JPS5923234A - Flameless atomizer of atomic absorption analytical device - Google Patents

Abstract

PURPOSE:To enable the prompt remedy to deterioration in a heating element by monitoring the deterioration of the heating element with a terminal voltage and displaying the same. CONSTITUTION:The secondary output of a transformer 309 is subjected constant current control with a thyristor control part 305, a current detection element 311 and a current control part 32 connecting to a current detection circuit 307 according to the program of a current setting part 325. The heating element 2 of a graphite cell is heated by the constant current of the time and current value corresponding to the program, and the sample injected into the element 2 is dried, ashed and atomized, whereby atomic absorption analysis is executed. The voltage at both terminals of the element 2 is detected with a voltage detection circuit 321 and a state monitoring part 323 generates the output on the deteriorated condition of the element 2 from the differential signal obtd. by the comparison with the set current in the part 325 and displays the deteriorated state on a display part 327. When the signal attains the threshold value or above, a life detection signal is applied from the part 323 and the output of the transformer 309 is interrupted by the part 325. The early and adequate remedy for the deterioration of the heating element such as exchanging or the like is made possible by the above-mentioned constitution by which said deterioration is monitored.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flameless atomizer for atomic absorption spectrometry, and more particularly to monitoring the deterioration of a heating element.

Conventional flameless atomizers for atomic absorption spectrometry have limited analytical accuracy (
(b) Was the affected heating element replaced under visual inspection by the analyst? J. - After completing the analysis of the number of steps, the heating element was replaced regardless of its lifespan.

Not only did this lead to wasted heating elements, but because the timing for replacing the heating element was missed, the conditions for a series of analysis results became inconsistent, and valuable samples were lost, requiring re-analysis to ensure analysis accuracy. Analysis time was wasted.

Apart from this, during continuous operation of the flameless atomizer involved in automatic analysis, deformation and damage due to deterioration of the heating element may occur.
There was a possibility of damaging peripheral equipment, such as damaging the tip of the automatic sample injector.

The purpose of the present invention is to eliminate the above-mentioned drawbacks, and to provide convenience to the analyst by monitoring and displaying the deterioration of the heating element, and to detect the end of the life of the heating element and interrupt the analysis. It is an object of the present invention to provide a flameless atomizer for atomic absorption spectrometry, which has a mechanism for emitting a signal of YES/NO.

As shown in FIG. 1, the flameless atomizer injects a sample 4 into a heating element 2 having pores, and dries the sample 4 by causing the heating element 2 to generate heat through an electric current from a power source 3.
It is processed in the order of ashing and atomization.

Excluding the effects of coexisting substances such as acids in the sample, the drying, ashing, and atomization procedures follow a program determined by the magnitude of the current and the duration of the current, depending on which substance in the sample is to be effectively atomized. executed.

This program is based on the assumption that the current value of the heating element 2 is constant for each analysis, and the current value applied to the heating element 2 corresponds to the temperature of the heating element 2, but in reality it is inactive. Because atmosphere 1 contains some impurities such as moisture and oxygen,
Although the two heating elements are energized and generate heat, they gradually deteriorate.

That is, the degree of deterioration varies depending on the type and concentration of acid contained in the sample and what remains to be atomized.

For example, in the analysis of cadmium at an atomization temperature of 2 (> 00 C) and the analysis of chromium at an atomization temperature of 280 Orr, the deterioration of the heating element for the latter is approximately 5 times more severe. The latter deteriorates about three times as much as when it contains several percent sulfuric acid.

FIG. 2 shows the results of an experiment in which chromium in the same sample was atomized according to Table 1, which was repeated 200 times using a graphite cell as a heating element.

■Drying: Loot;, 30 seconds ■Ashing: 600t? , 30 seconds ■ Atomization 7 2800U, 7 seconds In Figure 2, Ec is first passed through the graphite cell 7), j L
/ ζ The current that would correspond to the atomization temperature of 2800 U was determined through 200 analyzes using a fixed rate system? This is a graph plotting the terminal tube and pressure changes of a graphite cell each time when electricity is applied using AI.

ΔW is a graph showing the change in M■ of the graphite cell measured every 50 times.

S is a graph showing the rate of change in absorption sensitivity every 50 times with respect to the initial absorption sensitivity.

67m is the value of atomic absorption analysis every 20 times.
The coefficient of variation (
67m).

These experiments revealed how the terminal voltage increases as the graphite cell deteriorates, and the coefficient of variation σ of the atomic absorption analysis values.
It was found that there is a causal relationship in the manner in which /m increases.

