JP2022122597A - Preparation method of ozone indicator and ozone indicator - Google Patents

Abstract

To provide a preparation method of an ozone indicator capable of easily evaluating by visual observation whether a treatment is properly done as intended after a sterilization treatment by arranging a sterilization atmosphere due to an ozone gas.SOLUTION: An ozone indicator 21 is one that changes color according to the product of a concentration of ozone gas and its exposure time. The ozone indicator is prepared by dissolving bromophenol blue or Coomassie brilliant blue as a coloring agent in a pH buffer solution to prepare a basic solution, dropping this basic solution onto a filter made of a hydrophilic membrane made of, for example, polyvinylidene fluoride resin, and then drying this filter.SELECTED DRAWING: Figure 5

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for easily and visually evaluating whether sterilization by ozone gas or the like has been properly performed as intended.

Humanity has been plagued by epidemics of many infectious diseases so far, and since the beginning of the 20th century, the Spanish flu, Ebola hemorrhagic fever, acquired immunodeficiency syndrome (AIDS), severe acute respiratory syndrome (SARS), and highly pathogenic Recently, the infection of the new coronavirus (COVID-19) such as bird flu virus is progressing on a global scale.
By the way, it is known that ozone gas having an oxidizing action is effective for chemical decomposition such as deodorization and renders (sterilizes) harmful bacteria harmless. Ozone gas can be generated by a small portable device, and has the characteristic of being decomposed into oxygen in a short time without leaving traces, and is excellent for sterilizing closed spaces and material surfaces. Such ozone gas is reported to attenuate the activity of, for example, the novel coronavirus, which is prevalent worldwide at the time of filing the present application (Non-Patent Document 1).

This finding indicates the possibility that in medical settings such as hospitals, coronavirus-contaminated areas can be closed and ozone gas can be released into the contaminated space to inactivate the coronavirus in the contaminated area. In addition, sterilization treatment with ozone gas is a promising means in terms of the possibility of opening up a way to reuse the shortage of protective equipment for infection.
Here, it is widely known that the progress of sterilization treatment using ozone gas depends on the CT value, which is the product of the ozone gas concentration (ppm) and the contact time (minutes) in the treatment environment (for example, non-patent literature 2). Therefore, there is a measure to install an ozone concentration meter in a medical space such as a hospital or a space containing used protective equipment for infection, calculate the CT value based on the measured ozone gas concentration, and judge the end of sterilization treatment with ozone gas. Conceivable.

However, medical spaces such as hospitals are large, and the space containing used protective equipment for infection may also be large, and it is not easy to spread the ozone gas released into these spaces evenly throughout the space. Then, when air stagnation occurs, there is a greater possibility that the ozone gas concentration will be lower in the stagnation part than in other parts. If the concentration of ozone gas in a space where local retention is likely to occur is represented by, for example, the measurement value of one ozone concentration meter, there is a high possibility of insufficient decontamination in some spaces, protective equipment, and medical spaces after decontamination. use of personal protective equipment and reuse of protective equipment can cause the spread of infection.

In such a case, if there is an ozone indicator that can be prepared relatively cheaply and can visually determine the change before and after exposure to ozone gas, etc., it can be placed in each of the treatment spaces, for example, where there is a concern about stagnation. Using the change in the appearance of the ozone indicator as an index, it is possible to judge whether the decontamination of the entire treatment space has been completed as intended.
Here, the "ozone indicator" is an indicator that does not have an electric detector and chemically changes according to the time of exposure to ozone gas, and that change correlates with the progress of ozone treatment (decontamination, sterilization). say.

Patent Literature 1 proposes an integrator that serves as an index for sterilization treatment with an oxidative sterilant. The integrator contains an indicator chemical and ozone is listed as one of several oxidative disinfectants. An integrator (corresponding to an ozone indicator) described in Patent Literature 1 has an indicator chemical substance formed on a substrate (filter paper, glass filter, etc.).

