CA2129463A1 - Formaldehyde detecting paper - Google Patents
Formaldehyde detecting paperInfo
- Publication number
- CA2129463A1 CA2129463A1 CA 2129463 CA2129463A CA2129463A1 CA 2129463 A1 CA2129463 A1 CA 2129463A1 CA 2129463 CA2129463 CA 2129463 CA 2129463 A CA2129463 A CA 2129463A CA 2129463 A1 CA2129463 A1 CA 2129463A1
- Authority
- CA
- Canada
- Prior art keywords
- formaldehyde
- detecting paper
- yellow
- hydroxylamine
- hydrogen ion
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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- Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)
Abstract
Abstract Detecting paper for detecting the formaldehyde present in the atmosphere is prepared by applying hydroxylamine sulfate and Metanil Yellow that changes its color when exposed to sulfuric acid over a carrier of porous sub-stance. When the sample gas passes through the porous carrier, the formaldehyde contained in it produces sulfuric acid (H2SO4) by decomposing the hydroxylamine sulfate as a result of the following reaction: 2HCHO + (NH2OH)2H2SO4 ?
2H2C = NOH + H2SO4 + 2H2O. The sulfuric acid reacts with the Metanil Yellow on the porous carrier, thus leaving a trace of reaction proportional to the concentration of formaldehyde.
2H2C = NOH + H2SO4 + 2H2O. The sulfuric acid reacts with the Metanil Yellow on the porous carrier, thus leaving a trace of reaction proportional to the concentration of formaldehyde.
Description
21~ ~63 SPECIFICATION
Title of the Invention Formaldehyde Detecting Paper Background of the Invention This invention relates to formaldehyde detecting paper used for the detection of formaldehyde present in the atmo-sphere by using a coloring reaction. -Description of the Prior Art ~;
A large space such as a sickroom is sterilized by filling the space with formaldehyde generated from a liquid ;
prepared by dissolving formaldehyde in ethanol or a solid `
form of formaldehyde~. As formaldehyde remains intact in the sterilized space, it is necessary to confirm that the -concentration of residual formaldehyde is not highe~ than the level specified by environmental control standards.
Semiconductor gas sensors are often used for this kind of measurements. However, semiconductor gas sensors do not ;~
have sufficient sensltlvities to measures the concentra~
tions~specified by environmental control standards (TLV 1 ppm). ~Besides, they have high sensitivities to other gas~
es, such as ethanol used for preventing polymerization of `~
formaldehyde~and ammonia gas used for neutralizing the forma`ldehyde that remains after completion of steriliza~
tion. Therefore, semiconductor gas sensors do not have , high enough reliability required in the measurement of ~
, r ~12 ~ ~ ~ 3 , formaldehyde at such low concentrations as are specified by environmental control standards.
Many problem-solving methods so far proposed detect the presence of formaldehyde by utilizing colorations re- ~ ~ -sulting from the reaction with, for example, silver ethyl-enediamine, nickel potassium cyanide, pararosaniline hydro-chloride and acetylacetone, and in the AHMT process. Using .~ :
reagents, however, these conventional methods require ~ ~
considerable manipulative skill in analytical.work. On the :
,. . ~, other hand, introduction of automatic control in analysis~:
is costly Summary of the Invention To overcome these problems, the detecting paper of this invention comprises a carrying paper of porous -.
substance covered wi~h an acid salt of hydroxylamine and a hydrogen ion concentration indicator that changes its color in acidic environments and detects.the presence of an acid resulting from the reaction of the acid salt of hydroxyl-amlne with formaldehyde. ~ -;;: . Object and Effect of the Invention ~ A flrst object of this lnventlon~is to provide form~
.
al:dehyde detecting paper that detects the concentratiion of formaldehyde with high accuracy~and reliability based on . ~ . , -. . traces of reaction without using reagent and expensive.
equlpment.
. 2 ; ' - .
A second object of this invention is to provide form-aldehyde detecting paper that detects extremely low concen-trations o~ formaldehyde of the order of a few ppm's even -in the environment with a relative humidity lower than the ;
average.
The formaldehyde detecting paper of this invention detects and dlstinguishes formaldehyde from other gases present in the environment. This paper allows easy measur~
ement of formaldehyde concentration while eliminating the need for using liquid reagents. ~ ;
Furthermore, the formaldehyde detecting paper of this invention detects low concentrations of formaldehyde of the order of a few ppm's present in the environment with low relative humidities from traces of reaction formed on the ;-~
porous carrier. In addition, the formaldehyde detecting :: ., .: .
paper of this invention permit long storage as exposure to: ~
.
~ such weakly acidic gases as carbon dioxide present in the~ ~
.
environment does not cause discoloration.
