JP2576745B2 - Flameless atomic absorption spectrophotometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a flameless atomic absorption spectrophotometer.

[0002]

2. Description of the Related Art In a frameless atomic absorption spectrophotometer,
A sample is placed in a heating tube such as a graphite tube, the sample is heated to a high temperature by the heating tube to atomize, and a measurement light is passed through the sample to measure the absorbance.

When the content of a metal in an organic substance is to be measured by such a flameless atomic absorption spectrophotometer,
Ordinarily, a predetermined amount of an organic substance is dropped into a heating tube as an aqueous solution having a known concentration, atomized as described above, and the contained metal amount is measured. Here, in order to perform an accurate measurement, it is necessary to remove interfering components such as moisture and organic substances from the sample in advance before atomizing the target metal component. Therefore, conventionally, in the frameless atomic absorption spectrophotometer, the temperature of the heating tube is program-controlled in a pattern as shown in the upper part of FIG. That is, first, the sample is heated at a temperature of about 100 ° C. for about several tens of seconds to evaporate the moisture of the sample (drying). Next, it is heated in a temperature range of about 100 to 1000 ° C. for about several tens of seconds to vaporize an organic substance (ashing). After the water and organic substances are sufficiently removed in this way, the heating tube is heated to a high temperature (about 1000 to 3000 ° C.), and the remaining analytical components mainly composed of metal components are atomized to perform absorption spectrophotometry. In addition, the time of this absorption spectrophotometry is about several seconds.

[0004] Among the above-mentioned heating patterns, organic matter is burned during incineration, so that smoke is generated. As shown in FIG. 2A, the smoke generated during the ashes generated in the heating tube is also discharged from a sample loading inlet 22 provided on the side surface of the heating tube 21,
The measurement light is also diffused in the direction of the optical axis 23, and this smoke stays in the heating tube 21 until later atomization, which adversely affects the measurement.
Therefore, as shown in FIG. 2B, both ends of the heating tube 21 (actually, the electrodes 24 that sandwich and cover the heating tube 21)
windows 25a, 2 made of a transparent quartz plate
5b, and inner gas passages 2 provided at both ends of the electrodes 24a, 24b (but inside the windows 25a, 25b).
From 6, an inert gas (inner gas) such as Ar was allowed to flow into the heating tube 21. As a result, the smoke generated at the time of incineration does not spread in the direction of the optical axis 23, but is pushed by the inner gas and is forcibly and promptly discharged from the sample inlet 22. In addition, an inert gas (outer gas) is similarly fed into the space between the heating tube 21 and the electrodes 24a and 24b from the outer gas passage 27 to prevent the heating tube 21 made of graphite from being oxidized and consumed. The outer gas is discharged from the gap 28 between the electrodes 24a, 24b.

[0005]

However, even if the quartz windows 25a and 25b are thin, absorption of the measuring light is inevitable even if they are thin. In particular, S / S of the measuring signal is short in a short wavelength region of 200 nm or less. The problem is that the N ratio decreases (for example, at λ = 190 nm, a loss of about 10% occurs per quartz plate).

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to prevent both the influence of smoke at the time of ashing and the loss of measurement light due to a quartz window. Another object of the present invention is to provide a flameless atomic absorption spectrophotometer capable of performing highly accurate measurement.

[0007]

According to the present invention, which has been made to solve the above-mentioned problems, a heating tube having a sample loading inlet on a side surface, an outer envelope tube surrounding the heating tube, and an inside of the heating tube are provided. In a frameless atomic absorption spectrophotometer provided with an inner gas inlet provided in an outer tube for introducing gas and a heating control unit for program-controlling heating of the heating tube, a) from an inner gas inlet of the outer tube; B) a window plate which can be opened and closed at both outer openings, and b) an upper portion at the time of drying and incineration of the heating program of the heating tube.
Close the opening and open it during atomization.
It is characterized by and a window opening and closing controller for opening and closing the window plate.

[0008]

When the program heating is incinerated by the heating control unit, the window opening / closing control unit closes the window plate. As a result, the smoke generated during the incineration does not diffuse into the heating tube, but is quickly expelled from the sample loading inlet on the side surface of the heating tube following the inner gas. For this reason, the background due to the interfering component is minimized in the subsequent measurement. At the time of atomization of program heating, the window opening / closing control unit opens the window plate. As a result, the measurement light from the light source irradiates the atomized sample without attenuating due to passing through the window plate on the entrance side, and reaches the light receiver without being attenuated on the exit side, so that accurate measurement can be performed. Done. At the time of measurement, it is desirable to stop the inner gas in order to keep the atomized sample in the heating tube as long as possible. In this case, since the atomized sample spreads in the direction of the optical axis, the measurement light spatially passes through the sample gas for a longer time, and this also increases the measurement accuracy.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. The configuration of the flameless atomic absorption spectrophotometer of this embodiment is as shown in FIG. The measurement light emitted from the light source 31 passes through the heating tube 21 (FIG. 4) inside the furnace part 32, is separated by the spectroscope 34, and the intensity is detected by the detector 35. The control unit 37 controls the spectroscope 34, receives a signal from the detector 35 via the signal processing unit 36, and analyzes the measurement sample. Note that an operation unit 42 such as a keyboard and a display unit 41 such as an LCD are connected to the control unit 37.

