JP5794041B2 - Concentration measuring device and concentration measuring method - Google Patents

Description

  The present invention relates to a concentration measurement apparatus and a concentration measurement method for measuring an electrolytic current or a detection electrode potential corresponding to a concentration of a measurement target component in a sample solution by inserting a detection electrode into the sample solution. More specifically, a concentration measurement device that can stably measure the oxidation-reduction current (electrolysis current) and oxidation-reduction potential (detection electrode potential) of the polarographic method or galvanic cell method regardless of the interstitial substances in the sample solution. And a concentration measuring method.

Conventionally, a polarographic method or a galvanic cell type oxidation-reduction current measuring device has been used for the purpose of measuring residual chlorine, dissolved ozone, chlorine demand, chlorine dioxide, and the like. In these measurement methods, a detection electrode made of a noble metal such as platinum or gold or glassy carbon and a counter electrode made of silver or the like having a sufficiently large surface area with respect to the detection electrode are immersed in the sample solution. An appropriate constant voltage is applied during the period to cause electrolytic reduction (or oxidation) of the component to be measured in the vicinity of the detection pole, thereby obtaining an electrolytic current and measuring this to obtain the concentration of the predetermined component. .
This electrolytic current is a current that flows when the component to be measured transported to the surface of the sensing electrode is oxidized and reduced in a thin layer (diffusion layer) that forms a concentration gradient with the sample solution due to mass transfer due to diffusion. And is also called a diffusion current. In order to obtain a diffusion current according to the concentration of the component to be measured, the diffusion layer must always be newly replaced.
For this reason, the sample liquid is caused to flow relative to the detection electrode surface. In order to cause the sample liquid to flow relative to the surface of the detection electrode, an electrode (hereinafter referred to as “rotating electrode”) that rotates or vibrates (precesses) a detection electrode support provided with the detection electrode with a motor is used. There is a method.

In such a system, the rotating electrode rotates (vibrates) at a linear velocity much higher than the normal flow rate of the sample liquid. For this reason, a stable diffusion layer can be obtained regardless of the flow rate of the sample liquid, and the measurement value is hardly affected by fluctuations in the flow rate of the sample liquid.
However, the detection electrode surface is likely to be contaminated with electrolytes generated at the counter electrode and contaminants in the sample solution, and if these stains adhere, the current value flowing between the detection electrode and the counter electrode decreases. As a result, the concentration instruction value of the measurement target component is lowered.
For this reason, conventionally, by attaching a cap containing abrasive beads to a rotating electrode and rotating (vibrating) the rotating electrode in the abrasive beads, a constant linear velocity is obtained and the sensing electrode is polished. The adhesion of dirt is prevented and stable measurement can be performed (see Patent Document 1, Patent Document 2, and Patent Document 3).

Japanese Utility Model Publication No. 6-30764 JP 2002-90339 A JP 2004-340762 A

  However, if the rotation (vibration) speed of the rotating electrode is increased in order to obtain a stable diffusion layer, the polishing beads are scattered to reduce the cleaning effect, or the sample solution near the detection electrode moves with the rotating electrode. As a result, it appears that the sample solution is not moving, and a stable diffusion layer cannot be obtained. As a result, there may be a problem that the electrode output becomes small or the response speed of the electrode becomes slow and the measurement becomes unstable.

  The present invention has been made to solve the technical problems as described above. The purpose of the present invention is to reduce the cleaning effect of the detection electrode even if the rotation (vibration) speed of the rotating electrode is increased. Moreover, it is providing the density | concentration measuring apparatus and density | concentration measuring method which can obtain the stable diffused layer.

For this purpose, a concentration measuring device to which the present invention is applied is a concentration measuring device that inserts a detection electrode into a sample solution and measures an electrolytic current or a detection electrode potential corresponding to the concentration of a component to be measured in the sample solution. The detection electrode is provided on the lower end surface of the rotating or vibrating support, and a water-permeable abrasive that is located below the detection electrode and polishes the detection electrode; and below the abrasive is constituted by a position constituted by buoyant material or the abrasive to form a material with a buoyant, and buoyant pressing means presses with buoyancy the abrasive to the sensing electrode, wherein the abrasive is the rotation of the support or And a rotation restricting means for restricting the rotation in conjunction with the vibration .

