JPWO2021131521A5 - - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrochemical measurement unit, an electrochemical measurement device, and an electrochemical measurement method, which are used in, for example, a pH measuring device.

Conventionally, as a flow-type pH measuring device, a measurement electrode having a sensitive part and a reference electrode having a liquid junction are separately arranged in a channel through which a sample liquid flows, as in Patent Documents 1 and 2. there is something

In such a flow-type measuring device, the measuring electrode and the reference electrode are separately arranged in the flow path, so that the sample liquid flows through different positions in the sensing section and the liquid junction section during pH measurement. There is a problem that an error occurs in the measurement due to contact with the

Further, in the flow-type measuring apparatus, there is a problem that if air bubbles are mixed in the sample liquid and attached to the sensitive part or the liquid junction part, the pH measurement is adversely affected. In particular, when the amount of sample liquid is very small, the volume occupied by air bubbles becomes large with respect to the sample liquid, and the influence of air bubbles on the measurement appears remarkably.

JP-A-4-012262 Japanese Utility Model Publication No. 7-036277

The present invention has been made in view of the above-mentioned problems, and in a flow-type measuring device, for example, even if it is a trace amount of sample liquid, the electrochemical characteristic value such as pH can be measured with a simple configuration and with high accuracy. Main purpose is to measure.

That is, the electrochemical measurement unit according to the present invention is provided in a flow path through which a sample liquid flows, has an inlet for introducing the sample liquid and an outlet for discharging the sample liquid, and has a reservoir for storing the sample liquid. and a composite electrode for measuring the electrochemical properties of the sample liquid stored in the reservoir, wherein the introduction port is positioned below the outlet, and the sensitive portion of the composite electrode is located below the outlet. is provided so as to be positioned downward.
In addition, the vertical direction in this specification refers to the vertical direction along the vertical direction. Downward includes not only downward in the vertical direction but also oblique downward with respect to the vertical direction.

According to the electrochemical measurement unit configured in this way, since the composite electrode is used, the positions of the sensitive part and the liquid junction part can be brought as close as possible. As a result, the sensing part and the liquid junction part can come into contact with the sample liquid flowing at almost the same position, so electrochemical characteristics such as pH can be accurately measured without using a special electrode such as a chip type. can do.

Moreover, since a composite electrode is used, there is no need to dispose the measurement electrode and the reference electrode separately in the reservoir, and the reservoir can be made as small as possible.

Furthermore, since the inlet is positioned below the outlet, and the sensitive portion of the composite electrode is positioned below the outlet, the sample liquid flowing into the reservoir from the inlet is It flows upward from below the reservoir.
As a result, even if the sample liquid contains air bubbles, the air bubbles can be easily discharged from the outlet. can be measured well.

Since the sensitive part is provided above the introduction port, the sensitive part is positioned above the bottom wall of the reservoir.
Therefore, even if the internal liquid exuding from the liquid junction of the composite electrode has a large specific gravity and stays in the lower part of the reservoir, the influence of the internal liquid on the electrochemical measurement can be reduced. can be suppressed.

If the liquid junction provided in the composite electrode is provided so as to face the outlet, the internal liquid exuding from the liquid junction can be easily discharged from the outlet to the outside of the reservoir.
Therefore, it is possible to suppress the influence of the retention of the internal liquid in the reservoir on the pH and the like of the sample liquid.

If the diameter of the outlet port is larger than the diameter of the inlet port, it is possible to suppress an increase in the internal pressure of the reservoir due to the inflow of the sample liquid into the reservoir.
As a result, it is possible to suppress adverse effects on the measurement due to the sample liquid flowing into the composite electrode from the liquid junction of the composite electrode.

As an electrochemical measurement apparatus equipped with an electrochemical measurement unit according to the present invention, for example, the electrochemical measurement unit as described above is connected to the introduction port and the outlet port, and a sample liquid is supplied to the electrochemical measurement unit. and a calculator for calculating the electrochemical characteristic value of the sample liquid based on the measured value measured by the composite electrode.

Electrochemistry comprising: an inlet for introducing a sample liquid and an outlet for discharging the sample liquid, a reservoir for storing the sample liquid, and a composite electrode for measuring the electrochemical properties of the sample liquid stored in the reservoir The same effects of the present invention can also be obtained by an electrochemical characteristic measuring method characterized by using a measuring unit and providing the sensitive part of the composite electrode below the outlet to measure the electrochemical characteristic of the sample liquid. can be played.

Advantageous Effects of Invention According to the present invention, in a flow-type measuring device, for example, even a very small amount of sample liquid can be accurately measured with a simple configuration for its electrochemical characteristic value such as pH.

