Fluorescence inspection liquid

Abstract

This fluorescence inspection liquid contains: water; riboflavin or rhodamine (B) as a fluorescent dye dissolved in the water; and a degradation inhibitor for preventing degradation due to light from the fluorescent dye. The degradation inhibitor contains a paraoxybenzoic acid ester.

Description

Fluorescent test solution

[0001] The present invention relates to a fluorescent inspection liquid used in leak inspection.

[0002] Leak inspections are sometimes performed on equipment or piping that require a certain level of airtightness. One method of leak inspection is to use a test liquid containing a fluorescent dye (hereinafter referred to as a fluorescent test liquid).

[0003] For example, Japanese Patent Application Laid-Open No. 2018-132305 discloses a system for supplying a mist containing a fluorescent test liquid into a pharmaceutical work chamber to test for leaks in the work chamber. The above document also discloses the use of a solution of riboflavin or riboflavin phosphate sodium as the fluorescent test liquid.

[0004] It is also known to use an aqueous solution of rhodamine B as a fluorescent inspection liquid for leak inspection (for example, Japanese Patent Application Laid-Open No. 2000-107575).

[0005] Aqueous solutions of fluorescent dyes such as riboflavin and rhodamine B may gradually deteriorate due to exposure to indoor light, even during storage. This makes long-term storage difficult, and the fluorescent test solution must be prepared by dissolving riboflavin or rhodamine B powder in water immediately before use, which necessitates a complex preparation process.

[0006] In addition, in facilities where inspections using fluorescent inspection liquid are conducted periodically, it is necessary to wipe up any leaked fluorescent inspection liquid from the leaking area before the next inspection. However, in facilities such as factory piping systems and building air conditioning systems, cleaning up the fluorescent inspection liquid can be difficult depending on the leaking area.

[0007] Therefore, there is a need for a fluorescent inspection liquid that is more stable to indoor light and that can be decomposed over an appropriate period of time after inspection, eliminating the need for cleaning.

[0008] An object of the present invention is to solve the above-mentioned problems.

[0009] One aspect of the following disclosure is a fluorescent test solution comprising water, a fluorescent dye dissolved in the water, and an anti-degradation agent that prevents the fluorescent dye from deteriorating due to light, wherein the anti-degradation agent is a parahydroxybenzoic acid ester.

[0010] According to the fluorescent test solution of the above aspect, the stability of the fluorescent dye in aqueous solution to light is increased during storage, and the rate of photodegradation is suppressed. Furthermore, after being released into the environment, the fluorescent dye decomposes and the fluorescence disappears within a few hours to a few weeks, eliminating the need for cleaning after a leak test. Therefore, the fluorescent test solution of the above aspect eliminates the need for preparing the fluorescent test solution immediately before a leak test and the need for cleaning after the leak test, thereby reducing the labor required for leak tests.

[0011] The above objects, features and advantages will be easily understood from the following description of the embodiments, which will be described with reference to the accompanying drawings.