Here, the rotation restricting means includes a guide pin for restricting the rotation of the abrasive by engaging with the buoyancy material when the buoyancy pressing means is constituted by the buoyancy material, In the case where the abrasive is made of a material having buoyancy, it includes a guide pin that regulates the rotation of the abrasive by engaging with a container that accommodates the abrasive. it can. Further, the passage of the sample solution into which the detection electrode is inserted has an inner peripheral surface formed in a rectangular shape in cross section, and the rotation restricting means is provided when the buoyancy pressing means is constituted by the buoyancy material. When the buoyancy material has a rectangular shape in cross section that engages with the inner peripheral surface of the passage, and the buoyancy pressing means is formed by forming the abrasive material from a material having buoyancy, the abrasive material is the passage. the rectangular cross section shape der Rukoto for engagement with the inner peripheral surface can be characterized. Further, the permeability of the abrasive can be characterized that you polishing the sensing electrode in the depression-shaped portion formed on the upper surface.

  Moreover, the concentration measuring method to which the present invention is applied uses the concentration measuring apparatus according to any one of claims 1 to 4 and uses an electrolytic current or a sensing electrode corresponding to the concentration of a measurement target component in a sample solution. It is characterized by measuring a potential.

  According to the present invention, even if the rotation (vibration) speed of the rotating electrode is increased, the cleaning effect of the detection electrode is not lowered, and a stable diffusion layer can be obtained.

It is a figure explaining the structure of the density | concentration measuring apparatus which concerns on this Embodiment. It is a cross-sectional view of the concentration measuring apparatus of FIG. It is a figure explaining the structure of the 1st modification. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3. It is a figure explaining the 2nd modification. It is a figure explaining the 3rd modification.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
The concentration measuring apparatus 1 according to the present embodiment will be described.
FIG. 1 is a diagram for explaining the configuration of the concentration measuring apparatus 1 according to the present embodiment, and is partially shown in a vertical section for convenience of explanation.
As shown in FIG. 1, the concentration measuring device 1 includes a detection unit 10 and a converter 40. The detection unit 10 includes a sample solution passage unit 20 having a sample solution passage to be measured, and a rotating electrode 30 having means for detecting a diffusion current corresponding to the concentration of the measurement target component in the sample solution. . Moreover, the converter 40 calculates the output value of the rotating electrode 30 which the detection part 10 has, and converts it into the density | concentration of the measuring object component of a sample liquid.
More specifically, a concave portion that opens upward is formed in the sample liquid passage portion 20, and a lower portion of the rotating electrode 30 is inserted into the concave portion, and the sample liquid passage portion 20 and the rotating electrode 30 are connected to each other. They are fixed integrally with each other.

The rotating electrode 30 of the concentration measuring apparatus 1 includes an elongated electrode body 31, a detection electrode 32 that is held by the electrode body 31 and rotates or vibrates by a driving force of a motor 32 a, and a counter electrode disposed on the electrode body 31. 33. The detection pole 32 is mounted on a rotation shaft (substantially vertical shaft) 32c of a rotation shaft 32b that protrudes downward from the motor 32a, or is mounted at an inclination of, for example, 3 degrees with respect to the rotation shaft 32c. It is disposed on the lower end surface of the support 32d, and thereby the rotation or vibration (precession movement, precession movement) of the detection pole 32 is realized.
The detection electrode 32 may be formed of, for example, gold, platinum, an alloy, glassy carbon, or the like, and the counter electrode 33 may be formed of, for example, platinum, silver / silver chloride, or the like.

