KR19990014660A - Dissolved oxygen measuring device using solid electrolyte - Google Patents

Abstract

The present invention relates to a dissolved oxygen measuring apparatus for preventing the leakage of a liquid by using a gel-type solid electrolyte in a liquid, and stable, long-term use and miniaturization, and to measure the dissolved oxygen contained in the liquid An apparatus, comprising: a selective permeable membrane which permeates oxygen present in a liquid sample and an impermeable liquid component, an electrode which causes a current change according to the amount of oxygen that has permeated the membrane, and is located between the selective permeable membrane and the electrode Disclosed is an apparatus for measuring dissolved oxygen using a solid electrolyte including a solid electrolyte made of a gel type. In addition, the solid electrolyte is composed of a composite of polyethylene oxide (PEO) and potassium chloride, the composition of which is composed of about 5w / w% polyethylene oxide and 0.1M or more potassium chloride to form a gel. Meanwhile, the selective permeable membrane is made of a Teflon membrane, and in the electrode, the cathode is made of any one of gold (Au) and silver (Ag) platinum (Pt), and the anode is made of Ag / AgCl or Ag / AgO. .

Therefore, according to the present invention, the electrolyte is prevented from leaking and the device can be miniaturized and stable in use.

Description

Dissolved oxygen measuring device using a solid electrolyte.

The present invention relates to an apparatus for measuring dissolved oxygen (DO), and more specifically, by using a gel-type solid electrolyte in a liquid contained in an electrolyte, liquid leakage prevention and stable, long-term use, and miniaturization are possible. The present invention relates to a dissolved oxygen measuring apparatus using a solid electrolyte.

In general, water in various forms such as blood of the human body as well as water constituting rivers, rivers, lakes, etc., and various other liquids (hereinafter, such water and various liquids) A certain amount of oxygen is dissolved in water, and the amount of oxygen dissolved in such a liquid is called dissolved oxygen (DO). The dissolved oxygen depends on physical factors such as temperature and pressure and biochemical factors caused by various pollutants contained in water.

That is, under the same conditions, the lower the temperature and the higher the atmospheric pressure, the more the dissolved oxygen contained in the water. In addition, the amount of dissolved oxygen decreases as the degree of pollution, that is, water containing many chemicals and microorganisms. Therefore, since the amount of dissolved oxygen contained in the water can be a reference indicator indicating the degree of usefulness of water (water), there is a need for a device that can easily quantitatively measure the amount of dissolved oxygen contained in such water. In recent years, the necessity of such a dissolved oxygen detector has been particularly focused on the control of the biotechnology process and the application of environmental solutions. The dissolved oxygen measuring device is an industry that measures oxygen present in various water zones, such as seawater, blood, water and sewage, wastewater from various chemical plants, and soil, and various fields such as biochemistry, environmental research, and clinical medicine. Very importantly used throughout.

As described above, a method for measuring dissolved oxygen contained in water includes the Winkler method and the electrode method devised by L. Double Oil Winkler in 1988. The Winkler method is currently used as the standard method for all dissolved oxygen measurements and is a modified form of iodometry. When explaining the principle of oxygen measurement by the Winkler method, first, the sample to be measured is treated with excess Mn (II), KI, NaOH. The white Mn (OH) ₂ (s) formed here reacts rapidly with oxygen (O ₂ ) to form brown Mn (OH) ₃ (s). The reaction scheme is as follows.

4 Mn (OH) ₂ (s) + O ₂ + ₂ H ₂ O ⇒ 4 Mn (OH) ₃ (s)

When the reactants are acidified, manganese (III) is oxidized from iodine ions (I ⁻ ) to iodine. The reaction scheme is as follows.

_{4Mn (OH) 3 (s)} + 2I - + 6H + ⇒ I 2 + 3H 2 O + 2Mn 2+

By titrating the iodine liberated by the above reaction by the usual method, it becomes possible to quantitatively measure the dissolved oxygen. In addition, the dissolved oxygen measured by this method is used for the verification of many oxygen sensors because the quantitative unit can be up to 0.1 ppm, but has a drawback that it is not easy to determine the continuous dissolved oxygen.