[0012] Figure 1 is a table showing example compositions, fluorescent colors, and evaluation results for the first to sixth fluorescent test solutions according to Experimental Example 1, along with the sewage discharge standard. Figure 2A is a photograph taken of a leak site irradiated with ultraviolet light during a leak test, and Figure 2B is a photograph taken one week after the photograph in Figure 2A was taken. Figure 3A is a photograph showing the change in appearance of a riboflavin aqueous solution (20 ppm concentration) irradiated with fluorescent light (Experimental Example 2). Figure 3B is a photograph showing the change in appearance of a riboflavin aqueous solution (20 ppm concentration) irradiated with ultraviolet light (Experimental Example 3). Figure 4 is a photograph showing the change in appearance of a riboflavin aqueous solution (5-20 ppm concentration) containing methyl parahydroxybenzoate at concentrations ranging from 0 to 100 ppm irradiated with ultraviolet light (Experimental Example 4). Figure 5A is a graph showing the change in fluorescence intensity with irradiation time for the aqueous solution of Figure 4 containing 5 ppm riboflavin, and Figure 5B is a graph showing the change in fluorescence intensity with irradiation time for the aqueous solution of Figure 4 containing 10 ppm riboflavin. Figure 6 is a graph showing the change in fluorescence intensity with irradiation time for the aqueous solution of Figure 4 containing 20 ppm riboflavin. Figure 7 is a photograph showing the change in appearance of an aqueous solution of rhodamine B (concentration 1 to 5 ppm) containing methyl parahydroxybenzoate at concentrations ranging from 0 to 100 ppm, upon irradiation with a UV lamp (Experimental Example 5). Figure 8A is a graph showing the change in fluorescence intensity with irradiation time for the aqueous solution of Figure 7 containing 1 ppm rhodamine B, and Figure 8B is a graph showing the change in fluorescence intensity with irradiation time for the aqueous solution of Figure 7 containing 3 ppm rhodamine B. Figure 9 is a graph showing the change in fluorescence intensity with irradiation time for the aqueous solution of Figure 7 containing 5 ppm rhodamine B.

[0013] The fluorescent inspection liquid according to this embodiment is used, for example, to inspect leaks in piping systems in factories. The fluorescent inspection liquid is, for example, sprayed as a mist onto compressed air and introduced into the piping system together with the compressed air. The mist of the fluorescent inspection liquid is carried along with the compressed air and spreads to various parts of the piping. For example, if a part such as a pipe joint becomes loose, compressed air will leak from that part. The fluorescent inspection liquid flows out from the leaking point, such as the pipe joint, along with the leaking compressed air, and stains the leak point with a fluorescent dye. Leak points stained with the fluorescent inspection liquid can be easily detected visually by irradiating them with ultraviolet light, such as a black light.

[0014] The above example does not limit the use of the fluorescent inspection liquid to piping systems. The fluorescent inspection liquid can also be used to inspect leaks in water pipes, food manufacturing equipment, building air conditioning pipes, and other equipment that requires airtightness. Furthermore, the fluorescent inspection liquid may not only be added to high-pressure air in the form of a mist, but may also be introduced into pipes as a liquid diluted at a predetermined ratio.

[0015] The fluorescent inspection liquid of this embodiment is an aqueous solution in which a fluorescent dye and a degradation inhibitor are dissolved in water as a solvent. The fluorescent dye is made of a substance that is susceptible to decomposition by microorganisms, decomposition by reaction with oxygen in the atmosphere, or decomposition by visible or ultraviolet light in the environment, and is highly safe for the human body. Depending on the application, the fluorescent dye may be selected from, for example, food dyes or substances contained in food. Depending on the application, the fluorescent dye may be selected from substances that are less irritating to the skin when in contact with the skin. Blue fluorescent dyes, green fluorescent dyes, and red fluorescent dyes may be used as the fluorescent dye.

[0016] The blue fluorescent dye is a dye that absorbs ultraviolet light and emits blue fluorescence in the wavelength range of 360 to 500 nm. Examples of blue fluorescent dyes that can be used in the fluorescent test solution of this embodiment include flavin derivatives, quinine, pyrene, anthocyanin, and umbelliferone, which will be described later. These blue fluorescent dyes may be used alone or in combination.

[0017] Among blue fluorescent dyes, a mixture of quinine and a flavin derivative is suitable because it is safe for the human body and emits a bright, highly visible blue fluorescence. Quinine is used as a bittering agent in soft drinks (tonic water), and is highly safe for the human body even when taken orally, and is also highly biodegradable and easily decomposed in the atmosphere. The flavin derivative of this embodiment is derived from riboflavin, which has a flavin skeleton. Such a flavin derivative is a fluorescent dye obtained, for example, by photolysis of riboflavin, and contains formylmethylflavin and lumichrome as major components. These substances are produced by photolysis of riboflavin (vitamin B2), are contained in foods, are safe when taken orally, and are rapidly decomposed in the environment.