The integrator is placed in the sterilizer with a certain load of instruments to be processed. In the disinfection process, the oxidative disinfectant reacts with the indicator chemical and reduces the amount of indicator chemical on the integrator. After exposing the indicator chemical to an oxidative disinfectant (disinfecting), the indicator chemical reacts with the dye precursor chemical to form a colored product that remains on the substrate due to the intensity of the color of the colored product. Determine the amount of indicator chemicals. The amount of indicator chemical remaining correlates with the intensity of color development, which is assessed visually or spectrophotometrically and is a measure of the effectiveness of the disinfection treatment.

US Pat. No. 6,200,000 proposes a biological indicator for oxidative sterilants. The biological indicator is exposed to a first compartment containing spores of a microbial species pretreated with "a compound containing a transition metal ion that is reactive with an oxidative sterilant such as ozone" and an oxidative sterilant. A second compartment containing a growth medium adapted to combine with the contents of the first compartment after the first compartment is formed. In a biological indicator, the growth medium contains an agent selected to indicate the viability of the spores after exposure to an oxidative sterilant.

It is understood that the biological indicator is used in a sterilization process with the object to be sterilized in a sterile environment.
In addition, since the name of the treatment described above may not include complete sterilization, the term "sterilization" is used as a unified term except for the name.

JP 2006-280933 A Japanese Patent Publication No. 2016-511056

(World's first) confirmation of inactivation of new coronavirus by ozone, February 14, 2020, Nara Medical University, MBT Consortium (Internet, URL: http://www.naramed-u) .ac.jp/university/kenkyu-sangakukan/oshirase/r2nendo/documents/press_2.pdf) Report on Ozone Gas Disinfection in Bedding Laundry Work, January 19, 2007, Ministry of Health, Labor and Welfare, Bedding Laundry Special Committee (Internet, URL: http://www.mhlw.go.jp/shingi/2007/01/ s0119-7.html)

The integrator proposed in WO 2005/010001 requires a treatment to form a colored product after a sterilization treatment. The time required to form a colored product is about 5 to 6 minutes if the sterilization cycle is ineffective, that is, if the sterilization is incomplete. .
The biological indicator proposed in Patent Literature 2 also lacks convenience in that after the sterilization process is completed, a process for further growing the bacteria in the indicator is required.

The present invention has been made in view of the above-mentioned problems, and an ozone indicator that can easily and visually evaluate whether or not treatment has been appropriately performed as intended after sterilization by arranging it in a sterilization environment using ozone gas, etc.; The object is to provide a method for its preparation.

The ozone indicator prepared by the preparation method according to the present invention changes color depending on the exposure time of ozone gas.
The method for preparing this ozone indicator is to dissolve bromophenol blue or Coomassie brilliant blue as a coloring agent in a pH buffer solution to adjust the base solution, drop the base solution onto a filter made of a hydrophilic membrane, and then dry the filter. It is something to do.

As used herein, "drying" refers to the process of removing excess water from the filter. As drying means, natural drying, drying with hot or cold air, drying under reduced pressure at a low temperature, and the like can be employed.
The pH buffer preferably has a buffering range of pH 6-9.
The pH buffer is preferably a phosphate buffer.
Preferably, sodium thiosulfate is further added to the basic solution to prepare an adjustment solution, and the adjustment solution is added dropwise to a filter made of a hydrophilic membrane.

It is effective to increase the content of sodium thiosulfate in the adjustment liquid in order to delay the discoloration according to the ozone gas exposure time.
A PVDF hydrophilic membrane is preferred as the hydrophilic membrane.
The ozone indicator according to the present invention changes color depending on the exposure time of ozone gas, and is dried by dripping a pH buffer solution that dissolves bromophenol blue or Coomassie brilliant blue on a filter made of a hydrophilic membrane.

Another ozone indicator according to the present invention is dried by dripping bromophenol blue or Coomassie brilliant blue and a pH buffer solution that dissolves sodium thiosulfate on a filter made of a hydrophilic membrane.
A PVDF hydrophilic membrane or a PTFE hydrophilic membrane is preferred as the hydrophilic membrane.

According to the present invention, it is possible to provide an ozone indicator preparation method and an ozone indicator that can be easily evaluated by visual observation whether or not the treatment has been appropriately performed as intended after the sterilization treatment by placing it in a sterilization environment using ozone gas.

