JPH06148134A - Glass electrode type trace sodium ion measuring device - Google Patents

Abstract

PURPOSE:To precisely measure even a low ion concentration showing nonlinear characteristic by selecting either one of functions calibrated in an area where the index of sodium ion concentration and electromotive voltage show a proportional relation and an area where they show no proportional relation. CONSTITUTION:A sodium ion electrode 2, a comparing electrode 3, and a temperature compensating electrode 4 are inserted into a cell chamber 1. A sample- mixed sample water is charged therein at measuring, and a calibrating solution is charged at calibration. An instructing par 5 has first and second arithmetic parts. The boundary of areas where the index of sodium ion concentration and electromotive voltage show a proportional relation and show no proportional relation is set to 0.1ppb, and the electromotive voltage in the intersection between the line calibrated with this value or more and the line calibrated with an index less than it is taken as a threshold. When the measured voltage is larger than the threshold, the first arithmetic part is used, and when it is less than the threshold, the second arithmetic part is used. The first arithmetic part uses the function calibrated with 0.1ppb or more, and the second arithmetic part uses the function calibrated with the index less than 0.1ppb.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention not only accurately measures a value of 0.1 ppb or more in a conventional glass electrode type trace amount sodium ion measuring apparatus, but also exhibits a low ion concentration of less than 0.1 ppb showing a non-linear characteristic. Also relates to a glass electrode type trace amount sodium ion measuring device which can be used when measuring with a certain degree of accuracy.

[0002]

2. Description of the Related Art In recent years, water quality requirements in condensate systems of thermal power plants or nuclear power plants have become strict in various senses, and in accordance with the demands, it is necessary to measure ion concentrations in the condensate in even smaller amounts. Came.

As for the sodium ion, it is necessary to know the value in the range of 0.01 to 0.1 ppb as the value at the outlet of the condensate demineralizer.

Measurement of a high concentration of several ppb to several hundreds of ppb is used for determining seawater leak from a heat exchanger for cooling main steam in a power plant, and a sodium ion concentration of 0.1 ppb or less is used in a thermal power plant. , As an index for monitoring the adhesion status of turbine scale, and P
It is used as a control value to prevent alkali embrittlement in WR nuclear power plants. That is, as the sodium ion concentration, a wide range of measured values of several hundred ppb to 0.1 ppb is required.

As a device for measuring sodium ions, a glass electrode type trace amount sodium ion measuring device as shown in FIG. 4 is used.

The glass electrode type trace amount sodium ion measuring device utilizes the fact that the index of sodium ion concentration and the electromotive force generated inside and outside the glass electrode are in a proportional relationship, and the sodium ion concentration is measured by measuring the electromotive force. I am trying to get it.

In FIG. 4, a sodium ion electrode 2, a reference electrode 3 and a temperature compensating electrode 4 are inserted in the cell chamber 1, and the cell chamber 1 is filled with a reagent mixed sample water at the time of measurement and a calibration solution at the time of calibration. I am able to do it.

The calibration solution has a known concentration of 0.1 ppb.
Two kinds of calibration solutions having the above-mentioned concentrations and having a large difference in concentration are prepared, the two kinds of calibration solutions are alternately filled in the cell chamber, and the electromotive force of the reference electrode at that time is measured.
From the data of two points, the linear function (ax +
Identify b).

In the actual measurement, the reagent-mixed sample water is filled in the chamber, the concentration is obtained from the electromotive force of the sodium ion electrode, which is a variable actually obtained, and the temperature change is compensated by the temperature compensation electrode. is doing.

However, the relationship between the exponent of sodium ion concentration and the electromotive force shows a proportional relationship of about 0.1 ppb.
Up to the concentration of, and below this linearity (proportional relationship)
Was lost and the electromotive force did not change in a proportional relationship as shown in FIG. 6, so that the concentration measurement of 0.1 ppb or less could not be actually performed (calibration line L ₁ ). And by all means 0.
When measuring at 1 ppb or less, as shown in FIG. 5, a calibration line (calibration line L ₂ ) with a weight on the region of 0.1 ppb or less was used.

