JP2007071792A - Bubble removing method for electrode internal liquid, and electrochemical sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bubble removing method for an electrode internal liquid capable of removing easily bubbles generated in an internal liquid storage part for storing the electrode internal liquid; and also to provide an electrochemical sensor. <P>SOLUTION: A surfactant is dissolved in the electrode internal liquid, in this bubble removing method for the electrode internal liquid, of the present invention, in the electrochemical sensor provided with the internal liquid storage part for storing the electrode internal liquid. The surfactant is dissolved in the electrode internal liquid, in this electrochemical sensor provided with the internal liquid storage part for storing the electrode internal liquid, of the present invention. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for removing bubbles from an electrode internal liquid used in a measurement electrode such as a pH electrode, a comparison electrode, or an electrochemical sensor such as a composite electrode in which these measurement electrode and comparison electrode are integrally formed, and an electrochemical method. It relates to sensors.

  Conventionally, for example, a composite electrode for ion measurement in which a measurement electrode that is a glass electrode having ion selective sensitivity and a comparison electrode are integrally provided has been used. In the composite electrode, since the measurement electrode and the comparison electrode are integrally formed, the concentration of the object to be measured can be obtained simply by immersing a single electrode body in a test solution typically contained in a container. Can be measured. A pH composite electrode whose measurement object is hydrogen ions can be given as a typical example of a composite electrode for ion measurement.

  The pH composite electrode generally has a double tube structure (double glass tube structure) of an inner tube and an outer tube arranged concentrically. That is, the pH composite electrode has an inner tube in which a hydrogen ion-sensitive glass sensitive film is formed at the tip so that the inner space communicates, and an outer tube arranged outside the inner tube. Generally, a glass sensitive film is formed at the tip of the inner tube so as to protrude from the tip of the outer tube. Then, the inner space of the inner electrode and the inner side of the glass sensitive membrane connected to the inner tube (inner liquid container) are filled with the inner liquid of the measurement electrode. The measurement electrode inner electrode is immersed in the measurement electrode inner liquid. These inner tube, glass sensitive film, measurement electrode inner electrode and measurement electrode inner liquid constitute a glass electrode as a measurement electrode. Further, the internal space of the reference electrode is filled in an annular space (internal liquid storage portion) defined by the outer periphery of the inner tube and the inner periphery of the outer tube. The internal electrode of the reference electrode is immersed in the internal solution of the reference electrode. Furthermore, a liquid junction formed of ceramic or the like for electrically connecting the reference electrode internal solution and the test solution is enclosed in the outer tube. These outer tube, liquid junction, and reference electrode internal solution constitute a comparative electrode.

  Conventionally, the diameters of glass electrodes (inner tube and glass sensitive membrane) and outer tube have been made extremely small in order to enable measurement of a small amount of sample solution or a sample solution in a container having a small volume or opening. There is an ultrafine pH composite electrode (outer diameter of about 3 mm).

  In particular, in such an ultra-fine pH composite electrode, bubbles (air layer) are likely to be generated in the space containing the measurement electrode internal liquid or the comparison electrode internal liquid when the electrode is stored sideways or due to temperature change. . When this bubble is generated, the connection of the liquid is cut off, and the electrical circuit is cut off, resulting in a disconnected state. As a result, the measurement value may become unstable or measurement may not be possible.

  For example, in a conventional ultra-fine pH composite electrode, the internal solution of the measurement electrode is filled in the space inside the inner tube having an inner diameter of 0.8 mm, and the gap between the outer periphery of the inner tube and the inner periphery of the outer tube is zero. Some 135 mm annular spaces are filled with the internal solution of the reference electrode. Bubbles once generated in such a narrow space cannot be easily removed even if the electrode is stood still vertically or shaken. Further, if the electrode is shaken too much to remove the bubbles, the electrode may be damaged.

  By the way, in Patent Document 1, when manufacturing a double glass tube, a filamentous body is spirally wound around the inner tube, the inner tube is inserted into the outer tube, and the tip of the inner tube is welded to the inner surface of the outer tube. A method is disclosed. According to the invention of Patent Document 1, even if bubbles are generated in the annular space between the outer periphery of the inner tube and the inner periphery of the outer tube, the liquid inside the reference electrode flows through the filamentous body and suppresses disconnection. be able to.