FIG. 1 is a front view of the test apparatus used for ozone exposure to the ozone indicator. FIG. 2 is a plan view of the testing device. FIG. 3 is a diagram showing the concept of extracting the discolored portion from the ozone indicator. FIG. 4 is a photograph showing the degree of discoloration of potassium iodide starch paper due to exposure to ozone gas. FIG. 5 is a diagram showing changes in color density with respect to CT values in Table 1. FIG. FIG. 6 is a diagram showing changes in color density with respect to CT values in Table 2. In FIG. FIG. 7 is a diagram showing the relationship between the CT value and the color density of the ozone indicator to which the basic liquid was dropped. FIG. 8 is a diagram showing the relationship between the CT value and the color density of an ozone indicator to which an adjustment liquid containing 3% sodium thiosulfate was dropped. FIG. 9 is a diagram showing the relationship between the CT value and the color density of an ozone indicator to which an adjustment liquid containing 5% sodium thiosulfate was dropped. FIG. 10 is a diagram showing the relationship between the CT value and the color density of an ozone indicator to which an adjustment liquid containing 7% sodium thiosulfate was dropped. FIG. 11 is a diagram combining FIGS. 7 to 10 into one. FIG. 12 is a photograph showing the results of ozone gas exposure after preparing an ozone indicator using a solution in which potassium iodide was added to a base solution. FIG. 13 is a diagram showing changes in color density of the ozone indicator depending on the material of the hydrophilic film. FIG. 14 is a diagram showing the pH of the base liquid and the degree of color density reduction of the ozone indicator due to exposure to ozone gas. FIG. 15 is a photograph showing the results of preparing an ozone indicator using Coomassie Brilliant Blue and exposing it to ozone gas. FIG. 16 is a diagram showing the relationship between the CT value and color density of an ozone indicator using Coomassie Brilliant Blue.

FIG. 1 is a front view of a test device 1 used for ozone exposure to an ozone indicator, and FIG. 2 is a plan view of the test device 1. FIG.
The test apparatus 1 comprises a container 11, an ozone generator 12, a humidifier 13, a thermometer, a hygrometer 14, an ozone concentration meter 15 and a CT value recorder.
The container 11 is a rectangular parallelepiped hollow box, the top of which is closed with a removable lid 16 .

The container 11 is made of transparent vinyl chloride resin so that the inside can be easily observed from the outside.
The ozone generator 12 is a known stationary ozone gas generator that incorporates an ozone lamp (ultraviolet lamp) and a forced circulation fan.
The humidifier 13 is a device that vibrates a piezoelectric vibrator by applying a high-frequency AC voltage to generate ultrasonic waves to generate mist from water and discharge the fog to the outside from an outlet 17 .

The hygrometer 14 is a device that measures and displays the humidity inside the container 11 . A hygrometer 14 is housed in the container 11 .
The ozone concentration meter 15 is a known device installed inside the container 11 to measure the ozone gas concentration inside the container 11 . The ozone concentration meter 15 has an external control unit (not shown), which digitizes the measured ozone concentration and transmits it to the CT value recording device.

The CT value recording device calculates the increment of the CT value (=ozone concentration×interval time) from the ozone concentration and the interval (time) of transmission transmitted from the ozone concentration meter 15, and calculates this increment from the time when the decomposition process is started. is integrated and the integrated value is displayed on the display device. A personal computer is used as the CT value recording device.
The ozone indicator according to the present invention is placed in an environment exposed to ozone gas, and is used as an indicator for determining, for example, whether the sterilization treatment was performed as expected and whether the decomposition of harmful substances was completed as intended after treatment. Specifically, the ozone indicator is formed to have different degrees of color change depending on the concentration of ozone and the length of time of exposure to ozone (CT value). In the ozonation, if the ozone indicator placed near the object to be ozonized shows a color change corresponding to the CT value when the treatment is completed after the ozonation is completed, the object to be ozonized is the intended ozonation. is deemed to have been done appropriately.