The structure of the furnace section 32 will be described in detail with reference to FIG. The furnace part 32 is made of graphite heating tube 21 and heating tube 2.
1, two electrodes 24a and 24b, and a window plate 33 that can be opened and closed and provided at the ends of both electrodes 24a and 24b.
a, 33b (and their window frames 43a, 43b). As shown in FIGS. 5A and 5B, the opening / closing mechanism of the window plates 33a and 33b may be rotated by a motor 52 and a gear 53 to put the window plates 33a and 33b into the window frames 43a and 43b. Alternatively, as shown in FIG. 5C, a type in which the parallel movement is performed by a parallel movement device 54 such as a solenoid or a pneumatic device may be used.

The electrodes 24a and 24b serve as electrodes for sandwiching the heating tube 21 to allow a large current to flow and energize and heat the heating tube 21, and also as an outer tube for covering the heating tube 21. I have. Therefore, a sample loading port 29 is provided on the electrode 24a on the side covering the portion corresponding to the sample loading port 22 provided at the center of the side surface of the heating tube 21. In addition, both electrodes 24a and 24b are located outside of a portion in contact with both end surfaces of the heating tube 21 and are located outside the window frame 43a,
The inner gas passage 26 is located on the inner side than 43b.
However, the outer gas passage 27 is located on the center side of the contact point.
Is provided.

Returning to FIG. 3, the opening and closing of the window plates 33a and 33b are performed by opening and closing the window plate driving unit 38 (in the case of FIG.
In the case shown in FIG. 2B, the inert gas is supplied to the inner gas passage 26 and the outer gas passage 27 by the gas supply unit 39.
Further, electric power for energizing and heating the heating tube 21 is supplied from the heating power supply unit 40.

After the sample is loaded into the heating tube 21 and the operator presses the start switch of the operation unit 42, the control unit 37
Performs the following processing. First, by controlling the heating power supply unit 40 in accordance with a program previously input by an operator (or stored in a ROM or an external storage device or the like), the heating tube 21 is controlled in a pattern as shown in the upper part of FIG. Perform heating. Then, in synchronization with this heating program, the window plate drive section 38 and the gas supply section 39 are controlled as follows (middle and lower rows in FIG. 1). In the drying period and the incineration period, the window plates 33a and 33b are inserted into the window frames 43a and 43b to shield both sides of the heating tube 21, and an inert gas is sent from the inner gas passage 26 into the heating tube 21. The vapor in the drying period and the smoke in the incineration period generated in the heating pipe 21 are quickly discharged to the outside through the sample inlets 22 and 29. Therefore, at the end of the ashing phase, impurities that constitute a background during measurement are almost completely removed from the inside of the heating tube 21. The purpose of the window plates 33a and 33b is to shield the gas in this way, and the window plates 33a and 33b are not necessarily transparent because they are removed from the optical axis 23 during measurement.

At the time of starting the heating for atomization, the control unit 37 sends the window plates 33a and 33 to the window plate driving unit 38.
b is drawn out of the window frames 43a and 43b, and those that may absorb light from the optical axis 23 of the measurement light are excluded. At the same time, it instructs the gas supply unit 39 to stop supplying the inner gas. As a result, the gas of the sample atomized in the heating tube 21 spreads in the direction of the optical axis 23, and more of the gas participates in the absorption of the measurement light. The outer gas is supplied throughout the entire period.

[0015]

In the flameless atomic absorption spectrophotometer according to the present invention, both sides of the heating tube are shielded by window plates during the ashing period,
The generated smoke and the like are quickly discharged from the sample loading inlet without spreading in the optical axis direction in the heating tube. Then, when the sample is atomized and the measurement is performed, the window plate is removed. As a result, unnecessary components do not stay at the time of measurement, the background noise is reduced, and the measurement light is not absorbed, so that highly accurate measurement can be performed.

[Brief description of the drawings]

FIG. 1 is a timing chart of a heating program for a heating tube of a frameless atomic absorption spectrophotometer according to an embodiment of the present invention, a window plate opening / closing, and an inner gas supply.

FIG. 2 is a sectional view of a heating tube (a) and a conventional furnace section (b).

FIG. 3 is a block diagram illustrating a configuration of a frameless atomic absorption spectrophotometer according to the embodiment.

FIG. 4 is a cross-sectional view of a furnace part of the flameless atomic absorption spectrophotometer according to the embodiment.

FIG. 5A is a plan view showing two examples of a window plate opening / closing mechanism.
And side views (b) and (c).

[Explanation of symbols]

21 ... heating tubes 24a, 24b
... Electrode (envelope tube) 26 ... Inner gas passage 27 ... Outer gas passage 32 ... Furnace part 33a, 33b
... window plate 37 ... control unit 38 ... window plate drive unit 39 ... gas supply unit 40 ... heating power supply unit 43a, 43b ... window frame 52 ... window plate drive motor 53 ... window plate drive gear 54 ... window plate movement parallel Moving equipment

Claims (1)

(57) [Claims] 1. A heating tube having a sample loading inlet on a side surface, an outer tube surrounding the heating tube, an inner gas inlet provided in the outer tube for introducing gas into the heating tube, and a heating tube. A frameless atomic absorption spectrophotometer having a heating control section for program-controlling the heating of the tube, comprising: a) a window plate provided at both openings outside the inner gas inlet of the envelope tube so as to be openable and closable; b. ) Above during drying and incineration of heating program of heating tube
Close the opening and open it during atomization.
Flameless atomic absorption spectrophotometer comprising: a, a window opening and closing controller for opening and closing the window plate.