[0018] The green fluorescent dye absorbs ultraviolet light and emits green fluorescence in the wavelength range of 500 to 570 nm. Examples of green fluorescent dyes include riboflavin (vitamin B2), fluorescein, acridine orange, phloxine B (Red No. 104), and lycopene. These green fluorescent dyes may be used alone or in combination. Riboflavin, which is contained in foods as vitamin B2, is highly safe for the human body and has excellent biodegradability and atmospheric decomposition properties, making it suitable for use in the fluorescent test solution of this embodiment. In this embodiment, the fluorescent test solution containing riboflavin as the green fluorescent dye preferably contains riboflavin at a concentration of 5 to 27 ppm. In one preferred example, the fluorescent test solution may contain riboflavin as the green fluorescent dye at a concentration of 5 to 20 ppm.

[0019] The red fluorescent dye absorbs ultraviolet light and emits red fluorescence in the wavelength range of 590 to 830 nm. Examples of red fluorescent dyes include chlorophyll, rhodamine B, acid red (Red No. 106), eosin, cochineal pigment, tannin, phycocyanin (a spirulina pigment), carthamin (a safflower pigment), phycoerythrin, erythrosine (Red No. 3), and rose bengal (Red No. 105). These red fluorescent dyes may be used alone or in combination. In this embodiment, the fluorescent test solution containing rhodamine B as the red fluorescent dye preferably contains rhodamine B at a concentration of 1 to 123 ppm. In one preferred example, the fluorescent test solution may contain rhodamine B as the red fluorescent dye at a concentration of 1 to 5 ppm.

[0020] The fluorescent test liquid may be prepared so as to emit blue-green fluorescence by containing a blue fluorescent dye and a green fluorescent dye. The fluorescent test liquid may also be prepared so as to emit orange or yellow fluorescence by combining a green fluorescent dye and a red fluorescent dye. Furthermore, the fluorescent test liquid may also be prepared so as to emit pink or purple fluorescence by combining a blue fluorescent dye and a red fluorescent dye. The fluorescent test liquid of this embodiment can be appropriately selected to have the fluorescent color most visible under the test environment.

[0021] The anti-degradation agent suppresses the deterioration and alteration of the fluorescent dye in the aqueous solution contained in the fluorescent test solution due to light. A parahydroxybenzoic acid ester may be used as the anti-degradation agent. The anti-degradation agent may also have a preservative function to prevent the fluorescent dye in the aqueous solution from being decomposed by microorganisms. To enhance this preservative function, an isothiazolinone derivative may be added in addition to the parahydroxybenzoic acid ester.

[0022] In one embodiment, a parahydroxybenzoic acid ester may be used as the deterioration inhibitor. Examples of parahydroxybenzoic acid esters that can be used in the fluorescent test solution include methyl parahydroxybenzoate (methylparaben), ethyl parahydroxybenzoate (ethylparaben), propyl parahydroxybenzoate (propylparaben), isopropyl parahydroxybenzoate (isopropylparaben), butyl parahydroxybenzoate (butylparaben), isobutyl parahydroxybenzoate (isobutylparaben), heptyl parahydroxybenzoate (heptylparaben), and benzyl parahydroxybenzoate (benzylparaben). One or a combination of the parahydroxybenzoic acid esters listed above may be used as the deterioration inhibitor.

[0023] In another embodiment, an isothiazolinone derivative may be further added to enhance the preservative function. As the isothiazolinone derivative, any one of methylisothiazolinone (MI), methylchloroisothiazolinone (MCI), octylisothiazolinone (OI), dichlorooctylisothiazolinone (DOCI), and benzisothiazolinone (BI), or a combination thereof, may be used.

