Peracetic acid concentration meter

Abstract

The present invention provides a peracetic acid concentration meter, which can suppress contamination of the working electrode surface caused by organic matter and measure the peracetic acid concentration with higher accuracy than before. The peracetic acid concentration meter is a diaphragm-type peracetic acid concentration meter for measuring the peracetic acid concentration of a sample solution, and comprises: a diaphragm through which peracetic acid passes, an internal liquid in which peracetic acid is dissolved and permeated through the diaphragm, a working electrode and a counter electrode immersed in the internal liquid, and a permeation suppression layer laminated on the surface of the diaphragm on the side in contact with the sample solution and suppressing the permeation of organic matter.

Description

Technical Field

[0001] The present invention relates to a peracetic acid concentration meter for measuring the concentration of peracetic acid contained in a sample solution. Background Art

[0002] As a peracetic acid concentration meter, there is a diaphragm type peracetic acid concentration meter as described in Patent Document 1, for example.

[0003] Such a diaphragm-type peracetic acid concentration meter includes a diaphragm through which peracetic acid selectively permeates, and measures a change in current generated when peracetic acid that has permeated the diaphragm reacts on the surface of a working electrode.

[0004] However, the peracetic acid solution to be measured may contain organic matter from food or human body, and some of the organic matter may penetrate the diaphragm into the internal solution and reach the working electrode surface depending on the conditions.

[0005] There is a problem that the organic matter reaching the surface of the working electrode adheres to the working electrode and hinders the reaction of peracetic acid on the surface of the working electrode.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2015-230173 Summary of the invention

[0009] Technical issues

[0010] The present invention has been made in view of the above problems, and a main object of the present invention is to provide a peracetic acid concentration meter capable of suppressing contamination of the working electrode surface by organic matter and measuring the peracetic acid concentration with higher accuracy than before.

[0011] Technical Solution

[0012] That is, the peracetic acid concentration meter of the present invention is a diaphragm-type peracetic acid concentration meter for measuring the peracetic acid concentration of a sample solution, and is characterized in that it comprises: a diaphragm through which peracetic acid passes, an internal liquid in which the peracetic acid is dissolved and permeated through the diaphragm, a working electrode and a counter electrode immersed in the internal liquid, and a permeation suppression layer stacked on the surface of the diaphragm on the side in contact with the sample solution and suppressing the permeation of organic matter.

[0013] According to the peracetic acid concentration meter configured in this manner, since the permeation suppression layer is provided and the permeation suppression layer is laminated on the surface of the diaphragm in contact with the sample solution, permeation of organic matter contained in the sample solution into the internal solution can be suppressed.

[0014] As a result, contamination of the working electrode surface by organic matter can be suppressed, and the inhibition of the reaction of peracetic acid on the working electrode surface due to the contamination can be reduced, so that the peracetic acid concentration can be measured with higher accuracy than before.

[0015] If the permeation suppression layer includes a semipermeable membrane, the permeability can be controlled by the molecular weight, and thus the permeation of organic matter can be suppressed without inhibiting the permeation of peracetic acid.

[0016] If the permeation suppressing layer includes a supporting substrate for supporting the semipermeable membrane, there is no need to worry about the compatibility of the components of the separator and the semipermeable membrane and / or the strength of the semipermeable membrane, and a wider variety of semipermeable membranes can be used.

[0017] For example, if the supporting substrate is stacked on the surface of the diaphragm on the side in contact with the sample solution, and the semipermeable membrane is stacked on the surface of the supporting substrate on the opposite side of the diaphragm, even if it is difficult to stack the semipermeable membrane by directly coating the surface of the diaphragm due to the properties of the semipermeable membrane, the permeation inhibition layer can be stacked on the surface of the diaphragm through the intervention of the supporting substrate.

[0018] As a specific embodiment, the semipermeable membrane is a membrane containing one or more components selected from the group consisting of cellulose, cellulose acetate, polyacrylonitrile, polytetrafluoroethylene, polyester polymer alloys, and polysulfone.

