KR100475303B1 - PVC-silicon Rubber based solid state pH sensor - Google Patents

Abstract

The present invention relates to a solid polymer membrane sensor for measuring the concentration of hydrogen ions in a solution, and has excellent adhesion due to adhesion to a solid reference electrode, excellent stability, quicker reactivity to the measured ion species, and long-term use. The present invention relates to a solid-state hydrogen ion concentration measuring electrode using a polymer film made of FIV-silicon which can be miniaturized. The present invention provides a polymer membrane comprising a fibrous silicon-silicon mixture comprising a hydrogen ion permeable membrane prepared by adding an ion pore-forming polymer that selectively permeates hydrogen ions to a mixed solution containing fibC and silicone rubber as a main component. There is a technical subject to providing a body type hydrogen ion concentration measuring electrode. And preferably, the hydrogen ion permeable membrane is formed by mixing 5% and 5% by weight of the fibC and the silicone rubber, and the ion-porous polymer is formed at a ratio of 0.5-2% by weight of the mixed weight. And the ion-forming polymer is made of tridodecyl amine (TDDA). More preferably, the hydrogen ion permeable membrane is attached to the surface of the solid electrode made of solid carbon. Therefore, there is no need for an internal reference solution, excellent stability of the electrode, fast response time, and excellent linearity with respect to pH. have.

Description

Solid hydrogen ion concentration measuring electrode using polymer film composed of FBC-silicon mixture {PVC-silicon Rubber based solid state pH sensor}

The present invention relates to a solid polymer membrane sensor for measuring the concentration of hydrogen ions in solution. More specifically, it has excellent adhesion due to adhesion to a solid reference electrode, which is excellent in stability, has a faster reactivity to the measured ion species, and is used for a long time. The present invention relates to a solid-state hydrogen ion concentration measuring electrode using a polymer film made of FIVEC-silicon, which is not only possible but also miniaturized.

In general, pH is a unit representing the concentration of hydrogen ions (H +) present in the solution, and is a value obtained by taking the log value of the mole concentration (mole / liter) of the hydrogen ions. In general, for electrochemical detection of dissolved hydrogen ions, potentiometry is widely used to measure the potential change according to the activity (or concentration) of hydrogen ions. Potentiometric analysis is based on measuring the potential of an electrochemical cell in the absence of current. The concentration of ions is determined directly from the potential of the ion selective electrode that selectively reacts with the ions to be analyzed.

Therefore, the appropriate indicator and reference electrodes are immersed in the solution to be analyzed, and the concentration of the analyte is determined by measuring the potential. The electrode must be calibrated with standard solution. E _cell vs. Calibration lines, such as log concentration, can be prepared by making a series of standard solutions and measuring the potential.

There are several membrane electrodes available on the market for the rapid and selective quantification of various cations and anions by potentiometric measurements. The membrane electrode used as the indicator electrode is also called an ion-selective electrode (ISE) because of its high selectivity to dissolved ions. An ion selective electrode is prepared by fixing a sensitive material that selectively reacts with an ion to be analyzed on a polymer support, or by using a gas selective permeable membrane or a solid sensitive material.

All ion-selective membranes have a common property, which is their sensitivity and selectivity to any cation or anion. Most dissolved cations including hydrogen ions (NH ₄ ⁺ , Cd ²⁺ , Cu ²⁺ , Pb ²⁺ , Li ⁺ , NO _X , K ⁺ , Ag ⁺ , Na ⁺ , Ca ²⁺ , Mg ⁺² , X ^+), negative ions ^{_{(Br -, CO 3 2-,}} Cl -, CN -, F -, BF 4 -, I -, NO 3 -, ClO 4 -, S 2-, X -) and a gas (NH _3, Since ion selective electrodes for CO ₂ ) have been developed, their concentration can be easily and quickly measured by the potentiometric method.

Hereinafter, a hydrogen ion analysis method using an ion selective electrode will be introduced.