Brief Description of the Drawings Fig. 1 is a cross-sectional view of an example of a messuring device that uses the formaldehyde detecting paper oflthis invention. Fig. 2 plots the relative output ch~
aracteristic of a first embodiment of the formaldehyde -detecting paper of this invention. Fig. 3 plots the rela-tive output characteristic of a second embodiment of the , ~
r~ 2 ~ 2 ~ 1 6 3 formaldehyde detecting paper of this invention. Fig. 4 compares the relative output characteristic of a third em-bodiment of the formaldehyde detecting paper of this inven- ~
tion with that of a detecting paper covered with hydroxyl- ~ .
amine phosphate and methyl red.
Description of the Prererred Embodiments [Example 1]
A first solution was prepared by dissolving 1.0 gram of hydroxylamine sulfate in 100 milliliters of purified water. Then, a second sol.ution was prepared by dissolving 0.02 gram of Metanil Yellow, a hydrogen ion concentration indicator that changes its color when reacted with sulfuric acid, and 15 milliliter of glycerin in methanol.of the amount that makes the total quantity of the solution 100 milliliter.
A coloring liquid was prepared by mixing the first and second solutions. The carrier, such as filter paper of cellulose, was impregnated with the obtained coloring . ~ . .
liquid. After the excess coloring liquid has been squeezed .
out..by rubber rollers or other similar means,.the organic . solvent was air-dried a.t approx1mately 40 C.
Then, a detecting paper of porous substance covered~
with 0.35 gram of hydroxylamine sulfate, O.l5 gram of Met-: anil Yellow and 21 grams: of glycerin per square meter was ~ : obtained. .
.
~2~3 ~g3 .~ , ., .
Fig. 1 shows an example of an instrument that deter~
mines the concentration of formaldehyde by using the gas ;~
detecting paper of this invention. In the drawing, refer-ence numeral 1 designates a gas suction device provided in the path of a tape of detector tape 2. The gas suction ~; ~
device 1 has a through hole 3 having a diameter of approxi- ~;
mately 1 cm that opens in the surface thereof that faces i the detecting paper 2. A negative pressure is supplied from a suction pump, not shown, through a pipe 4.
Reference numeral 5 denotes a measuring head disposed ! . .
on the other side of the detecting paper 2 opposite to the ;- `
through hole 3 in the gas suction device 1. The measuring head 5 constitutes a light-shielding means having a gas inlet 6 located in a position opposite to the through hole 3 in the gas suction device 1. The measuring head 5 con~
tains a light-emitting diode 7 emitting a light having a ~ ;
peak wavelength of 555 nm`and a pin-type photodiode 8 that : , ,, exhlbits maximum sensitlvity to a light having a wavelength ~ -f 560 nm. Th~e light-emitting diode 7 and photodiode 8 are -~
disposed in such a position that they can detect a trace of ~ reaction formed on the~detecting paper 2.
I ! After the tape of gas detecting paper 2 is set-over ~ reels 10 and 11, the suction pressure supplied from the `~: pump not shown draws the object gas through an intake 9 to the measuring head 5. The object gas from the gas inlet 6 ' ~9~3 is discharged outside through the pipe 4 after passing through the tape of detecting paper 2 and the through hole 3. When the object gas passes through the tape of detecting paper 2, the water retained by the glycerin on the tape 2 absorbs formaldehyde therefrom.
The absorbed formaldehyde reacts with hydroxylamine sulfate present on the detecting paper 2 to produce sulfuric acid as a result of the following reaction:
2HCHO -~ (NH20H)2H2SO4 ~ :
?H2C = NOH + H2S04 + 2H20 The produced sulfuric acid reacts with Metanil yellow that then changes its color according to the concentration of formaldehyde.
After an exposure time of a given length, such as approximately 40 seconds, has passed, the suction of the object gas.is.stopped to determine the optical concentra-tlon of the trace of react.ion. The light from the light~
emitting:.diode 7 is absorbed according to the optical :
concentration of th~e trace of reaction formed on the sur- :
face of the detecting paper~2. Thereforej the -concentration~of the formaldehyde that has passed through:
the tape.can be obtained by ùetermining the difference in optical concentration between the optical concentration before the start of the measurement,~or-the background con~
centration of the tape, .and~the trace of reaction formed~
; ~ ~ . . - , ~ 6 ~ 2 ~ 3 .
thereon. When the measurement of one specimen is complete, the takeup reel 10 is turned to feed an unused portion of the tape 2 into the measuring zone.
With the de~ecting paper set on the measuring instr~
ument just described and the exposure time at ~0 seconds, optical concentrations of traces of reaction were measured by varying the concentration of formaldehyde-through lO00 . ~
ppm, 2000 ppm and so on. Detection with high reproducibi~
lity was possible up to approximately 3000 pm, as indicated by solid circles (O) in Fig. 2. ~ ~
When the exposure time was increased to 60 seconds, - ~-the relative detection output for the same formaldehyde concentration increased accordingly, as indicated by open circles (O).