[0019] If the peracetic acid concentration measuring device includes a light source for irradiating ultraviolet rays to the surface of the peracetic acid concentration meter in contact with the sample solution, contamination of the surface of the transmission suppression layer can be suppressed, thereby further improving the accuracy of peracetic acid concentration measurement.

[0020] Effects of the Invention

[0021] According to the peracetic acid concentration meter of the present invention, it is possible to suppress contamination of the working electrode surface by organic matter from a sample solution, thereby measuring the peracetic acid concentration with higher accuracy than before. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 1 is an overall schematic diagram of a peracetic acid concentration meter according to one embodiment of the present invention.

[0023] Figure 2 This is a schematic diagram of a peracetic acid concentration meter according to one embodiment of the present invention.

[0024] Figure 3 This is a schematic cross-sectional view of a peracetic acid concentration meter according to one embodiment of the present invention.

[0025] Figure 4 In one embodiment of the present invention, Figure 3An enlarged cross-sectional view obtained by enlarging portion A of FIG.

[0026] Figure 5 This is a schematic cross-sectional view of a peracetic acid concentration meter according to another embodiment of the present invention.

[0027] Explanation of symbols

[0028] 1…Peracetic acid concentration meter

[0029] 4…Working electrode

[0030] 5…Counter electrode

[0031] 11…Diaphragm

[0032] 12…Intermediate film

[0033] 13…Internal fluid DETAILED DESCRIPTION

[0034] Hereinafter, one embodiment of the peracetic acid concentration meter 1 of the present invention will be described with reference to the drawings.

[0035] The peracetic acid concentration meter 1 of this embodiment is a device that measures the peracetic acid concentration in the sample solution by immersing the peracetic acid concentration meter 1 in the sample solution. Figure 1 and Figure 2 As shown, the peracetic acid concentration meter 1 includes a container 1 a for storing an internal liquid and a cover 1 b for sealing the container 1 a.

[0036] The container 1a is in the shape of a hollow cylinder with one end surface open and the other end surface closed. When the cover 1b is installed in a manner to close the open end, a space is formed inside it for accommodating the internal liquid 13. In addition, a thread not shown is formed on the inner wall near the open end for installing the cover 1b.

[0037] Furthermore, a septum 11 is provided at a part of the other end surface so as to allow a specific substance contained in the sample solution to pass therethrough and enter the container 1 a .

[0038] The diaphragm 11 allows peracetic acid, hydrogen peroxide, dissolved oxygen, residual chlorine, etc. in the sample solution to pass through, and is made of a material including, for example, silicon, fluororesin, or polyethylene. It should be noted that, as the fluororesin, for example, Teflon (registered trademark) can be used. In addition, as the film thickness of the diaphragm 11, for example, a film thickness of 10 μm to 200 μm can be used.

[0039] The cover 1b seals the container 1a, and a holding member 16 for holding the working electrode 4 and the counter electrode 5 is protruded from the substantially central portion of the container 1a side. When the cover 1b is mounted on the container 1a, the holding member 16 is accommodated in the space formed between the container 1a and the cover 1b. In addition, a connection portion 6 is provided on the opposite side of the container 1a side, and a cable for connecting an external device is mounted on the connection portion 6.

[0040] The holding member 16 is made of an insulating material such as Figure 3 As shown in the figure, the holding member 16 surrounds the working electrode 4 to hold the working electrode 4, and is wound around to hold the counter electrode 5. In addition, the holding member 16 is provided with a spiral groove for mounting the cover 1b on the container 1a, and the cover 1b can be mounted on the container 1a by fitting with a threaded tooth (not shown) provided on the side of the container 1a. Furthermore, the holding member 16 is provided with an air hole 7 for exhausting gas to the outside. It should be noted that a filter for separating gas and liquid is provided at one end of the opening of the air hole 7.