  However, in such a prior art, it takes time and labor to wind the filamentous body around the inner tube when producing the double tube. In addition, there is concern over the long-term stability of the filamentous material, such as cotton yarn, in the internal solution of the comparative electrode, and it is considered that its replacement is extremely difficult. Furthermore, for example, it is impossible to cope with bubbles generated in the measurement electrode in the ultrafine composite electrode as described above.

Here, in particular, the conventional problems have been described using a pH composite electrode as an example. As described above, particularly in an ultra-fine composite electrode with an extremely small outer diameter and a very narrow internal liquid storage area in the measurement electrode and the reference electrode, the electrode internal liquid (measurement electrode internal liquid and reference electrode internal liquid) breaks down. Easy to do. However, the same problem may occur even when the measurement electrode such as a pH electrode is formed as a single body, or when the comparison electrode is formed as a single body, and in particular, the outer diameter of these electrodes. The problem can be noticeable if is small.
JP 2004-150957 A

  An object of the present invention is to provide a bubble removal method for an electrode internal liquid and an electrochemical sensor that can easily remove bubbles generated in an internal liquid storage portion that stores the electrode internal liquid.

  The above object is achieved by the method for removing bubbles from the electrode internal liquid and the electrochemical sensor according to the present invention. In summary, the present invention is a method for removing bubbles in an electrode internal liquid in an electrochemical sensor including an internal liquid storage part that stores the internal liquid of the electrode, characterized in that a surfactant is dissolved in the internal electrode liquid. This is a method for removing bubbles from the electrode internal liquid.

  According to an embodiment of the present invention, the surfactant is dissolved in the electrode internal solution at a concentration of 0.01% to 1%. The surfactant may be selected from the group consisting of an anionic surfactant, a cationic surfactant, and a nonionic surfactant. According to one embodiment of the present invention, the electrochemical sensor is an ion measurement electrode. According to another embodiment of the present invention, the electrochemical sensor is a reference electrode. According to another embodiment of the present invention, the electrochemical sensor is a composite electrode including a measurement electrode and a reference electrode, and the internal liquid storage portion included in the measurement electrode and the internal portion included in the comparison electrode. The surfactant is added to the electrode internal solution stored in either or both of the liquid storage portions. The measurement electrode may be an ion measurement electrode.

  According to another aspect of the present invention, there is provided an electrochemical sensor comprising an internal liquid storage part for storing an internal liquid of an electrode, wherein a surfactant is dissolved inside the electrode. .

  According to another aspect of the present invention, a double tube structure having an inner tube and an outer tube is provided, at least one end of the inner tube is sealed, and at least one end of the outer tube. The portion is connected and sealed to the inner tube, and a first internal liquid storage portion for storing the electrode internal liquid is formed in a space inside the inner tube, and an annular shape between the inner tube and the outer tube is formed. In the electrochemical sensor in which the second internal liquid storage part for storing the internal liquid is formed in the space, either one or both of the electrode internal liquids stored in the first and second internal liquid storage parts, respectively. An electrochemical sensor is provided in which a surfactant is dissolved.

  According to the present invention, it is possible to easily remove bubbles generated in the internal liquid storage part that stores the internal liquid of the electrode.

  Hereinafter, a method for removing bubbles from an electrode internal solution and an electrochemical sensor according to the present invention will be described in more detail with reference to the drawings.

Example 1
First, a pH composite electrode will be described as an embodiment of an electrochemical sensor to which the present invention can be applied. FIG. 1 shows the overall appearance of the pH composite electrode 100 of this embodiment. Moreover, FIG. 2 shows the principal part cross section of the pH composite electrode 100 of a present Example.

  The structure of the pH composite electrode 100 is not particularly different from the conventional one described above. That is, the pH composite electrode 100 has a double glass tube structure including the inner tube 10 and the outer tube 20. In particular, in this embodiment, the pH composite electrode 100 is an ultrafine pH composite electrode having an extremely small outer diameter.

  The inner tube 10 includes an inner tube small diameter portion 11 which is lower in the axial direction, and an inner tube large diameter portion 12 which is continuously and coaxially formed at an upper end portion of the inner tube small diameter portion 11. A glass sensitive film 13 sensitive to hydrogen ions is formed at the lower end of the inner tube 10 continuously and coaxially with the inner tube 11. Then, the inner electrode 10 and the space (inner liquid storage part) 31 inside the glass sensitive film 13 connected thereto are filled with the measurement electrode inner liquid Ia. In addition, a measurement electrode inner electrode 14 is disposed in the inner pipe large-diameter portion 12 and is immersed in the measurement electrode internal liquid Ia. The glass sensitive film 13 protrudes from the lower end of the outer tube 20.