The converter 40 of the concentration measuring apparatus 1 is provided with a voltage applying mechanism and an ammeter for applying a predetermined constant voltage between the detection electrode 32 and the counter electrode 33 when measuring the electrolytic current. Specifically, the applied voltage mechanism is a power supply that can be set to a predetermined voltage. Here, zero is included in the value of the predetermined applied voltage to be applied. In this case, the applied voltage mechanism can be configured by a simple wiring that connects the detection electrode and the counter electrode via an ammeter. Generally, when the applied voltage is not zero, it is called a polarographic method, and when the applied voltage is zero, it is called a galvanic cell method. In both types, the diffusion current (flowing when the substance to be reduced, etc. is transported to the surface of the sensing electrode only by natural diffusion due to the concentration gradient in the layer called the diffusion layer having a constant thickness, and flows when it is oxidized and reduced on the surface) (Redox current) is common and there is no essential difference.
Moreover, the converter 40 is provided with a voltmeter when measuring the detection electrode potential.
The converter 40 is further provided with a concentration conversion circuit that converts the measured electrolytic current or detected electrode potential into the concentration of the component to be measured. Further, it has a function of displaying and / or outputting the measured electrolytic current or detected electrode potential, converted concentration, and the like.
Depending on the measurement principle, it is conceivable to add a reagent, a diluent or the like to the sample solution as appropriate.

The sample liquid passage portion 20 of the concentration measuring apparatus 1 includes a flow cell 21 having a recess opening upward, an abrasive 22 positioned in the recess of the flow cell 21, and an abrasive 22 in the recess of the flow cell 21. And a buoyancy material 23 having a through hole 23a that is positioned below and linearly penetrates in the vertical direction. In addition, the sample solution passage portion 20 is inserted into the through hole 23 a of the buoyancy material 23, and a space between the guide pin 24 that functions as a detent of the buoyancy material 23 and the electrode body 31 of the flow cell 21 and the rotary electrode 30. And a sealing member 25 for watertight closing. The buoyancy material 23 is an example of a buoyancy pressing means.
The abrasive 22 is for polishing and cleaning the surface of the detection electrode 32, and is permeable to the sample liquid. The abrasive 22 is made of, for example, a porous resin. The abrasive 22 is fixed to the buoyancy material 23. For this reason, the guide pin 24 not only rotates the abrasive 22 but also the buoyancy material 23. The guide pin 24 is an example of a rotation restricting unit. It should be noted that at least two guide pins 24 are provided in order to achieve a detent action.

The buoyancy material 23 functions as a floating ring or a float, and acts to push up the abrasive 22 upward when the concave portion of the sample liquid passage 20 is filled with the sample liquid. The upper surface 22 a of the abrasive 22 contacts the lower surface of the detection electrode 32. It is also conceivable that the abrasive 22 is made of a material having buoyancy.
More specifically, the flow cell 21 has an inflow port 21a and an outflow port 21b communicating with the recess. The inflow port 21a is located below the recess, and the outflow port 21b is located above the recess. That is, the sample liquid that has flowed in from the inflow port 21a mainly passes through the through hole 23a of the buoyancy material 23, rises in the recess, passes through the abrasive 22, and flows out from the outflow port 21b. Such upward flow of the sample liquid (water pressure of the sample liquid) has the effect of pushing up the abrasive 22 upward, and together with the buoyancy by the buoyancy material 23, the upper surface 22a of the abrasive 22 is always detected. It becomes possible to press against the lower surface of 32.

2 is a cross-sectional view of the concentration measuring apparatus 1 in FIG. 1, and FIG. 2A is a diagram taken along line IIa- in FIG. 1 when the detection electrode support 32d is attached to be inclined with respect to the rotating shaft 32c. It is sectional drawing by IIa, (b) is a cross-sectional view by line IIb-IIb of FIG.
As shown in FIG. 2 (a), when the detection pole support 32d performs precession (grinding operation), the upper surface 22a of the abrasive 22 swings around the rotating shaft 32c so as to draw a circle (arrow). A). For this reason, compared with the case where the detection pole support body 32d is attached on the rotating shaft 32c, the area | region of the upper surface 22a of the abrasive 22 which the detection pole 32 contacts becomes wider.
Here, in a state in which the detection pole 32 is always in contact with the abrasive 22 due to the buoyancy of the buoyancy material 23 or the like, the detection pole support 32d is caused to precess by a driving force of the motor 32a (precession operation). When the detection electrode 32 is polished and cleaned by the water-permeable polishing material 22, the detection electrode 32 comes into contact with the polishing material 22 in a wider area. For this reason, it is possible to prevent a reduction in the polishing effect due to wear or deformation of the abrasive 22.

