JPH06331547A - Emission spectroscopic analytical apparatus - Google Patents

Abstract

PURPOSE:To perform an analytical operation with high reliability by excluding the influence of a change or the like in an emission condition in an emission spectoscopic analytical apparatus. CONSTITUTION:A voltage is applies across an electrode 2 and an object 3 to be measured, and light generated by an electric discharge is incident on a diffraction grating 5 via an entrance slit 4. Light which has been separated into its spectral components by the diffraction grating 5 is incident on a linear image sensor 6, the intensity of a spectral line is detected continuously with reference to a wavelength, and its detection signal is input to a microcomputer 11 as a digital signal via a data processing unit 7 and an interface board 8. The microcomputer 11 computes a background intensity Ib at the peak wavelength lambda0 of the spectral line of a chemical element to be analyzed or the like, the background intensity Ib is removed from a spectral-line intensity Ip, and a real intensity Is is obtained. The concentration of the chemical element to be analyzed is computed on the basis of the actual intensity Is.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical emission spectroscopic analyzer, and more particularly to an optical emission spectroscopic analyzer for performing qualitative and quantitative analysis of elements contained in an object to be measured.

[0002]

2. Description of the Related Art Emission spectroscopy is a method for determining the chemical composition of a substance by spectrally analyzing a wavelength peculiar to a chemical element contained in a conductive sample such as a metal material. Then, qualitative analysis can be performed by spectrally separating the spectral line of the light emitted from the object to be measured according to the length of the wavelength, and quantitative analysis can be performed by measuring the spectral line intensity of the element.

Further, as a method for exciting light to emit light,
There are various methods such as flame method, arc method or spark method,
The flame method can perform excited light emission only at a low temperature of about 1000 ° C. to 3000 ° C., and an arc method of arc discharge is mainly used to cause excited light emission at a high temperature of about 3000 ° C. to 6000 ° C. In order to excite and emit light at a high temperature of 6000 ° C. or higher, a spark method of performing spark discharge is mainly used. The arc method is suitable for qualitative analysis because of its high analytical sensitivity, but it has the drawback of poor reproducibility. Therefore, when performing quantitative analysis, a spark method with relatively good reproducibility is generally used. Target.

The principle of the quantitative analysis method using spark discharge will be described below.

In the spark discharge, it is impossible to generate a certain amount of light emission between the object to be measured and the electrode due to fluctuations in the discharge temperature, fluctuations in the light source, fluctuations in the light emission power source, and the like. Therefore, in addition to the spectrum line of the element to be quantified (hereinafter, this element is referred to as "analytical element"), other elements contained in the measured object in a known amount (hereinafter, this element is referred to as "internal standard element"). ) Is selected, and the intensity ratio between the spectrum line of the analytical element and the spectrum line of the internal standard element is measured to quantitatively analyze the analytical element based on the intensities of these two spectral lines.

Specifically, Is is the strength of the internal standard element, I
a is the strength of the analytical element, Ca is the concentration of the analytical element, N and A
Is a constant, it is known that the relationship between the ratio Ca of the analytical element strength Ia and the internal standard element strength Is and the analytical element concentration Ca is expressed by mathematical expression (1).

Log (Ia / Is) = log A + N logCa (1) Therefore, a calibration curve showing the relationship between log (Ia / Is) and logCa is stored in the microcomputer in advance,
The intensity Ia of the analytical element and the intensity Is of the internal standard element are simultaneously measured, and the concentration C of the analytical element is calculated from the intensity ratio (Ia / Is) of both.
a can be calculated.

As an emission spectroscopic analyzer embodied in accordance with the above principle, one disclosed in Japanese Patent Application Laid-Open No. 57-69231 or Japanese Patent Application Laid-Open No. 1-274043 is known. These devices use what is called a Paschen-Lunge photoelectric photoelectric spectroscope as a means to disperse the light emitted from the object to be measured, and the light generated by the discharge passes through the entrance slit and forms a diffraction grating. After being separated into spectral lines peculiar to the element, the light passes through a plurality of exit slits and is incident on a photomultiplier tube which is installed in a pair with the exit slits. The photomultiplier tube converts the light into an electric signal according to its intensity, the electric signal is integrated by an analog integrating circuit, and after being digitized by an A / D converter,
Captured by a microcomputer. The microcomputer performs predetermined arithmetic processing on the input signal to calculate the concentration of the analysis element, and outputs the calculation result to a CRT (cathode ray tube) display or printer.