1) glass electrode

Representative hydrogen ion-selective electrodes include glass electrodes for pH measurement. The tip of the glass electrode consists of a thin glass membrane that is sensitive to the pH of the solution. The glass sphere contains silver lead coated with silver chloride (AgCl) and filled with 0.1M hydrochloric acid solution saturated with silver chloride. Since the activity (a _{H +} ) of hydrogen ions inside the membrane is kept constant by HCl, the cell potential is sensitive to the pH of the sample solution. The potential for the concentration of hydrogen ions is defined by the equation

E = E ^* + 0.0591 pH

2) Liquid hydrogen ion measuring electrode using FIVEC polymer support

Liquid hydrogen ion measurement electrode using PVC polymer support adds hydrogen ions and selectively sensitive ionophores to the mixture containing PVC, plasticizer, stabilizer and solvent and then dried To prepare the membrane. The prepared membrane is installed at the end of the electrode body containing the internal reference solution having a constant pH so as to prevent the internal reference solution from leaking. Since the activity of the internal reference solution remains constant, the cell potential is sensitive to the pH of the sample solution. Where the potential for concentration in hydrogen ions is defined as

E = E ^* + 0.0591 pH

The pH meter measures the potential of the glass electrode relative to the external reference electrode and displays this output on a meter scale calibrated with a pH scale. The pH meter does not know the relationship with pH to measure the electrochemical cell potential, so it should be standardized to show an appropriate pH value. Standardization utilizes one or more standard buffer solutions of known pH.

3) Solid hydrogen ion measuring electrode using polymer support

Solid hydrogen ion measuring electrodes using only PVC or silicon polymer support may mix hydrogen ions and selectively reacting ionic pores with silicone rubber or add them to a mixture containing fives, plasticizers, stabilizers and solvents After the solution was prepared, a small amount was dropped on a conductive solid such as silver and carbon, followed by drying. When the membrane-coated conductive solid electrode is immersed in a sample solution containing hydrogen ions, the cell potential is sensitive to the pH of the sample solution. Where the potential for concentration in hydrogen ions is defined as

E = E ^* + 0.0591 pH

It can be seen that the hydrogen ion measuring electrode as described above is used in various ways. However, conventionally used hydrogen ion concentration measuring electrode has the following problems.

Since the first glass electrode and the second liquid electrode described above use glass electrodes, the glass is easily inadvertently broken during use, and the liquid solution must be filled therein, and the liquid solution must be kept at a constant concentration and quantity. There is a problem.

In addition, the electrode using the third polymer support solved the above problems, but this also has the following problems. The polymer film made of 100% PVC is not only unstable due to the measurement potential being lifted due to weak adhesion to the solid surface as a support, but also has a problem in that the electrode life is very short due to the weak adhesion.

Polymer membranes made of 100% silicone rubber are known to adhere strongly to most solid materials and receive much less negative ions in the anion. In addition, unlike PVC (PVC), since the polymer film can be made without a plasticizer and is easy to cure at room temperature, the utilization is increasing. However, polymer membranes made of only silicone rubber have disadvantages such as high electrical resistance and slow reaction time, and thus are not easily applied as ion sensor membranes.

Accordingly, the present invention has been made to solve the above-described problems, the polymer membrane containing the ion pores increases the adhesion and stability to the solid electrode, and the solid type using the fiybC-silicone polymer membrane that the electrical response is made in a short time The purpose is to provide a hydrogen ion concentration measuring electrode.

Another object of the present invention is to provide a solid-state hydrogen ion concentration measuring electrode using a fibC-silicone polymer membrane which not only maintains stability even for long time use but also withstands impact and is compact and miniaturized.

The present invention for achieving the above object is a fibrous C made of a hydrogen ion permeable membrane is prepared by the addition of an ion-porous polymer that selectively penetrates hydrogen ions to a mixed solution containing fiyb C and silicone rubber as a main component- There is a technical subject to provide a solid hydrogen ion concentration measuring electrode using a polymer film made of a silicon mixture.