1 is an overall schematic diagram of an electrochemical measurement device according to an embodiment of the present invention; FIG. FIG. 2 is an enlarged schematic diagram of an electrochemical measurement unit portion of the electrochemical measurement device according to the present embodiment. FIG. 2 is a cross-sectional view of the electrochemical measurement unit according to the present embodiment viewed from the axial direction of the composite electrode; FIG. 2 is a cross-sectional view of the electrochemical measurement unit according to this embodiment; FIG. 2 is an overall schematic diagram of an electrochemical measurement device according to another embodiment of the present invention; FIG. 3 is a schematic diagram showing an electrochemical measurement cell according to another embodiment of the present invention; FIG. 4 is an enlarged schematic diagram of an electrochemical measurement unit portion according to another embodiment of the present invention. The figure explaining the fixing method of the said electrochemical measurement unit which concerns on other embodiment of this invention. The figure explaining the fixing method of the said electrochemical measurement unit which concerns on other embodiment of this invention. FIG. 4 is a schematic diagram showing a positioning member of a composite electrode according to another embodiment of the present invention; FIG. 3 is a schematic diagram showing an electrochemical measurement cell according to another embodiment of the present invention; 4 is a graph showing measurement results (response speed) using the electrochemical measurement unit according to Example 1. FIG. 4 is a graph showing measurement results (response speed) using the electrochemical measurement unit according to Comparative Example 1. FIG. 4 is a graph showing measurement results (when the flow rate is changed) using the electrochemical measurement unit according to Example 1. FIG. 6 is a graph showing measurement results (when the flow rate is changed) using the electrochemical measurement unit according to Example 2. FIG. 4 is a graph showing measurement results (when the flow rate is changed) using the electrochemical measurement unit according to Comparative Example 1. FIG. 4 is a graph showing measurement results (influence of pump pulsation) using the electrochemical measurement unit according to Example 1. FIG. 4 is a graph showing measurement results (influence of pump pulsation) using the electrochemical measurement unit according to Comparative Example 1. FIG. 4 is a graph showing measurement results (continuous measurement) using the electrochemical measurement unit according to Example 1. FIG.

DESCRIPTION OF SYMBOLS 100...Electrochemical measuring apparatus 1...Electrochemical measuring unit 11...Storage part 11a...Introduction port 11b...Outlet port 12...Composite electrode 121b...Sensory part 122b... Liquid junction 2 ... Flow path 6 ... Mounting mechanism

An electrochemical measurement unit 1 and an electrochemical measurement device 100 according to one embodiment of the present invention will be described with reference to the drawings.

An electrochemical measuring device 100 according to this embodiment is, for example, a flow-type measuring device for measuring the pH and the like of a minute amount of sample liquid flowing out from an analyzer A, as shown in FIG.
In the present specification, a very small amount refers to the case where the flow rate of the sample liquid supplied to the electrochemical measurement unit 1 is 2 ml/min or less.

The analysis device A is, for example, a liquid chromatograph such as an ion chromatograph. More specifically, the analysis device A is, for example, a low-flow liquid chromatograph called nano liquid chromatograph, capillary liquid chromatograph, micro liquid chromatograph, or the like.

This electrochemical measurement apparatus 100 includes, for example, a channel 2 through which a sample liquid flows, an electrochemical measurement unit 1 provided in the channel for measuring the electrochemical properties of the sample liquid, and the electrochemical measurement unit 1 A calculator 3 for calculating an electrochemical characteristic value such as pH based on a measurement signal from the calculator 3 and a display unit 4 for displaying the electrochemical characteristic value calculated by the calculator 3 .

The channel 2 circulates a small amount of sample liquid flowing out from, for example, a liquid chromatograph device or the like to the electrochemical measurement unit 1, and an introduction channel 21 for introducing the sample liquid into the electrochemical measurement unit 1. and a lead-out channel 22 for leading the sample liquid from the electrochemical measurement unit 1 .

The introduction channel 21, for example, introduces a sample liquid flowing out from a liquid chromatograph or the like into the electrochemical measurement unit 1. For example, a general-purpose tube such as a 1/16-inch tube made of fluororesin is used. Those which are formed can be exemplified. A connection port for connecting the introduction channel 21 to the electrochemical measurement unit 1 is provided at the downstream end of the introduction channel 21 .

The lead-out channel 22 leads the sample liquid from the electrochemical measurement unit 1 to the outside. One formed by a tube, etc. can be mentioned. A connection port for connecting the outlet channel 22 to the electrochemical measurement unit 1 is provided at the upstream end of the outlet channel 22 .

The calculator 3 calculates electrochemical characteristic values such as pH based on the measurement signal from the electrochemical measurement unit 1 . The calculation unit 3 includes, for example, a digital electric circuit such as a CPU, a memory, and a communication port, an analog electric circuit such as an analog amplifier and a buffer, and an information processing circuit equipped with an ADC and a DAC that connect these circuits. The functions are carried out by the cooperation of the CPU and its peripheral devices according to a predetermined program stored in the device.
The calculator 3 may be provided in the electrochemical measurement unit 1, or may be provided in a general-purpose PC prepared separately outside.

The display unit 4 displays the electrochemical characteristic values such as the pH value calculated by the calculation unit 3. For example, the display of a general-purpose PC may be used. A display attached to the outer surface of the unit 1 may be used.

The electrochemical measurement apparatus 100 may further include a flow control unit (not shown) including valves, pumps, and the like for controlling the flow of the sample liquid. The control unit is not necessarily an essential component, and a flow control unit provided in a liquid chromatograph or the like may be used.