[0041] The working electrode 4 is made of a conductive material such as gold or platinum. Figure 2 and Figure 3 As shown, it is in the shape of a rod, and as Figure 4 As shown, one end thereof is arranged so as to slightly protrude from the front end surface 10 of the holding member 16. In addition, the surface of the working electrode 4 is provided with minute irregularities (not shown).

[0042] The counter electrode 5 is made of a conductive material such as platinum and / or silver-silver chloride (Ag / AgCl), and is configured in a linear shape in the present embodiment.

[0043] like Figure 3 As shown, the working electrode 4 and the counter electrode 5 are connected via a lead 8, and a voltage is applied from a power supply unit (not shown) provided outside via the lead 8. In addition, an ammeter 9 for detecting the current flowing in the lead 8 is provided on the lead 8. It should be noted that the lead 8 and / or the ammeter 9 may also be provided outside the cover 1b.

[0044] And, if Figure 1 and Figure 3 As shown, in a state where the cover 1 b is attached to the container 1 a , the internal liquid 13 is stored in a space formed between the cover 1 b and the container 1 a .

[0045] The internal liquid 13 uses a buffer having a buffering effect on hydrogen ion concentration and does not contain a substance that reacts with peracetic acid. In the present embodiment, the internal liquid 13 is composed only of a buffer. The buffer is not particularly limited as long as it is a buffer, and an acidic buffer, a neutral buffer, an alkaline buffer, etc. can be used, and an acidic buffer or a neutral buffer can be further preferably used. In the present embodiment, for example, a phosphate buffer, an acetate buffer, Tris (hydroxymethyl) methyl aminomethane (Tris, Tris (hydroxymethyl) methyl aminomethane), a boric acid buffer, a citric acid buffer, etc. can be used.

[0046] An intermediate film 12 having wettability to the internal liquid 13 is laminated on the diaphragm 11 disposed inside the container 1a. When the container 1a is attached to the lid 1b, the intermediate film 12 is disposed between the diaphragm 11 and the working electrode 4, so that the working electrode 4 is in contact with the diaphragm 11 via the intermediate film 12. Here, the wettability means that the intermediate film 12 has affinity with the internal liquid 13, the internal liquid 13 is retained in the intermediate film 12, the intermediate film 12 is wetted, and a liquid layer formed by the internal liquid 13 is formed on the surface of the intermediate film 12. As the film thickness of the intermediate film 12, a film thickness of 1 μm to 200 μm can be used.

[0047] In addition, as the material for the intermediate membrane 12, a material having an elastic modulus larger than that of the diaphragm 11 can be used, for example, a material composed of a polymer, particularly polycarbonate, polytetrafluoroethylene (PTFE), a mixed resin obtained by mixing polyethylene and polyimide, polyimide, cellulose, etc.

[0048] The intermediate film 12 is composed of a porous film having numerous pores 12a with a pore diameter of 0.05 μm to 100 μm, which are much smaller than the size of bubbles of oxygen or the like (500 μm or more).

[0049] In addition, a protective film 17 is laminated on the diaphragm 11 disposed outside the container 1a, avoiding the region where the diaphragm 11 contacts the intermediate film 12. The material constituting the protective film 17 is not particularly limited, and for example, polypropylene, PFA, PET, etc. can be used. It should be noted that the protective film 17 is preferably made of a material having a relatively high hardness and substantially preventing substances from passing through.

[0050] However, the peracetic acid concentration meter 1 of the present embodiment includes a permeation suppression layer 18 which is laminated so as to cover the entire surface of the diaphragm on the side in contact with the sample solution and suppresses permeation of organic matter.

[0051] The transmission suppression layer 18 includes, for example, a semipermeable membrane 18 a and a supporting substrate 18 b that supports the semipermeable membrane 18 a .

[0052] The semipermeable membrane 18a only needs to function as a molecular sieve that does not hinder the permeation of peracetic acid and inhibits the permeation of organic matter. Examples thereof include ion exchange membranes of cellulose, cellulose acetate, polyacrylonitrile, and the like, and membranes containing one or more components selected from the group consisting of polytetrafluoroethylene, polyester polymer alloys, and polysulfone.

