is detected by a detector 9. The detector 9 delivers a detection data to a signal processing section 11 where the absorbance of sample 5 is determined arithmetically and the results are delivered to an output unit 13.

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 for analyzing a metal element by atomizing a sample and subjecting the atom to absorption spectrometry.

[0002]

2. Description of the Related Art In the above-mentioned atomic absorption spectrophotometer, a sample is housed in a graphite tube, and an electric current is passed through the graphite tube to heat the sample, whereby the sample is atomized into atomic vapor. A magnetic field is applied to the atomic vapor by a magnet, a light flux from a light source is irradiated, and the absorbance is measured by the polarized Zeeman method. A magnet that applies a magnetic field to the atomic vapor of an atomic absorption spectrophotometer needs a magnetic flux density of 0.8 T or more at the center of the graphite tube. To reduce the size of the magnet, both poles of the magnet are brought close to generate the required magnetic flux density. Was there. Therefore, the magnet is placed as close to the graphite tube as possible. Conventionally, the distance between the poles of the magnet has been set to about 11 mm.

[0003]

In the arrangement of magnets as described above, the distance between the graphite tube and the magnet is 2 mm or less, and further,
Since only air was provided between the magnets, the magnets were heated to a high temperature by the radiant heat and the conductive heat of the graphite tube, and the magnets were easily corroded by the influence of the acid contained in the sample contained in the graphite tube. Therefore, as the use time elapses, the shape of the magnet changes due to high temperature and corrosion, which adversely affects the magnetic circuit, and rust at the time of corrosion enters the graphite tube. As a result, the magnetic flux density is reduced and the optimum Zeeman effect is not obtained, and the absorption sensitivity is reduced. Furthermore, the components contained in rust cause contamination, which deteriorates the measurement accuracy.

The object of the present invention is to minimize the effects of radiant heat and conductive heat of a graphite tube on a magnet, and acids contained in a sample, to prevent a decrease in absorption sensitivity and improve measurement accuracy. It is to provide an atomic absorption photometer.

[0005]

In order to achieve the above-mentioned object, the present invention provides a polarized Zeeman method in which a sample contained in a graphite tube is heated by applying an electric current to the graphite tube and a magnetic field is applied to the sample atoms by a magnet. An atomic absorption spectrophotometer for performing absorption analysis of sample atoms according to, characterized by having means for shielding the graphite tube between the graphite tube and the magnet.

[0006]

[Function] As described above, the graphite tube is shielded between the graphite tube and the magnet. Thereby, the radiant heat and the conductive heat emitted from the heated graphite tube are blocked and the temperature rise of the magnet can be suppressed. Furthermore, the corrosive gas vaporized by the acid contained in the sample contained in the graphite tube is blocked to prevent the magnet from corroding. Therefore, even if the magnet is used for a long period of time, the shape of the magnet does not change due to high temperature and corrosion, the magnetic circuit is not affected, and the optimum Zeeman effect is obtained under a stable magnetic flux density, so that the absorption sensitivity does not decrease. Furthermore, since rust does not occur on the magnet, contamination does not occur and the measurement accuracy is improved.

[0007]

EXAMPLE An example of an atomic absorption photometer according to the present invention will be described with reference to FIGS. FIG. 1 is a schematic diagram showing the overall configuration of the atomic absorption photometer according to this embodiment. FIG. 2 is a side view of the graphite tube and the shield tube of FIG.
FIG. 3 is a side view of an embodiment in which the shielding means of FIG. 1 is modified.

As shown in FIG. 1, in this atomic absorption spectrophotometer, a graphite tube 1 is attached to an electrode 3, and the electrode 3 is connected to a power source 7. A sample 5 to be measured is injected and housed in the center of the inside of the graphite tube 1. A shielding tube 4 arranged between the graphite tube 1 and the magnet 2 covers the graphite tube 1. Further, the magnet 2 applies a magnetic field to the sample 5 from the outside of the shield cylinder 4. The gas control unit 14 heats the Ar gas 15 when heating the graphite tube 1.
The carrier gas 16 and the sheath gas 17 are supplied to prevent the oxidation of the. The carrier gas 16 flows inside the graphite tube 1. The sheath gas 17 flows into the outside of the graphite tube 1 and the inside of the shielding cylinder 4. When a current is supplied to the electrode 3 from the power source 7, the graphite tube 1 generates resistance heat and the sample 5 is heated. Then, the sample 5 is atomized into atomic vapor. A magnetic field is applied to the atomic vapor by the magnet 2. The atomic vapor inside the graphite tube 1 is irradiated with a light beam from the light source 6, and when the light passing through the inside of the graphite tube 1 is applied with the magnetic field of the magnet 2, it is perpendicular to the polarized light and the magnetic field due to the Zeeman effect. It is divided into light with various polarization components,
In the light of parallel polarization component, the wavelength peculiar to the sample 5 is atomically absorbed and is also absorbed by the background component such as molecules and particles, and in the light of vertical polarization component, the wavelength peculiar to the sample 5 is slightly atomically absorbed. It is absorbed by background components such as molecules and particles. Each light that has been subjected to atomic absorption is taken into the spectroscope 8 and dispersed therein, and only each measuring light is sent to the detector 9 and detected. The detection data is sent from the detector 9 to the signal processing unit 11, the absorbance of the sample 5 is calculated by calculation processing, and the result is output to the output device 13.