  On the other hand, the outer tube 20 has an outer tube small-diameter portion 21 below the axial direction, and an outer tube large-diameter portion 22 formed continuously and coaxially at the upper end of the outer tube small-diameter portion 21. The outer tube 20 is arranged around the inner tube 10 coaxially with the inner tube 10 at a predetermined interval from the outer periphery of the inner tube 10. The lower end portion of the outer tube small diameter portion 21 is welded and sealed to the lower end portion of the inner tube small diameter portion 11. The annular space (internal liquid storage part) 32 between the outer periphery of the inner tube 10 and the inner periphery of the outer tube 20 is filled with the reference electrode internal liquid Ib. Further, a reference electrode inner electrode 24 is disposed in the outer tube large diameter portion 22 and is immersed in the reference electrode internal liquid Ib. Furthermore, a liquid junction (junction) 23 made of ceramics is enclosed in the side surface near the lower end of the outer tube small diameter portion 21. The liquid junction portion 23 penetrates from the outside of the outer tube small-diameter portion 21 to the inside, that is, the annular space 32, and enables electrical conduction between the outer tube 20 and the test solution outside the pH composite electrode 100. And

  The inner tube 10, the glass sensitive film 13, the measurement electrode inner electrode 14 and the measurement electrode internal liquid Ia constitute the glass electrode 1 as the measurement electrode. Further, the outer electrode 20, the liquid junction 23, the reference electrode inner electrode 24, and the reference electrode inner liquid Ib constitute the comparison electrode 2.

  In this embodiment, the outer diameter D1 of the pH composite electrode represented by the outer diameter of the outer tube small-diameter portion 21 (in this embodiment, the outer diameter of the glass sensitive film 13 and the outer diameter of the outer tube small-diameter portion 21 are (Substantially the same) was 2.8 mm. The inner diameter D2 of the inner tube small diameter portion 11 was 0.8 mm. The gap G1 between the outer periphery of the inner tube small diameter portion 11 and the inner diameter of the outer tube small diameter portion 21 was 0.135 mm. Further, the length L1 from the connecting portion of the outer tube small diameter portion 21 and the outer tube large diameter portion 22 to the tip of the glass sensitive film 13 was 69 mm.

  And according to this invention, surfactant is added and melt | dissolved in electrode internal solution (measuring electrode internal solution, comparative electrode internal solution) Ia and Ib.

  A surfactant is a molecule that has both a hydrophobic group such as a hydrocarbon chain and a hydrophilic group. Depending on the ionic nature of the surfactant body when dissolved in water, an anionic (anionic) or cationic ( Cationic) and non-ionic ones. Anionic surfactants (anionic surfactants) and cationic surfactants (cationic surfactants) are ionized in aqueous solution, and the surfactants are mainly anions and cations. It will be. Furthermore, nonionic surfactants (nonionic surfactants) are those that do not ionize in aqueous solutions.

  Examples of the anionic surfactant include fatty acid salt (soap), alpha sulfo fatty acid ester salt (α-SF), alkylbenzene sulfonate (ABS), linear alkylbenzene sulfonate (LAS), and alpha olefin sulfonate (AOS). ), Alkyl sulfate (AS), alkyl ether sulfate (AES), monoalkyl phosphate ester (MAP), alkyl sulfate triethanolamine, alkane sulfonate (SAS), and the like. For example, sodium dodecylbenzenesulfonate can be preferably used.

  Examples of the cationic surfactant include alkyltrimethylammonium salt, alkyldimethylbenzylammonium salt, dialkyldimethylammonium chloride, alkylpyridinium chloride, N-methylbishydroxyethylamine fatty acid ester hydrochloride and the like. For example, dodecyltrimethylammonium chloride can be suitably used.

  Nonionic surfactants include sucrose fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene fatty acid ester, fatty acid diethanolamide, fatty acid alkanolamide, polyoxyethylene alkyl ether (AE), alkyl glucoside (AG ), Polyoxyethylene alkylphenyl ether (APE), and the like. For example, polyoxyethylene (10) octylphenyl ether can be preferably used.

  As the surfactant, any of a cationic surfactant, an anionic surfactant and a nonionic surfactant may be used. Further, the surfactant is not limited to those exemplified above.

