JPH06100546B2 - Luminescence analysis method - Google Patents

Description

Detailed Description of the Invention a. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an emission spectroscopic analysis device using spark discharge as a light source.

B. 2. Description of the Related Art The emission curve of the spark discharge in the above-mentioned emission analysis is as shown in FIG. 5. Normally, the light quantity is integrated over the entire area of this emission, and the integration result is integrated for several hundred spark discharges. The variation in the amount of light emission in the discharge is averaged. However, in one sample, one element has higher sensitivity because the emission is more stable each time during the initial sharp peak emission period of the emission curve of discharge, and another element has a gentle slope in the latter half of the emission curve. Since it can be said that light emission is more stable and high sensitivity can be obtained in the portion, spark discharge that causes sharp light emission as shown in FIG. 6A and gentle light emission as shown in FIG. 6B are performed. An arc method is used in which arc-like discharge is continuously performed in one discharge to emit light as shown in FIG. 6C, and any element is simultaneously analyzed with high sensitivity. Further, Japanese Patent Application No. 58-157023 proposes a method of integrating the light quantity only during the period in which the most favorable measurement (high sensitivity, high reproducibility of measurement) is performed in each discharge depending on the type of element.

C. Problems to be Solved by the Invention The method of integrating the light quantity for a proper period by the above-mentioned elements has a technical difficulty in setting the timing of the start point and the end point of the integration in accordance with each discharge. To generate spark discharge, a gate pulse is applied to the control spark gap, so it is possible to use the rising edge of the gate pulse as the starting point for the timing measurement that determines the integration period. Since there is variation in the time from the rise to the spark discharge in the control spark gap, this method cannot accurately set the integration timing with respect to the discharge emission curve. Therefore, in the method proposed above, the light emission due to the discharge in the control spark gap is detected, and the timing of integration is determined by this detection signal. However, even in this case, the current waveform of the main spark gap for the light source, and hence the shape of the emission curve, changes to some extent every time, and the discharge from the control spark gap to the maximum value of the main spark gap discharge is reached. Since the time, etc. changes with each discharge, the integration timing varies from discharge to discharge when the emission curve of the discharge in the main spark gap is used as a reference. The reproducibility was not sufficient, and the advantage of high sensitivity was not fully utilized.

The present invention seeks to improve the reproducibility of the measurement results of the proposed method.

D. Means for Solving Problems The light of the element to be quantified and the light of the internal standard element were integrated at the same timing for each discharge, and the ratio of both integrated values was integrated for multiple discharges.

E. Action Both the element to be quantified and the internal standard element emit light under the same discharge current waveform in one sample.Therefore, if the timings of light quantity integration are the same, both elements will be affected by the variation of the emission curve. You are receiving the same. Therefore, when the ratio of the light amount integrals of both elements is taken, the influence of the variation of the emission curve is canceled out, and the reproducibility of the measurement result is improved.

F. EXAMPLE FIG. 1 shows an outline of the present invention. AG is the main spark gap for the light source, and S is the sample. CG is a spark gap for control,
A gate pulse is applied at a constant cycle, and a spark discharge is generated each time to trigger the spark discharge in the main spark gap AG. Sp is a spectroscope and D1, D2, and D3 are photodetectors, which are arranged on the emission line spectrum of one of the elements to be detected. D1 and D2 are for the two elements A and B to be quantified, and D3 is for the internal standard element. I1, I2, I3 are integrating circuits that integrate the outputs of D1, D2, D3. Dc is a photodetector that detects the light of the spark discharge between the control spark gaps CG, and T is the photodetector in the timing control unit.
The output pulse of Dc is used as the starting point of time measurement to control the timing of light intensity integration of the light emission of each element, and each integration circuit I1 to I3 is reset immediately before each discharge. SH1, SH2, SH3, SH3 'are sampling circuits, which sample and hold the outputs of the preceding integrating circuits I1 to I3 by the signal from the timing control section T, respectively. Sampling circuits SH1 and SH3 as shown
The same timing control signal is applied to the element A, the integrated output of the light of the element A and the internal standard element are sampled at the same timing, and the same timing control signal is applied to SH2 and SH3 ′ in the same manner to the element B and the internal standard. The integral output of each elemental light is sampled at a timing different from that of the element A.