[0024] In the fluorescent inspection solution, the anti-degradant can be used in a concentration range of 10 ppm or less or 100 ppm or less, depending on the application. Methylparaben at a concentration range of 10 ppm or less meets the standards acceptable for food additives and is highly safe for oral ingestion, making it suitable for use in fluorescent inspection solutions for food processing equipment, for example. Furthermore, an anti-degradant concentration of 100 ppm or less meets the standards acceptable for pharmaceuticals and medical devices, does not irritate the skin upon contact, and provides a highly safe fluorescent inspection solution. Furthermore, a concentration of the anti-degradant of 100 ppm or less does not prevent the rapid decomposition of the fluorescent dye by light in the environment after use. Therefore, the fluorescent inspection solution of this embodiment is suitable for reducing the labor required for cleaning after leak inspections.

[0025] (Experimental Example 1) In this experimental example, examples of the composition of the fluorescent inspection liquid, evaluation of the sewage discharge standards, and evaluation of the fluorescence dissipation were carried out.

[0026] Figure 1 is a table showing example compositions, fluorescent colors, and sewage discharge standard evaluation results for the first through sixth fluorescent test solutions of this experimental example. The first fluorescent test solution is an aqueous solution containing 27 ppm of riboflavin (vitamin B2) as the first fluorescent dye. The first fluorescent test solution also contains 100 ppm of methylparaben as a degradation inhibitor. The first fluorescent test solution emits a pale yellow fluorescence with a slight greenish tinge. The COD (chemical oxygen demand) and BOD (biochemical oxygen demand), which indicate the degree of water pollution, of the first fluorescent test solution were below the 160 mg / L standard value for discharge as sewage. Therefore, it was confirmed that the first fluorescent test solution can be discharged into the sewer.

[0027] The second fluorescent test solution is an aqueous solution containing 18 ppm of riboflavin as the first fluorescent dye, 6 ppm of quinine, a blue fluorescent dye, as the second fluorescent dye, and 100 ppm of methylparaben as a degradation inhibitor. The second fluorescent test solution emits yellow-green fluorescence. It was confirmed that the COD and BOD of the second fluorescent test solution were both below 160 mg / L, making it suitable for disposal in sewer systems.

[0028] The third fluorescent test solution is an aqueous solution containing 27 ppm of riboflavin as the first fluorescent dye and 2.7 ppm of the red fluorescent dye acid red as the second fluorescent dye. The third fluorescent test solution also contains 100 ppm of methylparaben as a degradation inhibitor. The third fluorescent test solution emits a slightly reddish yellow fluorescence. The third fluorescent test solution had COD and BOD levels both below 160 mg / L, confirming that it can be poured into sewerage.

[0029] The fourth fluorescent test solution is an aqueous solution containing 20 ppm of a flavin derivative, a blue fluorescent dye, as the first fluorescent dye, 7 ppm of quinine, a blue fluorescent dye, as the second fluorescent dye, and 100 ppm of methylparaben as a degradation inhibitor. The fourth fluorescent test solution emits blue fluorescence. It was confirmed that the fourth fluorescent test solution had COD and BOD levels both below 160 mg / L and was therefore suitable for disposal in sewer systems.

[0030] The fifth fluorescent test solution contains 123 ppm of rhodamine B, a red fluorescent dye, as the first fluorescent dye, and 100 ppm of methylparaben as a degradation inhibitor. The fifth fluorescent test solution emits orange (yellowish red) fluorescence. The fifth fluorescent test solution had COD and BOD levels both below 160 mg / L, confirming that it can be poured into sewer systems.

[0031] The sixth fluorescent test solution contains 210 ppm of the red fluorescent dye Acid Red as the first fluorescent dye and 100 ppm of methylparaben as a degradation inhibitor. The sixth fluorescent test solution emits red fluorescence. The sixth fluorescent test solution had COD and BOD levels both below 160 mg / L, and it was confirmed that the sixth fluorescent test solution can be poured into sewerage.

[0032] Next, the results of an investigation into the decomposition of fluorescent dyes in the atmosphere will be explained. A mist of fluorescent test solution was supplied along with compressed air to a test pipe with a loose joint that could become a leak point. In this experiment, the fluorescent test solution used contained riboflavin as the fluorescent dye at a concentration of 5 ppm and methyl parahydroxybenzoate as a degradation inhibitor at a concentration of 10 ppm.

