JP2022065206A - Element analyzer, element analyzer program, and element analysis method - Google Patents

Abstract

To further enhance analysis accuracy by performing baseline correction using a base line that simulates a temporal change of signal intensity caused by a gas generated from a graphite crucible.SOLUTION: An element analyzer 100 for analyzing a gas generated by heating a sample stored in a graphite crucible, includes: a signal intensity receiving unit 11 for receiving signal intensity obtained by a gas detector; and a baseline correction unit 12 for performing baseline correction of a spectrum S using a correction function with start point intensity that is signal intensity at a rising point A of a peak of the spectrum S showing a temporal change in the signal intensity and end point intensity that is signal intensity at a falling end point B of the peak as a parameter. The correction function converges to the start point intensity and the end point intensity, and has a portion X having an inclination different from an inclination of a straight line Z connecting the rising point A and the falling end point B between these two points.SELECTED DRAWING: Figure 3

Description

The present invention relates to an elemental analyzer, a program for an elemental analyzer, and an elemental analysis method.

As a conventional elemental analyzer, as shown in Patent Document 1, an element contained in a sample is measured by heating and melting a sample contained in a graphite crucible and analyzing the gas generated at that time. There is.

In such an elemental analyzer, the change over time of the signal intensity obtained by the gas detector, that is, the spectrum of the signal intensity is based on the signal intensity caused by the gas generated from the graphite pot, and is derived from the gas generated from the sample. Since the signal strength is superimposed, baseline correction is required to calculate the concentration of various components contained in the sample.

By the way, as shown in FIG. 6, the spectrum of the above-mentioned signal intensity is lower after the falling end point of the peak than before the rising point of the peak. This is because when the sample melts, the sample reacts with the graphite crucible and the resistance value to the current flowing through the graphite crucible changes, the temperature of the graphite crucible changes, and the amount of gas generated from the graphite crucible changes. Is. Depending on the type of sample and the element to be measured, the value may be higher after the peak fall end point than before the peak rise point in the signal intensity spectrum.

Therefore, until now, the straight line L shown in FIG. 6, that is, the straight line L connecting the rising point and the falling end point of the peak, is regarded as a change over time of the signal intensity caused by the gas generated from the graphite crucible, and the straight line L is used as a base. The baseline was corrected as a line.

Japanese Unexamined Patent Publication No. 2013-250061

Under such circumstances, the present inventor has made extensive studies in order to further improve the analysis accuracy, and the melting of the sample is not a phenomenon in which the melting of the sample progresses linearly as shown by the straight line L in FIG. For example, focusing on the phenomenon that progresses non-linearly at a certain timing, the conventional baseline (that is, the straight line L in FIG. 6) shows the change over time of the signal intensity caused by the gas generated from the graphite crucible. I found that there wasn't.

The present invention has been made by the above-mentioned diligent study, and by making it possible to correct the baseline by using a baseline simulating the change over time of the signal intensity caused by the gas generated from the graphite crucible, the analysis accuracy can be further improved. The main issue is to improve.

That is, the element analyzer according to the present invention is an element analyzer that analyzes the gas generated by heating the sample contained in the graphite pot, and is a signal intensity receiving unit that receives the signal intensity obtained by the gas detector. Using a correction function using the start point strength, which is the signal strength of the rising point of the peak of the spectrum showing the change over time of the signal strength, and the ending point strength, which is the signal strength of the falling end point of the peak, as parameters. It has a baseline correction unit that corrects the spectrum by baseline, and the correction function converges on the start point intensity and the end point intensity, and a straight line connecting these two points between the rising point and the falling end point. It is characterized in that it is a function having a slope portion different from the slope of.

In the elemental analyzer configured in this way, the correction function has a slope portion between the rising point and the falling end point of the peak, which is different from the slope of the straight line connecting these two points. Depending on the portion, it is possible to represent a baseline that simulates the change over time in the signal intensity caused by the gas generated from the graphite crucible. As a result, the analysis accuracy can be further improved by performing baseline correction using this correction function.

Considering that the change in the actual amount of gas generated from the graphite crucible is monotonically decreasing with the melting of the sample, the end point strength is lower than the start point strength, and the correction function is tilted more than the straight line. It is preferably a monotonic decrease function having a small portion of.