The carr~ier used in the example described above was impregnated with glycerin. When the formaldehyde concen-tration was above lOOO ppm, the détecting paper exhibited ~ . . .
substantially the same sensitivity whether glycerin was present or not.~ Thus, glycerin~proved to be an effectlve additive for the detection of lower concentrations of formaldehyde~
The substance that produces acid by reaction with formaldehyde in the example just described was hydroxyl-~amine sulfate. Hydroxylamine hydrochloride is another salt that hydroxylamine forms with a strong acid. When decom-.
r ~~
posed by formaldehyde, hydroxylamine hydrochloride producesan acid that forms a trace of reaction with Metanil Yellow that is a hydrogen ion concentration indicator. The det-ecting paper prepared with the use of hydroxylamine hydro-chloride proved to provide substantially the same relative detection output as hydroxylamine sulfate.
In addition to Metanil Yellow, allzarin yellow, benzyl yellow and methyl yellow are also hydrogen ion concentra-tion indicators that color when reacted with the acid formed by the reaction between formaldehyde and a salt formed by a strong acid and hydroxylamine.
¦ The detection paper prepared by the same method using, in place of Metanil Yellow, alizarin yellow, benzyl yellow and methyl yellow also proved to be capable of detecting formaldehyde.
Being a hydrogen ion concentration indicator that changes its color when the concentration of hydrogen ion is within the range of pH 1.2 to pH 2.3, Metanil Yellow does `
~ ~ not react at all with such weakly acidic gasès as carbon ~ ~
- , dioxide and hydrogen fluoride present in the air, alkaline ` -gases such as ammonia, and organic solvents such as alco-~, hol. This feature permits not only detecting formaldehyde with high selectivity but also long storage without dis-coloration.
, The example described above was the case of determin-, ~. ,.
^ ~2~3 ing the presence of formaldehyde of such high concentration as of the order emitted from sterilizers or other similar devices. The detecting paper of this inventlon is also applicable to the formaldehyde of as low a concentration as only a few ppm's by extending the length of exposure time ;
to approximately 3 minutes.
[Example 2]
A first solution was prepared by dissolving-1.0 gram of hydroxylamine phosphate in 100 milliliters of purified water. Then, a second solution was prepared by dissolving 0.04 gram of methyl red, a hydrogen ion concentration indi ~ -cator that changes its color when exposed to a weak acid, and 15 milliliter of glycerin in methanol of the amount that makes the total quantity of the solution i00 millili~
ter. ~ ; ;
To a coloring liquid prepared by mixing the first and ~
- . ...
~ second solutions was added a given amount, such as approxi~
., : ... ....
mately 30 V/V ~, of one of buffers to prevent the change of ; ~ c~olor by carbon dioxide in the atmosphere which consist of ; a-combination of NaCO3 and NaHCO3, Na2CO3 and NaOH, and NaHCO3 and NaOH.
.
The carrier of such material as cellulose, was im-pregnated with the obtained coloring liquid. After the excess coloring liquid has been squeezed out by rubber ;~ rollers or other similar means, the carrier was air-dried . .
~ ' ' , 9 .
~ ~12~3 at approximately 40 C. The amount of the buffer must be such as is enough to allow it to perform its buffering functlon to the carbon dioxide in the atmosphere. If the buffer is insufficient, the hydrogen ion concentration indicator is colored by such weakly acld gas as carbon dioxide in the air. By contrast, a coloring liquid con-taining too much buffer contains so watery that its drying process becomes time-consuming and inefficient. Therefore, an optimum amount of buffer should preferably be added.
Then, a detecting paper of porous substance covered with 0.03 gram of hydroxylamine phosphate, 0.05 gram of methyl red and 21.5 grams of glycerin per square meter was obtained Fig. 3 shows the measurements obtained by exposing the detecting paper thus obtained~and set on the measuring lnstrument described before for a period of three minutes to sample gases~containlng 0.2, 1.0 and 4.0 ppm of formal-dehyde.
Obviously, the formaldehyde detecting papèr prepared with the use of a hydrogen ion concentration indicator, such as the methyl red used in the example described above, that changes;its color in the presence of a salt of hydrox-ylamine and a weak acid and sulfuric acid resulting from the decomposition thereof has high enough sensitivity to detect the presence of formaldehyde of such low concentra-212~ 3 tions as not more than one-third of 1 ppm, which is the acceptable environmental limit (TLV), with a high degree of reliability. Therefore, the formaldehyde detecting paper -thus obtained is suited for use in the monitoring of the concentration of formaldehyde in the environment.
Another detecting paper prepared with the use of the same quantities of the same constituents but hydroxylamine phosphate, which was replaced with hydroxylamine oxalate, also provided similar relative detection outputs. ;''~
In addition to methyl red, lacmoid and neutral red also serve as hydrogen ion concentration indicators color-ing in the presence of phospholic and oxalic acids. Detec-ting papers prepared by using in place of methyl red, also -~
provided simil~r detection outputs.
The concentrations and quantities of the reagents used in the examples described above were selected to provide '~ ' high stabilities and sensitivities and keep the change of the original color of~the tape by the hydrogen ion concen~
tratlon lndicator to a mlnimum. Of course, similar effects ~ ~
are obtainable;even if thelr concentration and quantity are ' ~' increased or decreased within appropriate limits.
i [Example 3]
In 30 milliliters of''pure water was dissolved 1.0 gram .