The ozone indicator is an indicator for determining after the fact whether or not the intended treatment (sterilization, decomposition, etc.) of the object to be ozonized has actually been completed. The ozone indicator is estimated from the measured CT value, for example, in the dead zone (gas retention area, non-convection area) where the ozone gas does not spread sufficiently in the ozone treatment environment and the concentration tends to be lower than the measured value of the ozone concentration meter. It is used to evaluate the actual ozonation progress as opposed to the estimated ozonation progress.

Next, the basic preparation method of the ozone indicator according to the present invention will be explained.
For the ozone indicator, bromophenol blue (hereinafter referred to as "BPB") was used as a coloring (coloring) agent for visually determining whether or not the ozone gas exposure environment reached the target CT value.
The ozone indicator was first dissolved in 0.025 mol/L phosphate buffer (pH 6.8) so that BPB was 0.02%. In addition, "%" indicating a component ratio in this document refers to "% by weight" unless otherwise specified.

As BPB, special grade reagent sold by Fujifilm Wako Pure Chemical Industries, Ltd. was used. A 0.025 mol/L phosphate buffer was prepared using a neutral phosphate standard solution (pH 6.86) from the pH standard solution set 101-S in the LAQUA (registered trademark) series sold by Horiba.
A solution obtained by dissolving BPB in a phosphate buffer is hereinafter referred to as a "basic solution".
The ozone indicator was obtained by dripping the base liquid onto a hydrophilic membrane made of polyvinylidene fluoride resin (hereinafter referred to as "PVDF") and drying it naturally (by leaving it indoors). As the PVDF hydrophilic membrane, a membrane filter (registered trademark “Durapore”) manufactured by Merck & Co. with a pore size of 5.0 μm and a diameter of 47 mm was used.

The appearance of the ozone indicator obtained by natural drying is bluish-purple with blue emphasized, and does not visually give a sense of moisture.
Potassium iodide starch paper sold by Advantech Toyo Co., Ltd. was used for comparison with the ozone indicator for the display function (color change) of the presence or absence of exposure to ozone gas and the degree of exposure.
The purpose of the ozone exposure test of the ozone indicator is to determine the relationship between the degree of discoloration and the CT value, and to examine whether the ozone indicator clearly discolors as the CT value increases.

After the ozone indicators 21, 21, 21 are placed on the sample table 18 installed in the test apparatus 1, the container 11 is sealed, the ozone generator 12 is activated, and the CT value is obtained from the measurement value of the ozone concentration meter 15 and the elapsed time. An increase in CT value was observed by a recording device. At this time, when the test environment needed to be highly humid, the humidifier 13 was operated.
The control unit of the ozone concentration meter 15 controlled the operation of the ozone generator 12 so that the ozone gas concentration reached a predetermined concentration (5 ppm or 30 ppm) based on the measurement value of the ozone concentration meter 15 .

The temperature inside the container 11 was set by setting the temperature of the air conditioner in the room where the test apparatus 1 was installed so that the temperature inside the container 11 was maintained at 20° C. Checked periodically by pair.
The ozone gas exposure test always uses three ozone indicators prepared under the same conditions, and for the ozone indicator under one preparation condition, the final CT value for ending the ozone gas exposure test is variously changed, for example, the CT value in the case of Table 1 described later. The ozone gas exposure test was performed four times each at 50, 100, 200 and 300. In the case of a CT value of 0, the prepared ozone indicator was directly used as an object for color tone (color density) measurement.

The ozone indicator 21 is blue-purple before being exposed to ozone gas, and its color decreases as it is exposed to ozone gas, and finally becomes colorless.
Next, a method for evaluating the degree of color reduction of the ozone indicator 21 by an ozone gas exposure test will be described.
FIG. 3 is a diagram showing the concept of extracting the subtractive color measurement portion from the ozone indicator 21. As shown in FIG.

This evaluation method is limited to the present specification for determining the degree of color reduction in the ozone gas exposure test of the ozone indicator 21, and evaluates the degree of color reduction of the ozone indicator 21 used for actual ozone gas treatment such as sterilization and decomposition. not a thing Judgment of the degree of color reduction of the ozone indicator 21 in the ozone gas treatment at the practical stage is assumed to be performed visually because promptness is required.