[0033] In the area indicated by the white oval frame in Figure 2A, fluorescent test liquid is leaking from a pipe joint. The leaking area is illuminated with ultraviolet light from a black light. As shown in the figure, bright fluorescence is emitted from the leaking fluorescent test liquid, making the leaking area easily visible.

[0034] Next, the pipe and joint shown in Figure 2A were left for one week without cleaning with the fluorescent inspection liquid, and then the same locations were irradiated with ultraviolet light to check for the presence or absence of fluorescence. The results are shown in Figure 2B. As shown in Figure 2B, the fluorescence of the fluorescent inspection liquid disappeared in the joint, and the fluorescent dye (riboflavin) was quickly decomposed. Thus, it was confirmed that the fluorescent inspection liquid of this embodiment decomposes the fluorescent dye in a short period of time, within one week.

[0035] (Experimental Example 2) In this experiment, the photodegradation rate of an aqueous solution containing riboflavin as a fluorescent dye at a concentration of 20 ppm was evaluated. In this experiment, fluorescent lighting was used at an illuminance of 750 lx (lux). This illuminance corresponds to the illuminance required for a typical visual work environment in factories and offices, as specified in JIS Z9110 (General Provisions for Lighting Standards), and is equivalent to the illuminance of normal indoor light. The light irradiation lasted from 0 to 1200 minutes. In this experiment, the aqueous solution was irradiated with ultraviolet light at predetermined intervals, and the fluorescence emitted from the aqueous solution was photographed with a camera.

[0036] 3A shows the change in appearance of the riboflavin aqueous solution in Experimental Example 2. When the riboflavin aqueous solution was continuously irradiated with light from a fluorescent lamp, the fluorescence of the solution gradually changed from bright green-yellow to blue. Therefore, it was confirmed that the riboflavin aqueous solution containing no deterioration inhibitor deteriorates in a relatively short period of time.

[0037] (Experimental Example 3) In this experimental example, an accelerated test of the rate of photodegradation was attempted. In this experimental example, an aqueous solution containing riboflavin at a concentration of 20 ppm was used, as in Experimental Example 2. In this experimental example, light irradiation was performed using an ultraviolet lamp instead of a fluorescent lamp. The irradiation intensity of the ultraviolet light was 10.0 mW / cm. ２ In this experimental example, the fluorescence emitted from the aqueous solution was photographed at predetermined time intervals.

[0038] 3B shows the change in appearance of the riboflavin aqueous solution in Experimental Example 3. This Experimental Example confirmed that 60 minutes of ultraviolet light irradiation of the riboflavin aqueous solution resulted in a change in fluorescent color equivalent to that observed in 1200 minutes of fluorescent light irradiation in Experimental Example 2. Therefore, the results showed that ultraviolet light lamp irradiation can accelerate the rate of photodegradation by approximately 20 times compared to fluorescent light irradiation.

[0039] (Experimental Example 4) In this experimental example, fluorescent test solutions were prepared by adding methyl parahydroxybenzoate (methylparaben), a type of parahydroxybenzoic acid ester, as a deterioration inhibitor to aqueous riboflavin solutions (concentrations of 5 ppm, 10 ppm, and 20 ppm). The amounts of methyl parahydroxybenzoate added were 0 ppm, 50 ppm, and 100 ppm, and a total of nine types of fluorescent test solutions were prepared.

[0040] These fluorescent test solutions were irradiated with an ultraviolet lamp to evaluate the rate of photodegradation. The irradiation intensity of ultraviolet light from the ultraviolet lamp was 10.0 mW / cm. ２ In this experiment, the fluorescence of the fluorescent test liquid was also photographed with a camera at predetermined time intervals.