~ of hydroxylamine sulfate. After adding 0.02 gram of methyl ~ .
~ yellow, a hydrogen ion concentration indicator that changes 11 '. . ~, .
.
Title of the Invention Formaldehyde Detecting Paper Background of the Invention This invention relates to formaldehyde detecting paper used for the detection of formaldehyde present in the atmo-sphere by using a coloring reaction. -Description of the Prior Art ~;
A large space such as a sickroom is sterilized by filling the space with formaldehyde generated from a liquid ;
prepared by dissolving formaldehyde in ethanol or a solid `
form of formaldehyde~. As formaldehyde remains intact in the sterilized space, it is necessary to confirm that the -concentration of residual formaldehyde is not highe~ than the level specified by environmental control standards.
Semiconductor gas sensors are often used for this kind of measurements. However, semiconductor gas sensors do not ;~
have sufficient sensltlvities to measures the concentra~
tions~specified by environmental control standards (TLV 1 ppm). ~Besides, they have high sensitivities to other gas~
es, such as ethanol used for preventing polymerization of `~
formaldehyde~and ammonia gas used for neutralizing the forma`ldehyde that remains after completion of steriliza~
tion. Therefore, semiconductor gas sensors do not have , high enough reliability required in the measurement of ~
, r ~12 ~ ~ ~ 3 , formaldehyde at such low concentrations as are specified by environmental control standards.
Many problem-solving methods so far proposed detect the presence of formaldehyde by utilizing colorations re- ~ ~ -sulting from the reaction with, for example, silver ethyl-enediamine, nickel potassium cyanide, pararosaniline hydro-chloride and acetylacetone, and in the AHMT process. Using .~ :
reagents, however, these conventional methods require ~ ~
considerable manipulative skill in analytical.work. On the :
,. . ~, other hand, introduction of automatic control in analysis~:
is costly Summary of the Invention To overcome these problems, the detecting paper of this invention comprises a carrying paper of porous -.
substance covered wi~h an acid salt of hydroxylamine and a hydrogen ion concentration indicator that changes its color in acidic environments and detects.the presence of an acid resulting from the reaction of the acid salt of hydroxyl-amlne with formaldehyde. ~ -;;: . Object and Effect of the Invention ~ A flrst object of this lnventlon~is to provide form~
.
al:dehyde detecting paper that detects the concentratiion of formaldehyde with high accuracy~and reliability based on . ~ . , -. . traces of reaction without using reagent and expensive.
equlpment.
. 2 ; ' - .
A second object of this invention is to provide form-aldehyde detecting paper that detects extremely low concen-trations o~ formaldehyde of the order of a few ppm's even -in the environment with a relative humidity lower than the ;
average.
The formaldehyde detecting paper of this invention detects and dlstinguishes formaldehyde from other gases present in the environment. This paper allows easy measur~
ement of formaldehyde concentration while eliminating the need for using liquid reagents. ~ ;
Furthermore, the formaldehyde detecting paper of this invention detects low concentrations of formaldehyde of the order of a few ppm's present in the environment with low relative humidities from traces of reaction formed on the ;-~
porous carrier. In addition, the formaldehyde detecting :: ., .: .
paper of this invention permit long storage as exposure to: ~
.
~ such weakly acidic gases as carbon dioxide present in the~ ~
.
environment does not cause discoloration.
Brief Description of the Drawings Fig. 1 is a cross-sectional view of an example of a messuring device that uses the formaldehyde detecting paper oflthis invention. Fig. 2 plots the relative output ch~
aracteristic of a first embodiment of the formaldehyde -detecting paper of this invention. Fig. 3 plots the rela-tive output characteristic of a second embodiment of the , ~
r~ 2 ~ 2 ~ 1 6 3 formaldehyde detecting paper of this invention. Fig. 4 compares the relative output characteristic of a third em-bodiment of the formaldehyde detecting paper of this inven- ~
tion with that of a detecting paper covered with hydroxyl- ~ .
amine phosphate and methyl red.
Description of the Prererred Embodiments [Example 1]
A first solution was prepared by dissolving 1.0 gram of hydroxylamine sulfate in 100 milliliters of purified water. Then, a second sol.ution was prepared by dissolving 0.02 gram of Metanil Yellow, a hydrogen ion concentration indicator that changes its color when reacted with sulfuric acid, and 15 milliliter of glycerin in methanol.of the amount that makes the total quantity of the solution 100 milliliter.
A coloring liquid was prepared by mixing the first and second solutions. The carrier, such as filter paper of cellulose, was impregnated with the obtained coloring . ~ . .
liquid. After the excess coloring liquid has been squeezed .
out..by rubber rollers or other similar means,.the organic . solvent was air-dried a.t approx1mately 40 C.
Then, a detecting paper of porous substance covered~
with 0.35 gram of hydroxylamine sulfate, O.l5 gram of Met-: anil Yellow and 21 grams: of glycerin per square meter was ~ : obtained. .
.
~2~3 ~g3 .~ , ., .