However, unlike the above, the electrode method (or galvanic method) has been widely used in recent years because it can improve these disadvantages of the Winkler method. The basic principle of the electrode method is a basic method using the generation of current (or voltage) when two different metals enter a solvent, or lack of stability. Therefore, as a result of research to compensate for the problem of the electrode method, an improved clark-type galvanic sensor was developed.

As described above, the improved polarography method can measure stable dissolved oxygen by applying a constant potential (about 0.76 V) to the cathode to obtain a current proportional to the partial pressure of dissolved oxygen according to the redox reaction of the electrode. The method was developed. In addition, the three-electrode method, which was developed by the German company WTW, is one of the most widely used methods of improving reliability by adding one reference electrode in addition to the anode and the cathode.

In the above-described methods, the surface of the electrode is basically covered with a diaphragm to measure oxygen (O ₂ ) present in the liquid sample. Since the dissolved oxygen in the liquid sample may pass through the diaphragm, oxygen that has passed through the diaphragm reacts with an electrode to measure the amount of dissolved oxygen. That is, the oxygen diffused into the diaphragm in the environmental sample to measure the dissolved oxygen amount is reduced by the polarization voltage of the cathode, thereby quantitatively detecting the amount of dissolved oxygen according to the above reaction formula. The reaction scheme is as follows.

Cathodic _{reaction: O 2 + 2H 2 O +} 4e - ⇒ 4OH - ( reduction)

Anode reaction: 4Ag + 4Cl ⇒ 4AgCl + 4e - ( oxidation)

The reduction reaction occurring at the cathode in the above reaction generates a current which is directly proportional to the oxygen partial pressure of the environmental sample. Here, the peak current I _p generated by the reduction of oxygen is explained by the Rendles-Sevcik formula, and the formula is as follows.

I _p = (2.69 × 10 ⁵ ) n ^3/2 .AD ^1/2 C ⁰ v ^1/2

I _p : peak current

n: number of electrons moving in redox reaction

A: electrode area

D: diffusion coefficient

C ⁰ : concentration or partial pressure of oxygen

v: scan speed

The dissolved oxygen measuring device capable of measuring dissolved oxygen according to the basic principles described above is provided in various forms according to the shape of the negative electrode, the positive electrode, the electrolyte, and the membrane.

Materials that can be used as cathodes are pure metal Pt-Au alloys, such as Pd, Ir, Rh, Sb, Fe-Ni-Cr-Pb alloys, and nonmetallic materials (usually carbon). However, the most widely used materials are pure metals such as gold (Au), silver (Ag), and platinum (Pt). This is because the catalytic activity for oxygen reduction, which is a characteristic of the cathode, is large, and satisfies electrical conductivity, inertness, sufficient overvoltage for water, and ease of electrode production.

The anode material is widely used as an electrode for Ag / AgCl and Ag / AgO to stabilize the potential of the cathode for a long time. When Pb, Al, Cd, and Zn are used as the anode, the anode voluntarily causes Since reduction occurs, there is no need to apply a potential from the outside.

In addition, the electrolyte should facilitate the transfer of ions to the cathode and the anode, and there should be no unnecessary reactions and external influences. The diaphragm should have the function of protecting the system of electrodes from contamination by the composition of the measurement medium, minimizing any unnecessary changes in the electrolyte composition, and providing regeneration conditions of oxygen transfer to the cathode. Teflon membrane is most widely used as a diaphragm satisfying these requirements.

In addition, the electrode is divided into a planar shape and a cylindrical shape according to the shape of the cathode. There are discs, S-shapeds, rings, and helicals. The cylinders are hollow cylinders, wire spirals, and cylindricals. Or hemisperical form.

The dissolved oxygen detector with each of the above-described components is based on the Clark oxygen detector, which was patented by Clark in 1956, and is described with reference to FIG. Let's look at it.

As shown, the battery 2 of the detector 1 is composed of a cathode working electrode 2a enclosed at a bottom center position of the insulator rod 3 and a cathode electrode 2b surrounding the outer circumferential surface of the insulator rod 3. It is composed. The cathode working electrode 2a is made of platinum Pt, and the anode electrode 2b is made of silver (Ag). The surface of the detector 1 is provided with a thin and replaceable oxygen permeable membrane 5, and the oxygen permeable membrane 5 is fixed to the detector 1 by an O-ring (not shown). do. The permeable membrane 5 has a structure in which free oxygen can be freely permeated by its molecular structure, but water molecules cannot permeate. In addition, the liquid electrolyte 6 is filled in the detector 1, and a potassium chloride (KCl) solution is used as the liquid electrolyte 6. The thickness d of the solution of the electrolyte 6 existing between the cathode working electrode 2a and the oxygen permeable membrane 5 located on the bottom surface of the insulator rod 3 is maintained to be about 10 μm.