A current value from the power source 7 and the gas control unit 14
The gas flow rate from the is controlled by the controller 12. In addition, the signal processing unit 11 and the control unit 12 are the central processing unit 10.
It is summarized in.

In FIG. 3, the shielding means is changed, and a graphite plate 1 and a magnet 2 are provided by a shielding plate 18 arranged between the graphite tube 1 and the magnet 2.
Shield. In this embodiment, either of the means shown in FIGS. 1 and 3 may be used, but in the following description, the means shown in FIG. 1 is used.

In the polarized Zeeman atomic absorption spectrophotometer, it is important to protect the magnet 2 which constantly applies a magnetic field having a magnetic flux density of 0.8 T or more to the atomic vapor from high temperature and corrosive gas. Otherwise, it is highly sensitive. High precision analysis is not possible. In this embodiment, the shielding tube 4 is provided between the graphite tube 1 and the magnet 2 to cover the graphite tube 1, so that the shielding tube 4 prevents the radiant heat emitted from the graphite tube 1 from hitting the magnet 2 and at the same time conducts heat. To suppress the temperature rise of the magnet 2.
In addition, the corrosive gas vaporized by the acid or the like contained in the sample 5 contained in the graphite tube 1 can be blocked.

In this embodiment, the shielding tube 4 is used as a means for shielding the graphite tube 1, but the graphite tube 1 may be covered with different shapes as long as it can be covered. Further, the component to be shielded may be composed of a plurality of components.

According to this embodiment, the magnet 2 can be protected from high temperature and corrosive gas. Therefore, even if the magnet 2 is used for a long time, the shape of the magnet 2 does not change due to high temperature and corrosion, so that the magnetic circuit is not affected, and the optimum Zeeman effect is obtained under a stable magnetic flux density, so that the absorption sensitivity does not decrease. Further, since rust does not occur on the magnet 2, contamination does not occur and the measurement accuracy is improved. Further, in the present embodiment, it is necessary to widen the distance between the bipolar tubes of the magnet 2 to 15 mm in order to dispose the shield cylinder 4, and since the magnet 2 is a rare earth magnet, it is very weak against high temperatures. According to this, since the temperature rise of the magnet 2 can be suppressed within 50 ° C., the rare earth magnet can be easily used without increasing the cost. Furthermore, since the shielding tube 4 covers the graphite tube 1 with a narrow gap, the filling efficiency of the Ar gas 15 is increased, and the flow rate 3 L / min of the sheath gas 17 can be halved, and the consumption of the Ar gas 15 can be reduced. it can.

[0014]

According to the present invention, since there is a means for shielding the graphite tube between the graphite tube and the magnet, the radiant heat and the conductive heat emitted from the heated graphite tube to the magnet are shielded, and The corrosive gas vaporized by the acid contained in the sample contained in the graphite tube can be blocked. Therefore, even if it is used for a long time, the magnetic circuit of the magnet is not affected by high temperature and corrosion, and the measurement can be performed under a stable magnetic flux density, so that the absorption sensitivity does not decrease. Further, since the contamination due to the rust of the magnet does not occur, the measurement accuracy is improved.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a side view of the graphite tube and the shielding tube of FIG.

FIG. 3 is a side view of an embodiment in which the shielding means of FIG. 1 is changed.

[Explanation of symbols]

1 ... Graphite tube, 2 ... Magnet, 3 ... Electrode, 4 ... Shielding cylinder, 5 ... Sample, 6 ... Light source, 7 ... Power supply, 8 ... Spectrometer, 9 ... Detector, 1
0 ... Central processing unit, 11 ... Signal processing unit, 12 ... Control unit, 1
3 ... Output device, 14 ... Gas control unit, 15 ... Ar gas, 1
6 ... Carrier gas, 17 ... Sheath gas, 18 ... Shielding plate.

Claims (1)

[Claims] 1. An atomic absorption spectrophotometer for heating a sample contained in a graphite tube by applying an electric current to the graphite tube and applying a magnetic field to the atoms of the sample by a magnet to perform an absorption analysis of the sample atoms by a polarized Zeeman method. The atomic absorption spectrophotometer according to claim 1, further comprising means for shielding the graphite tube between the graphite tube and the magnet.