The ozone indicator 21 exposed to the ozone gas environment in the test apparatus 1 until reaching a predetermined CT value is placed on the filter paper 22 after being removed from the container 11 . The filter paper 22 to be used is a qualitative filter paper No. manufactured by Advantech. 2.
The ozone indicator 21 placed on the filter paper 22 is photographed under uniform conditions with a digital camera fixed to a stand under fluorescent lighting. “Unified conditions” means the same (unified) conditions such as the camera, the distance between the camera and the subject, the brightness of the shooting environment, the number of shooting pixels, the shooting sensitivity, the aperture value, the shutter speed, the white balance, etc. is.

The entire filter paper 22 including the ozone indicator 21 was photographed, and the image data was imported into a personal computer, and the ozone indicator was analyzed using analysis software ImageJ1.52v (URL: https://imagej.jaleco.com/). 21 color densities are determined.
In the personal computer, the captured image is decomposed into the elements of the three primary colors (RGB) of light by ImageJ1.52v, and the R (red) element is a part 23 of the ozone indicator 21 and the same area as this. The respective densities of portions 24 of filter paper 22 are determined. An image decomposed into three elements of RGB is monochrome with only light and dark, and the required "density" is actually "brightness" in the red element (red channel).

The aforementioned "color density of the ozone indicator 21" is a value obtained by subtracting the "density" value of the filter paper 22 from the "density" value of the ozone indicator 21 in the red element.
Each value of "color density" in each table below is a value obtained by multiplying the value obtained by the method described above (using ImageJ1.52v) by "-1".
FIG. 4 is a photograph showing the degree of discoloration of potassium iodide starch paper in the ozone gas exposure test.

Table 1 shows changes in color density of the ozone indicator 21 depending on the base liquid.
FIG. 5 is a diagram showing changes in color density with respect to CT values in Table 1. FIG.

The ozone gas exposure test of the potassium iodide starch paper and the ozone gas exposure test in Table 1 were performed by operating the humidifier 13 to maintain the humidity around 70%.
"Water (-)" in Fig. 4 indicates the result of using the obtained potassium iodide starch paper as it is for the ozone gas exposure test, and "water (+)" indicates the potassium iodide starch paper on which reverse osmosis water was dripped in advance. is used for the ozone gas exposure test.

When the potassium iodide starch paper was exposed to ozone gas ("water (-)"), it was lightly colored with a mottled purple pattern by a CT value of 10, but by a CT value of 50, the purple color faded slightly. Potassium iodide starch paper ("water (+)") to which water was dripped before exposure to ozone gas rapidly developed a purple color by a CT value of 10, but with continued exposure, the purple color weakened, and at a CT value of 50, the peripheral area It was the extent that a purple color remained.

From the above results, the potassium iodide starch paper, as it is, has a small color reduction fluctuation range, and is not practical as an index in an ozone gas exposure environment. In addition, although the potassium iodide starch paper on which water was dripped in advance was also clearly colored, it faded in spots and it was not clear which part to evaluate, and it was difficult to clarify the relationship with the reached CT value. In addition, since the color changes to a mottled pattern, the reproducibility of the color change is also unreliable, and it is judged that it is not suitable as an ozone indicator (index for a specific CT value) associated with the CT value.

On the other hand, with the ozone indicator 21 using the basic solution, as shown in FIG. 5, there is a clear correlation between the increase in CT value and the change in color density, and when the CT value exceeds a certain value, the coloring due to BPB disappears. Therefore, the ozone indicator 21 using the basic liquid can be used to determine whether or not the object to be treated is actually exposed to the ozone gas under the conditions corresponding to the attained CT value when the sterilization treatment or the like is performed using the ozone gas. .

Here, the "reached CT value" means a specific CT value for judging the end of decomposition and sterilization by ozone gas. As described above, the "CT value" is the product of the ozone gas concentration in the decomposition and sterilization environment and the treatment time.
Table 2 shows the result of examining the influence of the humidity of the ozone gas atmosphere on the discoloration (change in color density) of the ozone indicator 21 .