  That is, when bubbles (air layer) are generated in a narrow space such as in the glass electrode 1 or the comparison electrode 2 in the ultrafine pH composite electrode 100 of this embodiment, the bubbles are difficult to escape due to the surface tension of water. . If this surface tension is lowered, the bubbles rise when the electrode is set up vertically and can be easily removed. Therefore, in the present invention, in order to reduce the surface tension, a surfactant is added to the electrode internal liquid (measuring electrode internal liquid, comparative electrode internal liquid) Ia and Ib. Thereby, even if it is the ultrafine pH composite electrode 100, the bubble in the glass electrode 1 or the comparison electrode 2 can be easily removed now.

  The surfactant is dissolved in the electrode internal solution at a concentration sufficient to remove bubbles generated in the electrode internal liquid storage portion. Typically, bubbles generated in the electrode internal liquid storage portion rise and escape at a sufficiently high speed in a state where the axial direction of the electrode internal liquid, which is normally elongated, is substantially vertical. Is added to the electrode internal solution at a sufficient concentration. Even if the amount of the surfactant added to the electrode internal liquid (measuring electrode internal liquid, comparative electrode internal liquid) Ia and Ib is too small, the effect of removing bubbles by the surfactant cannot be obtained. In addition, the amount of the surfactant added to the electrode internal solution is higher in the range of the solubility in the electrode internal solution, and the bubble removal effect is higher. However, even if the amount of the surfactant added is too large, the influence on the stability of the potential of the internal electrode and the generation of the liquid junction potential cannot be ignored. Further, when the amount of the surfactant added is too large, there is another problem such that the indicated value of the electrode potential becomes unstable because the electrode internal liquid easily bubbles due to vibration in a normal measurement operation.

  As will be described in more detail below, according to the study by the present inventors, the concentration of the surfactant in the electrode internal liquid (measuring electrode internal liquid, comparative electrode internal liquid) Ia, Ib is 0.01% to 1%. % Is preferred. Here, the concentration of the surfactant is expressed as a percentage (%) based on weight.

  Hereinafter, using the pH composite electrode 100 of this example, the effect of removing bubbles and the fluctuation of the electrode potential by adding a surfactant to the electrode internal solution (measurement electrode internal solution, comparative electrode internal solution) Ia, Ib An experimental example in which the fluctuation of the liquid junction potential and the occurrence state of foaming were examined will be described.

(Experimental example 1)
A 3.3 mol / L · KCl solution + pH 7 buffer solution was used as the measurement electrode internal solution (base measurement electrode internal solution) Ia0 as a base. In addition, a 3.3 mol / L · KCl solution was used as the base reference electrode internal solution (base reference electrode internal solution) Ib0.

-Measurement electrode internal solution-
0.01% of a nonionic surfactant was added to the base measurement electrode internal solution Ia0.

  First, the state of bubble removal was examined. After intentionally forming bubbles in the space 31 inside the small diameter portion 11 of the inner tube 11, the pH composite electrode 100 was left standing vertically. Bubbles rose and disappeared after about 1 hour.

  At the same time, as a comparative test, the same test as described above was performed using the base measurement electrode internal solution Ia0 to which no surfactant was added as it was as the measurement electrode internal solution Ia. In this case, even if the pH composite electrode 100 was set up vertically and allowed to stand for one week, bubbles remained.

  Next, the fluctuation of the electrode potential of the glass electrode 1 was examined. That is, the fluctuation of the electrode potential of the glass electrode 1 can be considered by adding a surfactant to the measurement electrode internal liquid Ia. However, as will be described later, when the measurement electrode internal liquid Ia containing 0.01% nonionic surfactant is used, the fluctuation of the electrode potential of the glass electrode 1 is within 1 mV even after one month has elapsed. Compared with the case where the measurement electrode internal liquid Ia0 was used as it was, no significant difference causing a measurement problem was found.

  Here, the fluctuation of the electrode potential of the glass electrode 1 was examined as follows. As the standard electrode 200, a unipolar reference electrode (internal electrode: silver-silver chloride electrode) is prepared. The internal solution of the standard electrode 200 is the base reference electrode internal solution Ib0. As shown in FIG. 3A, the standard electrode and the glass electrode 1 of the pH composite electrode 100 are connected via a voltmeter 50. Then, the standard electrode 200 and the pH composite electrode 100 are immersed in a 3.3 mol / L · KCl solution, and the potential difference between the two electrodes is measured. This potential difference was changed by adding the surfactant to the glass electrode 1 of the pH composite electrode 100 with the base measurement electrode internal solution Ia0 before adding the surfactant, and 3 hours after adding the surfactant. Check each month later. The experiment was performed on three pH composite electrodes 100. The results are shown in Table 1.