Fig. 1 shows an example of an instrument that deter~
mines the concentration of formaldehyde by using the gas ;~
detecting paper of this invention. In the drawing, refer-ence numeral 1 designates a gas suction device provided in the path of a tape of detector tape 2. The gas suction ~; ~
device 1 has a through hole 3 having a diameter of approxi- ~;
mately 1 cm that opens in the surface thereof that faces i the detecting paper 2. A negative pressure is supplied from a suction pump, not shown, through a pipe 4.
Reference numeral 5 denotes a measuring head disposed ! . .
on the other side of the detecting paper 2 opposite to the ;- `
through hole 3 in the gas suction device 1. The measuring head 5 constitutes a light-shielding means having a gas inlet 6 located in a position opposite to the through hole 3 in the gas suction device 1. The measuring head 5 con~
tains a light-emitting diode 7 emitting a light having a ~ ;
peak wavelength of 555 nm`and a pin-type photodiode 8 that : , ,, exhlbits maximum sensitlvity to a light having a wavelength ~ -f 560 nm. Th~e light-emitting diode 7 and photodiode 8 are -~
disposed in such a position that they can detect a trace of ~ reaction formed on the~detecting paper 2.
I ! After the tape of gas detecting paper 2 is set-over ~ reels 10 and 11, the suction pressure supplied from the `~: pump not shown draws the object gas through an intake 9 to the measuring head 5. The object gas from the gas inlet 6 ' ~9~3 is discharged outside through the pipe 4 after passing through the tape of detecting paper 2 and the through hole 3. When the object gas passes through the tape of detecting paper 2, the water retained by the glycerin on the tape 2 absorbs formaldehyde therefrom.
The absorbed formaldehyde reacts with hydroxylamine sulfate present on the detecting paper 2 to produce sulfuric acid as a result of the following reaction:
2HCHO -~ (NH20H)2H2SO4 ~ :
?H2C = NOH + H2S04 + 2H20 The produced sulfuric acid reacts with Metanil yellow that then changes its color according to the concentration of formaldehyde.
After an exposure time of a given length, such as approximately 40 seconds, has passed, the suction of the object gas.is.stopped to determine the optical concentra-tlon of the trace of react.ion. The light from the light~
emitting:.diode 7 is absorbed according to the optical :
concentration of th~e trace of reaction formed on the sur- :
face of the detecting paper~2. Thereforej the -concentration~of the formaldehyde that has passed through:
the tape.can be obtained by ùetermining the difference in optical concentration between the optical concentration before the start of the measurement,~or-the background con~
centration of the tape, .and~the trace of reaction formed~
; ~ ~ . . - , ~ 6 ~ 2 ~ 3 .
thereon. When the measurement of one specimen is complete, the takeup reel 10 is turned to feed an unused portion of the tape 2 into the measuring zone.
With the de~ecting paper set on the measuring instr~
ument just described and the exposure time at ~0 seconds, optical concentrations of traces of reaction were measured by varying the concentration of formaldehyde-through lO00 . ~
ppm, 2000 ppm and so on. Detection with high reproducibi~
lity was possible up to approximately 3000 pm, as indicated by solid circles (O) in Fig. 2. ~ ~
When the exposure time was increased to 60 seconds, - ~-the relative detection output for the same formaldehyde concentration increased accordingly, as indicated by open circles (O).
The carr~ier used in the example described above was impregnated with glycerin. When the formaldehyde concen-tration was above lOOO ppm, the détecting paper exhibited ~ . . .
substantially the same sensitivity whether glycerin was present or not.~ Thus, glycerin~proved to be an effectlve additive for the detection of lower concentrations of formaldehyde~
The substance that produces acid by reaction with formaldehyde in the example just described was hydroxyl-~amine sulfate. Hydroxylamine hydrochloride is another salt that hydroxylamine forms with a strong acid. When decom-.
r ~~
posed by formaldehyde, hydroxylamine hydrochloride producesan acid that forms a trace of reaction with Metanil Yellow that is a hydrogen ion concentration indicator. The det-ecting paper prepared with the use of hydroxylamine hydro-chloride proved to provide substantially the same relative detection output as hydroxylamine sulfate.
In addition to Metanil Yellow, allzarin yellow, benzyl yellow and methyl yellow are also hydrogen ion concentra-tion indicators that color when reacted with the acid formed by the reaction between formaldehyde and a salt formed by a strong acid and hydroxylamine.
¦ The detection paper prepared by the same method using, in place of Metanil Yellow, alizarin yellow, benzyl yellow and methyl yellow also proved to be capable of detecting formaldehyde.
Being a hydrogen ion concentration indicator that changes its color when the concentration of hydrogen ion is within the range of pH 1.2 to pH 2.3, Metanil Yellow does `
~ ~ not react at all with such weakly acidic gasès as carbon ~ ~
- , dioxide and hydrogen fluoride present in the air, alkaline ` -gases such as ammonia, and organic solvents such as alco-~, hol. This feature permits not only detecting formaldehyde with high selectivity but also long storage without dis-coloration.