FIG. 6 is a diagram showing changes in color density with respect to CT values in Table 2. In FIG.
From Table 2 (see also FIG. 6), it seems that the humidity of the ozone gas exposure environment has no or negligible effect on the change in color density of the ozone indicator 21 as the CT value increases.
It is known that in the decomposition treatment of harmful substances using ozone gas, the humidity of the treatment environment affects the degree of decomposition (Japanese Patent No. 6301329). Even in a high-humidity environment, it is possible to determine the completion of decomposition, etc., based on the CT value. The CT value itself is the product of "ozone concentration" and "exposure time" and is not affected by the humidity of the environment. can be used as an index to replace or confirm the CT value obtained by measurement with an ozone concentration meter.

With the ozone indicator 21 using the basic liquid, the coloring due to BPB disappears when the CT value is around 50, and the color density becomes almost zero (achromatic color = colorless). . The ozone indicator 21 using the basic liquid is useful for visual judgment as to whether the CT value of the ozone gas treatment environment has reached 50 or not.
In order to further increase the CT value at which the fading of the ozone indicator 21, specifically colorlessness, can be visually confirmed, an ozone indicator was prepared by adding sodium thiosulfate, which has a reducing action, to the basic solution, and the ozone gas exposure test was performed to reduce the color reduction. examined the extent.

Table 3 shows ozone indicators obtained by dropping a solution prepared by dissolving sodium thiosulfate in a base solution so as to have a plurality of different concentrations (hereinafter referred to as "adjustment solution") on a PVDF hydrophilic membrane and air-drying it. shows the relationship between the CT value and the color density in the ozone gas exposure test.
Regarding the humidity in the ozone gas exposure environment, the humidifier 13 was operated to keep the humidity inside the test apparatus 1 at around 70%.

Figure 7 shows the results of an ozone gas exposure test using an ozone indicator with a basic solution without sodium thiosulfate, and Figures 8 to 10 show ozone indicators with adjusted solutions adjusted to 3, 5, and 7% sodium thiosulfate, respectively. As a result of the ozone gas exposure test in use, FIG. 11 is a diagram combining FIGS. 7 to 10 into one.
From FIGS. 8 to 10, even in the ozone indicator using the adjustment liquid, fading progresses as the CT value increases, and each eventually becomes colorless (color density is zero). Further, from FIG. 11, it can be seen that as the amount of sodium thiosulfate added to the base solution increases, the CT value for colorlessness increases.

The colorlessness of the ozone indicator prepared by dropping the adjustment liquid can be easily visually confirmed, and by placing it in an ozone gas treatment environment, it can be verified whether or not the ozone gas has been appropriately exposed.
By changing the amount of sodium thiosulfate added to the base solution (concentration of sodium thiosulfate in the adjustment solution), an ozone indicator showing any desired CT value can be prepared.

It is presumed that the fading (decrease) of the ozone indicator due to exposure to ozone gas progresses as BPB (bromophenol blue) is oxidized by ozone gas and its dyeing root changes. In addition, in the ozone indicator using the adjustment liquid, the ozone gas reaching the ozone indicator reacts with sodium thiosulfate, which has a reducing action, so that the effect of ozone gas on BPB is reduced compared to the ozone indicator using the basic liquid. and is thought to delay its fading (color reduction).

As a result, by adding sodium thiosulfate having a reducing property to the basic solution (as a conditioning solution) and using it to prepare an ozone indicator, the exposure amount at which BPB is decolored by ozone gas is in the range of CT value 50 to 400. can be adjusted in multiple steps.
Next, potassium iodide, which has a reducing action like sodium thiosulfate, was examined for the effect of delaying the fading of BPB.

FIG. 12 is a photograph showing the results of ozone gas exposure after preparing an ozone indicator using a solution in which potassium iodide was added to a base solution.
Referring to FIG. 12, the coloring due to BPB is clearly maintained at a CT value of 100 (FIG. 12(b)), and the coloring due to BPB remains light even at a CT value of 200 (FIG. 12(b)).

The effect of delaying BPB color reduction by adding 0.1% potassium iodide to the base solution corresponds to the effect of delaying BPB color reduction by adding 3% to 5% sodium thiosulfate shown in FIG. Excessive addition of potassium iodide (for example, 1%) to the base solution makes it difficult to determine the degree of color reduction of BPB due to the coloring caused by potassium iodide itself. It is recognized that it contributes to the delay of color reduction.