As shown in FIG. 2, the electrochemical measurement unit 1 has an inlet 11a for introducing a sample liquid and an outlet 11b for leading out a sample liquid, and a storage section (also referred to as an electrochemical measurement cell) 11 for storing the sample liquid. and a composite electrode 12 for measuring the electrochemical properties of the sample liquid stored in the storage part 11 .

The storage section 11 includes a storage space 11c for storing a sample liquid therein, an inlet 11a communicating with the storage space to introduce the sample liquid, and an outlet 11b communicating with the storage space for leading out the sample liquid. and

More specifically, the reservoir 11 is made of, for example, glass, vinyl chloride, PFA (perfluoroalkoxy fluororesin), or the like, and has a rectangular parallelepiped shape with a length of 2 cm, a width of 3 cm, and a width of 1 cm. is formed with a storage space 11c. The storage space 11c is, for example, a cylindrical space extending vertically. This storage space 11c has a size corresponding to the outer diameter (for example, 5 mm) of the portion of the composite electrode that is immersed in the sample liquid, and is desirably miniaturized so that accurate measurement can be performed with as little sample liquid as possible. . The volume of the storage space 11c is, for example, preferably 0.1 cm ³ or more and 10 cm ³ or less, more preferably 0.1 cm ³ or more and 5 cm ³ or less, and 0.1 cm ³ or more and 2 cm ³ or less. is particularly preferred. In this embodiment, the storage space 11c has, for example, a diameter of about 5 mm and a vertical height of about 1 cm.

The introduction port 11a is connected to the introduction channel 21 and supplies the sample liquid flowing from the introduction channel 21 to the storage space 11c. In this embodiment, the introduction port 11a is, for example, an opening in the side surface of the resin block, and the upper end of the introduction port 11a is below the center C of the storage space 11c in the vertical direction. It is formed so as to be located on the side. Further, the introduction port 11a is formed, for example, so that its lower end is at the same height as the bottom wall of the reservoir 11. As shown in FIG. The introduction port 11a is, for example, a circular opening with a diameter of about 0.8 mm, which communicates with the storage space 11c through a communicating passage formed in the horizontal direction and having the same diameter.

The outlet port 11 b is connected to the outlet channel 22 and guides the sample liquid flowing out from the storage space 11 c to the outlet channel 22 . The lead-out port 11b is formed above the lead-in port 11a. The lower end of the outlet 11b is positioned above the center C of the storage space 11c in the vertical direction. The outlet port 11b is, for example, a circular opening with a diameter of about 1.0 mm, which communicates with the storage space 11c through a communication passage formed in the horizontal direction and having the same diameter.
For example, as shown in FIG. 3, the inlet 11a and the outlet 11b are provided so as to face each other across the storage space 11c.

As shown in FIG. 2, the composite electrode 12 includes a pH electrode 121 (hereinafter also referred to as a measurement electrode) and a reference electrode 122 integrally formed. A pH electrode support tube 121a and a reference electrode support tube 122a are integrally provided so as to surround the outer periphery thereof. Both the pH electrode support tube 121a and the reference electrode support tube 122a are made of glass having the same composition.

A response glass, which is a sensitive part 121b, is joined to the tip of the pH electrode support tube 121a, the tip of which protrudes slightly from the reference electrode support tube 122a. A liquid junction 122b is provided so as to be positioned as close to the response glass as possible. The portion of the reference electrode support tube 122a that is immersed in the sample liquid is formed thinner than the portion that is not immersed in the sample liquid. Specifically, the portion of the reference electrode support tube 122a that is immersed in the sample liquid has a cylindrical shape with an outer diameter of about 3 mm, and the portion of the reference electrode support tube 112a that is not immersed in the sample liquid has an outer diameter of about 3 mm. is cylindrical with a length of about 10 mm. The responsive glass is sized to fit within the outer diameter of the reference electrode support tube 122a in the portion immersed in the sample solution. In this embodiment, a dome-shaped composite electrode 12 is employed in which the reference electrode support tube 122a and the tip of the pH electrode support tube 121a are joined on the same plane without forming a constriction.

The reference electrode support tube 122a and the pH electrode support tube 121a accommodate a reference electrode internal electrode 122c and a pH electrode internal electrode 121c made of Ag/AgCl, respectively. The inner electrodes are not limited to Ag/AgCl, and may be composed of Ag/AgBr, Ag/AgI, Hg/Hg2Cl2, or the like.

The reference electrode support tube 122a and the pH electrode support tube 121a are further filled with a high-concentration (3.33 M to saturated) KCl solution as an internal liquid. The internal liquid of the reference electrode support tube 122a is not limited to the KCl solution, and for example, an aqueous solution of CaCl2, NH4Cl, LiCl, NaCl, or the like can be used.

The composite electrode 12 is inserted through the electrode insertion port 5 formed in the resin block so that the sensitive part 121b and the liquid junction part 122b are immersed in the sample liquid stored inside the storage part 11. It is inserted into the portion 11 so that the tip faces downward. The electrode insertion port 5 is formed so as to communicate with the reservoir 11 from the upper wall of the resin block.