And preferably, the hydrogen ion permeable membrane is formed by mixing 5% and 5% by weight of the fibC and the silicone rubber, and the ion-porous polymer is formed at a ratio of 0.5-2% by weight of the mixed weight. And the ion-forming polymer is made of tridodecyl amine (TDDA). More preferably, the hydrogen ion permeable membrane is attached to the surface of the solid electrode made of solid carbon.

Hereinafter, the hydrogen ion concentration measuring electrode according to the present invention having the above characteristics will be described in detail with reference to the drawings. Figure 1 is a schematic view of a hydrogen ion concentration sensor with a pH-silicon polymer film solid pH electrode according to the present invention. As shown, the hydrogen ion concentration sensor, the body 10, the external connection wire 20, the solid electrode 30 and the polymer film 40 is composed of. First of all, the body 10 is made of F. C. material. Therefore, it is possible to withstand breakage by external impact or dropping. In addition, by using the solid electrode 30 as the reference electrode, the volume can be miniaturized. As the solid electrode 30, a conductive carbon rod is used. The external connection wire 20 is connected through one side of the carbon rod to receive the current by the potential difference applied to the solid electrode according to the hydrogen concentration, thereby measuring the hydrogen ion concentration. In addition, a permeable polymer membrane 40 for selectively transmitting hydrogen ions according to the present invention is provided on the surface of the solid electrode 30. The quality of the measurement sensor is determined according to the adhesion of the transparent polymer membrane 40 to the solid electrode 30 and the reactivity to hydrogen ions. In the present invention, by configuring the permeable polymer membrane 40 differently from the conventional one, there is a feature in pursuing the precision and stability of the measuring sensor. Hereinafter, the manufacturing process of the measuring sensor provided with the polymer film 40 will be briefly described.

First, such a polymer membrane 40 is made of a polymer membrane 40 in which the material is a mixture of FIVEC and silicone rubber, and an ion hole (ionophore) capable of selectively permeating hydrogen ions is formed in such a substrate. have. The ion hole is a function of transporting ions across a biofilm or artificial membrane containing lipids, and refers to an ion carrier. A hydrogen ion selective ion hole is added to a mixture of fibric acid (PVC) and silicone rubber dissolved in a solvent. Melt about 1% by weight of the mixture. Since the ion hole sufficiently maintains its function in a small amount, it was configured in the same amount as that used in a conventional polymer membrane. Then, a small amount of such a mixture of ionic holes is dropped on the solid electrode 30 made of a conductive carbon disk inserted into the PVC rod forming the electrode body 10, and then dried at room temperature for about one day. A hydrogen ion selective electrode is produced. The wire 20 is connected to the conductive carbon solid electrode 30 to be connected to an external measuring device. By configuring as described above, it is possible to miniaturize the solid pH electrode that does not require the internal reference solution. In addition, the film having only the advantages of FIVEC and silicone rubber is prepared by manufacturing a film mixed with the FIVEC and silicone rubber in an appropriate blending ratio to produce a polymer film having excellent adhesion and fast reactivity and long-term stability. Hereinafter, in order to characterize the pH electrode using the PVC-silicone rubber membrane support, the potential change, response time, long-term stability, surface structure characteristics according to the content ratio of the PVC and silicone rubber Will be described. EMBODIMENT OF THE INVENTION Hereinafter, with reference to an accompanying drawing, a PVC-silicone rubber membrane support body is demonstrated in detail.

Figure 2 shows a process for manufacturing a PVC-silicon rubber mixed film and a pH sensor. As shown, the bis (2-ethylh-exyl) adipate (DOA), a plasticizer, tridodecyl amine (TDDA), and potassium tetrakis (p-chl-orophenyl) borate, are plasticizers in F.C. (KTpClPB) was mixed and an appropriate amount of silicone rubber was added thereto. Finally, the weight ratio was adjusted so that the silicone rubber content was from 5 to 77% (wt / wt). The mixture thus prepared was dissolved in THF as a solvent and stirred for 30 minutes to uniformly mix. The polymer membrane was fixed to the electrode surface by immersing a carbon rod (2 mm in diameter) for 10 seconds in a THF mixed solution (5 times). Carbon electrodes coated with PVC-silicon rubber polymer membranes were dried at room temperature for 1 day and then immersed in distilled water for one day, and used for measurement.