When the clock oxygen detector 1 having the above configuration is immersed in a flowing solution or a stirring solution, oxygen contained in the solution passes through the permeable membrane 5 and is transferred into the potassium chloride electrolyte 6. Oxygen delivered into the electrolyte 6 diffuses and reacts with the cathode working electrode 2a. At this time, the battery 2 generates a current proportional to the amount of oxygen delivered as described above, and the dissolved oxygen amount can be measured by the current.

In addition to the normal hydrodynamic electrode, the detector 1 includes two diffusion processes, one through the oxygen permeable membrane 5, and the other between the permeable membrane 5 and the surface of the electrode 2. It is through the electrolyte (6) solution. In order to reach a rectified state at a suitable time (about 10 seconds or less), the thickness of the permeable membrane 5 and the thickness of the electrolyte 6 film should be about 20 μm. Under these conditions, the rate of reaching the rectified current is the transport equilibrium rate of oxygen passing through the permeable membrane 5. Determining this transport equilibrium rate is that the oxygen solubility in the thin sample solution layer made outside the permeable membrane 5, the oxygen diffusion rate into the permeable membrane 5, and the diffusion rate of the electrolyte 6 solution layer are the largest. Variable. Usually, the reduction potential of the cathode working electrode 2a is fixed at around -0.8V, and the oxygen concentration is determined by the calibration curve built into the device, so that the user can detect dissolved oxygen.

However, such a conventional detector for detecting dissolved oxygen present in a solution has the following problems.

Conventional detectors that use liquid as an electrolyte have limitations in miniaturizing their size, and thus have problems of wide use in many fields. In other words, as the size of the detector becomes smaller, there is an advantage that it can be used for various experimental applications. For miniaturization of such a detector, it is possible through the use of an ultra-fine electrode, etc., but there is a limit in miniaturizing the size of the detector by the concentration and the amount of the liquid electrolyte basically used. Therefore, the use of such a liquid electrolyte has a problem that can not be miniaturized any more.

In addition, the conventional detector uses a diaphragm to separate the environmental sample and the electrolyte, and uses an O-ring to seal the diaphragm. However, the O-ring is not completely sealed and leakage of the electrolyte is generated, which causes a problem of shortening the life of the detector.

In addition, as the detector is used for a long time, the concentration of the liquid electrolyte is changed, and the decrease in the concentration reduces the current response in the battery. That is, the detector using the liquid electrolyte has a problem that the concentration of the electrolyte decreases as it is used, thereby shortening the measurement life and making it difficult to use for a long time.

Therefore, the present invention is to solve the above problems, by using a gel-type solid electrolyte in the liquid contained in the electrolyte in the liquid does not leak, there is no change in concentration even long-term use can be used for a long time stably It is an object of the present invention to provide an apparatus for measuring dissolved oxygen using a solid electrolyte, the size of which can be reduced in size.

1-A partial cross-sectional view of a dissolved oxygen measuring device using a conventional liquid electrolyte.

2-A partial perspective view of a dissolved oxygen measuring instrument according to the present invention.

3 is a graph showing the current response of dissolved oxygen to a measuring instrument made of various concentrations of potassium chloride (KCl) liquid electrolyte and solid gel electrolyte.

4-Graph showing the current response of dissolved oxygen to the gel electrolyte made by maintaining the concentration of potassium chloride (KCl) to 2.34M constant and controlling the content of the matrix.

5 is a graph comparing the dissolved oxygen amount according to the temperature of the measurement solution for the liquid electrolyte and polyethylene oxide gel electrolyte.

6 is a graph showing the change of dissolved oxygen current with respect to the frequency change of square wave voltammetry for liquid electrolyte and gel electrolyte of polyethylene oxide.

