JP3187235B2 - Formaldehyde detection paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a detection paper for detecting formaldehyde present in the environment by a color reaction.

[0002]

2. Description of the Related Art In the case of disinfecting a wide environment such as a hospital room, formaldehyde is produced from formaldehyde dissolved in formaldehyde in ethanol or formaldehyde formed into a solid agent, and this is filled in the environment to be disinfected. A method is used. Since formaldehyde has high persistence, it is usually necessary to confirm that the concentration of formaldehyde remaining after disinfection is below environmental standards.

A semiconductor gas sensor is often used for such a purpose, but the semiconductor gas sensor does not have sufficient sensitivity to a concentration of an environmental standard (TLV 1 ppm). It has high sensitivity to other gases, especially ethanol used as a polymerization inhibitor for formaldehyde, and ammonia gas used to neutralize formaldehyde remaining after disinfection. There is a problem of low reliability in measuring formaldehyde at a low concentration.

[0004] In order to solve such a problem, there have been proposed many color detection methods utilizing a chemical reaction such as a silver ethylenediamine method, a potassium nickel cyanide method, a pararoseaniline hydrochloride method, an AHMT method and an acetylacetone method. However, all of these methods require the handling of reagents because of the use of liquid reagents, require skill in the analysis operation, or perform automatic measurement.
There is a problem that the device becomes expensive.

[0005] In order to solve such problems, it is conceivable to impregnate a porous carrier such as filter paper with a reagent used in each of these methods to eliminate the handling of the reagent. The test paper has low detection sensitivity, and the background color is large, and when trying to measure the reaction color with an optical densitometer or the like, the dynamic range is low and the detection range is narrow. There are many problems such as being easily discolored by gases other than the above, and there is a problem that it cannot be used for practical purposes.

[0006] In order to solve such a problem, the present applicant has previously developed a formaldehyde formed by developing an acidic salt of hydroxylamine and a hydrogen ion concentration indicator having a discoloration region in the acidic region on a porous carrier. A detection paper was proposed.
According to this, in a special environment where the relative humidity is 80% or more, it is possible to detect extremely low concentration of formaldehyde of about several ppm remaining in the environment after formaldehyde disinfection, Since it is limited, there is an inconvenience that the measurable range is limited.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and an object of the present invention is to provide a low concentration of very low concentration of several ppm or less even under an environment of a standard relative humidity. An object of the present invention is to provide a novel detection paper capable of detecting formaldehyde.

[0008]

According to the present invention, there is provided a method for solving the above-mentioned problems.
And methylation orange as a hydrogen ion concentration indicator, and benzyl orange, at least one selected from among Tropaeolin to deploy a porous support.

[0009]

The hydroxylamine sulfate reacts with formaldehyde to produce sulfuric acid at a concentration proportional to the formaldehyde concentration. Sulfuric acid causes a reaction scars concentrations proportional to the concentration of formaldehyde hydrogen ion concentration of 2 to 4 area of about a color transition range and be Rume chill Orange, benzyl orange, and discolor Tropaeolin on a porous support.
Further, methyl orange, benzyl orange, and tropeolin have a low degree of discoloration to sulfuric acid, which is naturally free on the porous carrier , and have high storage stability.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below based on embodiments. Dissolve 1.0 g of hydroxylamine sulfate in 30 ml of pure water, add 0.02 g of methyl yellow and 5 ml of glycerin as a hydrogen ion concentration indicator showing a color reaction to sulfuric acid, and add methanol or ethanol to this solution. Total amount of organic solvent such as 100
A color developing solution is prepared by adjusting the volume to milliliter.
This coloring solution is impregnated into a porous carrier such as filter paper made of cellulose or the like, and excess coloring solution is removed by a rubber roller or the like, and then the organic solvent is naturally dried at about 40 ° C. As a result, a detection paper having 1.3 g of hydroxylamine sulfate, 0.026 g of methyl yellow and 8 g of glycerin developed per square meter of the porous carrier is obtained.

FIG. 1 shows an example of an apparatus for measuring a gas concentration using a gas detection paper. In the figure, reference numeral 1 denotes a gas disposed opposite a conveyance path of a detection paper 2. In the suction part, the surface facing the tape 2 has a diameter of 1 cm.
A through-hole 3 having a pressure of about Torr is provided, and a negative pressure from a suction pump (not shown) acts via a pipe 4. 5
Is a measuring head unit 5 arranged on the other surface side of the detection paper 2 facing the through hole 3 of the gas suction unit 1, and a detected gas introduction port 9 is formed at a position facing the through hole 3 of the suction unit 1. A light-emitting diode 7 having a peak wavelength of 555 nm and a pin-type photodiode 8 having a maximum sensitivity at a wavelength of 560 nm are formed inside the light-shielding container so that a reaction mark formed on the detection paper 2 can be detected. It is arranged and housed in an incident / reflective relationship.