  As shown in Table 1, the potential difference between the glass electrode 1 and the standard electrode of the pH composite electrode 100 was 0.5 to 1 month after the addition of the surfactant, compared to before the addition of the surfactant. It was 0.8 mV. Thus, no electrode potential fluctuation (for example, a potential fluctuation exceeding 3 mV) of the glass electrode 1 that causes a measurement problem due to the addition of 0.01% nonionic surfactant was observed.

-Reference electrode internal solution-
0.01% nonionic surfactant was added to the base reference electrode internal solution Ib0.

  After intentionally forming bubbles in the annular space 32 between the outer periphery of the inner tube small diameter portion 11 and the inner periphery of the outer tube small diameter portion 21, the pH composite electrode 100 was left standing vertically. Bubbles rose and disappeared after about 1 hour.

  At the same time, as a comparative test, the same test as described above was performed using the base measurement electrode internal solution Ib0 to which no surfactant was added as it was as the measurement electrode internal solution Ib. In this case, even if the pH composite electrode 100 was set up vertically and allowed to stand for one week, bubbles remained.

  Next, the fluctuation of the liquid junction potential of the comparative electrode 2 was examined. That is, it is conceivable that the junction potential of the comparison electrode 2 is increased by adding a surfactant to the reference electrode internal liquid Ib. However, as described later, when the reference electrode internal liquid Ib containing 0.01% nonionic surfactant was used, the fluctuation of the liquid junction potential of the comparative electrode 2 was 1 mol / L sodium hydroxide solution and Even in the hydrogen chloride solution, the difference was a maximum of about 1 mV compared to the case where the base reference electrode internal solution Ib0 was used as it was, and no significant difference causing a measurement problem was observed.

  Here, the fluctuation of the liquid junction potential of the comparative electrode 2 was examined as follows. As the standard electrode 200, a unipolar reference electrode (internal electrode: silver-silver chloride electrode) is prepared. The internal solution of the standard electrode 200 is the base reference electrode internal solution Ib0. Since the liquid junction potential is also generated in the standard electrode 200, it is difficult to measure the absolute value of the liquid junction potential. Therefore, it evaluated by the relative difference with a standard electrode. The larger this difference is, the greater the fluctuation of the liquid junction potential due to the addition of the surfactant, compared to the liquid junction potential of the standard electrode 200. It can be evaluated by comparing with the difference between the standard electrodes how much the junction potential is different.

  That is, in this example, as the standard solution S, a pH standard solution (pH 6.86) (neutral phosphate standard solution), a pH 4.01 pH standard solution (phthalate standard solution), and a pH 9.18 pH standard solution. (Borate standard solution), 0.1 mol / L · NaOH, 1 mol / L · NaOH, 1 mol / L · HCl are prepared. First, as shown in FIG. 3B, two standard electrodes 200 are connected via a voltmeter 50, and both standard electrodes 200 are immersed in each standard solution S having a different pH. Each potential difference is measured. On the other hand, the standard electrode 200 and the comparison electrode 2 of the pH composite electrode 100 are connected via a voltmeter 50. Then, the standard electrode and the pH composite electrode 100 are immersed in each of the standard solutions, and the potential difference between both electrodes is measured. The experiment was performed on three pH composite electrodes 100. The results are shown in Table 2.

  As shown in Table 2, while the potential between the standard electrodes is a maximum of 0.4 mV, the reference electrode 2 and the standard electrode of the pH composite electrode 100 using the reference electrode internal liquid Ib to which the surfactant is added The maximum potential difference from 200 was 1.1 mV. Thus, the increase in the liquid junction potential of the comparative electrode 2 which causes a measurement problem due to the addition of 0.01% nonionic surfactant was not observed.

(Experimental example 2)
Next, the effective concentration of the surfactant was examined.

  In this example, as in Experimental Example 1, 3.3 mol / L · KCl solution + pH 7 buffer solution was used as the base measurement electrode internal solution Ia0. Further, a 3.3 mol / L · KCl solution was used as the base reference electrode internal solution Ib0.