7-A graph comparing the response to dissolved oxygen concentration with a dissolved oxygen measuring device made of a gel electrolyte containing a YSI dissolved oxygen measuring instrument and a polyethylene oxide matrix.

8 is a graph showing the current response to dissolved oxygen by a measuring device made of polyethylene oxide gel electrolyte and liquid electrolyte according to the concentration of sodium chloride (NaCl).

9-A graph showing the dissolved oxygen content and the current response to dissolved oxygen for a period of time by a dissolved oxygen measuring device made of a gel electrolyte.

Explanation of symbols for the main parts of the drawings

10: detector 20: oxygen permeable membrane

30 battery 32 cathode working electrode

34: anode 40: gel electrolyte

A first aspect of the present invention for achieving the above object is a device for measuring the dissolved oxygen contained in a liquid, the selective permeable membrane to permeate the oxygen present in the liquid sample and the liquid component is impermeable, and Disclosed is an apparatus for measuring dissolved oxygen using a solid electrolyte including an electrode causing a current change according to an amount of oxygen that has passed through a membrane, and a solid electrolyte positioned between the selective permeable membrane and the electrode.

And, the solid electrolyte is composed of a composite of polyethylene oxide (PEO) and potassium chloride, the composition is composed of about 2 to 10w / w% polyethylene oxide and 0.1M or more potassium chloride to form a gel or dry form. On the other hand, the selective permeable membrane is made of a Teflon membrane, in the electrode, the cathode is made of any one of gold (Au), silver (Ag) platinum (Pt), and the anode is made of Ag / AgCl or Ag / AgO In addition, it may be made of a three electrode further comprising a reference electrode made of platinum (Pt) or gold (Au).

Therefore, according to the present invention, the electrolyte is prevented from leaking and the device can be miniaturized and stable in use.

Next, a preferred embodiment of the dissolved oxygen measuring device using the solid electrolyte according to the present invention having the configuration as described above will be described in more detail.

Various materials were prepared for use as solid electrolyte matrix for this experiment. In the preparation of the solid electrolyte using the material, the experiment was conducted using a gel form or a dry form, and the results are not significantly different. Hereinafter, the solid electrolyte formed in the gel form will be described as an example.

As a matrix material, various experiments were conducted, and among the above materials, polyethyleneimnine (PEI: average molecular weight 750,000), chitosan, polyethylene oxide (PEO: average molecular weight 2,000,000) were described by Aldrich Chem. Co: USA. Purchased). Starch and gelatin agar used as gel electrolyte matrix materials were purchased from SYNYO PURE CHEMICALS Co. Meanwhile, potassium chloride (KCl) used as a supporting electrolyte was purified by a purification method, and tertiary distilled water was used to obtain distilled water up to 18 MΩ in Millipore system (Millipore system).

In this experiment, the electrode used in the dissolved oxygen measuring device was experimented with both a two-electrode consisting of a cathode and an anode and a three-electrode including a reference electrode in addition to the two-electrode, and platinum (Pt) and Although gold (Au) was used, it is of course also possible to use silver (Ag). Silver / silver chloride (Ag / AgCl) was used as the anode electrode, but silver / silver oxide (Ag / AgO) may of course be used. In addition, the experiment was performed using platinum (Pt) or gold (Au) as the reference electrode.

As the oxygen permeable membrane (membrane) was used FET Teflon, O-ring was used to fix the permeable membrane. Electrochemical cells were incubated at 25 ± 0.1 ° C. using products purchased from Polyscience Co., Ltd. (Polyscience Co.). Voltammetric experiments were conducted with IBM-PC clone and bioanalytical Systrm, Inc. model CV-50W. The normal scan rate of a gentle voltage current (CV) is 100mV / sec. In addition, the dissolved oxygen of the measurement solution was controlled with a purity of 99.999% nitrogen gas and a purity of 99.999% oxygen gas.

Meanwhile, in preparing a gel-type solid electrolyte, a gel electrolyte was prepared as follows in order to uniformly mix the gel electrolyte matrix and the supporting electrolyte of potassium chloride. Starch and agar are prepared by heating in potassium chloride (KCl) solution, which is a supporting electrolyte, and melting them. In addition, gelatin, polyethyleneimine (PEI) and polyethylene oxide (PEO) were added to potassium chloride (KCl) solution, and left to stand in an ultrasonic generator for 2 hours or longer to be mixed uniformly. In particular, PEO needs a time of about a day to obtain a uniform gel, so use a gel prepared for one day.