[0053] The thickness of the semipermeable membrane 18 a may be in the range of 1 nm to 50 μm, and is preferably in the range of 2 nm to 30 μm.

[0054] The supporting substrate 18b may be any substrate that does not hinder the permeation of peracetic acid, and examples thereof include porous films containing resins such as polyethylene, polytetrafluoroethylene, polyphenylene sulfide, and porous polypropylene. The size of the opening formed in the porous film may be, for example, 10 nm or more and 200 nm or less. In order not to hinder the permeation of peracetic acid, the thickness of the supporting substrate 18b is preferably as thin as possible, for example, 5 μm or more and 300 μm or less. The thickness of the supporting substrate 18b is preferably 10 μm or more and 50 μm or less, and more preferably 10 μm or more and 20 μm or less.

[0055] A method for manufacturing the peracetic acid concentration meter 1 , particularly a method for laminating the permeation suppression layer 18 on the separator 11 , will be described below.

[0056] Here, as an example, a case where a cellulose acetate membrane is used as the semipermeable membrane 18 a will be described.

[0057] First, a porous supporting substrate 18 b made of polyethylene, for example, is stacked on the surface of the membrane 11 that contacts the sample solution.

[0058] Next, cellulose acetate is dissolved in a solvent such as acetone or cyclohexane to prepare the above-mentioned semipermeable membrane composition liquid.

[0059] The semipermeable membrane composition liquid is applied to the surface of the porous supporting substrate 18 b using, for example, a 50 μm roll coater and then dried to produce the permeation suppression layer 18 .

[0060] Then, the separator 11 and the permeation suppression layer 18 are fixed by the protective film 17 as described above.

[0061] Next, the operation of the peracetic acid concentration meter 1 configured as above will be described.

[0062] If the cover 1b is mounted on the container 1a, Figure 4As shown, the working electrode 4 is in contact with the separator 11 via the intermediate film 12. Specifically, since the working electrode 4 is arranged so as to protrude from the front end surface 10, the working electrode 4 is in press contact with the separator 11 via the intermediate film 12.

[0063] In addition, an internal liquid 13 is sealed between the container 1a and the cover 1b. Figure 4 As shown, the sealed internal liquid 13 intrudes into the minute gap between the diaphragm 11 and the intermediate film 12 and the minute gap between the intermediate film 12 and the working electrode 4. Here, the intermediate film 12 has wettability to the internal liquid 13, so a liquid layer of the internal liquid 13 is formed on the surface of the intermediate film 12. In addition, since the intermediate film 12 is a porous film, the internal liquid 13 intrudes into the interior of the intermediate film 12 from the pores 12a provided in the intermediate film 12. Therefore, the working electrode 4 is in contact with the intermediate film 12 via the liquid layer, and the intermediate film 12 is also in contact with the diaphragm 11 via the liquid layer, but since the above-mentioned liquid layer is a very thin layer, it can be regarded that the working electrode 4 is substantially in contact with the diaphragm 11 via the intermediate film 12.

[0064] Furthermore, since the working electrode 4 is also immersed in the internal solution 13 , and the counter electrode 5 is also immersed in the internal solution 13 , the working electrode 4 is electrically connected to the counter electrode 5 via the internal solution 13 .

[0065] When the peracetic acid concentration meter 1 is immersed in a sample solution, specific substances such as peracetic acid, hydrogen peroxide, dissolved oxygen, and residual chlorine contained in the sample solution pass through the diaphragm 11, and the specific substances are dissolved in the internal liquid 13, which is contained in the space formed between the container 1a and the cover 1b. Furthermore, when a voltage is applied between the working electrode 4 and the counter electrode 5 via the lead 8 from an unillustrated power supply mechanism, peracetic acid undergoes an oxidation-reduction reaction at the surface of the working electrode 4, and an oxidation-reduction reaction occurs on the surface of the counter electrode 5. Due to these reactions, a current flows in the lead 8, and therefore, if the current value is measured by the ammeter 9, the peracetic acid concentration can be detected.