<Mounting structure of composite electrode to reservoir>
Next, a structure for attaching the composite electrode 12 to the reservoir 11 will be described.
The composite electrode 12 is arranged with respect to the reservoir 11 so that the sensitive portion 121b of the composite electrode 12 is located below the outlet 11b. Here, "located below" includes that half or more of the length in the vertical direction of the portion of the sensitive part 121b in contact with the sample liquid is located below the lower end of the outlet 11b. In terms of form, the entire portion of the sensitive part 121b that comes into contact with the sample liquid is positioned below the lower end of the outlet 11b.

Further, the composite electrode 12 is arranged with respect to the reservoir 11 so that the sensitive portion 121b of the composite electrode 12 is positioned above the introduction port 11a. Here, "arranged above" includes that half or more of the length in the vertical direction of the portion of the sensitive part 121b in contact with the sample liquid is above the upper end of the introduction port 11a. The entire portion of the sensitive part 121b that comes into contact with the sample liquid is positioned above the upper end of the introduction port 11a. When the composite electrode 12 is attached to the reservoir 11 in such a positional relationship, the lower end of the sensitive portion 121b of the composite electrode 12 is arranged above the bottom wall of the reservoir 11 with a space therebetween. . More specifically, the composite electrode 12 is attached to the storage portion 11 so that the bottom wall of the storage space 11c and the lower end of the sensitive portion 121b are separated by 1 mm or more. In this embodiment, the composite electrode is attached so that the distance between the lower end of the sensitive portion 121b of the composite electrode 12 and the bottom wall of the storage space 11c is about 2 mm.

Further, the composite electrode 12 is arranged such that the liquid junction portion 122b provided above the sensitive portion 121b faces the side where the lead-out port 11b is formed. At this time, the height of the liquid junction 122b is preferably arranged to be approximately the same height as the outlet 11b.
In this embodiment, the composite electrode 12 and the storage space 11c are coaxially arranged.

The positional relationship as described above is provided by the attachment mechanism 6 for attaching the composite electrode 12 to the reservoir 11 .

The attachment mechanism 6 includes, for example, a holding member 61 that holds the composite electrode 12 and a fixing portion 62 that fixes the holding member 61 to the storage portion 11, as shown in FIG. .

The holding member 61 has an electrode holding hole in which the composite electrode 12 is fitted. holds.

More specifically, the inner peripheral surface of the electrode holding hole and the outer peripheral surface of the composite electrode are in contact with each other but are not in close contact with each other, so that the composite electrode 12 is inserted into the electrode holding hole. In this state, the composite electrode 12 can be moved up and down or rotated.
The fixing portion 62 includes, for example, a male thread formed on the outer peripheral surface of the holding member 61 and a female thread formed on the inner peripheral surface of the electrode insertion port 5 and screwed into the male thread.

In this embodiment, for example, a deformable annular member 63 is arranged between the holding member 61 and the storage portion 11 so as to be fitted to the outer peripheral surface of the composite electrode 12. . This annular member 63 is, for example, an O-ring made of resin or the like. The annular member 63 has an upper surface in contact with the holding member 61 and a lower surface in contact with the resin block, and the upper surface is inclined downward toward the outer side in the circumferential direction.

When the holding member 61 is fixed to the storage portion 11 by the fixing portion 62 , the lower end of the holding member 61 presses the upper surface of the annular member 63 , and the inclination of the upper surface causes the annular member 63 to move toward the composite electrode 12 . It is pressed against the outer peripheral surface and closely attached. As a result, the composite electrode 12 cannot move up and down or rotate, and the composite electrode 12 is fixed with respect to the reservoir 11 .

According to the electrochemical measurement unit 1 and the electrochemical measurement apparatus 100 configured as described above, the composite electrode 12 in which the measurement electrode 121 having the sensitive portion 121b and the reference electrode 122 having the liquid junction portion 122b are integrally formed is provided. Therefore, the distance between the sensitive part 121b and the liquid junction part 122b can be reduced compared to the case where the measuring electrode 121 and the reference electrode are provided separately. As a result, even when the sample liquid is constantly flowing, the sensing part 121b and the liquid junction part 122b can come into contact with the sample liquid flowing at almost the same position. can be measured accurately.
In addition, since a composite electrode is used, there is no need to dispose the measurement electrode and the reference electrode separately in the reservoir, and the internal volume of the reservoir can be reduced to, for example, 10 cm ³ or less. .

Since the introduction port 11a is positioned below the outlet port 11b, the sample liquid flowing into the reservoir 11 from the introduction port 11a flows upward from the bottom of the reservoir 11. flow.
As a result, even if the sample liquid contains air bubbles, the air bubbles can be easily discharged from the outlet 11b to the outside. It is possible to further reduce the adverse effect on the measurement due to
If the reservoir 11 is made of glass, the hydrophilicity of the glass prevents air bubbles from adhering to the walls of the reservoir 11, making it easier to discharge air bubbles to the outside. Alternatively, a similar effect can be obtained by performing a treatment such as a coating that imparts hydrophilicity.