  In general, the measurement electrode internal solution Ia and the reference electrode internal solution Ib in the pH composite electrode 100 are high-concentration salt solutions such as 3.3 mol / L · KCl. Therefore, the surfactant is difficult to dissolve in the electrode internal solution. Surfactants include cationic surfactants, anionic surfactants, nonionic surfactants, etc., but the solubility in high-concentration salt solutions varies depending on the type of surfactant.

  From the experimental results, the solubility of each of the cationic surfactant, the anionic surfactant, and the nonionic surfactant in the 3.3 mol / L · KCl solution is as shown in Table 3.

  Here, the surfactants shown in Table 3 above were used to examine how bubbles were removed from the pH composite electrode 100.

  First, as a surfactant to be added to the measurement electrode internal solution Ia, sodium dodecylbenzenesulfonate, which is an anionic surfactant having a low solubility in a 3.3 mol / L · KCl solution, was used, and the test was performed in Experimental Example 1 described above. In the same manner as above, the degree of air bubble removal in the glass electrode 1 of the pH composite electrode 100 was examined. That is, bubbles were generated in the space 31 (inner diameter 0.8 mm) inside the inner tube small-diameter portion 11, and the pH composite electrode 100 was allowed to stand vertically, and the bubbles were observed.

  With 0.01% sodium dodecylbenzenesulfonate, bubbles were released within 1 hour. On the other hand, with 0.005% sodium dodecylbenzenesulfonate, bubbles did not escape even after standing for 1 day.

  Similarly, sodium dodecylbenzene sulfonate was used as a surfactant to be added to the internal liquid Ib of the comparative electrode, and the state of air bubbles in the comparative electrode 2 of the pH composite electrode 100 was examined. That is, bubbles are generated in the annular space 32 (gap 0.135 mm) between the inner tube small diameter portion 11 and the outer tube small diameter portion 21, and the pH composite electrode 100 is left standing vertically, and the bubbles are removed. Observed. Again, 0.01% sodium dodecylbenzene sulfonate released air bubbles within 1 hour. On the other hand, with 0.005% sodium dodecylbenzenesulfonate, bubbles did not escape even after standing for 1 day.

  Similarly, as a surfactant to be added to each of the measurement electrode internal liquid Ia and the comparative electrode internal liquid Ib, dodecyltrimethylammonium chloride, which is a cationic surfactant having high solubility in a 3.3 mol / L · KCl solution, is used. It was used to examine how bubbles were removed in the glass electrode 1 and the comparative electrode 2 of the pH composite electrode 100. Again, 0.01% dodecyltrimethylammonium chloride bubbled out within 1 hour. On the other hand, with 0.005% dodecyltrimethylammonium chloride, bubbles did not escape even after being left for 1 day.

  Further, similarly, polyoxyethylene (10) octylphenyl ether, which is a nonionic surfactant, is used as a surfactant to be added to each of the measurement electrode internal solution Ia and the comparative electrode internal solution Ib. Each of the glass electrode 1 and the comparative electrode 2 was examined for the degree of bubble removal. Again, 0.01% polyoxyethylene (10) octylphenyl ether released bubbles within 1 hour. On the other hand, in the case of 0.005% polyoxyethylene (10) octylphenyl ether, the bubbles did not escape even after standing for 1 day.

  Note that 0.01% sodium dodecylbenzenesulfonate did not cause foaming that would be a problem during vibration in a normal measurement operation. Similarly, in the case of 0.1% polyoxyethylene (10) octylphenyl ether, no problem bubble was generated due to vibration in a normal measurement operation.

  On the other hand, 5% or more of dodecyltrimethylammonium chloride, which is a cationic surfactant, is dissolved in a 3.3 mol / L · KCl solution. However, with 5% dodecyltrimethylammonium chloride, the electrode internal solution (measuring electrode internal solution, reference electrode internal solution) is too foamed due to vibration of the pH composite electrode 100, etc. As a result, it was found that the indicated value of the electrode potential is difficult to stabilize, which causes a problem in use. By setting the concentration to 1% or less, foaming that would cause a problem did not occur in vibration or the like in the normal measurement operation of the pH composite electrode 100.