In FIG. 2, L is the emission curve in one discharge, p is the peak of the light of the control spark discharge, and m is the light of the discharge in the main spark gap. A and B indicate the integration period of elements A and B, and A is from to
Light amount integration is performed until t1, and B performs light amount integration from t1 to t2. FIG. 3 is the integral of the emission curve of m in FIG.
For the integrated value from t1 to t1, the output of the integrating circuit may be taken out at the time of t1. The sampling circuits SH1 and SH3 sample the outputs of the integrating circuits I1 and I3 at time t1. t1 to t
The integration up to 2 is the integration from to to t2, i2 to to in Figure 3
It is obtained by subtracting the integral i1 from to t1. The sampling circuits SH2 and SH3 'sample the outputs of the integrating circuits I2 and I3 at time t2. Although simplified in FIG. 1, the processing circuits B1 and B2 perform the above-mentioned subtraction operation on the sampling data of the sampling circuits SH2 and SH3 ′ to obtain the integrated value from t1 to t2 for the element B and the internal standard element. ing.

The ratio of the integral of the light emission of the element A thus obtained from to to t1 and the integral of the internal standard element from to to t1 is calculated by the dividing means Va, and this ratio is integrated by the adding means Wa. It
Similarly, the ratio of the integral of the element B from t1 to t2 and the integral of the internal standard element from t1 to t2 is calculated by the dividing means Vb, and the ratio is integrated by the adding means Wb. When the discharging is performed a certain number of times in this way, the integrated data of the adding means Wa and Wb is displayed by the display means Dsp. The inside surrounded by the chain line in FIG. 1 is actually performed by a computer.

The outline of the present invention has been described above, and the embodiment shown in FIG. 4 will be described below. D1 to Dn are photodetectors, which are installed at predetermined wavelength positions along the spectral image plane of the spectroscope, and Dn is for the internal standard element. The output of each photodetector is input to an integrating circuit I1 to In composed of an operational amplifier and a capacitor. In each of the integrating circuits, the FETs q1 to qn in parallel with the integrating capacitor are turned on by the reset switch of the integrating circuit in response to the signal from the timing control circuit T at the emission timing of the control spark gap to discharge the integrating capacitor. The outputs of the integrator circuits I1 to In are applied to the multiplexer MP as it is, and the multiplexers MP1 to SHn respectively pass through the multiplexers MP1 to SHn.
It is designed to be applied to MP. The sample and hold circuit is composed of FETs Q1 to Qn which are sampling switches and hold circuits H1 to Hn. Sampling switch Q1 ~
Qn is a signal from the timing control circuit T, which is conducted for each discharge from time t0 to time t1 in FIG. 2 and holds the output of each integrator circuit I1 to In at the time t1 by the corresponding hold circuit. H1
Hold to ~ Hn. The CPU is a computer that controls the spectroscopic analyzer, operates the multiplexer MP, and after each discharge is completed, each hold circuit H1 to Hn and each integration circuit I1 to
The signals held in In are sequentially taken out, converted into digital data by the A / D converter AD, and read. After the discharge is completed, each integration circuit I1 to In holds the integration result of the total amount of light emitted by one discharge of each element until the next discharge. Therefore, this is the integration result from to to t2 in FIG. Is the same as. In this way, the CPU calculates the integrated value i1 in Fig. 3 for each element.
And I2 data is captured. After that, the CPU performs a predetermined calculation on the acquired data until the next discharge. That is, for the elements using the integration from to to t1 in FIG. 2, the data held in each sample hold circuit is used as it is, and for the elements using the integration from t1 to t2 in FIG. Output data i2 of the integration circuit
The data i1 held in each sample hold circuit is subtracted from, and each is divided by the data of the internal standard element. For example, assuming that the element A is an element that should use the integration from to to t1, and the photodetector D1 detects the light of the element A, the CPU holds the output data α of the hold circuit H1 for the internal standard element. Divide by the output data Sa of the circuit Hn.
Similarly, the element B is an element for which integration from t1 to t2 should be used, and if the photodetector D2 detects the light of the element B, the CPU uses the data held by the integrating circuit I2 to hold the circuit H2. Of the output data of the hold circuit Hn is subtracted from the data held by the integration circuit In to calculate Sb, and β / Sb is calculated. If it is appropriate to use the integral of the total emission of the spark discharge for the element C, it is assumed that the photodetector D3 receives the emission of the element C.
The CPU collects the data γ held by the integrating circuit I3 from the integrating circuit In
Divide by the data SC held by to obtain γ / SC. CPU
Is calculated as α / Sa, β / Sb,
The data such as γ / SC is integrated, the discharge is stopped when it is detected that the discharge has been performed a predetermined number of times, the above integration result is transferred to the host computer HCPU, and the HCPU transfers the data to the CRT. Display and output to printer Pr for printing.