[0041] Figure 4 shows the change in appearance of the fluorescent test solution in this experiment. As shown in the figure, no change in the initial fluorescent color was observed up to 100 ppm of methyl parahydroxybenzoate added. Therefore, it was confirmed that the addition of methyl parahydroxybenzoate does not affect the fluorescent color of the riboflavin aqueous solution.

[0042] Next, the G luminance value corresponding to the green fluorescence of each fluorescent test liquid was calculated based on the image in Figure 4. The G luminance value was calculated by extracting and averaging the R, G, and B luminance values ​​of the pixels in the bottle portion of the image. The G luminance value of each fluorescent test liquid was normalized so that the G luminance value at the start of irradiation was 1. The changes in the G luminance value with respect to irradiation time are shown in Figures 5A to 6.

[0043] As shown in Figures 5A to 6, regardless of the riboflavin concentration, the addition of methyl parahydroxybenzoate tended to suppress the decrease in the G brightness value corresponding to green fluorescence. Furthermore, the suppression of the decrease in the G brightness value was more effective in the fluorescent test solution containing methyl parahydroxybenzoate at a concentration of 100 ppm than in the fluorescent test solution containing methyl parahydroxybenzoate at a concentration of 50 ppm. These results confirmed that methyl parahydroxybenzoate is effective in suppressing photodegradation of riboflavin aqueous solution (fluorescent test solution).

[0044] Furthermore, even with a fluorescent test solution containing 100 ppm of methyl parahydroxybenzoate, the G brightness value decreased after sufficient exposure to light. These results confirmed that even when methyl parahydroxybenzoate was added to a riboflavin aqueous solution, the fluorescent test solution decomposed if left in a light-exposed environment for a sufficient period of time after a leak test. Therefore, this experimental example confirmed that adding methyl parahydroxybenzoate to the fluorescent test solution did not prevent the decomposition of the fluorescent dye when left unattended after a leak test, thereby reducing the labor required for cleaning.

[0045] (Experimental Example 5) In this experimental example, fluorescent test solutions were prepared by adding methyl parahydroxybenzoate (methylparaben) as a deterioration inhibitor to aqueous solutions of rhodamine B (concentrations of 1 ppm, 3 ppm, and 5 ppm). The amounts of methyl parahydroxybenzoate added were 0 ppm, 50 ppm, and 100 ppm, and a total of nine types of fluorescent test solutions were prepared.

[0046] These fluorescent test solutions were irradiated with an ultraviolet lamp to evaluate the rate of photodegradation. The irradiation intensity of ultraviolet light from the ultraviolet lamp was 10.0 mW / cm. ２ In this experiment, the fluorescence of the fluorescent test liquid was also photographed with a camera at predetermined time intervals.

[0047] Figure 7 shows the change in appearance of the fluorescent test solution in this experiment. As shown in the figure, no change in the initial fluorescent color was observed up to 100 ppm of methyl parahydroxybenzoate added. This confirms that the addition of methyl parahydroxybenzoate does not affect the orange fluorescent color of the rhodamine B aqueous solution.

[0048] Next, based on the image in Figure 7, the R brightness value of the red fluorescence that best reflected the characteristic fluorescent color was determined for each fluorescent test liquid. The R brightness value was calculated by extracting and averaging the R, G, and B brightness values ​​of the pixels in the bottle portion of the image. The R brightness value was normalized so that the R brightness value at the start of irradiation was 1. The changes in these R brightness values ​​with respect to irradiation time are shown in Figures 8A to 9.

[0049] As shown in Figures 8A to 9, the addition of methyl parahydroxybenzoate suppressed the decrease in R luminance value, regardless of the concentration of rhodamine B. Furthermore, the effect of suppressing the decrease in R luminance value was greater in the fluorescent test solution containing methyl parahydroxybenzoate at a concentration of 100 ppm than in the fluorescent test solution containing methyl parahydroxybenzoate at a concentration of 50 ppm. These results confirmed that methyl parahydroxybenzoate is effective in suppressing photodegradation of the rhodamine B aqueous solution (fluorescent test solution).