As shown in FIG. 2B, two through holes 23a of the buoyancy material 23 are formed closer to the center, and a guide pin 24 is inserted into each of the two through holes 23a. By such two guide pins 24, the buoyancy material 23 and the abrasive 22 rotate as the detection pole support 32d contacting the upper surface 22a of the abrasive 22 rotates or vibrates (precession). Is regulated.
In addition, these two through holes 23a are preferably formed at positions corresponding to the region of the upper surface 22a of the abrasive 22 (see FIG. 2A) with which the detection electrode 32 contacts. Further, the sample liquid mainly flows in the space between the through hole 23 a of the buoyancy material 23 and the guide pin 24. It is also conceivable that the number of through holes 23a is greater than the number of guide pins 24, and the through holes 23a into which the guide pins 24 are not inserted are used only as the sample solution passages.

  Thus, according to the present embodiment, it is possible to suppress a decrease in the detection electrode cleaning effect due to the abrasive even if the rotation (vibration) speed of the rotary electrode is increased. In addition, a stable diffusion layer can be obtained even if the rotation (vibration) speed of the rotating electrode is increased.

Various modifications can be considered for the above-described embodiment. Since various modifications described below have the same configuration as that of the present embodiment, the same reference numerals are used for common portions, and the description thereof may be omitted.
FIG. 3 is a diagram for explaining the configuration of the first modification, and FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. FIG. 3 corresponds to FIG. 1, and FIG. 4 corresponds to FIG.
As shown in FIG. 3, the concentration measuring apparatus 1 according to the first modification does not include a guide pin 24 (see FIG. 1) that is inserted into the through hole 23 a of the buoyancy material 23. Further, as shown in FIG. 4, in the concentration measuring apparatus 1 according to the first modification, the flow cell 21 has a concave portion having a rectangular cross section on the inner peripheral surface, and the transverse cross section of the outer peripheral surface of the buoyancy material 23. The surface is formed in a rectangular shape.
That is, in the above-described embodiment, the guide pin 24 functions as a rotation stopper for the buoyancy material 23 by being inserted into the through hole 23a of the buoyancy material 23 (see FIG. 2B). In the modified example, the buoyancy material 23 is prevented from rotating by making the inner peripheral surface of the recess of the flow cell 21 and the outer peripheral surface of the buoyancy material 23 have corresponding rectangular shapes (see FIG. 4). The through hole 23a of the buoyancy material 23 is used as a flow path through which the sample solution flows.
According to the first modification, the configuration can be simplified.

FIG. 5 is a diagram illustrating the configuration of the second modification. FIG. 5 corresponds to FIG. 1 or FIG.
As shown in FIG. 5, the concentration measuring apparatus 1 according to the second modified example is one in which the abrasive 22 itself has buoyancy, and therefore does not include the buoyancy material 23 (see FIG. 1). That is, the upper surface 22 a of the abrasive 22 is always pressed against the lower surface of the detection electrode 32 by the buoyancy caused by the abrasive 22 itself. The abrasive 22 in this case is an example of a buoyancy pressing means.

The abrasive 22 is accommodated in a relatively lightweight case 51. The case 51 is formed with a hole 51 a that engages with the guide pin 24 at the bottom. In other words, the sample solution is mainly supplied from the hole 51 a of the case 51 to the upper surface 22 a of the abrasive 22.
According to the second modification, the configuration can be simplified.