In the above-mentioned embodiment, the internal standard element is one kind and only one emission line is used, however, the present invention also includes the case where plural kinds of internal standard elements and plural emission lines are used according to the kind of the element to be quantified. Be done.

G. Effect According to the present invention, the measurement result for each discharge of the element to be quantified in the emission analysis method in which the range of light amount integration is appropriately set according to the element is divided by the measurement result of the internal standard sample under the same conditions. Since the values are integrated, the effect of variations in the emission curve for individual discharges is eliminated, and the variation in measured values for each discharge is reduced, and since it is integrated for a certain number of discharges, the integration range is simply appropriate. The S / N ratio is further improved and sensitivity is improved, and reproducibility of analysis results is also improved, compared to the method set to. The following table shows the relationship between the selection of the integration interval and the sensitivity in the present invention, the sample is steel, in the case of quantifying C, Si, Mn, P, S, 287.2 nm of Fe as an internal standard element. The bright line of was used. The numbers in the leftmost column are the wavelengths of the emission lines of each element used in the analysis, I and II are the types of emission lines, I is the neutral line, and II is the ion beam. In general, the neutral wire has a stable emission amount in arc-shaped discharge.
The method of taking the integration from to to t2 is suitable, and the emission of the ion beam is stable due to the spark-like discharge at the beginning of the light emission, and the method of taking the integration from to to t1 in FIG. 3 is suitable.
In the example in the table below, Mn corresponds to this. Column A in the table is from to to t1
, B is the integration from to to t2, X is the time from t1 to t2, and each number is when the signal level and the noise level are equal, that is, the SN ratio is 1.
Is the concentration. From this table, it can be seen that, for the neutral line, the sensitivity is about two times higher than the case of using the integration interval of t1 to t2 in the X column, compared to the case of using to to t1. It is also found that the sensitivity of the ion beam is better when the integration interval is from to 1 to t 1 than from t 1 to t 2.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining the outline of the present invention, FIG. 2 is a graph showing an emission curve and an integration section, FIG. 3 is an integration curve of a photodetector output, and FIG. 4 is an embodiment of the present invention. Block diagram FIG. 5 is a graph of emission of spark discharge over time (emission curve), FIG. 6A is emission curve of spark discharge, B is emission curve of arc like discharge, and FIG. 6C is spark curve. It is a light emission curve of the compound discharge which made discharge and arc-like discharge continuous.

Claims (1)

[Claims] 1. The light of spark discharge is spectrally divided, and for each emission line of the element to be quantified and the internal standard element, the light amount is integrated for each discharge in a time range suitable for the element to be quantified, and the integrated value is calculated. A luminescence analysis method, characterized by dividing by an integrated value of light amount in the same time range with respect to an internal standard element and integrating the result over a certain number of discharges to obtain a quantitative value of each element.