(Experimental example 3)
Next, it was performed in Experimental Example 1 with 0.01%, 1%, and 0.1% of the anionic surfactant, the cationic surfactant, and the nonionic surfactant shown in Table 3 above, respectively. Similarly, the fluctuation of the electrode potential of the glass electrode 1 was examined. As a result, the fluctuation of the electrode potential of the glass electrode 1 is about −1 to −1.5 mV after one month when any of an anionic surfactant, a cationic surfactant and a nonionic surfactant is added. It is. Thus, the electrode potential fluctuation | variation (for example, electric potential fluctuation | variation exceeding 3 mV) of the glass electrode 1 which becomes a measurement problem was not observed.

  Further, after the electrode potential fluctuated, the measurement electrode internal solution Ia was returned to the base measurement electrode internal solution Ia0 to which no surfactant was added, and the potential difference from the standard electrode was measured. In this case, the electrode potential recovered in about 10 minutes.

  Next, the anionic surfactant, the cationic surfactant, and the nonionic surfactant shown in Table 3 were set to 0.01%, 1%, and 0.1%, respectively, in Example 1. Similarly, the fluctuation of the liquid junction potential of the comparative electrode 2 was examined. As a result, the fluctuation of the liquid junction potential of the comparative electrode 2 is about ± 1 mV when any of an anionic surfactant, a cationic surfactant, and a nonionic surfactant is added. Thus, an increase in the liquid junction potential fluctuation of the comparative electrode 2 that causes a measurement problem was not observed.

  As can be seen from the experimental examples described above, in consideration of the bubble removal effect, electrode potential fluctuation, liquid junction potential fluctuation, and bubble generation, it is dissolved in the electrode internal liquid (measuring electrode internal liquid, comparative electrode internal liquid). The concentration of the surfactant is preferably 0.01% to 1%.

Example 2
Next, another embodiment according to the present invention will be described. In Example 1 described above, the electrochemical sensor is described as a pH composite electrode, but the present invention is not limited to this.

  For example, in the ultrafine composite electrode as described in the first embodiment, a space 31 inside the inner tube small diameter portion 11 and an annular space 32 between the outer periphery of the inner tube small diameter portion 11 and the inner periphery of the outer tube small diameter portion 21. Is extremely narrow, and bubbles are likely to be generated in the space when the electrode is stored sideways or due to a temperature change. Therefore, the present invention is extremely effective.

  However, the present invention can be equally applied to a case where a measurement electrode such as a pH electrode is formed as a single body, and a case where a comparison electrode is formed as a single body.

  For example, FIG. 4A shows a cross-section of the main part of a thin single pH electrode 1. In the pH electrode 1, a glass sensitive film 13 that is sensitive to hydrogen ions is formed continuously and coaxially at the axial end of the support tube 10 as an electrode indicator. The space (internal liquid storage part) 31 inside the support tube 10 and the glass sensitive film 13 is filled with the measurement electrode internal liquid Ia. Further, the measurement electrode inner electrode 14 is immersed in the measurement electrode inner liquid Ia. As the measurement electrode internal liquid Ia, a solution in which a surfactant is dissolved as in Example 1 can be used.

  Further, for example, FIG. 4B shows a cross-section of the main part of the single comparison electrode 2. In the comparison electrode 2, a liquid junction portion 23 made of ceramics is sealed at the tip of the support tube 20 in the axial direction. The space (internal liquid storage portion) 32 inside the support tube 20 is filled with the reference electrode internal liquid Ib. Further, the reference electrode inner electrode 24 is immersed in the reference electrode inner liquid Ib. And as this reference electrode internal liquid Ib, the thing in which surfactant was dissolved like Example 1 can be used.

  As mentioned above, although this invention was demonstrated according to the specific Example, this invention is not limited to the above-mentioned embodiment. For example, in each of the above embodiments, the measurement electrode is described as a pH measurement electrode, but the measurement electrode is not limited to this. For example, as an electrode for measuring ions, ion selective electrodes other than pH electrodes, that is, sodium ion electrodes, fluoride ion electrodes, potassium ion electrodes, calcium ion electrodes, nitrate ion electrodes, ammonia electrodes, carbon dioxide gas electrodes, etc. It is done. These measurement electrodes may be combined with the reference electrode to form a composite electrode, or may be a single electrode.

  In the composite electrode, the surfactant can be added only to the electrode internal liquid of either the measurement electrode or the comparison electrode. For example, in a redox potential measuring composite electrode in which a redox potential measuring electrode such as a platinum electrode and a comparative electrode are provided integrally, a surfactant can be added to the electrode internal solution of the comparative electrode. .