In order to more likely simulate the change over time of the signal intensity caused by the gas generated from the graphite crucible, it is preferable that the correction function has an inflection point between the rising point and the falling end point. ..

Since the reaction between the molten sample and the graphite crucible tends to converge before the timing when the amount of gas generated by the combustion of the sample reaches its peak, the inflection point is closer to the rising point side than the peak of the spectrum. It is preferable to be in.

As described above, considering that the reaction between the sample and the graphite crucible converges before the timing when the amount of gas generated by the combustion of the sample peaks, the correction function is larger than the peak of the spectrum or the peak. It is preferable that the end point strength is converged on the rising point side.

Further, the program for an element analyzer according to the present invention is a program used for an element analyzer that analyzes a gas generated by heating a sample housed in a graphite pot, and is a signal intensity obtained by a gas detector. Correction using the signal strength receiving unit, the start point strength, which is the signal strength of the rising point of the peak of the spectrum showing the change over time of the signal strength, and the end point strength, which is the signal strength of the falling end point of the peak, as parameters. The function is used by a computer as a baseline correction unit for correcting the spectrum, and the correction function converges on the start point intensity and the end point intensity, and at the same time, the rising point and the falling end. It is characterized in that it is a function having a slope portion between the points, which is different from the slope of the straight line connecting these two points.

Further, the element analysis method according to the present invention is an element analysis method for analyzing a gas generated by heating a sample housed in a graphite pot, and is a signal strength reception step for receiving a signal strength obtained by a gas detector. Using a correction function using the start point strength, which is the signal strength of the rising point of the peak of the spectrum showing the change over time of the signal strength, and the ending point strength, which is the signal strength of the falling end point of the peak, as parameters. It has a baseline correction step for correcting the spectrum with a baseline, and the correction function converges on the start point intensity and the end point intensity, and a straight line connecting these two points between the rising point and the falling end point. This method is characterized in that it is a function having a slope portion different from the slope of.

Even with such a program for an elemental analyzer or an elemental analysis method, the same effects as those of the above-mentioned elemental analyzer can be obtained.

According to the present invention configured in this way, it is possible to perform baseline correction using a baseline that simulates the time-dependent change in signal intensity caused by the gas generated from the graphite crucible, and further improve the analysis accuracy.

The schematic diagram which shows the structure of the elemental analyzer of this embodiment. The functional block diagram which shows the function of the arithmetic unit which concerns on the same embodiment. The figure for demonstrating the function of the baseline correction part which concerns on the same embodiment. The figure for demonstrating the correction function which concerns on the same embodiment. The figure for demonstrating the correction function which concerns on the same embodiment. The figure for demonstrating the conventional baseline correction.

Hereinafter, the elemental analyzer according to the present invention will be described with reference to the drawings.

The elemental analyzer 100 of the present embodiment heats and melts a metal sample or a ceramic sample (hereinafter, also simply referred to as a sample) housed in the crucible R, and analyzes the gas component generated at that time. It measures the elements contained in the sample.

Specifically, as shown in FIG. 1, the element analyzer 100 has a gas flow path 2 for flowing a sample gas generated in the heating furnace 1 together with a carrier gas (for example, He gas), and the gas flow path 2 A CO detector 3, an oxidation unit 4, a CO ₂ detector 5, an H ₂ O detector 6, a CO ₂ removal unit 7, an H ₂ O removal unit 8 and an N ₂ detector 9 are provided in series in this order. There is. It is not always necessary to have all of these detectors, and the number and arrangement of the detectors may be changed as appropriate.

The CO detector 3 detects (detects) carbon monoxide (CO) contained in the sample gas and measures (detects) the concentration thereof, and is composed of a non-dispersive infrared gas analyzer (NDIR).

The oxidizing unit 4 is provided on the downstream side of the CO detector 3 and oxidizes carbon monoxide (CO) contained in the sample gas to carbon dioxide (CO ₂ ) and hydrogen (H) to water (H ₂ O). It oxidizes to produce water vapor. The oxidized portion 4 of the present embodiment is configured by using, for example, copper oxide (CuO), and specifically, it is configured by filling a quartz tube with copper oxide (CuO), and the copper oxide (CuO) thereof. Is heated to about 600 degrees. As a method for heating this copper oxide (CuO), a method of heating with a heat generation resistor or the like can be considered.

