Fluorescent inspection liquid

Abstract

The present invention relates to a fluorescent inspection liquid which is highly safe to a human body and emits blue fluorescence having high visibility in the leakage inspection. The fluorescent inspection liquid contains water as a solvent and two blue fluorescent dyes selected from a flavin derivative, quinine, pyrene and anthocyanin. The flavin derivative is a derivative having a flavin skeleton and obtained from a starting material, riboflavin.

Description

Fluorescent inspection liquid

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

[0002] Leak inspections are conducted on equipment that requires airtightness and on piping systems in factories, etc. One type of leak inspection is a fluorescent leak inspection method that uses an inspection liquid containing a fluorescent dye (fluorescent inspection liquid). JP-A-10-221196 describes the use of food additives (Food Red No. 2, Food Red No. 106, Food Blue No. 1, Food Green No. 3) as the fluorescent agents in the fluorescent inspection liquid.

[0003] However, there is a problem in that there are almost no fluorescent test liquids that emit blue fluorescence (wavelength 360 to 500 nm) that are highly safe for the human body and emit bright blue fluorescence that is highly visible in leak tests.

[0004] Coumarin derivatives are an example of a blue fluorescent agent. However, coumarin derivatives are toxic to the human body and are therefore avoided for use in, for example, food equipment. Quinine is another example of a substance that emits blue fluorescence. Quinine is used as a bittering agent in soft drinks (tonic water) and is a substance that is safe for the human body. Quinine's fluorescence color is a deep blue. However, quinine's fluorescence lacks vividness and is difficult to distinguish from the external light that permeates the measurement location and the blue-purple light emitted from a black light as an ultraviolet light source, resulting in poor visibility during leak testing.

[0005] Therefore, the inventors of the present invention have considered the need for a fluorescent inspection liquid that emits a blue color and is safe for the human body and has excellent visibility in leak inspections.

[0006] An object of the present invention is to solve the above-mentioned problems.

[0007] One aspect of the following disclosure is a fluorescent test solution comprising water as a solvent, a first blue fluorescent dye selected from any one of a flavin derivative, quinine, pyrene, and anthocyanin, and a second blue fluorescent dye selected from any one of the flavin derivative, quinine, pyrene, and anthocyanin excluding the first blue fluorescent dye, wherein the flavin derivative has a flavin skeleton and is a derivative made from riboflavin as a starting material.

[0008] The fluorescent test liquid of the above aspect has a relatively low toxicity to the human body, and has improved saturation of the fluorescent color compared to when a single blue fluorescent dye is used, resulting in excellent visibility in leak testing.

[0009] Fig. 1 shows photographs of a flavin derivative aqueous solution, a quinine aqueous solution, a pyrene aqueous solution, and an anthocyanin aqueous solution (each at a concentration of 10 ppm) irradiated with ultraviolet light in a dark room. Fig. 2A shows photographs of a first fluorescent test solution containing a flavin derivative and quinine (each at a concentration of 10 ppm) irradiated with ultraviolet light in a dark room. Fig. 2B shows photographs of a second fluorescent test solution containing a flavin derivative and pyrene (each at a concentration of 10 ppm) irradiated with ultraviolet light in a dark room. Fig. 3A shows photographs of a third fluorescent test solution containing a flavin derivative and anthocyanin (each at a concentration of 10 ppm) irradiated with ultraviolet light in a dark room. Fig. 3B shows photographs of a fourth fluorescent test solution containing quinine and pyrene (each at a concentration of 10 ppm) irradiated with ultraviolet light in a dark room. Figure 4A is a photograph of the fifth fluorescent test solution containing quinine and anthocyanin (both at a concentration of 10 ppm) irradiated with ultraviolet light in a dark room, and Figure 4B is a photograph of the sixth fluorescent test solution containing pyrene and anthocyanin (both at a concentration of 10 ppm) irradiated with ultraviolet light in a dark room.