[0009]

In the case of the conventional emission spectroscopic analyzer described above, a spectral line selected from the plural spectral lines of the analytical element and the internal standard element so as not to be influenced by other elements. In order to detect the intensity of the above, when the device is manufactured, the exit slit and the photomultiplier tube arranged in pair with the exit slit are previously installed at the peak position of the above-mentioned spectral line.

However, in the spectral lines of the analytical element and the internal standard element, the background due to the light source, the background due to the incompleteness of the spectroscope, and other elements located near the spectral line of the analytical element The background intensity and the like are included due to the spectrum line of 1., and the intensity of the background varies depending on the instability of the light emission power source, the temperature change in the spectroscopic section, and the composition of the measured object.

However, as described above, in the conventional emission spectroscopic analyzer, the spectral intensity including the background is detected, and therefore the analytical result varies and the reproducibility is poor due to the background that fluctuates due to various causes. There was a problem.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical emission analyzer capable of performing analysis with good reproducibility.

[0013]

In order to achieve the above-mentioned object, the present invention has an electrode, and a voltage is applied between the electrode and an object to be measured having conductivity to form the electrode and the object to be measured. A light emitting means for causing a spark discharge between the light emitting means, a light emitting means for separating the light emitted from the light emitting means into a spectral line peculiar to an element contained in the object to be measured, and an intensity of the spectral line In an emission spectroscopic analyzer equipped with a measuring means for detecting, the background intensity calculating means for calculating the background intensity at the peak position of the spectral line corresponding to the element to be analyzed, and the spectral line detected by the measuring means. Concentration calculating means for calculating the concentration of the element to be analyzed by removing the background intensity from the intensity is provided.

Further, it is desirable that the measuring means be capable of continuously measuring the spectral line intensity with respect to the wavelength, and more specifically, a linear image sensor may be used.

[0015]

The background intensity at the peak position of the spectral line corresponding to the element to be analyzed is calculated, and the background intensity is removed from the spectral line intensity detected by the measuring means to calculate the concentration of the element to be analyzed.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram schematically showing an emission spectroscopic analyzer according to an embodiment of the present invention. In the figure, the light emitting power supply circuit 1 is connected to the DUT 3 and the electrode 2, and a voltage is applied between the DUT 3 and the electrode 2 to generate a spark discharge between them. Light emitting power supply circuit 1
Is a microcomputer (hereinafter referred to as "microcomputer")
11 is connected, and the discharge voltage and discharge time of the light emitting power supply circuit 1 are controlled by the microcomputer 11. An entrance slit 4 and a diffraction grating 5 are provided so as to face a portion where a discharge is generated, and light generated by the discharge is incident on the diffraction grating 5 through the entrance slit 4.

A linear image sensor 6 is provided so as to face the diffraction grating 5, and the light dispersed by the diffraction grating 5 into spectral lines peculiar to the element is linear image sensor 6.
Is incident on. The linear image sensor 6 converts the incident light into an electric signal according to its intensity and inputs the signal to the data processing unit 7.

A temperature controller 12 is connected to the linear image sensor 6, and the temperature controller 12 keeps the temperature of the sensor 6 at a constant value. The linear image sensor 6 has a scanning circuit composed of MOS transistors, a photodiode array for converting an optical signal into an electrical signal, a switching transistor array for addressing each photodiode array, etc., integrated on a single substrate of silicon. Since the sensor output reacts sensitively to changes in the outside temperature and the analysis result may vary, the temperature controller 12 keeps the temperature of the sensor 6 constant.

The data processing unit 7 includes an A / D converter for converting an analog signal into a digital signal, and a DMA for directly transferring data to the memory of the microcomputer 11.
(Direct Memory Access) function. The data processing unit 7 performs processing such as converting the output signal of the linear image sensor 6 into a digital signal, and outputs the processed signal to D
Transfer to the microcomputer 11 via the MA interface board 8.

The microcomputer 11 processes the signal input from the interface board 8 by a method described later to calculate the content of the plurality of analytical elements in the DUT 3,
The result is output to the CRT display 9 or the printer 10.

