JPH0783911A - Basic gas detection tape - Google Patents

Abstract

PURPOSE:To provide a tape which can detected basic gas without being affected by acid gas, etc. CONSTITUTION:Fluoresceine dye and strong acid organic acid are carried by a leaf body carrier along with a moisture-preservation agent. In normal state, colored fluoresceine dye exists in the paper leaf in discolored state due to the operation of strong acid organic acid. In this state, when basic gas is dissolved by the water of moisture-preservation agent for displacing the paper leaf to alkali side, the fluoresceine dye develops color corresponding its hydrogen ion concentration. By measuring the degree of color development, the concentration of basic gas can be determined.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tape for detecting a basic gas such as ammonia or amines present in a gas such as air by a color reaction.

[0002]

2. Description of the Related Art A basic gas such as ammonia or amines existing in the atmosphere is usually measured by using a hydrogen ion concentration measuring device provided with a glass electrode in an electrolytic solution. When the standard hydrogen ion concentration of the electrolyte changes due to the acidic gas, the sensitivity to basic gas with low concentration is extremely reduced, and it requires replacement of the electrolyte, which causes troublesome maintenance. . On the other hand, so-called detection tapes and detection tubes in which a paper sheet or the like is impregnated with a chemical agent exhibiting a color reaction are widely used for the purpose of simply and highly sensitively detecting a specific gas contained in the gas. A so-called fluorescein test paper in which a paper body is dyed with a neutral solution of fluorescein for the purpose of detecting a basic substance such as ammonia in the detection tape has been put into practical use. This test paper has an extremely high sensitivity of 0.2 ppm as a detection limit concentration to basic components such as ammonia present as an aqueous solution, but has extremely low sensitivity to basic gas contained in the gas.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and its object is to obtain a basic gas of ppb order regardless of the presence or absence of acidic gas in the atmosphere. A basic gas detection tape capable of measuring

[0004]

In order to solve such a problem, in the present invention, a fluorescein dye,
The strongly acidic organic acid was made to be carried by the carrier along with the moisturizer on the paper sheet.

[0005]

[Function] The fluorescein dye, which is colored in the normal state,
It is colorless due to the action of strongly acidic organic acids, and it exists in paper sheets in a non-fluorescent state. In this state, when the basic gas is dissolved in the moisture of the moisturizer to shift the paper sheet to the alkali side, the fluorescein dye develops a color corresponding to its hydrogen ion concentration.

[0006]

EXAMPLES The details of the present invention will be described below with reference to examples. Example 1 Rose benzal (C20H2Cl4Na2O5) which is a fluorescein dye (Color Index: Acid Re
d 94) 0.05 w%, p-toluenesulfonic acid 0.15
A reaction solution is prepared by dissolving it in water or an organic solvent, such as methanol, so as to have a wt% of glycerin of 15 vol%. In order to shorten the drying time, it is desirable to use an organic solvent. A paper sheet such as cellulose is immersed in this reaction solution to impregnate the paper sheet with the above components, and then the paper sheet is pulled out from the reaction solution and the solvent is naturally dried. As a result, rose benzal, p-toluenesulfonic acid, and glycerin are carried on the paper sheet, and the gas detection tape is completed by cutting the paper sheet into a form that can be loaded into the measuring device, for example, a tape. Since the glycerin impregnated in the paper sheet absorbs moisture in the atmosphere to form an aqueous solution system of paratoluenesulfonic acid, the hydrogen ion concentration is maintained at about pH 1 to 2, and therefore rose benzal is substantially colorless. It becomes transparent. As a result, in the state before being exposed to the test gas, the gas detection tape exhibits the background color of the paper sheet itself.

FIG. 1 shows an embodiment of a measuring apparatus suitable for the above-mentioned gas detecting tape, and is designated by reference numeral 1 in the drawing.
Is a gas suction portion which is arranged so as to face the transport path of the tape 2, and a through hole 3 having a diameter of about 1 cm is formed on the surface facing the tape 2 and a pipe 4 A negative pressure from a suction pump (not shown) acts via the. 5 is
In the measurement head portion 5 arranged on the other surface side of the tape 2 facing the through hole 3 of the gas suction portion 1, a gas to be detected introduction port 9 is formed at a position facing the through hole 3 of the suction portion 1. And a light-emitting diode 7 having a peak wavelength of 555 nm, and a p having maximum sensitivity at a wavelength of 560 nm.
The in-type photodiode 8 and the in-type photodiode 8 are arranged so as to have an incident / reflection relationship so that a reaction mark formed on the tape 2 can be detected.

