Fluorescent inspection solution

Abstract

The fluorescence detection solution of this invention contains water as a solvent and a flavin derivative as a blue fluorescent pigment that emits blue fluorescence. The flavin derivative has a flavin skeleton, is a derivative of riboflavin as a starting material, and contains methyl flavin and a photopigment as main components.

Description

Technical Field

[0001] This invention relates to a fluorescent detection liquid for leak detection. Prior Technology

[0002] For piping systems in machines or factories that require airtightness, leak detection is performed. One method of leak detection is the fluorescent leak detection method, which uses a detection solution containing fluorescent dye (fluorescent detection solution). Japanese Patent Application Publication No. 10-221196 describes the use of food additives as fluorescent agents in fluorescent detection solutions. Summary of the Invention

[0003] However, the problem with fluorescent detection solutions that emit blue (wavelength 360nm to 500nm) fluorescence is that there are almost none that are both highly safe for the human body and emit sufficient brightness.

[0004] Coumarin derivatives can be cited as an example of blue fluorescent agents. However, due to their toxicity to humans, their use, for example, in food processing machinery, is avoided. Quinine can also be cited as another example of a substance that emits blue fluorescence. Quinine is used as a bittering agent in soft drinks (tonic water) and is considered a safe substance for humans. However, because quinine has low water solubility at room temperature, its aqueous solution for fluorescence detection cannot achieve sufficient fluorescence brightness.

[0005] Therefore, the inventors believe that there is a need for a fluorescent detection liquid that is safe for human use, has high fluorescence brightness, and emits blue light.

[0006] The purpose of this invention is to solve the above-mentioned problems.

[0007] One of the points disclosed below is a fluorescence detection solution containing water and a flavin derivative as a blue fluorescent pigment that emits blue fluorescence; wherein the aforementioned flavin derivative has a flavin skeleton and is a derivative of riboflavin as a starting material; and the aforementioned blue fluorescent pigment contains methyl flavin and a light pigment as main components.

[0008] The fluorescent detection solution described above is highly safe for human use and emits blue fluorescence with high brightness, making it suitable for leak detection in various fields.

[0009] The aforementioned objectives, features, and advantages should be readily understood from the following description of embodiments with reference to the accompanying drawings. Simple Explanation of the Diagram

[0010] [Figure 1] is a diagram illustrating the manufacturing method of flavin derivatives using riboflavin as a raw material.

[0011] [Figure 2A] is a photograph of the fluorescence detection solution (first fluorescence detection solution) of Experiment Example 1 under indoor fluorescent lamp illumination; [Figure 2B] is a photograph of the first fluorescence detection solution under ultraviolet light irradiation in a dark room.

[0012] [Figure 3A] is a photograph of the metal sheet coated and dried with ultrapure water (Comparative Example 1) in Experimental Example 2 under indoor lighting and ultraviolet light irradiation; [Figure 3B] is a photograph of the metal sheet coated and dried with the first fluorescent detection solution (Experimental Example 1) in Experimental Example 2 under indoor lighting and ultraviolet light irradiation.

[0013] [Figure 4] is a photograph showing the result of irradiating the simulated test object with ultraviolet light after supplying the first fluorescent detection solution to the simulated test object in Experiment Example 3.

[0014] [Figure 5] is a table showing the COD and BOD evaluation results of the first fluorescence detection solution, the second fluorescence detection solution, and the aqueous solution of the reference example. Implementation

[0015] (Implementation Mode) The fluorescence detection solution contains water as a solvent and a fluorescent agent (blue fluorescent pigment) that emits blue fluorescence. The blue fluorescent pigment contains one or more flavin derivatives. The flavin derivatives may, for example, contain various flavin derivatives produced by the photolysis of riboflavin. As one embodiment, the flavin derivative may contain at least one of methyl flavin obtained from the photolysis of riboflavin and the fluorescent pigment as a main component. For example, the fluorescent pigment (7,8-dimethylphosphonoline) has a fluorescence emission peak at 450 nm to 480 nm, absorbs ultraviolet light, and emits blue fluorescence.