, The example described above was the case of determin-, ~. ,.
^ ~2~3 ing the presence of formaldehyde of such high concentration as of the order emitted from sterilizers or other similar devices. The detecting paper of this inventlon is also applicable to the formaldehyde of as low a concentration as only a few ppm's by extending the length of exposure time ;
to approximately 3 minutes.
[Example 2]
A first solution was prepared by dissolving-1.0 gram of hydroxylamine phosphate in 100 milliliters of purified water. Then, a second solution was prepared by dissolving 0.04 gram of methyl red, a hydrogen ion concentration indi ~ -cator that changes its color when exposed to a weak acid, and 15 milliliter of glycerin in methanol of the amount that makes the total quantity of the solution i00 millili~
ter. ~ ; ;
To a coloring liquid prepared by mixing the first and ~
- . ...
~ second solutions was added a given amount, such as approxi~
., : ... ....
mately 30 V/V ~, of one of buffers to prevent the change of ; ~ c~olor by carbon dioxide in the atmosphere which consist of ; a-combination of NaCO3 and NaHCO3, Na2CO3 and NaOH, and NaHCO3 and NaOH.
.
The carrier of such material as cellulose, was im-pregnated with the obtained coloring liquid. After the excess coloring liquid has been squeezed out by rubber ;~ rollers or other similar means, the carrier was air-dried . .
~ ' ' , 9 .
~ ~12~3 at approximately 40 C. The amount of the buffer must be such as is enough to allow it to perform its buffering functlon to the carbon dioxide in the atmosphere. If the buffer is insufficient, the hydrogen ion concentration indicator is colored by such weakly acld gas as carbon dioxide in the air. By contrast, a coloring liquid con-taining too much buffer contains so watery that its drying process becomes time-consuming and inefficient. Therefore, an optimum amount of buffer should preferably be added.
Then, a detecting paper of porous substance covered with 0.03 gram of hydroxylamine phosphate, 0.05 gram of methyl red and 21.5 grams of glycerin per square meter was obtained Fig. 3 shows the measurements obtained by exposing the detecting paper thus obtained~and set on the measuring lnstrument described before for a period of three minutes to sample gases~containlng 0.2, 1.0 and 4.0 ppm of formal-dehyde.
Obviously, the formaldehyde detecting papèr prepared with the use of a hydrogen ion concentration indicator, such as the methyl red used in the example described above, that changes;its color in the presence of a salt of hydrox-ylamine and a weak acid and sulfuric acid resulting from the decomposition thereof has high enough sensitivity to detect the presence of formaldehyde of such low concentra-212~ 3 tions as not more than one-third of 1 ppm, which is the acceptable environmental limit (TLV), with a high degree of reliability. Therefore, the formaldehyde detecting paper -thus obtained is suited for use in the monitoring of the concentration of formaldehyde in the environment.
Another detecting paper prepared with the use of the same quantities of the same constituents but hydroxylamine phosphate, which was replaced with hydroxylamine oxalate, also provided similar relative detection outputs. ;''~
In addition to methyl red, lacmoid and neutral red also serve as hydrogen ion concentration indicators color-ing in the presence of phospholic and oxalic acids. Detec-ting papers prepared by using in place of methyl red, also -~
provided simil~r detection outputs.
The concentrations and quantities of the reagents used in the examples described above were selected to provide '~ ' high stabilities and sensitivities and keep the change of the original color of~the tape by the hydrogen ion concen~
tratlon lndicator to a mlnimum. Of course, similar effects ~ ~
are obtainable;even if thelr concentration and quantity are ' ~' increased or decreased within appropriate limits.
i [Example 3]
In 30 milliliters of''pure water was dissolved 1.0 gram .
~ of hydroxylamine sulfate. After adding 0.02 gram of methyl ~ .
~ yellow, a hydrogen ion concentration indicator that changes 11 '. . ~, .
.
2 1 2 ~ 3 its color in the presence of sulfuric acid, and 5 millili-ters of glycerin, an organic solvent, such as methanol or ethanol, was added to make the total quantity of the ob-tained liquid 100 milliliter. The carrier of porous sub-stance, such as cellulose, was impregnated with the ob-tained coloring liquid. After the excess coloring liquid ~' has been squeezed out by rubber rollers or other similar means, the organic solvent was air-dried at approximately '~
40 C.
Then, a detecting paper of porous substance covered with 1.3 gram of hydroxylamine sulfate, 0.026 gram of methyl yellow and 8 grams of glycerin per square meter was ' ;~
obtained.
When the detecting paper 2 was set on the measuring ''~
instrument described earlier for detection of formaldehyde in a sample gas, the paper absorbs formaldehyde when the sample gas passes therethrough. Then, as muGh sulfuric '' ~' acld~as is proportional to the concentration of formalde-hyde was produced by the followi'ng reaction between the hy- ~' droxylamine sul'fate on the detectlng paper 2 and formalde-hyde":
2XCHO +i(NH20H)2H2SO4 -~
~ . :
2H2C = NOH ~ H2SO4 ~ 2H2O -The methyl yellow on the detecti'ng paper, which -changes its color when the pH lS between 2.9 and 4.0, 12 ''' ' ' " ~- '~, .