[0010] The fluorescent test liquid according to this embodiment is used for leak testing of equipment or piping that requires a certain degree of airtightness. During leak testing, the fluorescent test liquid is sprayed as a mist into compressed air and introduced into the equipment under test. If a leak is found in the test object, the fluorescent test liquid leaks out from the leak and stains the leak with a blue fluorescent dye. When ultraviolet light is then irradiated from outside the test object using a light source such as a black light, the fluorescent test liquid emits blue fluorescence at the leak, making it possible to visually detect the leak.

[0011] The fluorescent test solution of this embodiment is a composition in which a blue fluorescent dye is dissolved in water as a solvent. In this embodiment, the blue fluorescent dye is a dye that is excited by irradiation with ultraviolet light and emits blue fluorescence (wavelength 360 to 500 nm). The fluorescent test solution of this embodiment contains two types of blue fluorescent dyes selected from flavin derivatives, quinine, pyrene, and anthocyanin. That is, the fluorescent test solution contains a first blue fluorescent dye and a second blue fluorescent dye. The fluorescent test solution may also contain a third blue fluorescent dye.

[0012] The flavin derivative is a derivative derived from riboflavin (vitamin B2), which has a flavin skeleton. The fluorescent test solution may contain at least one of formylmethylflavin and lumichrome as a major component of the flavin derivative. Of these, lumichrome (7,8-dimethylalloxazine) absorbs ultraviolet light and emits blue fluorescence with a peak emission wavelength of 450 to 480 nm. The flavin derivative of this embodiment is obtained by irradiating an aqueous solution of riboflavin with light for a sufficient amount (time), and emits blue fluorescence.

[0013] The above-mentioned flavin derivatives are substances generated in vivo as metabolic products of riboflavin, and if ingested in excess, they are excreted from the body through the same metabolic mechanism as riboflavin. Furthermore, flavin derivatives are also contained in foods as photodecomposition products of riboflavin, and are ingested daily. Therefore, fluorescent test solutions containing flavin derivatives are considered to have relatively low toxicity to the human body and excellent safety.

[0014] Quinine absorbs ultraviolet light and emits deep blue fluorescence with a peak at 440-490 nm. Quinine is used as a bittering agent in soft drinks (tonic water) and as a treatment for malaria, and has extremely low toxicity to the human body.

[0015] Pyrene absorbs ultraviolet light and emits bright blue fluorescence with a fluorescence emission peak at 450 to 500 nm.

[0016] Anthocyanins are pigments found in plants that absorb ultraviolet light and emit deep blue fluorescence. Anthocyanins are also found in foods and are considered to be highly safe for oral ingestion.

[0017] The total concentration of the blue fluorescent dye contained in the fluorescent test solution of this embodiment is set within a range that satisfies the COD (Chemical Oxygen Demand) and BOD (Biochemical Oxygen Demand) standards for allowable discharge into sewage. For example, the COD and BOD standards in Japan are 160 mg / L. In fluorescent test solutions used in Japan, it is preferable that the total concentration of the blue fluorescent dye satisfy the COD and BOD standards. From this perspective, it is preferable that the total concentration of the blue fluorescent dye be, for example, 30 ppm or less.

[0018] Furthermore, since the blue fluorescent dye used in the fluorescent inspection solution of this embodiment is a substance that is easily decomposed (putrefied) by microorganisms, a preservative may be added to prevent deterioration due to putrefaction during transportation and storage. Examples of the preservative include parahydroxybenzoic acid esters such as butylparaben, isopropylparaben, propylparaben, ethylparaben, and methylparaben, and isothiazolinone derivatives such as methylisothiazolinone.

[0019] The preservative concentration can be set appropriately depending on the application. A preservative concentration of 10 ppm or less is within the range approved for use as a food additive. Therefore, a fluorescent inspection solution containing 100 ppm or less of a preservative can be used more safely in food handling equipment. Furthermore, a preservative concentration of 100 ppm or less is within the range approved for medical devices that come into contact with the human body. Therefore, if the preservative concentration is 100 ppm or less, it is expected that there will be little or no skin irritation to the user even if the fluorescent inspection solution is exposed to the skin.