It is also conceivable to apply the above-described first modification to the second modification. That is, the guide pin 24 (see FIG. 1) is omitted as in the first modification, the buoyancy material 23 (see FIG. 1) is omitted as in the second modification, and the case 51 (see FIG. 5) is further omitted. ) Is also omitted. In this case, the abrasive 22 is prevented from rotating by making the inner peripheral surface of the recess of the flow cell 21 and the outer peripheral surface of the abrasive 22 have rectangular shapes corresponding to each other.
It is also conceivable to prevent the abrasive 22 from rotating by making the through hole 23a and the guide pin 24 have a rectangular shape corresponding to each other or a cross shape.

FIG. 6 is a diagram illustrating the configuration of the third modification. This figure is an enlarged cross-sectional view of the periphery of the abrasive 22 when the detection electrode support 32d of the concentration measuring apparatus 1 is attached to be inclined with respect to the rotating shaft 32c.
As shown in FIG. 6, in the concentration measuring device 1 according to the third modified example, a recessed portion 61 is formed on the upper surface 22 a of the abrasive 22. The hollow portion 61 is formed in a mortar shape. Such a recessed portion 61 makes it possible to more reliably contact the detection electrode 32 provided on the lower end surface of the detection electrode support 32d that precesses with the upper surface 22a of the abrasive 22. In addition, it is possible to secure a wider contact area between the lower surface of the detection electrode 32 and the upper surface 22a.
As described above, according to the third modified example, the contact between the detection electrode 32 and the abrasive 22 becomes more reliable, and a wider contact area can be secured.

DESCRIPTION OF SYMBOLS 1 ... Concentration measuring apparatus, 10 ... Detection part, 20 ... Sample liquid passage part, 21 ... Flow cell, 22 ... Abrasive material, 22a ... Upper surface, 23 ... Buoyancy material, 23a ... Through-hole, 24 ... Guide pin, 25 ... Seal member 30 ... rotating electrode, 31 ... electrode body, 32 ... sensing electrode, 32a ... motor, 32b ... rotating shaft, 32c ... rotating shaft, 32d ... sensing electrode support, 33 ... counter electrode, 40 ... converter, 51 ... case, 51a ... hole, 61 ... indented portion, A ... arrow

Claims (5)

A concentration measuring device that inserts a detection electrode into a sample solution and measures an electrolytic current or a detection electrode potential corresponding to the concentration of a measurement target component of the sample solution,
The detection electrode is provided on the lower end surface of the rotating or vibrating support, and a water-permeable abrasive that polishes the detection electrode located below the detection electrode.
A buoyancy pressing means configured to form a buoyancy material located below the abrasive or by forming the abrasive from a material having buoyancy, and pressing the abrasive to the detection electrode with buoyancy;
A rotation restricting means for restricting the abrasive from rotating in conjunction with rotation or vibration of the support;
A concentration measuring device comprising: The rotation restricting means includes a guide pin that restricts rotation of the abrasive by engaging with the buoyancy material when the buoyancy pressing means is constituted by the buoyancy material, and the buoyancy pressure means is the abrasive material. 2. A guide pin that restricts rotation of the abrasive by engaging with a container that accommodates the abrasive when it is formed of a material having buoyancy. Concentration measuring device. The passage of the sample solution into which the detection electrode is inserted has an inner peripheral surface formed in a rectangular cross section,
When the buoyancy pressing means is constituted by the buoyancy material, the rotation restricting means has a rectangular cross section that engages the inner peripheral surface of the passage, and the buoyancy pressing means is the abrasive. the concentration measurement according to claim 1, wherein the cross-sectional rectangular shape der Rukoto which the abrasive is engaged with the inner peripheral surface of said passage when constituted by forming a material with buoyant apparatus. The permeability of abrasive concentration measuring apparatus according to any one of claims 1 to 3, wherein that you polishing the sensing electrode in the depression-shaped portion formed on the upper surface.   5. A concentration measuring method, comprising: using the concentration measuring apparatus according to claim 1 to measure an electrolysis current or a detection electrode potential corresponding to a concentration of a measurement target component of a sample solution.

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