. , : :' :. .-' 99', 2~29~ ~3 colored when exposed to a slight amount of sulfuric acid resulting from the reactlon with formaldehyde, thereby leaving a trace of reaCtion of op~ical concentration corresponding to the concentration of formaldehyde.
With the detecting paper set on the measuring instr-ument described before and the exposure time at 5 minutes, optical concentrations of traces of reaction were measured by varying the concentration o~ formaldehyde in an atmos-phere with as low a relative humidity as 30 % through 1, 2, 3 and 4 ppm. Then, relative detection outputs between 0.3 and 4 ppm were obtained, as indicated by solid circles (~
in Fig. 4.
~ The detection paper just described thus proved to be ; suited for the detection of formaldehyde at low concentr-ations in atmospheres with low humidities. ~ -~
For comparisonj measurements were made in the same atmosphere with a relative humidity of 30 % using a detec-tion paper prepared by the use of hydroxyamlne phosphate as the reagent that produces an acid as a result of a reaction wlth formaldehyde-and methyl red as a hydrogen ion Concen-tration indicator. The relàtive detection outputs obtained 1 were only approximately one-tenth those of the detecting paper-according to this 1nvention, as indicated by open circles (O) in the same figure.
~ Thus; the detectlon paper just described~proved to `~ ~ 13 2 ~ 2 ~
have a high sensitivity to formaldehyde at low concentra-~ ' tions in atmospheres with particularly low relative humi- ;
dities.
Being a hydrogen ion concentration indicator that , changes its color within the pH range of 2.9 to 4.0, methyl yellow does not react at all with such weakly acidic gases as carbon dioxide and hydrogen fluoride present in the air and alcohol and other organic solvents used as the solvent for formaldehyde. Having adequate durability in the pre-sence of hydro~en ions freed from the hydroxylamine sulfate on the tape while it is not in use, the tape remains as sensitive as it was immedia'tely after production even after ' '~
long storage. '"
The tape just described was prepared by the use of methyl yellow as a hydrogen ion concentration indicator.
Methyl orange (coloring within the pH range of 3.1 to 4.4), benzyl orange (coloring'within the~pH range of 1.9 to 3.3) and'tropeolln (colorlng wlthin the pH range of 1.9 and 3.2), which all change their color within the pH ranges slmilar to the;range for methyI yellow, also proved to '' ' provide similar relative detecti-on outputs and have as long ,' `' sheif life as methyl yellow. : ;~
... , .~, .
-~' The concentrations and quantities of the reagents ~ - used in the~examples described above were selected to ,~' provide high stabilities and;sensitivities and keep the " ' ~ ~ 14 ~
: ~, 2~2~3 change of the original color of the tape by the hydrogen on concentration indicator to a minimum. Of course, similar effects are obtainable even if their concentration :~:
and quantity are increased or decreased within appropriate limits.
' - ; ' :. ~'"' . ~
;,~ ' , ' ;' . ~:
40 C.
Then, a detecting paper of porous substance covered with 1.3 gram of hydroxylamine sulfate, 0.026 gram of methyl yellow and 8 grams of glycerin per square meter was ' ;~
obtained.
When the detecting paper 2 was set on the measuring ''~
instrument described earlier for detection of formaldehyde in a sample gas, the paper absorbs formaldehyde when the sample gas passes therethrough. Then, as muGh sulfuric '' ~' acld~as is proportional to the concentration of formalde-hyde was produced by the followi'ng reaction between the hy- ~' droxylamine sul'fate on the detectlng paper 2 and formalde-hyde":
2XCHO +i(NH20H)2H2SO4 -~
~ . :
2H2C = NOH ~ H2SO4 ~ 2H2O -The methyl yellow on the detecti'ng paper, which -changes its color when the pH lS between 2.9 and 4.0, 12 ''' ' ' " ~- '~, .
. , : :' :. .-' 99', 2~29~ ~3 colored when exposed to a slight amount of sulfuric acid resulting from the reactlon with formaldehyde, thereby leaving a trace of reaCtion of op~ical concentration corresponding to the concentration of formaldehyde.
With the detecting paper set on the measuring instr-ument described before and the exposure time at 5 minutes, optical concentrations of traces of reaction were measured by varying the concentration o~ formaldehyde in an atmos-phere with as low a relative humidity as 30 % through 1, 2, 3 and 4 ppm. Then, relative detection outputs between 0.3 and 4 ppm were obtained, as indicated by solid circles (~
in Fig. 4.
~ The detection paper just described thus proved to be ; suited for the detection of formaldehyde at low concentr-ations in atmospheres with low humidities. ~ -~
For comparisonj measurements were made in the same atmosphere with a relative humidity of 30 % using a detec-tion paper prepared by the use of hydroxyamlne phosphate as the reagent that produces an acid as a result of a reaction wlth formaldehyde-and methyl red as a hydrogen ion Concen-tration indicator. The relàtive detection outputs obtained 1 were only approximately one-tenth those of the detecting paper-according to this 1nvention, as indicated by open circles (O) in the same figure.