[0050] Furthermore, it was confirmed that even with a fluorescent test solution containing 100 ppm of methyl parahydroxybenzoate, the R brightness value decreased and the fluorescence was lost after sufficient time of light exposure. These results confirmed that even when methyl parahydroxybenzoate was added to an aqueous solution of rhodamine B, the fluorescent dye was decomposed by leaving the solution in a light-exposed environment for a sufficient time after a leak test. Therefore, this experimental example also confirmed that adding methyl parahydroxybenzoate to the fluorescent test solution did not prevent the decomposition of the fluorescent dye when left unattended after a leak test, thereby reducing the labor required for cleaning.

[0051] In addition, the following supplementary notes are further disclosed in relation to the above disclosure.

[0052] (Supplementary Note 1) One aspect of the disclosure is a fluorescent test solution that includes water, a fluorescent dye dissolved in the water, and a deterioration inhibitor that prevents deterioration of the fluorescent dye due to light, the deterioration inhibitor being a parahydroxybenzoic acid ester. The fluorescent test solution can prevent deterioration of the fluorescent dye due to ultraviolet light during storage.

[0053] (Appendix 2) The fluorescent inspection solution described in Appendix 1 may contain methyl parahydroxybenzoate as the deterioration inhibitor at a concentration of 50 ppm or more. This fluorescent inspection solution can prevent deterioration of the fluorescent dye due to ultraviolet light during storage, and after being released into the environment, the fluorescent dye decomposes and loses its fluorescence within several hours to several days. As a result, the fluorescent inspection solution of the above aspect can simplify the preparation work of the fluorescent inspection solution before a leak inspection and the cleaning work after a leak inspection, thereby enabling labor-saving leak inspections.

[0054] (Appendix 3) The fluorescent inspection solution described in Appendix 2 may contain methyl parahydroxybenzoate as the deterioration inhibitor at a concentration of 100 ppm or less. Since this fluorescent inspection solution satisfies the BOD discharge standard and the COD discharge standard, the fluorescent inspection solution after use can be discharged into the sewer for treatment.

[0055] (Appendix 4) The fluorescent test solution according to any one of Appendices 1 to 3 may contain riboflavin as the fluorescent dye at a concentration of 5 to 27 ppm. This fluorescent test solution is safe for humans and can prevent deterioration due to ultraviolet light during storage. Furthermore, this fluorescent test solution is decomposed by sufficient light irradiation, which is advantageous in that cleaning after use can be omitted.

[0056] (Appendix 5) The fluorescent inspection solution according to any one of Appendices 1 to 3 may contain rhodamine B as the fluorescent dye at a concentration of 1 to 123 ppm. This fluorescent inspection solution is safe for humans and can prevent deterioration due to ultraviolet light during storage. Furthermore, this fluorescent inspection solution is decomposed by sufficient light irradiation, which is advantageous in that cleaning after use can be omitted.

[0057] Although the present disclosure has been described in detail, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible in these embodiments without departing from the gist of the present disclosure or the spirit of the present disclosure derived from the content of the claims and their equivalents. These embodiments can also be implemented in combination. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical expressions are used in the description of the above-described embodiments.

Claims

1. A fluorescent inspection solution comprising: water; a fluorescent dye dissolved in the water; and a deterioration inhibitor that prevents deterioration of the fluorescent dye due to light, the deterioration inhibitor being a paraoxybenzoic acid ester.

2. The fluorescent inspection liquid according to claim 1, containing methyl paraoxybenzoate as the deterioration inhibitor in a concentration of 50 ppm or more.

3. The fluorescent inspection liquid according to claim 2, containing said methyl paraoxybenzoate in a concentration of 100 ppm or less.

4. The fluorescent inspection liquid according to any one of claims 1 to 3, comprising riboflavin as the fluorescent dye at a concentration of 5 to 27 ppm.

5. A fluorescent inspection liquid according to any one of claims 1 to 3, comprising Rhodamine B as said fluorescent dye at a concentration of 1 to 123 ppm.

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