With reference to Figure 2 showing an embodiment of the instantaneous using the gel-type solid electrolyte and the electrode formed as described above.

As shown, the oxygen permeable membrane 20 made of Teflon is installed on the surface of the cylindrical detector 10, the permeable membrane 20 is the detector 10 by the O-ring (not shown) It is fixed to the outer surface of the cylinder. In addition, a cathode working electrode 32 made of gold (Au) or platinum (Pt) is installed on the inner surface of the permeable membrane 20 in the form of a ring, and is spaced apart from the cathode 32 by a predetermined distance to silver / silver chloride (Ag / A positive electrode 32 made of AgCl) is provided to form a battery 30. On the other hand, between the positive electrode 32 and the negative electrode 34 is the solid electrolyte 40 of the gel form described above, the experiment was performed by changing the type of the solid electrolyte 40 in various ways. On the other hand, as described above, the electrode according to the present invention was tested as a three-electrode in addition to the two-electrode shown in FIG. 2, it will be described as a two-electrode for convenience of description. Meanwhile, a comparative experiment was performed using the dissolved oxygen measuring device of the solid electrolyte according to the present invention and the dissolved oxygen measuring device (DO meter) of YSI incorporating the existing liquid electrolyte, which will be described below.

Current Reaction of Liquid Electrolyte and Gel Electrolyte

3 is a diagram showing the current response of dissolved oxygen to a measuring instrument made of various concentrations of potassium chloride (KCl) liquid electrolyte and gel electrolyte.

As shown, liquid electrolytes were measured for concentrations of 0.1M, 1.0M, 2.34M and saturated potassium chloride (KCl), respectively. The gel electrolyte is 0.5w / w% chitosan, 10w / w% starch, 10w / w% gelatin, 4w / w% agar, 5w / w% polyethyleneimine (PEI) and 5w / w% polyethylene oxide (PEO). Each prepared and prepared by varying the above-described potassium chloride (KCl) concentration. On the other hand, all dissolved oxygen measurement solution was measured by unifying with distilled water and keeping the dissolved oxygen constant.

As shown in the graph, it can be seen that as the concentration of potassium chloride (KCl) contained in the gel electrolyte increases, the current response to dissolved oxygen generally appears large. However, it can be seen that the gel electrolyte containing 5w / w% polyethylene oxide (PEO) causes a constant current reaction with respect to dissolved oxygen regardless of the concentration of potassium chloride (KCl), and the current reaction is larger than that of the liquid electrolyte solution. On the other hand, gel electrolyte containing 5w / w% polyethyleneimine (PEI) and 10w / w% gelatin containing 2.34M potassium chloride appears to have an increased current response than 2.34M potassium chloride liquid electrolyte. Other gel-supported electrolytes exhibit similar current responses as liquid electrolytes.

According to the above experimental results, as a result, 5w / w% polyethylene oxide (PEO) gel electrolyte can be seen that the maximum current response to the dissolved oxygen can be obtained if it contains only 0.1M potassium chloride. However, like other gel electrolytes, gel electrolytes containing only 5w / w% polyethylene oxide (PEO) do not have a current response to dissolved oxygen. Thus, polyethylene oxide gel electrolytes containing a predetermined amount of potassium chloride are more useful. Gelatin and polyethyleneimine can also be used.

Effect of Matrix on Gel Electrolyte

Through the experiment of FIG. 3, the matrix usable as the gel electrolyte was found. Therefore, the effects of the matrix on gelatin, polyethyleneimine (PEI) and polyethylene oxide (PEO) that can be used as gel electrolytes were investigated. Figure 4 is a graph showing the current response of dissolved oxygen to the gel electrolyte prepared by maintaining the concentration of potassium chloride (KCl) to 2.34M constant and controlling the content of the matrix. (1), (2) and (3) are graphs showing the current response to the starch, polyethyleneimine (PEI) and polyethylene oxide (PEO) matrices, respectively.