[0020] A decrease in methylparaben of 100 ppm only increases COD by 14 mg / L and BOD by 11 mg / L, and the addition of preservatives has a relatively small effect on the sewage discharge standards for the fluorescent test liquid.

[0021] The fluorescent test liquid of this embodiment includes the following six types based on the combination of blue fluorescent dyes: First fluorescent test liquid: flavin derivative and quinine Second fluorescent test liquid: flavin derivative and pyrene Third fluorescent test liquid: flavin derivative and anthocyanin Fourth fluorescent test liquid: quinine and pyrene Fifth fluorescent test liquid: quinine and anthocyanin Sixth fluorescent test liquid: pyrene and anthocyanin

[0022] Among the fluorescent test solutions listed above, the first fluorescent test solution containing a flavin derivative and quinine is safe even when taken orally and has high saturation (S) and bright fluorescence, resulting in excellent visibility. Therefore, the first fluorescent test solution is suitable for leak testing. For example, a first fluorescent test solution containing a flavin derivative at a concentration of 5 ppm to 20 ppm and a quinine at a concentration of 1 ppm to 10 ppm exhibits an excellent balance of hue (H), saturation (S), and brightness (V), resulting in good visibility. Note that if the flavin derivative concentration is below the above range, the fluorescence intensity decreases, making it difficult to use in leak testing. If the quinine concentration is below 1 ppm, a vivid blue fluorescence cannot be obtained. A quinine concentration of 10 ppm is close to the upper limit of quinine's solubility in water at room temperature. Furthermore, the first fluorescent inspection solution with such a concentration satisfies the sewage discharge standard of 160 mg / L or less for COD and BOD, making it easy to dispose of after use. Furthermore, the first fluorescent inspection solution decomposes in the atmosphere in a relatively short time, from a few hours to a few days. Therefore, its impact on the environment can be minimized.

[0023] The following describes the results of investigating the brightness (amount of light) of the fluorescent color, hue H, saturation S, and value V of the aqueous solution of a single blue fluorescent dye and the first to sixth fluorescent test solutions.

[0024] First, the fluorescent light intensity of the first to sixth fluorescent test solutions was investigated when irradiated with ultraviolet light. The results showed that the first, second, and third fluorescent test solutions exhibited an increase in fluorescent light intensity of approximately 1.1 to 1.5 times that of the blue fluorescent dye alone. However, the third, fifth, and sixth fluorescent test solutions, which contain anthocyanin, did not exhibit an increase in fluorescent light intensity. Because anthocyanin absorbs light with a wavelength around 500 nm, it is thought that it does not contribute much to the increase in light intensity. Next, the hue (H), saturation (S), and brightness (V) were investigated.

[0025] Figure 1 shows photographs of aqueous solutions of a flavin derivative (e.g., a photolyzed product of riboflavin), quinine, pyrene, and anthocyanin under ultraviolet light irradiation. Below each aqueous solution, the HSV color space values, which represent the color of each solution as determined from the image, are shown. These values ​​are a combination of hue (H), saturation (S), and value (V).

[0026] An aqueous solution of a flavin derivative with a concentration of 10 ppm had a hue H of 208°, a saturation S of 74%, and a brightness V of 31%. An aqueous solution of quinine with a concentration of 10 ppm had a hue H of 233°, a saturation S of 81%, and a brightness V of 20%. An aqueous solution of pyrene with a concentration of 10 ppm had a hue H of 212°, a saturation S of 75%, and a brightness V of 23%. An aqueous solution of anthocyanin had a hue H of 231°, a saturation S of 75%, and a brightness V of 10%.

[0027] The first fluorescent test solution shown in Figure 2A is an aqueous solution containing a 10 ppm flavin derivative and a 10 ppm quinine. The first fluorescent test solution had a hue H of 215°, a saturation S of 85%, and a value V of 29%. These results demonstrate that the saturation S value of the first fluorescent test solution (85%) is higher than the saturation S value of the flavin derivative aqueous solution (74%) and the saturation S value of the quinine aqueous solution (81%), confirming improved visibility.