[0066] For example, the connection portion 6 of the peracetic acid concentration meter 1 may be connected to an external device via a cable or the like, and an output signal indicating the current value measured by the ammeter 9 may be sent to the external device, so that the external device can calculate the concentration of peracetic acid.

[0067] According to the peracetic acid concentration meter 1 configured as described above, the following effects can be achieved.

[0068] A permeation suppression layer 18 that suppresses permeation of organic matter without blocking peracetic acid is laminated on the surface of the membrane 11 that contacts the sample solution. This suppresses permeation of organic matter contained in the sample solution through the membrane 11 .

[0069] As a result, the possibility of the surface of the working electrode 4 being contaminated by organic substances can be reduced, so the accuracy of peracetic acid concentration measurement can be improved compared with the related art.

[0070] Since the permeation suppression layer 18 includes a cellulose acetate membrane as the semipermeable membrane 18 a , permeation of substances having a molecular weight of 200 Da or more can be suppressed. Therefore, permeation of high molecular weight organic substances that may cause contamination of the surface of the working electrode 4 can be suppressed more reliably.

[0071] If the semipermeable membrane composition liquid containing cellulose acetate is directly applied to the surface of the separator 11, the cellulose acetate is repelled from the surface of the separator 11, making it difficult to form a cellulose acetate membrane.

[0072] In this regard, in the peracetic acid concentration meter 1 of the present embodiment, the permeation suppression layer 18 includes a supporting substrate 18b supporting a semipermeable membrane, and a material that does not repel a semipermeable membrane composition liquid containing cellulose acetate is selected as the material of the supporting substrate 18b.

[0073] Therefore, if the supporting substrate 18 b is first laminated on the surface of the separator 11 , and then a semipermeable membrane composition liquid containing cellulose acetate is applied to the surface of the supporting substrate 18 b , the permeation suppressing layer 18 can be easily laminated.

[0074] It should be noted that a semipermeable membrane composition liquid containing cellulose acetate may be first coated on the surface of the supporting substrate 18b and dried to prepare the permeation inhibition layer 18 in advance, and then the permeation inhibition layer 18 may be laminated on the surface of the diaphragm 11 of the peracetic acid concentration meter 1 on the side in contact with the sample solution so that the supporting substrate 18b and the diaphragm 11 are in contact with each other on the surface of the diaphragm 11.

[0075] Since the working electrode 4 is in contact with the diaphragm 11 via the intermediate film 12, the distance between the working electrode 4 and the diaphragm 11 can be shortened, and the intermediate film 12 can prevent the working electrode 4 and the diaphragm 11 from being in close contact without a gap. In addition, the intermediate film 12 has wettability with the internal liquid 13, and a liquid layer formed by the internal liquid 13 is formed on the surface of the intermediate film 12, so that a specific substance dissolved in the internal liquid 13 can be supplied from the liquid layer to the surface of the working electrode 4. Therefore, while the distance between the diaphragm 11 and the working electrode 4 is shortened to improve the responsiveness of the sensor, the situation where the reaction at the surface of the working electrode 4 is prevented from being hindered can be prevented, thereby preventing the sensitivity of the sensor from being deteriorated.

[0076] In the present embodiment, the surface of the working electrode 4 is provided with minute irregularities. The minute irregularities increase the specific surface area in contact with the internal liquid 13 , thereby further improving the responsiveness of the reaction on the surface of the working electrode 4 .

[0077] Furthermore, the internal liquid 13 in which the specific substance is dissolved is supplied to the surface of the working electrode 4 through the fine pores 12a provided in the intermediate film 12, so that the distance until the peracetic acid reaches the surface of the working electrode 4 can be further shortened, and the responsiveness at the surface of the working electrode 4 can be further improved. In addition, since the internal liquid 13 can be supplied to the surface of the working electrode 4 through the fine pores 12a, the peracetic acid can be stably detected.

