JPS6042413B2 - Emission spectroscopy method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an emission spectroscopic analysis method for emitting discharge light from a sample and measuring the content of the element to be analyzed from the intensity of the spectral line of the element in the sample.

In the emission spectroscopic analysis method, a high voltage is applied between the sample and the electrode to generate a discharge, and the energy stored in the capacitor is released by the discharge to vaporize and excite the sample at the discharge point and its vicinity. This is an analysis method that performs quantitative determination by measuring the spectral intensity emitted from the component atoms.

This analysis method has the advantage of being able to quickly quantify even trace elements, but the discharge point and the amount of vaporization excitation differ for each discharge due to the influence of the microscopic composition, shape, etc. of the sample.

For this reason, there is a problem in that the reproducibility of the luminescence intensity every time is extremely low and the accuracy of analysis is low. For this reason, in the past, analysis accuracy was improved by averaging the emission intensity by integrating the emission intensity many times, or by taking a ratio with the integrated value of an internal standard element (an element whose content is already known). We are using the so-called integral method to improve the results.

Another method is to obtain a representative value (for example, the median value of the intensity) by taking individual transmissions of the emission intensity many times, and convert this into an analytical value. These conventional methods can improve analysis accuracy when the element to be analyzed is contained in a uniform form in the sample, but when elements in different forms are included, such as Al in steel, the emission intensity of each If they are different, the accuracy of analysis of the element to be analyzed will be significantly degraded. In other words, Af in steel is homogeneous Ae dissolved in iron.
and heterogeneous Ae, which exists dispersed in the steel with a composition such as A'203. For example, in a sample with almost no heterogeneous Af, as shown by the black dots in Figure 1, the emission intensity (S axis) of the spectral line of the analyte element (Ae) and the A' content (horizontal axis) are determined by the conventional integration method. ) has a linear proportional relationship. On the other hand, in a sample containing a considerable amount of heterogeneous Al, the same A
The luminescence intensity is relatively high compared to a sample with almost no heterogeneous system A' even in terms of content, and this causes an error in the analysis value. The reason why the intensity increases is that selective discharge mainly occurs in the heterogeneous system Ae at the initial stage of discharge.

Therefore, as a conventional method, there is also a method of performing analysis after taking measures such as preliminary discharge and deletion of abnormally high values.

However, in this case as well, the emission intensity is higher and the analysis accuracy is lower than in the case of homogeneous Af. Based on this, the present inventor conducted research on the emission intensity or emission intensity ratio of samples containing heterogeneous analytical elements, and found that the emission intensity differs when the discharge level is different, and that as the proportion of heterogeneous analytical elements increases, We focused on the fact that the emission intensity increases with the ratio.

The present invention was made based on the above-mentioned knowledge, and its purpose is to measure the spectral intensity (or intensity ratio) at different discharge levels in advance, and to identify only homogeneous analysis elements from these measured values. By determining a correction coefficient to correspond to the spectral intensity of the sample contained in the sample and correcting the spectral intensity of the analyte element based on this correction coefficient, we aim to obtain an emission spectroscopic analysis method that can improve analysis accuracy. It is something to do.

In other words, when measuring the content of an analyte element contained in a uniform solid solution form and a non-uniformly dispersed form by optical emission spectroscopy, the present invention is capable of The correction coefficient K for correcting the increase in luminescence intensity to the luminescence intensity when the analyte element is uniformly dissolved in solid solution is calculated using a standard sample in which the analyte element is uniformly dissolved in solid solution and a non-uniformly dispersed sample. The emission intensity ratio Xa, Xb of the sample to be analyzed is determined experimentally in advance by performing an emission spectroscopic analysis of a standard sample containing the analytical element at different discharge energy levels, and the emission intensity ratio Xa, Xb of the sample to be analyzed is determined at the above-mentioned different discharge energy levels. There is an emission spectroscopic analysis method characterized by determining the emission intensity ratio X of the analysis element as:

The method of the present invention will be explained below based on the spectroscopic analyzer shown in FIG. First, a voltage is applied between the generated electrode 2 of the controller 1 and the sample 3 to generate a discharge between them.

During this discharge, a discharge energy level (hereinafter referred to as a discharge level) selected based on the applied voltage, capacitor capacity, etc. is instructed by the central processing unit 4 to the generation controller 1.
The light generated by the discharge passes through an entrance slit 5, is divided into each spectrum by a diffraction grating 6, passes through a plurality of exit slits 7 set at specific spectral positions,
The photomultiplier tube 8 converts the current intensity into a current intensity.

This current intensity is integrated by the analog signal processing circuit 9 and then digitized by the analog-to-digital converter 10, and the digitized signal is stored in the storage device 11 by the central processing unit 4. This central processing unit 4
Now, the discharge level of the light emission controller 1 is changed for each discharge, and the light emission intensity (current intensity) for each discharge level is sequentially stored in the storage device 11.

After collecting the respective luminescence intensities while changing the discharge level for a certain period of time in this way, the content of the analyte element is determined based on the individual luminescence intensities as follows. First, for each discharge, the spectral line A of the element to be analyzed, for example, Af of Ae in steel.
and an internal standard element whose content is already known, such as Fe.
Find the intensity ratio X with spectral line B.

If it is carried out at two discharge levels A and B, what are the typical values for each? ，? (e.g. average value).

Are these representative values? ，? correspond to the white point and white triangular point in FIG. 3, respectively, and these two values are located on the vertical axis indicating the predetermined A1 content. ) Using these representative values, ■, make a correction that corresponds to point X in Figure 3? Find X from the formula below.