As shown, the starch gel electrolyte exhibits the largest current response to dissolved oxygen when the matrix contains 0.1 w / w%, and at higher metric contents there is no difference in the current response to dissolved oxygen. Can be. In other words, it can be seen that in the starch gel electrolyte, when the matrix content is 0.1%, a slight current increases more than the 2.34 M potassium chloride liquid electrolyte. However, if it is 1% or more, it has a current response almost like liquid electrolyte.

On the other hand, the polyethyleneimine (PEI) gel electrolyte, on the contrary, has a current reaction such as liquid electrolyte at 0.1% content, and when it exceeds, the current reaction increases, and when 20% or more, it becomes like liquid electrolyte without increasing the current reaction.

On the other hand, the gel electrolyte of polyethylene oxide (PEO) shows a constant current response to the dissolved oxygen irrespective of the content of the matrix, and in accordance with the results of FIG. It can be seen that there is a tendency.

It can be seen from the experimental results of FIGS. 3 and 4 that the gel electrolyte of polyethylene oxide (PEO) is the most suitable solid electrolyte. However, solids, unlike liquids, are temperature sensitive, and solid electrolytes are expected to affect the diffusion of dissolved oxygen. Hereinafter, the influence of the temperature of the gel electrolyte will be described.

Effect of temperature on the temperature of gel electrolyte

Figure 5 compares the dissolved oxygen content according to the temperature of the measurement solution for the gel electrolyte of (1) 2.34M potassium chloride solution and (2) 5w / w% polyethylene oxide containing 2.34M potassium chloride in the YSI DO meter (DO meter) One graph.

As shown, the gel electrolyte of 5w / w% polyethylene oxide shows a phenomenon that the response to dissolved oxygen at the low temperature of the measurement solution is slightly lower than the response measured by the liquid electrolyte. However, at a temperature above room temperature, a similar response is exhibited. It is speculated that the gel electrolyte has a low sensitivity to dissolved oxygen at low temperatures due to the polyethylene oxide matrix effect, but this sensitivity does not appear to be a major obstacle in the practical use. And, for accurate measurement, the same measurement as the liquid electrolyte can be made through the numerical compensation according to the low temperature.

Square wave voltammetry for dissolved oxygen measurement

In order to confirm the maximum current response to dissolved oxygen of polyethylene oxide matrix which can be used as a gel electrolyte, square wave voltammetry, which is one of the techniques of electrochemistry, was used. Figure 6 (1) is a gel electrolyte of 5w / w% polyethylene oxide containing 2.34M potassium chloride, (2) is the dissolved oxygen current for the frequency change of the square wave voltammetry for a 2.34M potassium chloride liquid electrolyte solution This graph shows a change.

As shown, at low frequencies, the dissolved oxygen meter made of gel electrolyte has a larger current response corresponding to dissolved oxygen than the liquid electrolyte solution. However, as the frequency increases, the difference in the current response is almost disappeared, and at the frequency of about 100 Hz, the current response is almost the same. As can be seen from the above fact, when measuring the dissolved oxygen by the square wave voltammetry technique, it can be seen that the gel electrolyte is much more sensitive than the liquid electrolyte solution when the frequency is measured at a lower frequency.

Calibration curve

A calibration curve for dissolved oxygen was prepared with a dissolved oxygen meter made of gel electrolyte containing 5w / w% polyethylene oxide matrix. 7 is a graph comparing the response to dissolved oxygen concentration with a dissolved oxygen measuring device made of a gel electrolyte containing a YSI dissolved oxygen measuring instrument and 5w / w% polyethylene oxide matrix. Here, the concentration of dissolved oxygen was controlled by the difference in flow rates of 99.999% nitrogen gas and 99.999% oxygen gas.

As shown, it can be seen that the meter made of gel electrolyte shows almost the same response to the concentration of dissolved oxygen obtained in the YSI dissolved oxygen meter. The reaction to the dissolved oxygen measuring device made of gel electrolyte had a linearity of dissolved oxygen concentration of 2ppm-8ppm, which indicates that the gel electrolyte can be used as a gel electrolyte.

Effect of the measurement solution on the matrix (salinity)

In practice, there are many metrics for measuring dissolved oxygen. In general, the amount of dissolved oxygen varies depending on the concentration of the salt. 8 is a graph comparing current response to dissolved oxygen with a measuring device made of 5w / w% polyethylene oxide gel electrolyte and 2.34 M potassium chloride liquid electrolyte according to the concentration of sodium chloride (NaCl). (1) is a graph using a gel electrolyte, and (2) is a graph using a liquid electrolyte.