Since the inlet 11a, the sensitive part 121b, and the outlet 11b are arranged in this order from the bottom, the sample liquid flowing from the inlet 11a reliably flows near the sensitive part 121b toward the outlet 11b.

If the liquid junction 122b is arranged to face the outlet 11b, the internal liquid exuding from the liquid junction 122b can be easily discharged out of the storage section 11 through the outlet 11b. If the height of the liquid junction part 122b is the same as that of the outlet 11b, it is easier to discharge the internal liquid from the outlet 11b to the outside.

In addition, since the lower end of the inlet 11a is provided so as to be at the same height as the bottom wall of the storage space 11c, when using a liquid with a high specific gravity as the internal liquid, the internal liquid is introduced into the inlet 11a. It is also easy to discharge from the storage space.
Therefore, it is possible to suppress the influence of the retention of the internal liquid in the reservoir 11 on the pH and the like of the sample liquid.

Since the diameter of the outlet port 11b is made larger than the diameter of the inlet port 11a, an increase in the internal pressure of the reservoir 11 due to the inflow of the sample liquid into the reservoir 11 can be suppressed.
As a result, it is possible to suppress adverse effects on the measurement due to the sample liquid flowing into the composite electrode 12 from the liquid junction 122b of the composite electrode 12.

Since the composite electrode 12 is arranged so that the sensitive portion 121b of the composite electrode 12 is separated from the bottom wall of the reservoir 11 by 1 mm or more, the internal liquid such as a high-concentration KCl aqueous solution having a large specific gravity does not reach the reservoir 11. Even if it stays at the bottom, the pH and the like can be measured by avoiding the part where the high-concentration KCL aqueous solution is accumulated. Therefore, the measurement accuracy can be kept higher than when the composite electrode 12 is inserted so that the lower end of the composite electrode 12 touches the lowest bottom wall of the reservoir 11 .

On the other hand, the lower end of the sensitive portion 121b of the composite electrode 12 is positioned so that the tip of the composite electrode 12 does not touch the lowest bottom wall of the storage portion 11. is too high, the volume of the storage space 11c becomes too large, and when the amount of the sample liquid is very small, the response of the measured value to changes in electrochemical properties such as pH of the sample liquid becomes poor.

In this regard, according to the electrochemical measurement unit 1 according to the present embodiment, since the lower end of the sensitive part 121b is separated from the bottom wall of the storage space 11c by about 2 mm, the volume of the storage space 11c is increased. Therefore, it is possible to suppress the deterioration of the measured value response to changes in the electrochemical properties such as the pH of the sample liquid .
The volume of the storage space 11c after attaching the composite electrode 12 to the storage part 11 depends on the size of the storage space 11c and the mounting position of the composite electrode 12, but it is about 0.1 cm ³ or more and 10 cm. ³ or less.

Since the resin block is made of vinyl chloride, PFA, or the like, which has high chemical resistance, deterioration of the reservoir 11 due to the sample liquid is unlikely to occur.
Since the storage space 11c is cylindrical, it is easy to accommodate the cylindrical composite electrode 12, and the flow of the sample liquid can be prevented from stagnation inside the storage space 11c.

Since the storage space 11c formed inside the resin block has a relatively small diameter of about 5 mm and a vertical height of about 1 cm, the volume of the storage space 11c is relatively small compared to when the volume of the storage space 11c is large. Measurement response to liquid flow can be improved.

Since the composite electrode 12 is a dome-shaped electrode, the composite electrode 12 can be further miniaturized, and the storage space 11c that accommodates the composite electrode can also be miniaturized.

The electrochemical measurement unit and electrochemical measurement device according to the present invention are not limited to the above-described embodiments.
The analyzer is not limited to a liquid chromatograph, but preferably includes an analyzer main body and a reagent preparation mechanism that prepares a reagent and changes the pH and the like of the reagent over time.
By arranging the electrochemical measurement unit according to the present invention in the rear stage of an analyzer equipped with such a reagent preparation mechanism, it is possible to check whether the pH of the reagent prepared by the reagent preparation mechanism deviates from the desired value. It can be confirmed by measurement.
Furthermore, the analysis result by the analyzer can be associated with the actually measured pH or the like.
When the analyzer main body and the reagent preparation mechanism are connected via a flow path, the electrochemical measurement unit according to the present invention is arranged behind the reagent preparation mechanism and before the analyzer main body. You may make it

It is not limited to introducing all of the liquid flowing out of the analysis device or the reagent preparation mechanism into the electrochemical measurement device. For example, as shown in FIG. may be branched using, for example, a cheese joint or the like.
In this way, the electrochemical measurement device can be provided on a bypass flow channel separate from the main flow channel through which the liquid flowing out from the analysis device or the reagent preparation mechanism flows.
Which of the branched flow paths the liquid is to flow may be adjusted, for example, by the inner diameter of each flow path, or may be adjusted by providing a needle valve, an orifice, or the like in each branched flow path. Alternatively, a three-way valve or the like for switching the flow path may be provided.