In general, the theoretical gradient of potential change with respect to the concentration of hydrogen ions is 59.1 mV / pH, and the electrode close to the theoretical value has excellent linearity.

Figure 3 shows the manufacturing process of the PVC-silicone rubber (PVC-SR) polymer membrane electrode prepared by changing the concentration of the ion hole to 1% and changing the weight of the silicone rubber to 0%, 5%, 15%, 23.5% The content ratio of each component used is shown. To compare the properties of PVC-silicone rubber membranes, a membrane was prepared using 100% silicone rubber without silicone rubber and 100% silicone rubber without PVC. The response characteristics were compared.

Figure 4 shows the slope response to pH, linearity using a regression analysis, pH measurement range of the response characteristics of the pH of the electrode prepared in Figure 3 different. In the case of a pH electrode using a conventional PVC membrane, a sensor made of a fibrous membrane containing 1% (wt / wt) of ion pores can measure a pH range of 4 to 10.5, and the reactor can be reduced at a low pH. There was a difficulty of measurement as it decreased. On the other hand, even in the case of using the same type and content of ionic pores, the FBC-silicon rubber mixed polymer membrane electrode shows linearity and stable electrochemical response even in the range of pH 2.1 to pH 11.5. Especially, in case of 15% of silicone rubber, the slope of response is 59.5 mV, which is closest to the theoretical slope of 59.1 mV / pH than other electrodes of other contents, and also shows the most linear value in the linearity test using regression analysis. (R ² = 0.9987). In other words, except for the electrode to which 15% silicone rubber was added, other solid electrodes had a large degree of deviation from linearity and dislocation drift was observed during dislocation change measurement. Their slope is larger or smaller than the theoretical slope and the deviation from the straight line is considered to be due to the weak adhesiveness of the polymer electrode due to the difference in the content of PVC and silicone rubber.

5 is a response time of the change in potential with the change of pH using a 15% PVC-silicon rubber polymer membrane electrode. The time-potential curve appears when the pH is changed by dipping the PVC-silicon rubber polymer membrane electrode into the solution and adding 10 ^-4 M NaOH to the solution little by little. As shown in FIG. 5, the PVC-silicone polymer membrane electrode exhibits a rapid change in potential corresponding to a change in pH. The reaction time (time to reach 90% of the limit signal) of these electrodes was very fast, about 5 seconds. The reaction time of the PVC-silicon rubber membrane showed a short reaction time almost the same as that of the conventional PVC membrane electrode. As can be seen from the above experimental results, it was confirmed that the fibC (PVC) -silicone rubber polymer membrane electrode has a fast response characteristic to measure the hydrogen ion concentration in the solution.

Figure 6 shows the slope of the hydrogen ion response measured for 90 days at 5 days intervals using a variety of PVC-silicon rubber polymer film. As a result of the experiment, the electrode made of PVC polymer film only began to drop the slope of the electrode reaction after 35 days of manufacture, and after 40 days, the electrode function was lost. In contrast, the 5% and 15% PVC-silicon rubber polymer membrane electrodes produced by the present invention showed reproducible slopes within the measurement period. In addition, the standard deviation of the slope was 1.6% when the hydrogen ion concentration was measured five times continuously under the same experimental conditions using a 15% PVC-silicon rubber polymer membrane electrode. This is because the polymer film of 15% silicone rubber mixed precisely by the mixing of FIVEC and silicone rubber according to the present invention shows an increase in adhesion to solid materials, and the electrode life is reduced due to the decrease in electrode resistance. It can be seen that it is longer than the PVC polymer electrode.