The CO ₂ detector 5 detects carbon dioxide (CO ₂ ) contained in the sample gas and measures the concentration thereof, and is composed of a non-dispersive infrared gas analyzer (NDIR).

The _H2O detector 6 detects water (water vapor) contained in the sample gas and measures the concentration thereof, and is composed of a non-dispersive infrared gas analyzer (NDIR).

The CO ₂ removing unit 7 adsorbs and removes carbon dioxide (CO ₂ ) from the sample gas that has passed through the oxidizing unit 6, and does not react or adsorb to nitrogen (N ₂ ) contained in the sample gas. For example, ascarite or a zeolite-based molecular sieve can be used.

The H ₂ O removing unit 8 adsorbs and removes water (water vapor) from the sample gas that has passed through the oxidizing unit 6, and does not react or adsorb to the nitrogen (N ₂ ) contained in the sample gas. For example, magnesium perchlorate, calcium chloride, or the like can be used.

The N ₂ detector 9 detects nitrogen (N ₂ ) contained in the sample gas and measures the concentration thereof, and is composed of a thermal conductivity type analyzer (TCD).

The measurement signal (measured value indicating the concentration of each gas component) obtained by each detector is output to the arithmetic unit 10.

The arithmetic unit 10 is a general-purpose or dedicated computer including, for example, a CPU, an internal memory, an input / output interface, an AD converter, and the like. The arithmetic unit 10 may be configured by using a discrete analog circuit using a buffer, an amplifier, a comparator, or the like without using a computer.

As shown in FIG. 2, the arithmetic unit 10 operates a CPU, its peripheral devices, and the like based on a program stored in a predetermined area of the internal memory, and obtains a measurement signal obtained by each detector. The signal strength receiving unit 11 to receive, the baseline correction unit 12 that baseline-corrects the spectrum showing the change of the measured signal strength with time, and the concentration of various components contained in the gas are calculated based on the measured signal strength corrected by the baseline. It is configured to exert the function of the concentration calculation unit 13 and the like.

Here, the baseline correction unit 12 is characteristic, and will be described in detail below.

First, in the spectrum S of the measured signal intensity (hereinafter, also referred to as the measured spectrum S), as shown in FIG. 3, a peak having a height corresponding to the concentration of the detected component contained in the gas appears. Here, for example, when the signal intensity receiving unit 11 receives the measured signal intensity from the non-dispersive infrared gas analyzer (NDIR) constituting the CO detector 3 and the CO ₂ detector 5, the measurement spectrum S is graphite. The signal strength caused by the gas generated from the sample is based on the signal strength caused by the gas generated from the sample, and the signal strength caused by the gas generated from the sample is superimposed on the signal strength.

Therefore, the baseline correction unit 12 removes the influence of the signal intensity caused by the gas generated from the graphite crucible from the measurement spectrum S, and specifically, as shown in FIG. 3, the gas caused by the graphite crucible. A baseline BL simulating the change with time of the signal strength of the above is created, and the baseline BL is subtracted from the measurement spectrum S to correct the baseline.

That is, the baseline correction referred to here is to remove the influence of the signal intensity caused by the gas generated from the graphite crucible from the measurement spectrum S, and specifically, according to the distance from the baseline BL to the measurement spectrum S. It is to obtain the signal strength and the time-series change of the signal strength as the correction result data.
As the baseline correction, a value obtained by subtracting the signal strength of the baseline BL from the signal strength of the measurement spectrum S at each time may be calculated as the correction result data, or a predetermined section (for example, from the rising point A). The value obtained by subtracting the integrated value of the signal strength of the baseline BL in the section up to the falling end point B from the integrated value of the signal intensity of the measurement spectrum S in the same section may be calculated as the correction result data.

The baseline correction unit 12 of the present embodiment is configured to create a correction function representing the baseline BL and to perform baseline correction using the correction function. The correction function is a function that expresses the signal strength with time as a variable.