Further, as shown in FIG. 5, the flow path outflowing from the electrochemical measurement apparatus may also be branched so that the flow path can be switched in the same manner as the flow path in the preceding stage of the electrochemical measurement apparatus. In particular, when the liquid flowing out of the electrochemical measurement device is returned to the sample channel or flows into another analysis device provided in the subsequent stage, branching the latter channel in this way can It is possible to select whether the liquid flowing out of the electrochemical measurement device is introduced into the sample channel or the analysis device or is discharged from the drain.

The introduction port and the outlet port are not limited to those provided so as to face each other across the storage space. For example, as shown in FIGS. They may be provided on the same side with respect to the storage space, or may be provided on adjacent walls among the walls forming the storage space. Further, the electrochemical measurement cell shown in FIG. 6 may be attached in any direction as long as it is attached to the flow channel so that the outlet is located above the inlet. . The introduction port is not limited to one in which the lower end of the introduction port is at the same height as the bottom wall of the storage section. may be provided so that the height of the lower end of is different from the height of the bottom wall of the reservoir.

Although the outlet is made larger than the inlet, the present invention is not limited to this. For example, the outlet and the inlet may be equal in size.
The liquid junction does not necessarily need to be arranged at the same height as the outlet, and may be arranged at a position higher than or lower than the outlet.

In the above embodiment, the resin block is connected to the flow channel in such a direction that the outlet and the inlet are located on the side surface of the resin block. and the resin block may be connected to the channel so that the inlets are arranged on the upper surface and the lower surface of the resin block, respectively, or the resin block may be connected to the channel at an arbitrary angle different from these. may be connected to

Note that regardless of the angle of the resin block when the resin block is connected to the flow path, the vertical direction means the vertical direction along the vertical direction, and the bottom wall of the reservoir means the reservoir. is connected to the channel and forms the lowermost surface in the vertical direction of the storage space.

The connection port that connects the flow path to the inlet or the outlet may be connected by a screw with an O-ring interposed, but is not limited to this. It may be adhered or welded to the outlet, may be connected using a sealing tape or the like, may be screwed with a ferrule or the like, or may be connected using a one-touch joint or the like.

The sizes of the aforementioned resin block, reservoir, inlet, outlet, composite electrode, channel diameter, etc. can be appropriately changed depending on the flow rate of the sample liquid to be measured.
The shape of the reservoir may be changed as appropriate according to the shape of the composite electrode.
The shape of the composite electrode is not limited to a cylindrical shape, and may be a prismatic shape or an irregular cylindrical shape.
The shape of the storage space may be changed in accordance with the shape of the composite electrode, and may be prismatic or deformed cylindrical.
The shape of the inlet and the outlet is not limited to circular, but may be polygonal or irregular.

In the above embodiment, the measurement electrode is described as a pH electrode, but the measurement electrode is not limited to the pH electrode, and may be an ion-selective electrode or a measurement electrode for measuring the oxidation-reduction potential. can be
In the case of the measuring electrode for measuring the oxidation-reduction potential, instead of the response glass, a part of the internal electrode exposed to the sample liquid side may be used as the sensitive part.

The composite electrode is not limited to being inserted from the upper surface of the resin block. For example, as shown in FIG. It may be inserted into the storage section.

When the composite electrode is inserted from the side surface of the resin block or when it is inserted obliquely into the resin block, the composite electrode is arranged so that the liquid junction faces upward. By doing so, it is possible to reduce the amount of the internal liquid that seeps into the sample liquid from the liquid junction.

In the mounting structure, the holding member has a contact surface that contacts the resin block, and the contact surface contacts the resin block to position the composite electrode vertically.

For example, as shown in FIG. 8, the resin block is fixed to a housing CS in which the resin block 11 and the composite electrode 12 are housed or to a back plate supporting the resin block 11 from behind. It is good as
More specifically, the resin block 11 is attached to the housing CS by, for example, tightening a screw hole H formed in the resin block 11 and a screw hole H provided in the housing CS with a bolt or the like. It may be fixed. However, the mounting method is not limited to this.

For example, as shown in FIG. 8, the composite electrode 12 has one or a plurality of bands B made of resin attached to the housing CS or the back plate, part of the portion of the composite electrode 12 not immersed in the sample liquid. Alternatively, as shown in FIG. 9, a hook F provided in a portion not immersed in the sample liquid is hooked on a hook receiver FH provided on the housing CS or the back plate. You can fix it.
Also, the composite electrode 12 may be positioned with respect to the resin block 11 by a positioning member V as shown in FIG. The positioning member V accommodates the composite electrode 12 inside so as to cover not only the side surface of the portion of the composite electrode 12 that is immersed in the sample liquid, but also the side surface of the portion of the composite electrode 12 that is not immersed in the sample liquid. For example, a rectangular parallelepiped block is formed with a through hole along the outer shape of the composite electrode 12 . The positioning member V holds the shoulder portion formed between the portion of the composite electrode 12 which is not immersed in the sample liquid and the other portion by accommodating the composite electrode 12 inside the through hole. , to position the height of the composite electrode 12 . The positioning member V may be formed separately from the resin block 11 or integrally with the resin block 11 .