  In each of the above examples, the electrode internal solution (measuring electrode internal solution, comparative electrode internal solution) to which the surfactant is added is a 3.3 mol / L · KCl solution (or further a pH buffer solution). However, the base electrode internal solution is not limited to this. A saturated KCl solution may be used if desired. For example, in ion concentration measurement using an ion electrode, a potassium nitrate solution (sodium ion electrode, chloride ion electrode, bromide ion electrode, cyanide ion electrode, cadmium ion electrode, copper ion electrode, Each ion electrode of silver ion) and lithium acetate solution (potassium ion electrode, nitrate ion electrode) are used.

It is an external view of one Example of the electrochemical sensor which can apply this invention. It is principal part sectional drawing of the electrochemical type sensor of FIG. It is a schematic diagram for demonstrating the measuring method of (a) electrode potential fluctuation | variation, and the (b) measuring method of liquid junction part electric potential fluctuation | variation. It is principal part sectional drawing of the other Example of the electrochemical type sensor which can apply this invention.

Explanation of symbols

10 Inner tube 20 Outer tube 31 Space inside inner tube and glass sensitive membrane (electrode internal liquid storage part)
32 Annular space between inner tube and outer tube (electrode internal liquid storage part)
Ia Measurement electrode internal liquid Ib Reference electrode internal liquid

Claims (16)

  A method for removing bubbles in an electrode internal liquid in an electrochemical sensor having an internal liquid containing portion for containing the electrode internal liquid, wherein a surfactant is dissolved in the electrode internal liquid. .   The method of removing bubbles in the electrode internal solution according to claim 1, wherein the surfactant is dissolved in the electrode internal solution at a concentration of 0.01% to 1%.   The method for bubbling an electrode internal liquid according to claim 1, wherein the surfactant is selected from the group consisting of an anionic surfactant, a cationic surfactant, and a nonionic surfactant.   4. The method of removing bubbles in an electrode internal liquid according to claim 1, wherein the electrochemical sensor is an ion measurement electrode.   4. The method of removing bubbles in an electrode internal liquid according to claim 1, wherein the electrochemical sensor is a reference electrode.   The electrochemical sensor is a composite electrode including a measurement electrode and a comparison electrode, and is accommodated in either or both of the internal liquid storage unit included in the measurement electrode and the internal liquid storage unit included in the comparison electrode. 4. The method of removing bubbles in an electrode internal liquid according to claim 1, wherein the surfactant is added to the electrode internal liquid.   The method for removing bubbles in an electrode internal liquid according to claim 6, wherein the measurement electrode is an ion measurement electrode.   An electrochemical sensor comprising an internal liquid storage part for storing an internal liquid of an electrode, wherein a surfactant is dissolved inside the electrode.   9. The electrochemical sensor according to claim 8, wherein the surfactant is dissolved in the electrode internal solution at a concentration of 0.01% to 1%.   The electrochemical sensor according to claim 8 or 9, wherein the surfactant is selected from the group consisting of an anionic surfactant, a cationic surfactant, and a nonionic surfactant.   The electrochemical sensor according to claim 8, 9 or 10, wherein the electrochemical sensor is an ion measuring electrode.   The electrochemical sensor according to claim 8, 9 or 10, wherein the electrochemical sensor is a reference electrode.   A composite electrode comprising a measurement electrode and a reference electrode, wherein the interfacial activity is applied to an electrode internal liquid contained in either or both of the internal liquid storage part provided in the measurement electrode and the internal liquid storage part provided in the comparison electrode. The electrochemical sensor according to claim 8, 9 or 10, wherein an agent is added.   The electrochemical sensor according to claim 13, wherein the measurement electrode is an ion measurement electrode. It has a double tube structure having an inner tube and an outer tube, and at least one end of the inner tube is sealed, and at least one end of the outer tube is connected to the inner tube and sealed. A first internal liquid storage portion for storing the electrode internal liquid is formed in a space inside the inner pipe, and a second internal for storing the internal liquid in an annular space between the inner pipe and the outer pipe In the electrochemical sensor in which the liquid container is formed,
An electrochemical sensor, wherein a surfactant is dissolved in one or both of the electrode internal solutions stored in the first and second internal liquid storage portions.   16. The electrochemical sensor according to claim 15, wherein the surfactant is dissolved in the electrode internal solution at a concentration of 0.01% to 1%.

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