[0016] The aforementioned flavin derivatives, for example, can produce fluorescence with brightness easily discernible to the naked eye even at low concentrations of approximately 5 ppm, making them suitable as fluorescence detection solutions. Furthermore, while the concentration of flavin derivatives in the fluorescence detection solution is not particularly limited, it can range from 5 ppm to 20 ppm. Fluorescence detection solutions containing flavin derivatives at concentrations of 5 ppm or higher are suitable because they exhibit sufficiently bright fluorescence. Additionally, fluorescence detection solutions with flavin derivative concentrations of 20 ppm or lower are suitable from the perspective of meeting the standard values ​​(below 160 mg / L) for COD (Chemical Oxygen Demand) and BOD (Biochemical Oxygen Demand) stipulated in Japanese domestic wastewater discharge standards. However, the concentration of flavin derivatives in the fluorescence detection solution can be set at a concentration higher than 20 ppm, depending on national and regional environmental standards.

[0017] Flavin derivatives are derivatives with a flavin backbone, manufactured from riboflavin (vitamin B2) as a starting material. In this embodiment, the flavin derivative may contain at least one of methyl flavin and a photopigment as a main component. As an example, as shown in Figure 1, riboflavin can be reacted with sodium periodate (NaIO4) to obtain methyl flavin. Furthermore, all or part of the obtained methyl flavin can be reacted with acetic acid to form a photopigment, another type of flavin derivative.

[0018] Furthermore, flavin derivatives can also be obtained by irradiating riboflavin with light. By irradiating an aqueous solution of riboflavin with light, riboflavin decomposes to produce flavin derivatives such as methyl flavin, luteoflavin, carboxymethyl flavin, and luciferin. Sufficient light irradiation of a neutral aqueous solution of riboflavin emitting green fluorescence yields a blue fluorescent pigment emitting strong blue fluorescence. This blue fluorescent pigment may contain at least one of methyl flavin and luciferin as a main component of the flavin derivative. In addition to luciferin and methyl flavin, the fluorescence detection solution may also contain luteoflavin, carboxymethyl flavin, and undecomposed riboflavin.

[0019] The aforementioned flavin derivatives, derived from riboflavin, are substances produced in the body as metabolic products of riboflavin. When ingested in excess, these flavin derivatives, like riboflavin, are excreted from the body through metabolic mechanisms. Furthermore, as photodegradation products of riboflavin, flavin derivatives are also found in food and are ingested daily. Therefore, it is believed that fluorescent detection solutions containing flavin derivatives as fluorescent agents have relatively low toxicity to humans and excellent safety.

[0020] To prevent the flavin derivative from spoiling (decomposing), the fluorescence detection solution may further contain preservatives. As preservatives, parabens such as butylparaben, isopropylparaben, propylparaben, or ethylparaben, or isothiazolinones such as methylisothiazolinone, can be used. Methylparaben, as a preservative, is a substance used in cosmetics or pharmaceuticals and is highly safe for human use. In one embodiment, the amount of preservative added may be, for example, 10 ppm. A preservative concentration of 10 ppm meets food hygiene standards (Japan) and is suitable for, for example, the detection of food processing equipment. Furthermore, the amount of preservative added may also be, for example, 100 ppm or less. A preservative concentration of 100 ppm meets pharmaceutical and medical device standards (Japan) and is safe for use in non-oral applications.

[0021] (Experimental Example 1) Experiment 1 tested the color of a fluorescence detection solution containing a 5 ppm concentration of flavin derivative (hereinafter referred to as the first fluorescence detection solution). Furthermore, the flavin derivative in Experiment 1 was obtained by photolysis of an aqueous riboflavin solution. Additionally, the fluorescence detection solution containing a 5 ppm concentration of flavin derivative refers to an aqueous solution obtained by photolysis of a 5 ppm concentration of riboflavin solution. That is, the feed concentration of the raw material riboflavin is referred to as the concentration of the flavin derivative in the experiment. As shown in Figure 2A, the first fluorescence detection solution is colorless and transparent under indoor lighting. On the other hand, as shown in Figure 2B, when the first fluorescence detection solution is irradiated with ultraviolet light in a dark room, it is confirmed to emit a blue fluorescence with easily identifiable brightness.