[0078] In addition, since the pores 12a of the porous film have a pore diameter of 0.05 μm to 100 μm, even if bubbles are generated in the sensor, the bubbles are much larger than the pores 12a and do not remain in the pores 12a. Therefore, the internal liquid 13 can be supplied to the surface of the working electrode 4 through the pores 12a without being blocked by the bubbles, thereby preventing the sensitivity of the sensor from being deteriorated.

[0079] The above-mentioned effects will be described in detail below.

[0080] In conventional diaphragm-type peracetic acid concentration meters, bubbles contained in the sample solution and / or bubbles attached to the sensor may penetrate the gas-permeable diaphragm 11 and enter the sensor, or bubbles may be generated due to the redox reaction on the surface of the working electrode 4. The bubbles remain between the working electrode 4 and the diaphragm 11, thereby hindering the reaction on the surface of the working electrode 4, resulting in a problem of deteriorating the sensitivity of the sensor.

[0081] When measuring peracetic acid contained in a sample solution, peracetic acid naturally decomposes to generate oxygen, and oxygen is also generated by a redox reaction, so bubbles are inevitably generated in the sensor, which deteriorates the sensitivity of the sensor.

[0082] However, the peracetic acid concentration meter 1 of the present embodiment includes an intermediate film 12 composed of a porous film, and the pore size of the pores 12a of the porous film is much smaller than the size of oxygen bubbles (500 μm or more), so the bubbles do not remain in the intermediate film 12. Therefore, the reaction at the surface of the working electrode 4 is not hindered by the bubbles, and the deterioration of the sensor sensitivity due to the generation of bubbles can be prevented.

[0083] In addition, in the peracetic acid concentration meter 1 of the present embodiment, the elastic modulus (bulk elastic modulus) of the intermediate film 12 is greater than the elastic modulus of the diaphragm 11, so the intermediate film 12 is less likely to deform than the diaphragm 11, and can reliably prevent the intermediate film 12 itself from being tightly attached to the surface of the working electrode 4, thereby improving the responsiveness at the working electrode 4.

[0084] Furthermore, since the working electrode 4 is in press contact with the separator 11 via the intermediate film 12 , the distance between the working electrode 4 and the separator 11 can be further shortened, and the responsiveness of the surface of the working electrode 4 can be further improved.

[0085] In addition, since the air hole 7 is provided in the retaining part 16, the internal pressure applied when the cover part 1b is installed in the container 1a can escape from the air hole 7, and as mentioned above, even if bubbles (gas) are generated in the sensor, the bubbles can escape from the air hole 7, thereby preventing failure of the sensor.

[0086] Furthermore, since the protective film 17 is provided on the surface of the diaphragm 11 in contact with the sample solution except for the area of ​​the diaphragm 11 in contact with the intermediate film 12, the diaphragm 11 can be prevented from being damaged by the protective film 17, and the internal liquid 13 can be prevented from leaking to the sample solution side. Moreover, since the protective film 17 having a relatively large hardness is used, damage to the diaphragm 11 can be more reliably prevented. In addition, impurities in the sample solution can be prevented from invading the internal liquid 13 through the diaphragm 11, and the detection accuracy can be improved. Furthermore, if the protective film 17 is composed of a dense material to the extent that it does not substantially allow substances to pass through, the protective film 17 inhibits the penetration of substances, and thus it is possible to more reliably prevent the internal liquid 13 from leaking to the sample solution side and / or impurities in the sample solution from invading the internal liquid 13 through the diaphragm 11.

[0087] Furthermore, by forming the intermediate film 12 with a polymer or the like, and in particular, by forming the intermediate film 12 with polycarbonate, the responsiveness of the working electrode 4 can be further improved.

[0088] The present invention can be modified in various ways without departing from the spirit and scope of the present invention.