As described above, if the portion of the composite electrode not immersed in the sample liquid is supported, only the portion of the composite electrode with a small outer diameter that is immersed in the sample liquid can be fixed to the resin block by the mounting structure. The risk of the composite electrode breaking can be reduced as compared with the case where the composite electrode is provided.

The electrochemical measurement unit is not limited to one that is used alone. For example, as shown in FIG. 11, a plurality of electrochemical measurement units may be connected and used. In this case, the multiple units may be of the same type or of different types.
For example, a measurement unit having an electromagnetic sensor for measuring electrical conductivity, etc., a measurement unit for measuring ion concentrations other than pH, a measurement unit for measuring oxidation-reduction potential, etc. are arranged and liquid-tightly connected via an O-ring or the like. You can do it. In this case, for example, as shown in FIG. 11, the electrochemical measurement cells of the respective electrochemical measurement units are arranged such that the sample liquid flows from bottom to top in each cell. It is preferable to connect so that the outlet is higher than the outlet of the upstream cell.
A plurality of electrochemical measurement cells as described above may be integrally formed as one resin block. These electrochemical measurement units are not necessarily limited to those in which a rod-shaped electrode such as the composite electrode described above is inserted, and for example, a planar sensor is fitted in an internal storage space or flow path. It may be something like
In addition, various modifications and combinations are possible without departing from the gist of the present invention.

Examples of the present invention will be described in detail below, but it goes without saying that the present invention is not limited to these.
In this example, the effect of the flow direction of the sample liquid in the reservoir on the measurement results was investigated. In addition, we investigated the influence of the position of the sensor in the reservoir on the measurement results.

(Example 1)
Same as described in the above embodiment (the outlet is positioned above the sensitive part, the inlet is positioned below the sensitive part, and the sensitive part positioned at the tip of the composite electrode is positioned at the bottom of the storage part). The pH of the sample liquid was measured using an electrochemical measurement device equipped with an electrochemical measurement unit (located about 2 mm above the wall).

(Example 2)
The pH of the sample solution was measured using the same electrochemical measurement apparatus equipped with the same electrochemical measurement unit as in Example 1, except that the responsive glass placed at the tip of the composite electrode was placed in contact with the bottom wall of the reservoir. .

(Comparative example 1)
Using the same electrochemical measurement device as in Example 1 except that the outlet was positioned below the sensitive part and the inlet was positioned above the sensitive part, the sample liquid was measured. was measured.

<Response speed>
Using the electrochemical measurement apparatus of Example 1 or Comparative Example 1, the response speed (T95) when the sample liquid was switched from the pH 4 standard solution to tap water was investigated. The results are shown in FIGS. 12 and 13. FIG. FIG. 12 shows the results when the flow rate of the sample liquid is 450 μl/min, and FIG. 13 shows the results when the flow rate of the sample liquid is 2000 μl/min.

12 and 13, when the electrochemical measurement device of Example 1 is used, T95 is 70 seconds at a flow rate of 2000 μl/min, which is sufficient for flow-type pH measurement. It turns out there is. On the other hand, when the electrochemical measuring device of Comparative Example 1 was used, the measured values drifted and the response speed could not be specified.

In Comparative Example 1, in which the sample liquid flows downward from the top of the reservoir, the cause of the drift in the measured value is considered to be the internal liquid. In the measurement device of Comparative Example 1, the sample liquid flows downward from the top of the reservoir, so the internal liquid (3.3 M KCl aqueous solution) that seeps out of the liquid junction also follows this flow downward from the liquid junction. It is thought that the water flows in the direction of the arranged sensitive part and affects the pH response on the surface of the responsive glass.

<Influence of sample liquid flow rate on measurement results>
Next, the effect of flow rate on pH measurement was investigated. A pH 4 standard solution was used as the sample solution, and the measurement results when the flow rate was 0 μl/min, 450 μl/min, 1000 μl/min or 2000 μl/min are shown in FIGS. 14 to 16. FIG.

FIG. 14 is a graph showing pH measurement results when sample liquids were supplied to the electrochemical measurement apparatus of Example 1 at various flow rates.
FIG. 15 is a graph showing pH measurement results when sample liquids were supplied to the electrochemical measurement apparatus of Example 2 at various flow rates.
FIG. 16 is a graph showing pH measurement results when sample liquids were supplied to the electrochemical measurement apparatus of Comparative Example 1 at various flow rates.

Among these results, comparing each graph when the flow rate is other than 0 μl/min, in Examples 1 and 2, the measured pH value is stable regardless of the flow rate (within ±0.01 pH ), in Comparative Example 1, when the flow rate was 2000 μl/min, the pH value fluctuated greatly after 15 minutes from the start of measurement. It is considered that this is due to the inclusion of air bubbles in the sample liquid.

In the case of Examples 1 and 2, even if bubbles exist in the sample liquid, the sample liquid flows upward from the bottom of the reservoir, so regardless of the flow rate of the sample liquid, Air bubbles are easily discharged from the outlet, and it is considered that the air bubbles have almost no effect on pH measurement.