[0022] (Experimental Example 2) Experiment 2 investigated whether the first fluorescence detection solution emitted ultraviolet light after drying. Two rectangular metal sheets were prepared for Experiment 2. One sheet was immersed in ultrapure water (Comparative Example 1), and the other was immersed in the first fluorescence detection solution (refer to Experiment 1). Both metal sheets were then dried. The surfaces of the dried metal sheets were then observed under indoor lighting and under ultraviolet light in a dark room. A photograph of the metal sheet immersed in ultrapure water is shown in Figure 3A. As shown, the metal sheet immersed in ultrapure water was colorless under indoor lighting. Furthermore, it did not exhibit fluorescence under ultraviolet light in a dark room.

[0023] Figure 3B shows a photograph of a metal sheet immersed in the first fluorescent detection solution. The metal sheet immersed in the first fluorescent detection solution did not fluoresce under indoor lighting. After drying the metal sheet with the first fluorescent detection solution, it was confirmed that it emitted blue fluorescence under ultraviolet light. The fluorescence on the surface of this metal sheet has a hue and brightness that can be clearly distinguished from the blue-violet illumination light emitted by a black light source illuminating the ultraviolet light along with the ultraviolet light. This result confirms that the first fluorescent detection solution retains its fluorescent state after drying, making it suitable for use at specific leak locations. Furthermore, it was confirmed whether the fluorescence disappeared when water was applied to the metal sheet with the fluorescent agent from the first fluorescent detection solution adhering to it. The results showed that the fluorescence disappeared immediately upon the application of water, confirming that the fluorescent agent contained in the first fluorescent detection solution can be easily washed away with water.

[0024] (Experimental Example 3) In Experiment 3, a first fluorescent detection fluid was supplied to a cylinder, as shown in Figure 4, to simulate a leak. The cylinder was connected to an air inlet via a tubing, and the connection between the inlet and the tubing was intentionally loosened (leaking point). In Experiment 3, the first fluorescent detection fluid was filled in a lubricator and supplied as a mist to the compressed air. The mist of the first fluorescent detection fluid was supplied to the interior of the simulated cylinder along with the compressed air.

[0025] As shown in the figure, in the leak detection of Experiment 3, a leak of the first fluorescent detection liquid occurred at the leak location. The leak was confirmed by the visible blue fluorescence after being irradiated with ultraviolet light. The leak location was easily identified from the point of strongest fluorescence. Furthermore, the distribution of the first fluorescent detection liquid around the leak location allowed for estimation of the leakage flow rate.

[0026] (Experimental Example 4) Experiment 4 evaluated the COD and BOD of the first and second fluorescence detection solutions. The second fluorescence detection solution was prepared by adding 100 ppm methylparaben as a preservative to the first fluorescence detection solution. COD was calculated by converting the amount of oxidant consumed by the oxidation of organic matter in the fluorescence detection solution with potassium permanganate into oxygen content. Furthermore, BOD was calculated by measuring the amount of oxygen consumed by microorganisms in the water due to respiration during a 5-day measurement period at 20°C in the presence of dissolved oxygen.

[0027] As shown in Figure 5, the COD of the first fluorescence detection solution in Experiment 1 was 17 mg / L, and the BOD was 29 mg / L. Furthermore, the COD of the second fluorescence detection solution was 16 mg / L, and the BOD was 45 mg / L. These results confirm that both the first and second fluorescence detection solutions are below the wastewater discharge control standards of 160 mg / L for COD and 160 mg / L for BOD, and will not cause problems when discharged into the sewer system. Additionally, Figure 5 shows the COD and BOD of an aqueous solution containing methylparaben (as a preservative) at a concentration of 100 ppm, as a reference example. As shown in the reference example, the increase in COD and BOD due to the addition of the preservative was relatively small.