[0011]

However, the characteristic line of concentration vs. electromotive voltage of the calibration line L ₂ based on one characteristic curve shown in FIG. 5 is a general calibration method in a specific region of 0.1 ppb or less. Although a measurement accuracy can be obtained from the calibration line L _{1 according to the} above, a considerable error is still included and sufficient measurement accuracy cannot be obtained, and conversely, high accuracy measurement is possible for 0.1 ppb or more. However, I could not get enough accuracy.

The present invention solves the above-mentioned problems of the related art, and a sufficient accuracy of measurement can be obtained even if it is less than 0.1 ppb, and a very small amount of glass electrode type that can measure highly accurately even at 0.1 ppb or more. An object is to provide a sodium ion measuring device.

[0013]

The calibration for realizing the object of the present invention is as set forth in the claims, and specifically, a region where the concentration index and the electromotive voltage show a proportional relationship,
The boundary of the region that does not show the proportional relationship is 0.1 ppb
A characteristic curve is a straight line calibrated at 0.1 ppb or more and a straight line calibrated at less than 0.1 ppb, and the electromotive voltage at the intersection of the two straight lines is used as a threshold, and the characteristic used to calculate the trace sodium ion concentration according to the measured voltage. Make sure you select a curve.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. The configuration of the glass electrode type trace amount sodium ion measuring device according to the present embodiment is the same as that of FIG. 4, and only the configuration of the indicator 5 is different. Therefore, the configuration of the indicator will be described below.

In this embodiment, the instruction section 5 has a first operation section, a second operation section, and a measured voltage comparison section. As shown in FIG. 3, the voltage set in the measured voltage comparison section is set. When the measured voltage is higher than the voltage Vi with Vi as the threshold value, the voltage of the electromotive force measured by using the first operation unit, and when it is less than the voltage Vi, the second operation unit is used. Based on, the sodium ion concentration is output, and the value is displayed or printed out.

The first arithmetic unit, the second arithmetic unit and the measured voltage comparing unit may be configured digitally or in an analog manner, and for the first arithmetic unit, the function V ₀ (V ₀
= A ₀ x + b ₀ ) and the function V ₁ (V ₀ = a ₁ x + b ₁ ) shown in FIG. 1 is used for the second computing unit.

As for the function V ₀ , one or two kinds of calibration solutions having a known concentration of 0.1 ppb or more are prepared, coefficients a ₀ and b ₀ are obtained, and a straight line is identified. The function V ₁ is 0.1 pp
Prepare one or two kinds of calibration solutions of known concentration less than b, obtain coefficients a ₁ and b ₁ , and identify a straight line. In this case,
The slope of the straight line V _{1 has} a positive value (a ₀ > a ₁ > 0) smaller than that of the straight line of the function V ₀ . When a linear function is obtained using only one kind of calibration liquid, a predetermined value is used as the inclination of the linear line for both V ₀ and V ₁ .

The identification of the functions V ₀ and V ₁ is performed by the calibration unit provided in the instruction unit 5, and the calibration unit determines the intersection (Vi, Xi) of the straight lines of the obtained functions V ₀ and V _1. Calculate A flowchart of the operation of this calibration unit is shown in FIG. Further, the calibration unit transmits the calculated intersection (Vi, Xi) to the above-mentioned measured voltage comparison unit and uses it as a threshold value.

The glass electrode type trace amount sodium ion measuring device of the present embodiment having the above-mentioned structure is arranged so that the calibration straight line at less than 0.1 ppb and the calibration straight line at 0.1 or more are determined according to the electromotive voltage of the sodium ion electrode. The concentration of sodium ion can be measured with sufficiently high accuracy even if the concentration is 0.1 ppb or more or less than 0.1 ppb. In particular, the accuracy currently required for the concentration of 0.0X order is the accuracy of the instrument for which the value of X is generally considered (± 5% of full scale, for example, 0.1p in this case).
pb × 5% / 100% = 0.005 ppb)
In view of the fact that it is not required, and therefore, there is sufficient indication accuracy of approximately the absolute value of the value of X, it can be said that the accuracy obtained by the function V ₁ which is not a curve is sufficient.

