JPH0762649B2 - Atomic absorption spectrophotometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is applicable to environmental analysis such as air pollution and water pollution, analysis of heavy metals in drugs, foods, analysis of metallic materials, analysis of trace metals in living bodies, etc. The present invention relates to an atomic absorption spectrophotometer used, and particularly to an atomic absorption spectrophotometer suitable when a sample is a solid.

[Prior Art] In the conventional atomic absorption spectrophotometer, when an attempt is made to analyze (quantify) a metal element in a solid sample, the solid sample is generally dissolved, and particularly a complex composition or a trace element At the time of analysis, if necessary, the solution obtained by the solvent extraction operation is injected into a flame or flameless atomic absorption spectrophotometer for analysis.

On the other hand, although a solid sample is also directly analyzed without pretreatment, in this case, the atomization part is constituted by a solid pyrolytic graphite tube (furnace) (see, for example, JP-A-59). -94043 gazette). At this time, the sample is introduced by inserting it with a boat (sample pan) from the opening of the end face.

In addition, when a solid sample is directly analyzed, no sample treatment is performed and the background is very large. Therefore, the Zeeman method, which is highly accurate for background correction, is generally used for solid sample analysis. Absorption spectrophotometers are also in practical use.

[Problems to be Solved by the Invention] In the conventional atomic absorption spectrophotometer, when a solid sample is used as a solution sample, a pretreatment operation requires a great deal of time and labor, so that rapid analysis can be achieved. There was a problem that it could not be done. Further, there is a problem that sample loss, contamination, dilution error, etc. may occur in the pretreatment.

On the other hand, when a solid sample is directly analyzed without pretreatment, using a large-diameter graphite tube (furnace) increases the emission intensity and relatively lowers the light source intensity, increasing baseline noise and peaking. There is a problem that it is difficult to introduce a large-diameter graphite tube because of the large variation in the value, and it is difficult to introduce the sample into the atomization furnace.

Also, in the case of a Zeeman atomic absorption spectrophotometer, since there is originally a light amount loss due to the polarizer, a considerable energy loss occurs in combination with the light amount loss due to the background from the solid sample, and the S / N ratio drops significantly. There was a problem to do.

The present invention is a method of directly analyzing a solid sample without pretreatment, increasing noise even if the atomizing furnace has a large diameter to facilitate sample introduction, and variation in peak value does not increase,
The purpose is to obtain an atomic absorption spectrophotometer capable of highly accurate analysis.

[Means for Solving the Problems] In order to achieve the above object, in the atomic absorption spectrophotometer of the present invention, a lamp that is turned on by alternately passing a small current and a large current is used as a light source and passes through. At least one of the entrance and exit windows of the atomization furnace of the emission line spectrum is made movable by driving means, and after the sample is inserted into the atomization furnace, it is opened during drying and ashing of the heating program, and atomization is performed. Sometimes it is configured to interlock so that it is in a closed state. A cylindrical graphite furnace or the like is used as the atomization furnace.

Further, in order to discharge the inner gas introduced into the reactor and the gas generated from the sample during heating to the outside of the reactor, it is effective to provide a gas jet port on the outer wall or window of the reactor.

[Operation] When the light source of the atomic absorption spectrophotometer configured as described above is turned on, as is well known, the emission line spectrum of the lamp has a recessed center that receives background absorption at high currents, while at the time of small currents Since it becomes one peak that receives both background absorption and atomic absorption,
Atomic absorption corrected for background absorption can be measured from the difference in absorbance between the two, but since the light source of such a lighting method has a high light intensity without loss of light quantity, the atomization furnace accompanying the increase in diameter of the atomic reactor It reduces the relative decrease in emission intensity between the light source and the light source, and enables a large diameter of the atomic reactor.

In addition, the gas outlet provided on the outer wall or window of the nuclear reactor,
Particularly, the smoke generated from the sample at the time of drying and ashing is helped to be discharged to the outside of the furnace by the action of the inert inner gas introduced into the furnace, so that it is less affected by the background. Smoke generated from the sample is effectively diffused by making the inlet and outlet of both ends of the atomization furnace open ends, but on the other hand, when the air outside the furnace flows into the interior of the atomization furnace (graphite This shortens the life of the furnace and causes diffusion of atomized elements at the time of atomization, resulting in reduced sensitivity.