Table 4 shows the results of examining the difference between the PVDF hydrophilic membrane and the PTFE hydrophilic membrane when used as the ozone indicator.
The PVDF hydrophilic membrane is a 0.45 μm pore size, 47 mm diameter membrane filter (“Durapore®”) manufactured by Merck. The PTFE hydrophilic membrane is a membrane filter with a pore size of 0.5 μm and a diameter of 47 mm sold by Advantech Toyo Co., Ltd.

Each ozone indicator with a different hydrophilic membrane material was prepared using an adjustment liquid in which potassium iodide was dissolved to a predetermined concentration. Same as Create.
The humidifier 13 was operated so that the humidity in the ozone gas exposure environment was around 70%.

Further, the relationship between the CT value and the degree of discoloration (color density) of these ozone indicators was determined by the same procedure as Tables 1 and 2, etc., obtained by exposure to ozone gas using test apparatus 1.
The ozone gas concentration during exposure to ozone gas was 30 ppm.
Note that Table 4 shows only the average of three points of color density.

FIG. 13 is a diagram showing changes in color density of the ozone indicator depending on the material of the hydrophilic film.
From Table 4 and FIG. 13, when PTFE is adopted as the hydrophilic membrane of the ozone indicator, the degree of color reduction of the ozone indicator is moderated compared to the case where the hydrophilic membrane of PVDF is used, and as an ozone indicator with a larger CT value Expected use.

The pore size (0.45 μm) of the PVDF hydrophilic membranes (Runs 50 to 54) used here is different from the pore size (5.0 μm) in Runs 22 to 28 in Table 3. Since they are almost the same, it is considered that the pore size of the hydrophilic membrane does not greatly affect the color reduction of the ozone indicator.
Table 5 shows the results of examining the relationship between the CT value and the degree of color reduction of the ozone indicator using the basic solution prepared by changing the pH of the solvent for dissolving BPB.

The pH 4, pH 7, and pH 9 buffers in Table 4 are pH standard solutions (phthalate standard solution (pH 4.01), phosphate standard solution (pH 6.86), and boric acid standard solution (pH 6.86) sold by Horiba, Ltd.). pH 9.18)) was used. The solvent used for pH 13.5 is 1 N (1 N, 1 mol/L) potassium hydroxide (KOH). The pH of the KOH solution is a value actually measured with a pH meter.

BPB was dissolved in each of these solvents to a concentration of 0.02%. These are also hereinafter referred to as "adjustment liquids".
The method for producing the ozone indicator using each adjustment liquid having a different pH is the same as the method for producing the ozone indicator using the PVDF hydrophilic film described above.
The humidifier 13 was operated so that the humidity in the ozone gas exposure environment was around 70%. The ozone gas concentration during exposure to ozone gas is 30 ppm.

Further, the color density of each pH in Table 5 was obtained by the same procedure as that for obtaining the color density in Tables 1, 2 and the like.

FIG. 14 is a diagram showing the pH of the base liquid and the degree of color reduction (decrease in color density) of the ozone indicator due to exposure to ozone gas, created based on Table 5. FIG.
From Table 5 and FIG. 14, it can be seen that there is no difference in color density change of the ozone indicator within the range of pH 4 (strictly speaking, pH 4.01) to pH 13.5. Here, the ozone indicator prepared using 1N KOH is somewhat difficult to put into practical use because the coloring due to BPB is decolorized before one day elapses.

The buffer used for the base solution or adjustment solution is not limited to phosphate buffer, and various buffers can be used. BPB is said to have a color change range (yellow in acidity, bluish purple in basicity) at pH 3.0 to 4.6 (“Acid dissociation equilibrium and change in absorbance”, URL: http://kuchem.kyoto-u .ac.jp/ubung/yyosuke/uebung/abindeq/abindeq1.htm, Hayashi Pure Chemical Industries Co., Ltd., "Color change range of indicators", URL: https://direct.hpc-j.co.jp/page/color ). Therefore, if the pH of the base solution and the adjustment solution is at least in the range of pH 6 to pH 9, the color tone (bluish purple) of the ozone indicator does not change over time and during use, and only the gradation can be visually observed during use.