The present invention has been made with attention to the above points, and is an invention that attempts to monitor the deterioration of a heating element by monitoring its terminal voltage. The present invention is characterized in that the operation of the flameless atomizer is controlled by displaying and detecting the lifespan of the heating element.

More specifically, as shown in Figure 2, we will try to detect the deterioration and lifespan of graphite cells by capturing the phenomenon that deterioration of graphite cells progresses rapidly after a certain number of analyzes (for example, around 100 times). That is.

Next, an embodiment of the present invention is shown in FIG.

The primary side of the transformer 309 is connected to the power supply 301 via an iris register 303 . Secondary side d of the transformer
, the current detection element 311, the voltage detection circuit 321, and the graphite cell 2.

The current control section 329 includes the current detection element 311, the current detection circuit 307, the Zyristor control section 1 section 305, the entire fltlJ control loop, and the current value setting section 325. constant current control of the output.

The current value setting section 325 inputs a current value setting signal according to a predetermined program to the current control section 329, the display section 327, and the state monitoring section 323.

The condition monitoring section 323 compares the signal detected by the voltage detection circuit 321 of the voltage across the graphite cell with the current value setting signal, and sends a display signal to the display section 327 in accordance with the difference signal. This makes it possible to display the deterioration state of the heating element based on the magnitude of the difference signal. When the difference signal exceeds a certain threshold value, a life detection signal is sent to the current value setting section 325 to cut off the output of the transformer 309 or issue an alarm.

More specifically, the current value setting unit 32 in the status monitoring unit 323
5, for example, when the output current of the transformer 309 is 10 OA, the signal detected by the voltage detection circuit 321 and the current value setting signal are compared, and one display word is sent out in accordance with the difference between the two. This comparison is performed every analysis or after a certain number of analyses.

The current value setting signal is preferably a current value corresponding to a temperature lower than the atomization temperature. This is because, for each analysis, the graphite cell is heated through a temperature corresponding to the current value, so that it is possible to monitor the graphite cell for each analysis.

The current value setting signal is determined separately and uniformly from the relationship between the current flowing through the graphite cell and the terminal voltage at that time, or it is detected from the voltage detection circuit 321 during the first analysis after replacing the graphite cell with a new one. There are cases where one word is memorized.

In the former case, the structure of the condition monitoring section 323 is simple, and in the latter case, it is not affected by individual variations in graphite cells.

The status monitoring unit 323 may send a signal to the display unit 327 if the comparison result exceeds a certain threshold value.

The display unit 327 may display the results of the comparison by the status monitoring unit 323 in stages, such as when the difference from the current value setting signal is 5% or 10%. Further, this display may be performed using an audio level meter, LED, liquid crystal, or the like. The reason for this is that the concentration is calibrated using a standard solution, such as by creating a calibration curve.
Although the reproducibility (σ/rn l &j) deteriorates, the absorption sensitivity may fall within a practical range of 111 depending on the analysis.

[k,+le'f! After printing out tJl and life in the +E viewing unit 323 and sending a signal to the 'ir)'lul setting value setting 25, a signal for interrupting the analysis may be sent.

As described above, according to the present invention, deterioration of the heating element can be dealt with early without monitoring the deterioration of the heating element, and the time for replacing it can be dealt with at an early stage. ``We can provide a flameless atomizer for atomic absorption spectrometry that prevents deterioration in accuracy and wastes time analyzing samples and heating elements.

Figure 1 is a diagram showing the principle of a flameless atomizer, Figure 2 is a diagram showing the results of repeated experiments to check the deterioration state of the heating element, and Figure 3 is a diagram showing the results of repeated experiments to check the deterioration state of the heating element. It is a figure showing one example of the whole composition of such a flameless atomizer.

321... Voltage detection circuit, 323... Status monitoring unit,
325... Current value setting section, 327... Display section, 32
9EXw match 3rd figure

Claims (1)

[Scope of Claims] 1. In a flameless atomizer for an atomic absorption spectrometer having a power supply section that supplies current to a heating element on which a sample is placed in accordance with a current value setting signal, a voltage for detecting a terminal voltage of the heating element is provided. a detection circuit, which compares the signal from the voltage detection circuit with the current value setting signal and sends a signal for displaying the state of the heating element according to the magnitude of the difference signal between the two; a condition monitoring unit that issues a signal to interrupt the operation of the atomic absorption spectrometer when the magnitude of the atomic absorption spectrometer exceeds a threshold; and a display that displays the status of the heating element in response to the signal from the status monitoring unit. A flameless atomizer for an atomic absorption spectrometer, comprising: