JPH0718795B2 - Luminescence analyzer - Google Patents

Description

TECHNICAL FIELD The present invention relates to an optical emission spectrometer, and relates to a wide range of fields such as environment, various materials, clinical, and chemicals, and particularly to analysis of trace components in main components. Suitable for analysis of samples with high matrix,
The present invention relates to an emission spectroscopic analyzer.

[Conventional technology]

Conventionally, as a spectroscopic analyzer, the one disclosed in Japanese Patent Laid-Open No. 60-122357 is known. That is, by scanning the vicinity of the analysis line wavelength of the target element, the maximum value of the signal in the specified wavelength section including the analysis line wavelength and the specified wavelength section on the short wavelength side and the long wavelength side of the specified wavelength section. Means for detecting the minimum value of the signal in the specified wave arrangement section, and the difference between the maximum value and the minimum value is calculated, and from the result, the true line spectrum intensity of the element not affected by the continuous light component And a means for obtaining a value corresponding to.

As a result, the interference of continuous light that disturbs the analysis value is automatically and promptly corrected.

[Problems to be solved by the invention]

Usually, in the spectroscopic analysis method, the wavelength having the highest intensity, that is, the sensitivity of analysis is selected from a plurality of wavelengths emitted by the element to be analyzed, and the wavelength is analyzed. In the above-mentioned conventional technology, when the most sensitive wavelength is interfered with by the light of the adjacent wavelength emitted by another atom or molecule, the first wavelength is abandoned and the second most sensitive wavelength is used. Or, I was preparing for the error of the quantitative calculation value and measured with interference. In particular, since rare earth elements have a large number of emission lines, it is difficult to find a wavelength that is not interfered with in the analysis of a small amount of rare earth elements in rare earth elements. In addition to rare earth elements, transition metals such as iron, nickel and cobalt also have many emission lines, so that interference is likely to occur in the analysis of trace elements in iron. Further, in the aqueous solution sample, H ₂ O water molecules are decomposed in the light source to generate a large amount of OH molecules, and O extends to the long wavelength side at 306.4 nm and the band head.
The H band is formed, and countless emission lines exist in the wavelength range of several tens of nm. In particular, since aluminum and vanadium have a highly sensitive light emission line in this wavelength range, it is unavoidable to use another wavelength having low sensitivity.

It is an object of the present invention to provide an optical emission spectrometer capable of removing interference by mathematically solving a spectrum affected by interference of near lines and performing quantitative measurement with high sensitivity and high accuracy. .

[Means for solving problems]

In order to solve the above problem, it is necessary to study the spectrum in the emission spectrometry. High temperature plasma is used as a light source for emission analysis. From the high-temperature plasma, emission lines of atoms, emission lines of two-atom molecules, and a continuous spectrum due to black body radiation are emitted. Therefore, if the above continuous spectrum is subtracted as the back ground, the other above and above line spectra should be considered. Further, in order to solve the interference problem, it is only necessary to eliminate the spectrum of the interference line. Therefore, the above-described object can be achieved by mathematically combining the line spectra to match the spectrum of the interference line and subtracting the spectrum to leave only the spectrum of the analysis line.

That is, the present invention is an emission analysis method using light having a wavelength peculiar to an element as a means for analysis. Is being disturbed by
Only the interference line spectrum is mathematically synthesized by a linear combination of a Gaussian distribution and a Lorentz distribution, and a means for clarifying the spectrum of the analysis line is obtained by taking the difference between the measured spectrum and the synthesized spectrum. is there.

[Action]

In order to mathematically simulate the line spectrum, it is necessary to understand the shape of the spectrum. As a spectroscope used for emission analysis, a large spectroscope having a focal length of 0.5 to 1 m is usually used, and a half value width showing a resolution is often about 0.01 nm. On the other hand, the full width at half maximum of the emission line in the high temperature plasma, which is the light source, is on the order of 0.001 nm, which is smaller than the resolution of the spectrometer by almost an order of magnitude, and it can be said that the spectrum determined by the emission analyzer is determined by the spectrometer. Among spectrographs,
The slit plays an important role in determining the spectral shape. In particular, in order to achieve a high resolution of about 0.01 nm, the slit width is required to be as narrow as about 10 to 20 μm, and the unevenness of the end face cannot be ignored with respect to the slit width, which affects the spectrum shape. Further, the relationship between the widths of the entrance slit and the exit slit also has a decisive effect on the spectral shape. In addition, factors such as the sphericity of the collimating mirror and the camera mirror, whether the image of the light source is formed on the incident slit, and whether the light source is on the spectroscope optical axis are also the spectral shape. Is affecting. It is very difficult and theoretically impossible to theoretically calculate and obtain the degree of influence of the above individual factors on the spectrum shape. In view of this, in the present invention, by using a function that combines the Gaussian distribution and the Lorentz distribution,
The above object can be achieved by establishing a method of synthesizing so as to match the spectrum shape of the interference line of the spectrum actually measured. The use of a mathematically combined function of the Gaussian distribution and the Lorentz distribution for spectrum synthesis can be appropriately applied when the complicated interference spectrum shape cannot be simulated with only the Gaussian distribution or the Lorentz distribution.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. Second
In the figure, inductively coupled plasma (hereinafter abbreviated as ICP) is used as the light source.
2 shows an optical system of an ICP emission spectrometer using the. High frequency power supply 2
The high frequency power supplied from 4 to the coil 19 through the automatic matching circuit 23 forms the plasma 18 of the ICP. The sample 21 is introduced into the plasma 18 through the torch 20 and emits light having a wavelength peculiar to each element. This light is a lens
An image is formed on the incident slit 27 by the mirror 25 and the mirror 26. Also, a collimating mirror 28 that collimates the light flux, a grating 29 that extracts light of a single wavelength, and an output slit.
Camera mirror 31 for forming an image of the incident slit 27 on 32
The grating 29 composed of is attached to the grating table 30, and by rotating the grating table 30, the angle between the luminous flux and the grating is changed, and the wavelength of the light passing through the emission slit 32 can be changed. The light passing through the emission slit 32 is incident on the photomultiplier 33 and converted into an electric signal.

FIG. 3 shows an electric system of the ICP emission spectrometer.
In the figure, the light from the plasma 18 is made to be monochromatic by the spectroscope 34, and this spectroscope is the mounting of the Zuelnitana. Photomultiplier 33
The light emission signal from the plasma, which has been converted into an electric signal by the amplifier, is amplified by the preamplifier 35, further amplified by the main amplifier 36 having a multiplexer, converted into a digital signal by the A / D converter 37, and input to the CPU bus 38. The CPU 42 not only receives the signal from the plasma 18, but also controls the high voltage supplied to the photomultiplier 33 through the PIA 39, and further controls the stepping motor 41 through the stepping motor control circuit 40. The rotation of the stepping motor 41 can rotate the grating table 30 shown in FIG. 2 through the driving force transmission mechanism to take a spectrum in an arbitrary wavelength range. The CPU 42 is connected to the host computer 44 through the GPIB 43, and the measurer is the computer 44
You can show it from the keyboard while looking at the CRT.
The computer 44 is connected to the printer 45 or XY via GPIB43.
The output device of the plotter 46 is connected.

In the above system, the contents of the present invention are computer
It is stored in 44 memories. A sequence for removing the influence of the interference peak will be described with reference to FIGS. 1 (a) and 1 (b). When a START (step 1) instruction is issued from the computer 44, the stepping motor drive circuit 40 rotates the stepping motor 41 to actually measure a spectrum in a wavelength section designated in advance (step 2). The measured spectrum is displayed on the CRT of the computer 44, and if there is a peak that disturbs the analysis line, the disturbing peak is simulated and synthesized by the method shown in FIG. 1 (b) described later (step 3). ). If the disturbing peaks are well simulated, then the disturbing can be removed from the analysis line by subtracting the measured spectrum (step 4). In this case, the peak height of the analysis line can be easily obtained (step 5), and the measurement of the sample is completed (step 6).

FIG. 1 (b) shows the sequence of interference spectrum interference. To start the simulation (step 7), the measured spectrum is first smoothed to reduce noise (step 8). Then, confirm the presence or absence of a peak that interferes with the analysis line peak (step 9),
At this time, if there are interference peaks, the number (= N)
Also count (steps 10 and 11). Interfere peak simulation is performed one by one. For the first disturbing peak, specify the center wavelength (step 12) and its peak height and background level (step 13). In addition, specify the half width of the peak (step 1
4) By inputting the ratio of the Gaussian distribution and the Lorentz distribution which are the simulation functions used in this embodiment (step 15), the simulation of one disturbing peak is completed (step 17). From the specification of the central wavelength (step 12) to the input of the ratio of the Gaussian distribution and the Lorentz distribution (step 15), the simulation is performed while observing the simulated spectrum displayed on the CRT. In any process, a sequence is set up so that redoing is possible even after inputting each pyramid. When the simulation of the first disturbing peak is completed, the simulation is completed by simulating the second and third disturbing peaks and simulating all the peaks that are disturbing the analysis line.

Here, the simulation function will be described. The Gaussian distribution (1) and the Lorentz distribution (2) are frequently used as peak-like functions.

I _G (λ) = b · exp {−a ² (λ ₀ −λ) ² } (1) where I _L (λ) = d / {1 + C ² (λ ₀ −λ) ² } (2) where The Gaussian distribution is a function known as a normal distribution, while the Lorentz distribution is a function with a wider peak base than the Gaussian distribution. Note that Δλ is the half-value width λ _{0 of the} peak and is the center wavelength. If both distributions are considered at the same time, the function becomes a little complicated, and it takes time to calculate. Therefore, it is appropriate to use the approximate combination function of the linear combination of the Gaussian distribution and the Lorentz distribution shown in the equation (3).

I _GL (λ) = M / (1 + A) + (1-M) ・ exp (-A ・ ln
2) …… (3) However, A = 4. (Λ ₀ −λ) ² / (Δλ) ² M = 0 to 1 Here, M represents a ratio between the Gaussian distribution and the Lorentz distribution. When M = 0, the equation (3) is Gaussian distribution, and when M = 1, the equation (3) is Lorentz distribution.

Next, the effect of this embodiment will be shown with reference to FIGS. FIG. 4 shows a spectrum around Pr406.281 nm in 100 ppm of Ce. Pr concentration is 0ppm (shown as 47 in the figure), 0.5ppm
(Indicated by 48 in the figure), 1.0 ppm (indicated by 49 in the figure) and 2.0 pp
m (indicated by 50 in the figure). The analytical lines of Pr are two wavelengths of Ce, which exists at high concentration, 406.256 nm (shown as 51 in the figure) and 40.
Interfering with 6.294 nm (shown as 52 in the figure), Pr406.2
Quantitative measurement in the ppm order using the 81 nm wavelength is virtually impossible. FIG. 5 shows the spectrum simulation. The parameters input in FIG. 5 are as shown in the following table.

In the example of FIG. 4, since a 0 ppm Pr sample, that is, a blank solution was present, the spectrum of the blank solution was used for the simulation of interference peaks, but the method is also effective when no blank solution is present. In actual analysis, a blank solution often does not exist, and in this case, the spectrum of the sample with the lowest concentration may be simulated.

FIG. 6 shows a spectrum obtained by subtracting the simulated spectrum from the measured spectrum. Pr0ppm (54 in the figure
Are shown), 0.5 ppm (shown as 55 in the figure), 1.0 ppm (shown as 56 in the figure) and 2.0 ppm (shown as 57 in the figure).

FIG. 7 shows a calibration curve prepared from the intensity of Pr406.281 nm obtained from FIG. Good linearity is shown up to a concentration range of 1 ppm or less, and it is understood that the influence of the interference peak can be removed by using this example.

〔The invention's effect〕

As is apparent from the above description, according to the present invention, in the emission analysis method, when the analysis line is interfered by the adjacent emission line, only the spectrum of the interference line is analyzed by the linear combination of the Gaussian distribution and the Lorentz distribution. In addition to the central wavelength, peak height, and inverse width, the means of mathematically combining can use the ratio of Gaussian distribution and Lorentz distribution as one parameter in the simulation of interference spectrum. The difference can be properly taken, and the interference can be removed. Accordingly, it is possible to save the trouble of searching for the second or third light emitting line and again examining the presence or absence of interference. Further, when the second or third emission line is used, a decrease in sensitivity cannot be avoided, but by using the first emission line, it becomes possible to perform analysis with high sensitivity.

[Brief description of drawings]

1 (a) and 1 (b) are flow charts of a spectrum simulation showing an essential part of an emission analysis apparatus according to the present invention, and FIGS. 2 and 3 are optical systems of the emission analysis apparatus according to the present invention, respectively. 4 and 7 are graphs showing the effects of the optical emission analyzer according to the present invention. 18 …… ICP plasma, 24 …… high frequency power supply, 29 …… grating, 34 …… light emitter, 40 …… stepping motor drive circuit, 41 …… stepping motor, 42
…… CPU, 44 …… Computer.

Claims (1)

[Claims] 1. An emission analyzer using light having a wavelength peculiar to an element as means for analysis, means for wavelength-scanning around a specific wavelength of an element to be analyzed and measuring emission spectrum.
When the analysis wavelength is disturbed by a near line, the following equation, which is a linear combination of a Gaussian distribution and a Lorentz distribution, I _GL (λ) = M / (1 + A) + (1−M) exp (− A / 1n
2) (where A = 4 · (λ ₀ −λ) ² / (Δλ) ² , M = 0 to 1, {0 ... Gaussian distribution, 1 ... Lorentz distribution}, M is the ratio of Gaussian distribution and Lorentz distribution) , Λ is the wavelength variable, λ ₀ is the central wavelength, and Δλ is the inverse value width.) Is used to synthesize only the spectrum of the interference line, and the difference between the measured spectrum and the synthesized spectrum is calculated to obtain And a means for clarifying the spectrum of the analysis line.