Here, as shown in FIG. 3, the measurement spectrum S is lower after the peak falling end point B than before the peak rising point A, and is higher than the starting point strength which is the signal strength of the rising point A. , The end point strength, which is the signal strength of the falling end point B, is lower. This is because when the sample melts, the melted sample reacts with the graphite crucible, the resistance value to the current flowing through the graphite crucible changes, the temperature of the graphite crucible changes, and the amount of gas generated from the graphite crucible changes. Because. In this case, examples of the gas generated from the graphite crucible include CO and CO ₂ generated by the reaction between oxygen contained in the graphite crucible and carbon, which is the material of the graphite crucible.

Therefore, the baseline correction unit 12 first identifies the rising point A of the peak of the measurement spectrum S and the falling end point B of the peak lower than the rising point A, and the coordinates of these points, that is, the time of the rising point A. And the start point intensity, the time of the falling end point B, and the end point intensity are acquired.

Then, the baseline correction unit 12 creates a correction function representing the baseline BL with the start point strength and the end point strength as parameters.

More specifically, as shown in FIG. 3, the baseline correction unit 12 is configured to create, as a correction function, a function representing at least the signal strength in the section from the rising point A of the peak to the falling end point B. The correction function here is a non-linear function that decreases monotonically.

Here, since the measured signal intensity hardly changes and is stable before and after the peak of the measurement spectrum S, the baseline correction unit 12 of the present embodiment converges to the start point intensity and the end point intensity, in other words, the peak. A correction function is created so that the pre-peak line L1 before the rising point A and the post-peak line L2 after the falling end point B are asymptotes.

Then, as shown in FIG. 3, this correction function has a steep portion X between the rising point A and the falling end point B, which is a portion having a smaller inclination than the straight line Z connecting these two points.

More specifically, the correction function has a larger value than the straight line Z on the rising point A side than the steep part X, and a smaller value than the straight line Z on the lowering end point B side than the steep part X. Here, for example, it is a function including an arctangent function. The inflection point is included in the steep portion X described above, and is set here on the rising point A side of the peak of the measurement spectrum S.

In this way, the baseline correction unit 12 creates a correction function representing the baseline BL, calculates the signal strength according to the distance from the baseline BL to the measurement spectrum S as the correction result data, and the correction result. Based on the data, the concentration calculation unit 13 calculates the concentration and the like of the components contained in the gas.

According to the elemental analyzer 100 configured in this way, the baseline correction unit 12 provides a steep portion X having a smaller inclination than the straight line connecting these two points between the rising point A and the falling end point B of the peak. Since the baseline is corrected using the correction function provided, it is possible to create a baseline BL that simulates the change over time in the signal intensity caused by the gas generated from the graphite crucible by the steep portion X. Then, since the baseline correction is performed using the baseline BL created in this way, the analysis accuracy can be further improved.

Further, since the correction function has an inflection point on the rising point A side of the peak of the measurement spectrum S, it is possible to more likely simulate the change with time of the signal intensity caused by the gas generated from the graphite crucible.

The present invention is not limited to the above embodiment.

For example, the correction function of the above embodiment uses an arctangent function having an inflection point on the rising point A side of the peak of the measurement spectrum S, but as shown in FIG. 4, a plurality of straight lines are used. It may be a combined function, or as shown in FIG. 5, it may be a function having an inflection point on the end point B side, which is lower than the peak of the measurement spectrum S.
Further, the correction function may be one using one or a plurality of trigonometric functions such as a sine function, a cosine function, and a tangent function.

Further, the baseline correction unit 12 is configured to create a correction function in the above embodiment, but is configured to acquire a correction function from a correction function storage unit in which one or a plurality of correction functions are stored in advance. It may have been done.
Specifically, if the correction function storage unit stores a plurality of correction functions created in advance according to the type of sample, for example, in association with the type of the sample, the baseline correction unit Example 12 includes a configuration in which a type of sample is accepted and a correction function associated with the type is acquired. Further, as another aspect, the baseline correction unit 12 may be configured to acquire a correction function selected by the operator from a plurality of correction functions stored in the correction function storage unit.
As the plurality of correction functions, in addition to the function representing the baseline having the steep portion X described in the above embodiment, for example, a function that passes through the rising point A or the falling end point B and represents a straight line parallel to the horizontal axis. And a function representing a straight line Z connecting the rising point A and the falling end point B.