For this reason, the detachable window of the nuclear reactor is driven in conjunction with the temperature raising program of the nuclear reactor.For example, in the case of a solid sample in which a large amount of smoke is generated, drying and ashing are performed. It is preferable to keep the window open to effectively diffuse the smoke and close it during atomization to avoid a loss of sensitivity. Of course, in the case of a sample that does not generate much smoke, the window may be maintained in a closed state after the sample is introduced into the furnace, and the smoke may be discharged from the gas outlet of the furnace wall or the window.

[Embodiment] An embodiment will be described with reference to the drawings. In FIG. 1, a light source 1 is a hollow cathode lamp and has three states of small current, large current and preliminary lighting (base) or current off.
Lights at high frequency (100Hz) as a cycle. The lamp of such a lighting method is not affected by the emission noise of the nuclear reactor, has no loss of light quantity, and has a light intensity of 100 times or more that of a small current at a large current. When a small current and a large current are alternately applied to the hollow cathode lamp 1, the bright line spectrum of the lamp has a concave shape at the center when the current is large, and is mainly absorbed by the background. Since both the ground absorption and the atomic absorption are absorbed, therefore, the true atomic absorption corrected for the background absorption can be measured by obtaining the difference between the two absorbances.

The light flux from the light source 1 enters from the window plate 3, passes through the atomization furnace 2, and enters the spectroscope 6. As is well known, the atomization furnace 2 is a graphite furnace, and by controlling the supplied current, the atomization furnace 2 is controlled to a temperature according to each set heating temperature in the furnace, that is, drying, ashing and atomization. Inert gas is introduced as an inner gas into the atomization furnace 2 and dried from the gas ejection port 5 opened on the outer wall of the furnace or / and the gas ejection port 5 '(see FIG. 2) provided on the window plates 3 and 4. The smoke generated from the sample during ashing is discharged to the outside of the furnace. Usually, the movable window plate 4 is closed after the sample is placed on a boat (sample dish) and inserted into the atomization furnace 2. However, when a large amount of smoke is generated by the sample, the movable window plate 4 is preferably It is preferable that the fixed window plate 3 is also movable and both the window plates are dried and opened at the time of ashing. At the time of atomization, the window plate 4 is closed and the introduction into the inert gas furnace is also stopped. This is to prevent the atomized target element from diffusing and lowering the sensitivity.

The movable window plate 4 can be driven by an appropriate means. Considering the above-mentioned point, it is preferable to drive the movable window plate 4 in conjunction with the temperature raising program of the nuclear reactor 2. It is also possible to interlock with the operation of the push button of.

The light flux passing through the atomization furnace 2 selectively and strongly absorbs the bright line spectrum, the spectroscope 6 disperses the bright line spectrum, and the detector 7 detects it as an electric signal. As described above, the difference in absorbance between the bright line spectrum at high current and the bright line spectrum at small current is obtained by the signal processing unit 8, and this is displayed on the display unit 11 via the control unit 9 as a value proportional to the concentration of the target element. Give instructions. These signal processing systems are well known. Reference numeral 10 is an operation unit such as a keyboard.

[Effects of the Invention] Since the present invention is configured as described above, it is possible to increase the size (large diameter) of the atomization furnace, and it becomes easy to introduce a solid sample into the atomization furnace, Further, smoke in the atomization furnace can be effectively diffused, and a solid sample can be directly analyzed with high sensitivity and high accuracy.

[Brief description of drawings]

FIG. 1 is a system block diagram of the atomic absorption spectrophotometer of the present invention, and FIG. 2 is a diagram showing the shape of a window plate. 1 ... Light source, 2 ... Atomic furnace, 3, 4 ... Window plate 5, 5 '... Gas ejection port, 6 ... Spectrometer, 7 ... Detector, 8 ... Signal processing unit

Claims (1)

[Claims] 1. An atomization furnace for atomizing a target element contained in a sample by thermally decomposing an emission line spectrum from a light source with a temperature rising program for drying, ashing and atomization after inserting a solid sample. , Only the emission line of the target element is selected by the spectroscope, in the atomic absorption spectrophotometer to detect this with a detector, with a lamp that is lit by alternately passing a small current and a large current to the light source, At least one of the windows of the entrance or exit of the emission spectrum of the atomization furnace is configured to be openable and closable, and the windows are opened during drying and ashing in conjunction with a temperature raising program, and the windows are opened during atomization. An atomic absorption spectrophotometer, characterized by comprising window driving means for driving so as to be in a closed state.