The linear image sensor 6, the data processing unit 7 and the temperature controller 12 are, for example, a linear image sensor S39 manufactured by Hamamatsu Photonics KK
24-1024Q, multi-channel detector C4627
And a temperature controller C3434.

The arithmetic processing in the microcomputer 11 of the emission spectral analyzer configured as described above will be described with reference to FIG.

FIG. 2 shows the wavelength λ of a general spectrum line.
FIG. 3 is a diagram showing the relationship between the intensity Ip and the intensity Ip at the peak wavelength λ ₀ of the spectrum line in the same figure, as shown in the following equation (2): It is expressed as the sum of ground intensities Ib.

Ip = Is + Ib (2) The background intensity Ib in the equation (2) is the same as that of the standard sample in which the concentration of coexisting elements other than the analysis element is equal and the analysis element does not contain any analysis element. If so, the background intensity Ib at λ ₀ in FIG. 2 can be known, so the background can be corrected. However, in reality, the coexisting elements and their concentrations in the measured object are unknown. In many cases, it is difficult to prepare these standard samples, and without background correction,
As described above, the background fluctuates and the analysis results vary.

In the present application, it is not necessary to prepare such a difficult sample, and the background intensity can be obtained from the measured object itself.

Therefore, as the present embodiment, the linear image sensor 6 is used to continuously measure the intensities of the spectral lines with respect to wavelengths to obtain the intensities Im and In of the respective spectral lines at λm and λn in FIG. The back ground intensity Ib at the peak wavelength λ ₀ of the analytical element, which is automatically detected by the microcomputer 11 and stored in the memory of the microcomputer 11 in advance, is calculated.
For example, in FIG. 2, the calculation can be performed as in the following expression (3). Then, using the formula (2), the actual intensity Is of the analysis element at the wavelength λ ₀ is obtained.

[0028]

[Equation 1] Based on the actual intensity Is of the analytical element thus obtained, a calibration curve obtained from the results of measuring various standard samples is used in advance by the same method, and the microcomputer 11 automatically determines the The content (concentration) of the analytical element is calculated.

As described above, according to the present embodiment, since the light split by the diffraction grating is detected by the linear image sensor, the intensity of the spectral line can be continuously measured with respect to the wavelength. Yes, background intensity Ib
Can be calculated.

Then, the actual intensity Is and the background intensity Ib at the peak wavelength λ ₀ of the spectral lines of the analytical element and the internal standard element are completely separated, and the background component is removed from the spectral line intensity. It is possible to obtain highly reliable (good reproducibility) analysis results even when there is a change in the value or the composition of the measured object.

Further, as shown in the conventional example, when a photomultiplier tube is used as a means for converting an optical signal on a spectral line into an electric signal, an analog integrating circuit is required in the next stage. However, since the linear image sensor used in this embodiment is a current integration type, the exposure amount (light intensity × accumulation time)
Since an output proportional to is obtained, it is possible to simplify the device without requiring an analog integrating circuit.

[0032]

As described above in detail, according to the present invention, the background intensity at the peak position of the spectrum line corresponding to the element to be analyzed is calculated, and the background intensity is calculated from the spectrum line intensity detected by the measuring means. Since the concentration of the element to be analyzed is calculated excluding, the analysis result having a good reproducibility, that is, a highly reliable analysis result can be obtained even if the light emission conditions change or the composition of the measured object changes.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an emission spectroscopic analyzer according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between wavelength and intensity of a general spectrum line.

[Explanation of symbols]

 1 Light Emitting Power Supply Circuit 2 Electrodes 3 DUT 5 Diffraction Grating 6 Linear Image Sensor 11 Microcomputer

Claims (1)

[Claims] 1. A light-emitting device having an electrode, which applies a voltage between the electrode and a conductive object to be measured to generate a spark discharge between the electrode and the object to be measured; In an emission spectroscopic analyzer comprising a spectroscopic means for spectroscopically dividing the light emitted from the means into spectral lines peculiar to the elements contained in the object to be measured, and a measuring means for detecting the intensity of the spectroscopic spectral lines. , The background intensity calculation means for calculating the background intensity at the peak position of the spectrum line corresponding to the element to be analyzed, and the background element to remove the background intensity from the spectrum line intensity detected by the measuring means And a concentration calculation means for calculating the concentration of