Further, in the above embodiment, the case where the signal intensity receiving unit 11 receives the measured signal intensity from the non-dispersive infrared gas analyzer (NDIR) has been described, but the signal intensity receiving unit 11 is from another optical analyzer. It may be the one that accepts the measurement signal of.
Further, the signal strength receiving unit 11 is not necessarily limited to receiving the measured signal strength from the CO detector 3 and the CO ₂ detector 5, but also receives the signal strength from the detector that detects other components. Is also good.
That is, the baseline correction of the above embodiment can be used not only for the non-dispersive infrared gas analyzer (NDIR) but also for other optical analyzers, and not only for the CO detector 3 and the CO ₂ detector 5. It can also be used as a detector for detecting other components.
Depending on the type of sample and the element to be measured, the falling end point B may be higher than the signal strength of the rising point A. In such a case, the correction function determines the starting point strength and the ending point strength. It may be a function that converges and has a portion having a slope larger than the straight line connecting these two points between the rising point A and the falling end point B.

In addition, the present invention is not limited to each of the above-described embodiments, and it goes without saying that various modifications can be made without departing from the spirit of the present invention.

100 ・ ・ ・ Elemental analyzer 10 ・ ・ ・ Arithmetic unit 11 ・ ・ ・ Signal strength reception unit 12 ・ ・ ・ Baseline correction unit S ・ ・ ・ Measurement spectrum A ・ ・ ・ Rising point B ・ ・ ・ Falling end point BL ・・ ・ Baseline L1 ・ ・ ・ Pre-peak line L2 ・ ・ ・ Post-peak line X ・ ・ ・ Steep part Z ・ ・ ・ Straight line

Claims (7)

An elemental analyzer that analyzes the gas generated by heating a sample contained in a graphite crucible.
A signal strength reception unit that receives the signal strength obtained by the gas detector,
Using a correction function with parameters of the start point strength, which is the signal strength of the rising point of the peak of the spectrum showing the change over time of the signal strength, and the end point strength, which is the signal strength of the falling end point of the peak, the spectrum is displayed. It has a baseline correction unit that corrects the baseline,
An element, which is a function in which the correction function converges on the start point strength and the end point strength, and has a slope portion between the rising point and the falling end point, which is different from the slope of the straight line connecting these two points. Analysis equipment. The end point strength is lower than the start point strength,
The elemental analyzer according to claim 1, wherein the correction function is a monotonic decreasing function having a portion having a portion having a slope smaller than that of the straight line. The elemental analyzer according to claim 2, wherein the correction function is a function having an inflection point between the rising point and the falling end point. The elemental analyzer according to claim 3, wherein the inflection point is on the rising point side of the peak of the spectrum. The elemental analyzer according to claim 4, wherein the correction function converges to the end point intensity at the peak of the spectrum or on the rising point side of the peak. A program used in elemental analyzers that analyze the gas generated by heating a sample contained in a graphite crucible.
A signal strength reception unit that receives the signal strength obtained by the gas detector,
Using a correction function with parameters of the start point strength, which is the signal strength of the rising point of the peak of the spectrum showing the change over time of the signal strength, and the end point strength, which is the signal strength of the falling end point of the peak, the spectrum is displayed. It is intended to be demonstrated by the computer as a baseline correction unit that corrects the baseline.
An element, which is a function in which the correction function converges on the start point strength and the end point strength, and has a slope portion between the rising point and the falling end point, which is different from the slope of the straight line connecting these two points. Program for analyzer. An elemental analysis method that analyzes the gas generated by heating a sample contained in a graphite crucible.
A signal strength reception step that accepts the signal strength obtained by the gas detector,
Using a correction function with parameters of the start point strength, which is the signal strength of the rising point of the peak of the spectrum showing the change over time of the signal strength, and the end point strength, which is the signal strength of the falling end point of the peak, the spectrum is displayed. Has a baseline correction step to correct the baseline,
An element, which is a function in which the correction function converges on the start point strength and the end point strength, and has a slope portion between the rising point and the falling end point, which is different from the slope of the straight line connecting these two points. Analysis method.

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