[0028] The second fluorescent test solution shown in Figure 2B is an aqueous solution containing a 10 ppm flavin derivative and a 10 ppm pyrene. The second fluorescent test solution had a hue H of 212°, a saturation S of 92%, and a brightness V of 45%. The saturation S of the second fluorescent test solution (92%) was higher than the saturation S of the flavin derivative aqueous solution (74%) and the saturation S of the pyrene aqueous solution (75%), confirming improved visibility due to the improved saturation S.

[0029] The third fluorescent test solution shown in Figure 3A is an aqueous solution containing a 10 ppm flavin derivative and a 10 ppm anthocyanin. The third fluorescent test solution had a hue H of 209°, a saturation S of 82%, and a brightness V of 28%. The saturation S value of 82% for the third fluorescent test solution was higher than the saturation S value of 74% for the aqueous solution of the flavin derivative and the saturation S value of 75% for the aqueous solution of the anthocyanin, confirming improved visibility.

[0030] The fourth fluorescent test solution shown in Figure 3B is an aqueous solution containing 10 ppm quinine and 10 ppm pyrene. The fourth fluorescent test solution had a hue H of 225°, a saturation S of 92%, and a value V of 36%. The saturation S value of 92% for the fourth fluorescent test solution was higher than the saturation S value of 81% for the quinine aqueous solution and the saturation S value of 75% for the pyrene aqueous solution, confirming improved visibility.

[0031] The fifth fluorescent test solution shown in Figure 4A is an aqueous solution containing 10 ppm quinine and 10 ppm anthocyanin. The fifth fluorescent test solution had a hue H of 235°, a saturation S of 97%, and a value V of 13%. The saturation S value of 97% for the fifth fluorescent test solution was higher than the saturation S value of 81% for the quinine aqueous solution and the saturation S value of 75% for the anthocyanin aqueous solution, confirming improved visibility.

[0032] The sixth fluorescent test solution shown in Figure 4B is an aqueous solution containing 10 ppm pyrene and 10 ppm anthocyanin. The sixth fluorescent test solution had a hue H of 217°, a saturation S of 88%, and a brightness V of 23%. The saturation S value of 88% for the sixth fluorescent test solution was higher than the saturation S value of 75% for the pyrene aqueous solution and the saturation S value of 75% for the anthocyanin aqueous solution, confirming improved visibility.

[0033] As described above, according to the embodiment, a fluorescent inspection liquid that emits blue fluorescence with high saturation S can be obtained, thereby improving visibility during leak inspection. Furthermore, the fluorescent inspection liquid of the embodiment has little impact on the human body and the environment, and can be used for a variety of purposes.

[0034] The present invention is not limited to the above disclosure, and various configurations can be adopted without departing from the gist of the present invention.

[0035] (Supplementary Note 1) One aspect is a fluorescent test solution comprising water as a solvent, a first blue fluorescent dye selected from any one of a flavin derivative, quinine, pyrene, and an anthocyanin, and a second blue fluorescent dye selected from any one of the flavin derivative, quinine, pyrene, and anthocyanin, excluding the first blue fluorescent dye, wherein the flavin derivative has a flavin skeleton and is derived from riboflavin. Such a fluorescent test solution is highly safe and, compared to aqueous solutions of the first or second blue fluorescent dye alone, exhibits higher saturation and superior visibility in leak tests.

[0036] (Appendix 2) In the fluorescent test solution according to Appendix 1, the first blue fluorescent dye may be the flavin derivative, and the second blue fluorescent dye may be quinine. Since the blue fluorescent dye in this fluorescent test solution is a substance contained in food, it is highly safe even when orally ingested. Therefore, this fluorescent test solution can be suitably used, for example, in leak testing of food equipment, etc., where safety is required.

[0037] (Appendix 3) The fluorescent test solution described in Appendix 2 may contain the flavin derivative as the first blue fluorescent dye at a concentration of 5 ppm to 20 ppm, and quinine as the second blue fluorescent dye at a concentration of 1 ppm to 7 ppm. This fluorescent test solution exhibits vivid blue fluorescence and has COD and BOD values ​​below the sewage discharge standard of 160 mg / L, so it can be discharged into sewerage, and wastewater after testing can be poured into the sewerage.