Next, the results of examination of Coomassie Brilliant Blue (hereinafter referred to as "CBB") as a coloring agent for ozone indicators are shown.
Table 6 shows the relationship between the CT value of the ozone indicator and the degree of color reduction depending on the base solution prepared using CBB.
The base solution used in this study was obtained by dissolving CBB in 0.025 mol/L phosphate buffer (pH 6.8) so that the concentration in the base solution was 0.1%.

Here, the "basic solution" refers to a solution obtained by dissolving CBB in a solvent (phosphate buffer), and has the same meaning as the basic solution for BPB, although the coloring agent is different.
Special grade CBB sold by Fujifilm Wako Pure Chemical Industries, Ltd. was used.
The preparation of the ozone indicator using this basic solution, the apparatus for ozone gas exposure using this ozone indicator, and the exposure conditions such as ozone gas concentration, humidity and temperature are the same as when Table 3 was obtained. Also, the method of determining the color density after exposure to ozone gas is the same as in the case of the ozone indicator using BPB.

FIG. 15 is a photograph showing the results (ozone indicator) of preparing an ozone indicator using CBB as a coloring (coloring) agent and exposing it to ozone gas, and FIG. 16 is a diagram showing the relationship between the CT value and color density in Table 6. be.
15 and 16, the ozone indicator using CBB remains colored at an ozone gas exposure CT value of 1000, and is slightly bluish even at a CT value of 3000 (although it is difficult to distinguish from monochrome FIG. 15). ing. An ozone indicator using CBB is useful when a high CT value (for example, 4000 or more) is required at the end of sterilization treatment by exposure to ozone gas.

As a substrate for dripping the base liquid or adjustment liquid in the ozone indicator, other hydrophilic resin films can be used instead of the PVDF hydrophilic film and the PTFE hydrophilic film. The hydrophilic resin film is, for example, a polycarbonate film, a hydrophilic polyethersulfone film, or the like.

INDUSTRIAL APPLICABILITY The present invention can be used when it is necessary to easily visually evaluate whether or not sterilization by ozone gas has been properly performed as intended.

21 ozone indicator

Claims (9)

A method for preparing an ozone indicator that changes color depending on the time of exposure to ozone gas, comprising:
Bromophenol blue or Coomassie brilliant blue as a coloring agent is dissolved in a pH buffer solution to prepare a basic solution,
Dropping the base liquid onto a filter made of a hydrophilic membrane,
A method for preparing an ozone indicator, comprising drying the filter. The method for preparing an ozone indicator according to claim 1, wherein the pH buffer solution has a buffer range of pH 6 to pH 9. The method for preparing an ozone indicator according to claim 2, wherein the pH buffer is a phosphate buffer. Further sodium thiosulfate is added to the base solution to adjust the adjustment solution,
The method for preparing an ozone indicator according to any one of claims 1 to 3, wherein the adjustment liquid is dropped onto the filter made of a hydrophilic film in place of the base liquid. Discoloration according to the exposure time of the ozone gas,
5. The method for preparing an ozone indicator according to claim 4, wherein the retardation is achieved by increasing the content of sodium thiosulfate in the adjustment liquid. The method for preparing an ozone indicator according to any one of claims 1 to 5, wherein the hydrophilic membrane is a PVDF hydrophilic membrane or a PTFE hydrophilic membrane. An ozone indicator that changes color according to the exposure time of ozone gas,
1. An ozone indicator, comprising: a filter comprising a hydrophilic membrane; and a pH buffer solution for dissolving bromophenol blue or Coomassie brilliant blue dripped onto the filter and dried. An ozone indicator that changes color according to the exposure time of ozone gas,
1. An ozone indicator, characterized in that bromophenol blue or Coomassie brilliant blue and a pH buffer solution that dissolves sodium thiosulfate are dripped onto a filter comprising a hydrophilic membrane and dried. The ozone indicator according to claim 7 or 9, wherein the hydrophilic membrane is a PVDF hydrophilic membrane or a PTFE hydrophilic membrane.

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