[0089] For example, in the above embodiment, the transmission suppression layer 18 is shown to include a semipermeable membrane 18a and a supporting substrate 18b, but the supporting substrate 18b may be omitted if the semipermeable membrane 18a can be directly laminated on the surface of the diaphragm 11 and strength sufficient to maintain the membrane structure can be ensured.

[0090] The peracetic acid concentration meter 1 can also be incorporated into a peracetic acid concentration measuring device, which includes the lead 8, the ammeter 9, a calculation unit that receives a signal output from the ammeter 9 and calculates the peracetic acid concentration, and a display unit that displays the peracetic acid concentration calculated by the calculation unit, etc. The calculation unit and / or the display unit, etc., can function by operating in accordance with a predetermined program through a computer including an amplifier, an A / D converter, a CPU, a memory, a communication port, a display, etc.

[0091] Such a peracetic acid concentration measuring device may further include a light source L for irradiating ultraviolet rays from the outside to the housing of the peracetic acid concentration meter 1 and / or the surface of the transmission suppression layer 18 on the side in contact with the sample solution.

[0092] Examples of the light source L include an LED chip (light emitting diode chip) that emits light having a wavelength of approximately 400 nm or less, more preferably 370 nm or less.

[0093] The light emitted from the light source L only needs to have a wavelength of about 500 nm or less, and may be, for example, blue light having a wavelength of 500 nm or less, or violet light having a wavelength of 430 nm or less.

[0094] In this embodiment, as long as the ultraviolet rays emitted from the light source L are set at the outer surface of the transmission suppression layer 18, for example, 8 mW / cm 2 Ultraviolet light of about 100% intensity will suffice.

[0095] More specifically, the light source L can emit 1mW / cm 2 Above and 15mW / cm 2 The following light is sufficient, and more preferably, as long as it can emit 2mW / cm 2 Above and 12mW / cm 2 of light.

[0096] The protective film 17 for protecting the diaphragm may not be separately provided, and for example, the front end portion of the container 1 a may cover the diaphragm 11 as a protective member so as to avoid the region where the diaphragm 11 and the intermediate film 12 are in contact.

[0097] Example

[0098] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0099] In this example, a simulated sample containing an organic substance was used to examine whether the presence of a transmission suppression layer affects the sensitivity of a peracetic acid concentration meter.

[0100] (Example 1)

[0101] In Example 1, a peracetic acid concentration meter having the permeation suppression layer on the sample solution side of the diaphragm is used. As the permeation suppression layer, a permeation suppression layer having a supporting substrate laminated on the surface of the diaphragm and a semipermeable membrane supported by the supporting substrate is used. In this example, a polyethylene film is used as the supporting substrate, and a cellulose acetate film is used as the semipermeable membrane. At this time, the average thickness of the polyethylene film is 100 μm, and the average thickness of the cellulose acetate film is 2 to 3 nm. In addition, a silicon film is used as the diaphragm, a polypropylene film is used as the protective film, and a polycarbonate film is used as the intermediate film.

[0102] As the simulated sample, an aqueous solution containing 0.4% peracetic acid, 10 ppm of C16 saturated fatty acid, and 10 ppm of C18 saturated fatty acid was used.

[0103] The peracetic acid concentration of the simulated sample was measured for 5 consecutive days to examine changes in the sensitivity of the peracetic acid concentration measurement. The temperature of all simulated samples was set to 25°C.

[0104] The peracetic acid concentration of the same simulated sample as that measured by the peracetic acid concentration meter of this embodiment was measured in parallel with the benchtop peracetic acid monitor, and the peracetic acid concentration measured by the peracetic acid concentration meter was compared with the peracetic acid concentration measured by the benchtop peracetic acid monitor to calculate the sensitivity change of the peracetic acid concentration meter. The experiment was performed twice.

[0105] As the above-mentioned desktop peracetic acid monitor, RK-POXII model manufactured by Riko Kyo Corporation was used. This peracetic acid detector measures the peracetic acid concentration by utilizing the reaction between peracetic acid and iodine.