[0020]

As described above, according to the present invention, the region where the relationship between the concentration index and the electromotive voltage is not proportional, that is, the region where the concentration less than 0.1 ppb is proportional to the relationship between the concentration index and the electromotive voltage. That is, at a concentration of 0.1 ppb or more, the function used for the concentration calculation is selectively used.
Especially, since the calibration of the function in the concentration range of less than 0.1 ppb is not the same as the calibration line of 0.1 ppb or more as in the past but is a completely different straight line, the concentration at 0.1 ppb or less It has become possible to measure with a certain degree of accuracy over a wide range, and also to measure concentrations of 0.1 ppb or higher with high accuracy as before.

[Brief description of drawings]

FIG. 1 is a diagram showing a characteristic curve of concentration index and electromotive voltage showing an embodiment of a glass electrode type trace amount sodium ion measuring device according to the present invention.

FIG. 2 is a flowchart showing calibration of functions V ₀ and V ₁ shown in FIG.

FIG. 3 is a flowchart showing a measuring operation of an embodiment of a glass electrode type trace amount sodium ion measuring device according to the present invention.

FIG. 4 is a schematic view of a conventional glass electrode type trace amount sodium ion measuring device.

FIG. 5 is a view showing a characteristic curve of an index of concentration and an electromotive voltage showing an embodiment of a conventional glass electrode type trace amount sodium ion measuring device.

FIG. 6 is a diagram showing details of FIG. 5;

[Explanation of symbols]

 1 cell chamber 2 sodium ion electrode 3 reference electrode 4 temperature compensation electrode 5 indicator

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[Procedure amendment]

[Submission date] November 12, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

Measurement of a high concentration of several ppb to several hundreds of ppb is used for determining seawater leak from a heat exchanger for cooling main steam in a power plant, and a sodium ion concentration of 0.1 ppb or less is used in a thermal power plant. , As an index for monitoring the adhesion status of turbine scale, and P
It is used as a control value to prevent alkali embrittlement in WR nuclear power plants. In other words, as the sodium ion concentration, a wide range of measured values of several hundred ppb to 0.01 ppb is required.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

However, the relationship between the exponent of sodium ion concentration and the electromotive force shows a proportional relationship of about 0.1 ppb.
Up to the concentration of, and below this linearity (proportional relationship)
Is lost, and the electromotive force does not change in a proportional relationship as shown in FIG . In the actual measurement, 0.1 pp
In order to correctly measure concentrations above b, the one shown in FIG.
Perform the measurement using the calibration line L _{1 according} to a general calibration method.
Inevitably, I also knew the approximate concentration below 0.1 ppb.
If not, as shown in FIG. 5, the measurement is performed using a calibration line (calibration line L ₂ ) with an emphasis on the region of 0.1 ppb or less.
I was doing .

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

The first arithmetic unit, the second arithmetic unit and the measured voltage comparing unit may be configured digitally or in an analog manner, and for the first arithmetic unit, the function V ₀ (V ₀
= A ₀ x + b ₀ ) and the function V ₁ ( V ₁ = a ₁ x + b ₁ ) shown in FIG. 1 is used for the second computing unit.

Claims (3)

[Claims] 1. A glass electrode type trace amount sodium ion measuring device having a calculating means for calculating a trace amount of sodium ions in the measured liquid from the electromotive voltage of a glass electrode immersed in the measured liquid, the calculating means comprising: A first function calibrated in a region where the density index and the electromotive voltage have a proportional relationship, and a second function calibrated in a region where the density index and the electromotive voltage do not have a proportional relationship. Glass electrode type trace sodium, characterized in that the first function or the second function is selected in accordance with the measured electromotive voltage, with the electromotive voltage at the intersection of the above function and the second function as a threshold value. Ion measuring device. 2. The first function according to claim 1, wherein the first function is 0.1.
A glass electrode type trace sodium ion measuring device characterized in that it is calibrated in the vicinity of ppb or more and the second function is calibrated in the vicinity of less than 0.1 ppb. 3. The glass electrode type trace sodium ion measuring device according to claim 1 or 2, wherein the calculating means separately calibrates the first function and the second function.