[0028] Furthermore, after leak detection, the machine being tested is washed with water to remove the fluorescent detection solution. During this washing process, the fluorescent detection solution is typically diluted 200 times or more. Therefore, the actual COD and BOD values ​​of the first or second fluorescent detection solution discharged through wastewater are 1 / 200th or less of the values ​​shown in Figure 5. Thus, when used under normal operating conditions, the first or second fluorescent detection solution meets the discharge standards for lakes and seas (e.g., COD and BOD of 8 mg / L to 10 mg / L).

[0029] (Example of a variation of the implementation) This variation illustrates an example of adding red or green fluorescent dye to the above-mentioned fluorescence detection solution to make the fluorescence detection solution multicolor.

[0030] Modification 1 examines a fluorescence detection solution in which riboflavin is added to a flavin derivative of the present embodiment that emits blue fluorescence. Compared to the yellow-green fluorescence emitted by riboflavin, the fluorescence detection solution of the mixture of the flavin derivative and riboflavin of the present embodiment emits green fluorescence (wavelength 500 nm to 570 nm). Furthermore, by increasing the proportion of the flavin derivative of the present embodiment, a blue odor is increased, resulting in a fluorescence detection solution that emits blue-green fluorescence.

[0031] Modification 2 examines a fluorescent detection solution containing the addition of Rhodamine B to the flavin derivative of this embodiment. The Rhodamine B aqueous solution emits orange fluorescence. In this modification, mixing the flavin derivative of this embodiment with Rhodamine B yields a fluorescent detection solution emitting purple fluorescence. Furthermore, by increasing the proportion of the flavin derivative in the fluorescent detection solution of this modification, it can be confirmed that the fluorescence gradually increases from a pinkish-purple hue to a bluish-purple fluorescein, resulting in a fluorescent detection solution emitting a bluish-purple fluorescence.

[0032] The above modifications 1 and 2 make it possible to produce multi-color fluorescent detection solutions. These modifications increase the selection of fluorescent detection solution colors, providing fluorescent detection solutions with excellent visibility depending on the environment in which the object being detected is located.

[0033] Furthermore, the present invention is not limited to the above disclosure, and various configurations may be adopted without departing from the spirit of the invention. The following notes further disclose the foregoing disclosure.

[0034] (Postscript 1) One approach involves a fluorescent detection solution containing water and a flavin derivative that emits blue fluorescence as a blue fluorescent pigment. The flavin derivative possesses a flavin backbone and is derived from riboflavin. The blue fluorescent pigment contains methyl flavin and a photopigment as its main components. This fluorescent detection solution is highly safe for human use and, upon exposure to ultraviolet light, emits a highly visible blue fluorescence with high brightness, making it suitable for leak detection in various fields.

[0035] (Postscript 2) [] The fluorescence detection solution described in Appendix 1 may contain the aforementioned flavin derivatives at concentrations ranging from 5 ppm to 20 ppm. This fluorescence detection solution is below wastewater discharge standards and has a low environmental impact.

[0036] (Note 3) [] The fluorescence detection solution described in Note 1 or 2 may further contain a preservative. This fluorescence detection solution prevents the spoilage (decomposition) of the flavin derivatives used as fluorescent agents.

Claims

1. A fluorescence detection solution comprising: water; and a flavin derivative as a blue fluorescent pigment emitting blue fluorescence; wherein the aforementioned flavin derivative has a flavin skeleton and is a derivative derived from riboflavin as a starting material; contains the aforementioned flavin derivative at a concentration of 5 ppm to 20 ppm; and the aforementioned blue fluorescent pigment, as a flavin derivative, comprises methyl flavin and a photopigment.

2. The fluorescence detection solution described in claim 1 further contains a preservative.

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