As shown, the slope of oxygen solubility with salinity was similar to that obtained with gel electrolyte. It can be seen that the matrix effect on salinity is less when using gel electrolyte than when using liquid electrolyte.

Gel electrolyte stability

In general, a dissolved oxygen measuring device using a liquid electrolyte has a problem when used continuously for a long time. That is, the concentration of the liquid electrolyte changes with use for a long time, and the change of the concentration of the liquid electrolyte causes a change in the current response. Therefore, a low concentration in the reaction to the liquid electrolyte causes a phenomenon that the current response is reduced. The concentration change of the liquid electrolyte shortens the lifetime of the dissolved oxygen measuring instrument.

The purpose of this experiment is to measure the stability of the measuring instrument according to the use for a long time. FIG. 9 shows the dissolved oxygen measuring device made of gel electrolyte in the solution for several days and measured the dissolved oxygen and the current response to dissolved oxygen daily. to be. As shown, the meter made of the gel electrolyte can be seen that the current response to the dissolved oxygen and the dissolved oxygen amount is almost constant for a month. Therefore, since it can be used without any problem for a long time, it can be seen that the stability is much better than the liquid electrolyte.

conclusion

According to the above experimental results, a gel electrolyte composed of agar, gelatin, chitosan polyethyleneimine and polyethylene oxide was compared with a liquid electrolyte, and the gel electrolyte containing polyethylene oxide in the gel electrolyte had better performance than the liquid electrolyte. Able to know. That is, as shown in the experimental data, 5w / w% polyethylene oxide gel electrolyte shows better performance than liquid electrolyte in terms of magnitude of current response to dissolved oxygen, minimization of matrix effect on measurement sample, stability with prolonged use, etc. And it was found. Therefore, it can be seen that the polyethylene oxide gel electrolyte has excellent usability as well as excellent performance in dissolved oxygen measuring device.

As described above, according to the dissolved oxygen measuring device using the solid electrolyte according to the present invention, there is an advantage that can be miniaturized. That is, miniaturization of the dissolved oxygen measuring instrument is essential, and this can be achieved by using a small amount of electrolyte. However, when the liquid electrolyte is used, the miniaturization is difficult because of its volume. Therefore, since the volume can be reduced by using the electrolyte as a solid, the dissolved oxygen can be miniaturized.

In the dissolved oxygen measuring device using the conventional liquid electrolyte, the life of the measuring device is shortened by the leakage of the liquid electrolyte. However, in the solid electrolyte according to the present invention, such a leak phenomenon does not occur, and thus it can be used for a long time.

In addition, in the liquid electrolyte, it is difficult to accurately measure not only the lifespan of the measuring device, but also accurate measurement according to the concentration change according to the use for a long time. There is another advantage that can be achieved.

Claims (5)

An apparatus for measuring dissolved oxygen contained in a liquid, comprising: a selective permeable membrane for permeating oxygen present in a liquid sample and impermeable to a liquid component; An electrode causing a current change according to the amount of oxygen that has passed through the membrane; And a dissolved oxygen measuring device positioned between the selective permeable membrane and the electrode and comprising a solid electrolyte. According to claim 1, The solid electrolyte, dissolved oxygen measuring device using a solid electrolyte, characterized in that consisting of a composite of polyethylene oxide (PEO) and potassium chloride. The dissolved oxygen measuring device using a solid electrolyte according to claim 2, wherein the solid electrolyte is composed of 2 to 10 w / w% of polyethylene oxide and 0.1 M or more of potassium chloride. The selective permeable membrane of any one of claims 1 to 3, wherein the selective permeable membrane is made of Teflon membrane, the cathode is made of any one of gold (Au), silver (Ag) platinum (Pt), Dissolved oxygen measurement apparatus using a solid electrolyte, characterized in that the anode is made of silver / silver chloride (Ag / AgCl) or silver / silver oxide (Ag / AgO). The apparatus of claim 4, wherein the electrode comprises a tri-electrode further comprising a reference electrode composed of gold (Au) or platinum (Pt).