In this equation, K is determined experimentally based on the relationship between the discharge level and the intensity ratio determined in advance using a standard sample in which the analyte element is uniformly dissolved in solid solution and a standard sample containing the analyte element that is non-uniformly dispersed. The obtained value shows the same value even if the content of the element to be analyzed or the proportion of its content changes, if the discharge level is the same. The reason why it is possible to accurately obtain the corrected intensity representative x using this formula even if the content and proportion of the content form of the element to be analyzed changes is theoretically as follows.

In other words, the amount S of excited light emitted by one discharge (excited sample amount) varies from discharge to discharge, but on average,
Depends on discharge energy. Therefore, at discharge levels A and b having different discharge energies, the excited sample amounts are different from Sa and Sb. In addition, each component in the excited sample is
In the case of uniform composition, the composition is the same as that of the entire sample.
Therefore, the emission intensity 1 is expressed by the following formula. IFe: Emission intensity of Fe and A': SOe. Emission intensity of A' CFe: content of Fe, C, A': content of SOeA', S: excitation sample amount or discharge level A, b, the relationship between emission intensity and content is as follows:
It is shown by the formula below.

However, IJ-.

represents the j emission intensity of the X component at the discharge level J. On the other hand, a heterogeneous system A' (1..,0f
In A1), the excited sample amount SIAf of InsOfA′ is
I received a popular discharge.

All excited samples S of EAe grains! It is included in AfD and the surrounding excited sample. Excitation sample amount S, A' at 'A'. It becomes the sum of Here, S and A'0 are on average in the sample. It is proportional to the amount of EA'. S again.

AfE is proportional to the excited sample amount S and the content ClA'.
The luminescence amount of 1--2InS0'Ae is In
Since SO'A' is proportional to the amount of excited sample, (3) ~ (
5) When the formula is substituted, it is transformed as shown below.

By the way, the value 1A1 actually obtained as the intensity of Ae is
It is the sum of the emission intensities of the solid-dissolved homogeneous Ae ((SO'A')) and the dispersed heterogeneous Af (1 μSO'A').

Therefore, when formula (6) is transformed by proxy, the following formula is obtained.
View 61
Further, the internal standard ratio X (=IA'/IFe) can be expressed by the following formula.

Therefore, at discharge levels A and b, the intensity ratios Xa and Xb can be expressed by the following equations. Here, the correction strength Y to be sought is SO'Ae
(In order to make the light emission contribution of 51nS0eA' the same, it is expressed by the following formula.

From equations (9) and (10), CllllAe/CFe,C!
By finding A'/CFe and substituting it into equation (11), the following equation is obtained. K2-k'4-k''31SaSa.SbHere, are 53 constants?Sb-Sa, etc.If we set this as K (correction coefficient), then X=Xa+K(X
a-Xb) is obtained.

After determining x in this way, prepare a standard sample (homogeneous system A
The content of the analyte element in this sample is determined from the relational expression between the representative intensity value and the content (for example, a regression line connecting the black dots in FIG. 1) created using the sample containing e.g.

In addition, from the above formulas (9) and (10), the content C of each form
It is also possible to obtain SA' and CIAe.

According to this emission spectroscopic analysis method, the emission intensity depending on the content form is corrected by taking advantage of the difference in the emission intensity depending on the discharge level, so the analysis accuracy of analyte elements including heterogeneous morphological elements is improved. Significantly improved.

Note that in the method of the present invention, direct emission intensity may be used in place of the emission intensity ratio when there is little variation in the amount of excited sample at the same discharge energy.

Next, the present invention will be explained in detail.

Example total A' amount is 0.005 to 0.07% (average 0.032%
), the heterogeneous Ae contained in the form of Af2O3 etc. is 0.
Spectroscopic analysis according to the present invention was performed on 31 samples containing 0.001 to 0.012% (average 0.005%),
The accuracy ■ was investigated based on the formula below.

x: analysis value c: Standard value N: Number of samples As a result, the accuracy was 0.0025%.

On the other hand, when using the conventional method, 1 is 0.001
The accuracy was as large as ~0.012% (average 0.006%), and the accuracy was low. In this example, the discharge levels (two types) were set as follows.

discharge level Further, the correction coefficient K was 2.2.

The conventional method used for comparison is an analysis method using an integral method. As is clear from the above results, the method of the present invention has the remarkable effect of significantly increasing analysis accuracy.

[Brief explanation of drawings]

Figure 1 shows the relationship between Af content and emission intensity in a homogeneous system A.
Fig. 2 is an explanatory diagram of the principle of the method of the present invention, and Fig. 3 is a representative value of luminous intensity and corrected intensity for each discharge level. FIG. 3 is an explanatory diagram showing a plot of the relationship between Ae content and Ae content. DESCRIPTION OF SYMBOLS 1... Light emission controller, 2... Electrode, 3... Sample, 4... Central processing unit, 6...
...Diffraction grating, 8...Photomultiplier tube, 9.
...Analog signal processing circuit, 10...Analog-digital converter, 11...Storage device.

Claims (1)

[Scope of Claims] 1. When measuring the content of an analyte element contained in a uniform solid solution form and a non-uniformly dispersed form by optical emission spectrometry, a non-uniformly dispersed element The correction coefficient K is used to correct the increase in luminescence intensity due to the increase in luminescence intensity to the luminescence intensity when the analyte element is uniformly dissolved in solid solution. experimentally determined in advance by performing emission spectroscopic analysis of a standard sample containing the element to be analyzed at different discharge energy levels;
At the above different discharge energy levels, the emission intensity ratio Xa, Xb of the sample to be analyzed is measured, and the emission intensity ratio
An emission spectroscopic analysis method characterized by determining the following as X=Xa+K(Xa-Xb).