When the above-mentioned gas detecting paper is cut into a tape shape and set on reels 10 and 11 and a suction pressure from a pump (not shown) is applied to the suction unit 4, a measuring head unit is introduced from the inlet 9. The test gas is sucked into 5. The test gas is discharged from the through hole 6 to the outside through the through hole 3 via the detection paper 2. The test gas takes in formaldehyde in the process of passing through the detection paper 2, and the hydroxylamine sulfate originally present is reacted as follows: 2HCHO + (NH ₂ OH) ₂ H ₂ SO ₄ → 2H ₂ C = NOH + H ₂ SO ₄ + 2H ₂ O Generates sulfuric acid in an amount proportional to the concentration of formaldehyde. Since methyl yellow present in the porous carrier has a discoloration range in the range of hydrogen ion concentration of 2.9 to 4.0, it is discolored by a small amount of sulfuric acid generated by the reaction with formaldehyde, and the concentration is proportional to the amount. To produce reaction marks.

Thus, a predetermined sampling time,
For example, when about 5 minutes have elapsed, the suction is stopped and the process proceeds to the step of measuring the optical density of the reaction mark. Since the light from the light emitting diode 7 is absorbed in accordance with the optical density of the reaction mark formed on the surface of the detection paper, the optical density before the start of the measurement,
That is, the concentration of formaldehyde that has passed through the detection paper can be known by determining the optical density difference from the background density of the detection paper tape. When the measurement for one sampling is completed, the winding reel 10 is driven to release the reel.
The unused portion of the detection paper stored in the cartridge 11 is moved to the measurement area.

The detection paper was set on the measuring apparatus, and formaldehyde in an atmosphere having a relative humidity of 30% was sampled for 5 minutes while changing its concentration to 1, 2, 3, and 4 ppm. When the target concentration was measured, the concentration was 0.3 to 4
A calibration curve up to about ppm could be obtained, and a low concentration of formaldehyde could be detected with high reliability.

On the other hand, for comparison, a detection paper using hydroxylamine phosphate as a reagent for generating an acid by reaction with formaldehyde and methyl red as a hydrogen ion concentration indicator was also used under an environment of a relative humidity of 30%. As a result of the measurement, as indicated by the mark 同, the detection paper of the present invention showed only about 1/10 sensitivity. From this, it was confirmed that the detection paper of the present invention has high sensitivity particularly to a low concentration of formaldehyde existing in an atmosphere having a low relative humidity.

By the way, since methyl yellow is a hydrogen ion concentration indicator having a discoloration range in a hydrogen ion concentration range of 2.9 to 4.0, carbon dioxide gas present in the air,
It does not react at all with weakly acidic gases such as hydrogen fluoride or organic solvents such as alcohol, which is a solvent for formaldehyde, and also with hydrogen ions released from the hydroxylamine sulfate of the tape when not in use. It also has sufficient durability and can maintain the sensitivity at the time of manufacture even after long-term storage.

Needless to say, the concentrations and amounts of the reagents and the like shown in the above-described embodiments are both high in stability and sensitivity, and the background color of the tape by the hydrogen ion concentration indicator is as low as possible. Although the data is for data whose concentration can be suppressed, it is apparent that the same effect is obtained even if the above-mentioned concentration and amount are changed within an appropriate range centering on the values.

In the above-described embodiment, the case where methyl yellow is used as the hydrogen ion concentration indicator has been described. However, methyl orange having a hydrogen ion concentration similar to that of methyl yellow having a color changing region (the color changing region has a hydrogen ion concentration of 3 .1 to 4.4), benzyl orange (the discoloration area has a hydrogen ion concentration of 1.9 to 3.3), and tropeolin (the discoloration area has a hydrogen ion concentration of 1.4 to 3.2). And storage stability.

[0019]

As described above, in the present invention,
Hydroxylamine sulfate and hydrogen ion concentration indicator
Methylation Orange, benzyl orange Te, since expanded to at least one porous body selected from among tropaeolin, and color transition range free regions of about the hydrogen ion concentration of 2 to 4 sulfuric acid from hydroxylamine sulfate by formaldehyde By reacting with a hydrogen ion concentration indicator, formaldehyde with a low concentration of about several ppm, present in an environment with a low relative humidity, can be detected as a reaction mark on the porous carrier. Does not change color even with a weakly acidic gas, and the detection sensitivity can be maintained for a long period of time .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a measuring device used for detection paper of the present invention.

FIG. 2 is a diagram showing the calibration characteristics of the formaldehyde detection paper of the present invention and the calibration characteristics of a sample using methyl red as a hydrogen ion concentration indicator.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01N 31/22 121 G01N 31/22 122 G01N 21/78 G01N 31/00

Claims (1)

(57) [Claims] 1. A hydroxylamine sulfate, and methylation orange as a hydrogen ion concentration indicator, benzyl orange, formaldehyde detection paper made to expand to at least one porous carrier selected from among Tropaeolin.