On the other hand, in Comparative Example 1, the sample liquid flows downward from the top of the reservoir. It is thought that the bubbles adhered to the liquid junction and the surface of the responsive glass, which greatly affected the pH measurement.

By the way, when comparing the results of Example 1 and Example 2 when the flow rate is 0 μl/min, in Example 2, the pH value gradually decreases with time.
This is because the sample liquid does not flow, so the internal liquid seeping from the liquid junction stays at the bottom of the reservoir, and the response glass placed at the tip of the composite electrode where this internal liquid stays. is located, it is thought that the cause is that the pH in this part changes with time.

<Influence of pump pulsation on measured values>
FIG. 17 and FIG. 18 respectively show the measurement results when the standard solution of pH 4 is used as the sample solution and the flow rate of the sample solution is decreased in Example 1 and Comparative Example 1. FIG. It can be seen that when the flow rate of the sample liquid slows down, the influence of the internal liquid seeping into the sample liquid appears on the measured values.

From FIG. 17, when the electrochemical measuring device of Example 1 is used, although the pH value fluctuates due to pump pulsation, the fluctuation is regular and the measured value is relatively stable.
On the other hand, in the case of Comparative Example 1 in FIG. 18, it can be seen that the fluctuation of the pH value due to pump pulsation is large and the measured value is not stable.

This is because, in Comparative Example 1, the sample liquid flows from top to bottom in the storage section, so that the internal liquid exuding from the liquid junction flows into the sensing section below the liquid junction due to the flow of the sample liquid. It is considered that this is because the internal liquid flows around.

<Continuous measurement>
FIG. 19 shows the results of continuous long-term pH measurement of a pH 4 standard solution using the electrochemical measurement apparatus of Example 1. FIG. From this result, it was found that although the measured value seems to fluctuate depending on the temperature of the sample liquid, the electrochemical measurement apparatus of Example 1 can perform a very stable measurement of ±0.01 pH/24 hours. .
In FIG. 19, air bubbles were mixed in the sample liquid, but the air bubbles did not affect the pH measurement.

Advantageous Effects of Invention According to the present invention, in a flow-type measuring device, for example, even a very small amount of sample liquid can be accurately measured with a simple configuration for its electrochemical characteristic value such as pH.

Claims (12)

It is provided in a channel through which a sample liquid flows,
a reservoir for storing the sample liquid, having an inlet for introducing the sample liquid and an outlet for discharging the sample liquid;
a composite electrode for measuring the electrochemical properties of the sample liquid stored in the storage unit;
The inlet is provided so as to be positioned below the outlet,
The electrochemical measurement unit, wherein the sensitive part of the composite electrode is provided so as to be located below the outlet in the storage part. 2. The electrochemical measurement unit according to claim 1, wherein said inlet is provided so as to be located below said sensitive part. 3. The electrochemical measurement unit according to claim 1, further comprising a mounting mechanism for mounting said composite electrode such that said sensitive portion is located below said lead-out port. The electrochemical measurement according to any one of claims 1 to 3, wherein the composite electrode is attached to the reservoir so that the liquid junction of the composite electrode faces the outlet. unit. 5. The electrochemical measurement unit according to claim 1, wherein the outlet has a diameter larger than that of the inlet. the storage unit has a storage space for storing the sample liquid,
6. The electrochemical measurement unit according to any one of claims 1 to 5, wherein the lower end of the sensitive part is arranged at a position spaced upward by 1 mm or more from the bottom wall of the storage space. 7. The electrochemical measurement unit according to any one of claims 1 to 6, wherein the composite electrode is dome-shaped. The composite electrode is cylindrical, and the outer diameter of a portion of the composite electrode immersed in the sample liquid is formed to be smaller than the outer diameter of the other portion of the composite electrode. The electrochemical measurement unit according to any one of claims 1 to 7. 9. The electrochemical measurement unit according to claim 8, wherein the portion of said composite electrode which is immersed in the sample solution has an outer diameter of 5 mm or less. an electrochemical measurement unit according to claim 1;
a channel connected to the outlet and the inlet for circulating the sample liquid to the electrochemical measurement unit;
an electrochemical measuring device comprising: a calculator that calculates an electrochemical characteristic value of the sample liquid based on the measured value measured by the composite electrode. a reservoir for storing the sample liquid, having an inlet for introducing the sample liquid and an outlet for discharging the sample liquid;
using an electrochemical measurement unit comprising a composite electrode for measuring the electrochemical properties of the sample liquid stored in the storage part;
The inlet is provided below the outlet,
A method for measuring electrochemical characteristics, wherein the sensitive part of the composite electrode is provided below the outlet to measure the electrochemical characteristics of the sample liquid. It is provided in a channel through which a sample liquid flows,
an inlet for introducing the sample liquid and an outlet for leading it out;
a storage space for storing the sample liquid;
an electrode insertion port for inserting a composite electrode for measuring the electrochemical properties of the sample liquid into the storage space;
An electrochemical measurement cell, wherein the introduction port is positioned below the outlet port.