The gas detection tape described above is attached to the reel 10,
11. Set the tape to 11, set the sampling flow rate to 400 ml / min, and set the sampling time to 30.
When the suction pressure from a pump (not shown) is applied to the suction portion 4 by setting to 2 seconds, the test gas is sucked into the measurement head portion 5 from the inlet 9. This test gas is discharged from the through hole 6 to the outside through the detecting tape 2 and the through hole 3. Ammonia, which is the test gas, is taken into the water retained by glycerin on the tape 2 in the process of passing through the detection tape 2 and shifts the hydrogen ion concentration to the alkaline side. As a result, the colorless and transparent rose benzal develops color at a concentration corresponding to the hydrogen ion concentration.

When the sampling time of 30 seconds elapses in this way, the suction is stopped and the step of measuring the optical density of the reaction trace is started. The light from the light emitting diode 7 is absorbed according to the optical density of the reaction mark formed on the tape surface, so that the optical density before the start of measurement, that is, the optical density of the background of the tape, The concentration of ammonia gas can be known by obtaining the difference in optical concentration of the reaction trace. When the measurement for one sampling is completed, the winding reel 10 is driven to move the unused portion of the detection tape to the measurement area.

When the change of the optical density of the reaction mark was measured while the concentration of ammonia gas was changed by setting the detection tape in the above measuring device, when the sampling time was set to about 30 seconds, (I) in FIG. 2 was obtained. A calibration curve as shown could be obtained. From this, the detection limit of 100
It was confirmed that ammonia gas in the atmosphere can be detected with extremely high sensitivity of about ppb and with high linearity. Further, when the same investigation was conducted by setting the sampling time to 60 seconds, it was possible to obtain an output almost double that of the calibration curve (I) as shown in FIG. From this, it was confirmed that there is no volatilization of the drug due to sampling, and therefore the detection sensitivity shows high linearity in the sampling time. This means that when detecting a gas having an extremely low concentration, the measurement result has high reliability even if the sampling time is extended.

In the above-mentioned embodiment, the reaction solution is prepared by dissolving all the chemicals in the organic solvent, but only some reagents, for example, paratoluenesulfonic acid are dissolved in water to prepare an aqueous solution. By using a method of injecting this into a solution in which rose benzal and glycerin are dissolved in alcohol, the hydrogen ion concentration of the reaction solution can be adjusted relatively easily.

Example 2 Phloxine (C20H2O5Br4Cl4Na2) which is a fluorescein dye (Color In
dex: Acid Red 92) 0.1 w%, paratoluene sulfonic acid 0.3 wt% and glycerol 15 vol% are dissolved in water or an organic solvent such as methanol to prepare a reaction solution. A paper sheet such as cellulose is immersed in this reaction solution to impregnate the paper sheet with the above components, and then the paper sheet is pulled out from the reaction solution and the solvent is naturally dried. As a result, phloxine, paratoluenesulfonic acid, and glycerin are carried on the paper sheet, so that the gas detection tape is completed by cutting the paper sheet into a form that can be loaded into the measuring device, for example, a tape. Since the glycerin impregnated in the paper sheet absorbs moisture in the atmosphere to form an aqueous solution system of paratoluenesulfonic acid, the hydrogen ion concentration p
It is maintained at about H1 to H2, so that phloxine becomes substantially colorless and transparent. As a result, in the state before being exposed to the test gas, the gas detection tape exhibits the background color of the paper sheet itself.

(Example 3) Eosin yellow (C20H6O5Br4Na2) (Co which is a fluorescein dye)
lour Index: Acid Red 87) 0.1w%, paratoluenesulfonic acid 0.3wt%, and glycerin 15vol%
A reaction solution is prepared by dissolving it in an organic solvent such as methanol so that A paper sheet having water absorption and acid resistance such as cellulose is immersed in this reaction solution to impregnate the paper sheet with the above components. Then, the paper sheet is pulled out from the reaction solution and the solvent methanol is naturally dried, whereby a detection tape carrying eosin yellowish, paratoluenesulfonic acid, and glycerin is completed. Since the glycerin impregnated in the paper sheet absorbs moisture in the atmosphere to form an aqueous solution system of paratoluenesulfonic acid, the hydrogen ion concentration is maintained at about pH 1 to 2, and therefore eosin yellow ash is as much as possible. Has an extremely pale pink color that is transparent to the eye. By cutting this paper sheet into a shape convenient for use, for example, a tape shape, a gas detection tape is obtained.