[0106] As a result, the sensitivity after 5 days decreased by -6% in the first measurement and -7% in the second measurement compared with the initial measurement. The decrease in sensitivity in both experiments fell within the measurement error range of ±7% of the above-mentioned desktop peracetic acid monitor obtained in advance.

[0107] (Comparative Example 1)

[0108] The peracetic acid concentration of the simulated sample was measured for 5 consecutive days in the same manner as in Example 1 using a peracetic acid concentration meter that differed from the peracetic acid concentration meter of Example 1 only in that it did not include the transmission inhibition layer. The peracetic acid concentration was compared with the peracetic acid concentration measured by the desktop peracetic acid monitor to examine changes in the sensitivity of the peracetic acid concentration measurement.

[0109] As a result, the sensitivity after 5 days was -51% in the first time and -26% in the second time, which were significantly lower than those in Example 1 in both times.

[0110] The peracetic acid concentration meters of Example 1 and Comparative Example 1 differ only in the presence or absence of the transmission suppression layer. Therefore, it is considered that the sensitivity change of the peracetic acid concentration meter is affected by the presence or absence of the transmission suppression layer.

[0111] Therefore, from the results of Example 1 and Comparative Example 1, it can be seen that the peracetic acid concentration meter of Example 1 has a transmission suppression layer, and thus the sensitivity of the peracetic acid concentration meter hardly changes even when a sample containing organic matter is continuously measured for a long period of time.

[0112] In the peracetic acid concentration meter having the transmission suppression layer, it is possible to suppress the mixing of organic matter contained in the sample solution into the internal solution, thereby suppressing the contamination of the working electrode surface. As a result, it is considered that the sensitivity of peracetic acid concentration measurement is stabilized.

[0113] Industrial Applicability

[0114] According to the peracetic acid concentration meter of the present invention, contamination of the working electrode surface by organic matter from a sample solution can be suppressed, and the peracetic acid concentration can be measured with higher accuracy than before.

Claims

1. A peracetic acid concentration meter, characterized in that A diaphragm-type peracetic acid concentration meter for measuring the peracetic acid concentration of a sample solution, comprising: a diaphragm for peracetic acid to pass through; an internal liquid dissolving the peracetic acid that has permeated the diaphragm; a working electrode and a counter electrode immersed in the internal liquid; A permeation suppression layer is stacked on the surface of the membrane in contact with the sample solution and suppresses the permeation of organic matter, wherein the permeation suppression layer covers the entire surface of the membrane in contact with the sample solution; as well as fixing the diaphragm and the protective film of the permeation suppression layer, The permeation suppression layer includes a semipermeable membrane and a supporting substrate, and the supporting substrate supports the semipermeable membrane so that the permeation suppression layer can be laminated on the surface of the diaphragm on the side in contact with the sample solution.

2. The peracetic acid concentration meter according to claim 1, characterized in that: The supporting substrate is a porous film.

3. The peracetic acid concentration meter according to claim 1, characterized in that: The permeation suppression layer includes the support substrate laminated on the surface of the diaphragm in contact with the sample solution, and the semipermeable membrane laminated on the surface of the support substrate on the opposite side to the diaphragm.

4. The peracetic acid concentration meter according to claim 2, characterized in that: The permeation suppression layer includes the support substrate laminated on the surface of the diaphragm in contact with the sample solution, and the semipermeable membrane laminated on the surface of the support substrate on the opposite side to the diaphragm.

5. The peracetic acid concentration meter according to any one of claims 1 to 4, characterized in that: The semipermeable membrane is a membrane containing one or more components selected from the group consisting of cellulose, cellulose acetate, polyacrylonitrile, polytetrafluoroethylene, polyester polymer alloys, and polysulfone.

6. A peracetic acid concentration measuring device, characterized in that: A peracetic acid concentration meter according to any one of claims 1 to 5 is provided.

7. The peracetic acid concentration measuring device according to claim 6, characterized in that: The device further includes a light source for irradiating ultraviolet rays to the surface of the peracetic acid concentration meter in contact with the sample solution.

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