Next, an experiment was conducted to determine the degree of interference caused by other cations that interfered with accurate hydrogen ion concentration measurement. That is, generally, cations such as potassium, sodium, and calcium are known as ions that interfere with the measurement of hydrogen ions. In FIG. 7, the interfering effects of these ions were examined and a selection coefficient indicating the degree of interfering action was obtained by the fixed solution method. The selection coefficients of calcium, potassium, and sodium shown in 5% PVC, 5% PVC-silicone rubber, and 15% PVC-silicone rubber polymer membrane electrode are shown in FIG. 7. The selectivity coefficients for potassium, sodium and calcium ions in the 15% PVC-silicone rubber polymer film were -9.2 and -10.1. At -11.0, the selectivity is almost the same as that of the conventional PVC film. Therefore, it can be seen that the polymer membrane prepared by mixing FIVEC and silicone rubber according to the present invention does not generate any error because there is no specific selectivity due to interference ions.

Next, FIG. 8 is a BAM diagram of various PVC-silicon rubber electrodes having different content ratios of silicone rubber. As shown, as the concentration of the silicone rubber added to the PVC increases, the size of the ion channel increases and the rate at which these holes are uniformly increased. The formation of uniform and many ion channels by the addition of silicone rubber quantitatively explains the rapid electrode reaction and high reactivity. However, as described in FIG. 4, when more than a suitable amount of silicone rubber is added, the drift of the potential is observed during the measurement of the potential change, and the degree of deviation from the linearity is large. It can be seen that due to the difference in the content of the silicone rubber and the weakness of the adhesion in the solid electrode of the polymer film is not preferable.

As described above, according to the solid-type pH electrode made of the PVC-silicon rubber membrane according to the present invention, the problem of adhesion of the conventional PVC polymer membrane electrode and low sensitivity of the silicone polymer membrane There is an effect that can solve the problem.

In addition, as the polymer membrane according to the present invention is attached to the solid electrode, there is another effect that can solve the problem of the risk of miniaturization and miniaturization of the glass electrode and the use of the internal reference solution.

1-Schematic diagram showing a structure of a solid pH measurement sensor is installed electrode made of a polymer film made of PVC-silicon rubber mixture according to the present invention.

FIG. 2 is a view illustrating a manufacturing process of a solid pH electrode composed of PVC-silicon rubber polymer membrane according to the present invention. FIG.

FIG. 3 shows various composition ratios for the preparation of polymer membranes comprising a mixture of PVC-silicon rubber. FIG.

4 is a view showing the pH response characteristics of the solid-type pH electrode using the PVC-silicon rubber polymer membrane according to the present invention.

5 is a view showing the response characteristics according to the response time of the solid-state pH electrode using the PVC-silicon rubber polymer film according to the present invention.

FIG. 6 shows the long term stability of a solid pH electrode using a PVC-silicone rubber polymer membrane. FIG.

FIG. 7 is a diagram showing the action of interference ions of a solid pH electrode using a PVC-silicon rubber polymer membrane. FIG.

FIG. 8-Surface photograph of FIBC-silicon rubber polymer membrane.

* Description of the symbols for the main parts of the drawings *

10: body 20: external connection lead

30: solid carbon electrode 40: FBC silicon film

Claims (5)

In the solid polymer membrane sensor for measuring the concentration of hydrogen ions, To the mixed solution in which the weight ratio of FIVEC and silicone rubber is mixed at 25-35%: 5-20%, an ion pore-forming polymer which selectively permeates hydrogen ions at a ratio of 0.5-2% to the mixed weight is added. A solid-state hydrogen ion concentration measuring electrode using a polymer membrane composed of FBC-silicon mixture, characterized in that the hydrogen ion permeable membrane. delete The electrode of claim 1, wherein the ion-forming polymer is tridodecyl amine (TDDA). The solid-state hydrogen ion concentration measuring electrode according to any one of claims 1 to 3, wherein the hydrogen ion permeable membrane is attached to the surface of the solid electrode. 5. The solid hydrogen ion concentration measuring electrode according to claim 4, wherein the solid electrode is made of solid carbon.