By the way, the gas detection tape is usually stored in an airtight container because it changes by reacting with various components contained in the atmosphere because it carries chemicals. On the other hand, when used, it is taken out of the container, loaded into a measuring device that is normally open to the atmosphere, and exposed to the atmosphere, which causes a problem of deterioration during use. Therefore, in order to confirm the storability in the air, when the gas detection tape was left in the air in the light-shielded state for several days, no change in the skin color was observed and no change in the detection sensitivity was observed. On the other hand, hydrochloric acid was used as an acid that does not deteriorate the cellulose in place of paratoluene sulfonic acid, and a gas detection tape was manufactured by the same method as described above. Moreover, the detection sensitivity also decreased with time. From these, it was confirmed that the use of paratoluenesulfonic acid as the acid was extremely effective in improving the storage stability of the gas detection tape.

Since the fluorescein dyes used in the second and third embodiments are substances that generally emit fluorescence, the gas detection tape is irradiated with light having a wavelength of 520 nm to give a fluorescence intensity of 555 nm. As a result of measurement, it was confirmed that fluorescence was emitted at an intensity that matched the concentration of ammonia gas.

By the way, as described above, in the present invention, the fluorescein dye is always as colorless as possible,
And supported on the paper sheet in the state of not emitting fluorescence, the relationship is characterized in that it is colored by the test gas, the higher the concentration on the carrier, the higher the detection sensitivity, the fluorescein-based dye on the carrier The concentration is limited to such an extent that the color development can be suppressed by the strongly acidic organic acid, and that it does not precipitate on the carrier. On the other hand, when the strongly acidic organic acid is carried in a sufficient amount, the sensitivity to the test gas can be adjusted by adjusting the amount of the moisturizing agent. In other words, in a state where a sufficient amount of strongly acidic organic acid is present on the paper sheet, hydrogen ions are present in proportion to the amount of moisturizing agent, so the detection sensitivity depends on the amount of moisturizing agent. become.

In the above embodiments, the case where rose benzal, phloxine, and eosin were used as the fluorescein dyes was explained, but other fluorescein dyes such as eosin blue ish (C20H6Br2) were used.
ClNa2O9) (Colour Index: Acid Red 91), erythrosine (C27H29N2O7S2) (Colour Index: Aci
It was confirmed that the basic gas can be detected even with d Red 52), although there is some variation in the detection sensitivity.

Although paratoluene sulfonic acid is used as the hydrogen ion concentration adjusting agent, even if other strongly acidic organic acids such as naphthalene sulfonic acid and benzyl sulfonic acid are used, it is still very high in improving the preservability. I confirmed that it was effective.

Further, although glycerin is used as a moisturizer in the above-mentioned embodiments, the same effect can be obtained by using a substance which does not change the hydrogen ion concentration such as ethylene glycol, for example, a polyhydric alcohol. .

[0020]

As described above, according to the present invention, the fluorescein dye and the strongly acidic organic acid are carried on the carrier together with the moisturizing agent on the paper sheet.
Ammonia and basic gases such as amines, which have extremely low concentrations, can be detected. Since an organic acid, which has a large molecular weight, is used as a hydrogen ion concentration regulator, the carrier can be stored even after long-term storage. The sensitivity can be maintained stable for a long period of time even when the hydrogen ion concentration does not deteriorate and the hydrogen ion concentration can be kept constant and exposed to the atmosphere. Therefore, it is extremely useful for applications requiring long-term measurement such as environmental measurement.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a measuring device suitable for a gas detection tape of the present invention.

FIG. 2 is a diagram showing an example of a measurement result by the gas detection tape of the present invention.

Claims (4)

[Claims] 1. A basic gas detection tape comprising a fluorescein dye and a strongly acidic organic acid, together with a humectant, supported on a paper sheet carrier. 2. The basic gas detection tape according to claim 1, wherein the dye is selected from rose benzal, phloxine, erythrosine, eosin yellow osh, and eosin bruisch. 3. The basic gas detection tape according to claim 1, wherein the strongly acidic organic acid is paratoluenesulfonic acid, naphthalenesulfonic acid, or benzenesulfonic acid. 4. The basic gas detection tape according to claim 1, wherein the humectant is high alcohol.