[0038] (Appendix 4) In the fluorescent test solution according to Appendix 1, the first blue fluorescent dye may be the flavin derivative, and the second blue fluorescent dye may be pyrene. Such a fluorescent test solution has higher saturation than an aqueous solution of the first blue fluorescent dye or the second blue fluorescent dye alone, and is therefore excellent in visibility during leak testing.

[0039] (Appendix 5) In the fluorescent test solution according to Appendix 1, the first blue fluorescent dye may be the flavin derivative, and the second blue fluorescent dye may be anthocyanin. Such a fluorescent test solution has higher saturation than an aqueous solution of the first blue fluorescent dye or the second blue fluorescent dye alone, and is therefore superior in visibility during leak testing.

[0040] (Appendix 6) In the fluorescent test solution according to Appendix 1, the first blue fluorescent dye may be quinine, and the second blue fluorescent dye may be pyrene. Such a fluorescent test solution has higher saturation than an aqueous solution of the first blue fluorescent dye or the second blue fluorescent dye alone, and is therefore superior in visibility during leak testing.

[0041] (Appendix 7) In the fluorescent test solution according to Appendix 1, the first blue fluorescent dye may be quinine, and the second blue fluorescent dye may be anthocyanin. Such a fluorescent test solution has higher saturation than an aqueous solution of the first blue fluorescent dye or the second blue fluorescent dye alone, and is therefore superior in visibility during leak testing.

[0042] (Appendix 8) In the fluorescent test solution according to Appendix 1, the first blue fluorescent dye may be pyrene, and the second blue fluorescent dye may be anthocyanin. Such a fluorescent test solution has higher saturation than an aqueous solution of the first blue fluorescent dye or the second blue fluorescent dye alone, and is therefore superior in visibility during leak testing.

[0043] (Appendix 9) The fluorescent test solution according to any one of Appendices 1 to 8, wherein the flavin derivative may contain at least one of formylmethylflavin and lumichrome as a main component. This fluorescent test solution is highly safe, reduces environmental impact, and exhibits highly visible blue fluorescence, making it suitable for leak testing.

Claims

1. A fluorescence test solution comprising water as a solvent, a first blue fluorescent dye selected from any one of flavin derivatives, quinine, pyrene, and anthocyanin, and a second blue fluorescent dye selected from any one of the flavin derivatives, quinine, pyrene, and anthocyanin excluding the first blue fluorescent dye, wherein the flavin derivative is a derivative having a flavin skeleton and using riboflavin as a starting material.

2. The fluorescence test solution according to claim 1, wherein the first blue fluorescent dye is the flavin derivative and the second blue fluorescent dye is quinine.

3. The fluorescence test solution according to claim 2, comprising the flavin derivative as the first blue fluorescent dye at a concentration of 5 ppm or more and 20 ppm or less, and quinine as the second blue fluorescent dye at a concentration of 1 ppm or more and 7 ppm or less.

4. The fluorescence test solution according to claim 1, wherein the first blue fluorescent dye is the flavin derivative and the second blue fluorescent dye is pyrene.

5. The fluorescence test solution according to claim 1, wherein the first blue fluorescent dye is the flavin derivative and the second blue fluorescent dye is anthocyanin.

6. The fluorescence test solution according to claim 1, wherein the first blue fluorescent dye is quinine and the second blue fluorescent dye is pyrene.

7. The fluorescence test solution according to claim 1, wherein the first blue fluorescent dye is quinine and the second blue fluorescent dye is anthocyanin.

8. The fluorescence test solution according to claim 1, wherein the first blue fluorescent dye is pyrene and the second blue fluorescent dye is anthocyanin.

9. The fluorescence test solution according to any one of claims 1 to 8, comprising at least one of formylmethylflavin and lumichrome as a main component as the flavin derivative.

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