~ Thus; the detectlon paper just described~proved to `~ ~ 13 2 ~ 2 ~
have a high sensitivity to formaldehyde at low concentra-~ ' tions in atmospheres with particularly low relative humi- ;
dities.
Being a hydrogen ion concentration indicator that , changes its color within the pH range of 2.9 to 4.0, methyl yellow does not react at all with such weakly acidic gases as carbon dioxide and hydrogen fluoride present in the air and alcohol and other organic solvents used as the solvent for formaldehyde. Having adequate durability in the pre-sence of hydro~en ions freed from the hydroxylamine sulfate on the tape while it is not in use, the tape remains as sensitive as it was immedia'tely after production even after ' '~
long storage. '"
The tape just described was prepared by the use of methyl yellow as a hydrogen ion concentration indicator.
Methyl orange (coloring within the pH range of 3.1 to 4.4), benzyl orange (coloring'within the~pH range of 1.9 to 3.3) and'tropeolln (colorlng wlthin the pH range of 1.9 and 3.2), which all change their color within the pH ranges slmilar to the;range for methyI yellow, also proved to '' ' provide similar relative detecti-on outputs and have as long ,' `' sheif life as methyl yellow. : ;~
... , .~, .
-~' The concentrations and quantities of the reagents ~ - used in the~examples described above were selected to ,~' provide high stabilities and;sensitivities and keep the " ' ~ ~ 14 ~
: ~, 2~2~3 change of the original color of the tape by the hydrogen on concentration indicator to a minimum. Of course, similar effects are obtainable even if their concentration :~:
and quantity are increased or decreased within appropriate limits.
' - ; ' :. ~'"' . ~
;,~ ' , ' ;' . ~:
Claims
Claims What is claimed is:
(1) Formaldehyde detecting paper prepared by applying an acid salt of hydroxylamine and a hydrogen ion concen-tration indicator whose color changes in acidic atmospheres over a carrier of porous substance.
(2) Formaldehyde detecting paper according to claim 1, in which the acid salt is hydroxylamine sulfate and the hydrogen ion concentration indicator is selected from the group of Metanil Yellow, alizarin yellow, benzyl yellow and methyl yellow.
(3) Formaldehyde detecting paper according to claim 1, in which the acid salt is at least one selected from the group of hydroxylamine phosphate and hydroxylamine oxalate and the hydrogen ion concentration indicator is one select-ed from the group of methyl red, lacmoid and neutral red, and a buffering constituent is added thereto.
(4) Formaldehyde detecting paper according to claim 3, in which the buffering constituent is at least one selected from the group of NaCO3 and NaHCO3, Na2CO3 and NaOH, and NaHCO3 and NaOH.
(5) Formaldehyde detecting paper according to claims 1 to 3, in which the porous carrier contains a polyalcohol.
(6) Formaldehyde detecting paper prepared by applying hydroxylamine sulfate and a hydrogen ion concentration indicator selected from the group of methyl yellow, methyl orange, benzyl orange and tropeolin over a carrier of porous substance.
(1) Formaldehyde detecting paper prepared by applying an acid salt of hydroxylamine and a hydrogen ion concen-tration indicator whose color changes in acidic atmospheres over a carrier of porous substance.
(2) Formaldehyde detecting paper according to claim 1, in which the acid salt is hydroxylamine sulfate and the hydrogen ion concentration indicator is selected from the group of Metanil Yellow, alizarin yellow, benzyl yellow and methyl yellow.
(3) Formaldehyde detecting paper according to claim 1, in which the acid salt is at least one selected from the group of hydroxylamine phosphate and hydroxylamine oxalate and the hydrogen ion concentration indicator is one select-ed from the group of methyl red, lacmoid and neutral red, and a buffering constituent is added thereto.
(4) Formaldehyde detecting paper according to claim 3, in which the buffering constituent is at least one selected from the group of NaCO3 and NaHCO3, Na2CO3 and NaOH, and NaHCO3 and NaOH.
(5) Formaldehyde detecting paper according to claims 1 to 3, in which the porous carrier contains a polyalcohol.
(6) Formaldehyde detecting paper prepared by applying hydroxylamine sulfate and a hydrogen ion concentration indicator selected from the group of methyl yellow, methyl orange, benzyl orange and tropeolin over a carrier of porous substance.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP220623/1993 | 1993-08-12 | ||
| JP22062393A JP3187215B2 (en) | 1993-08-12 | 1993-08-12 | Formaldehyde detection tape |
| JP41930/1994 | 1994-02-16 | ||
| JP04193094A JP3187235B2 (en) | 1994-02-16 | 1994-02-16 | Formaldehyde detection paper |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2129463A1 true CA2129463A1 (en) | 1995-02-13 |
Family
ID=26381578
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2129463 Abandoned CA2129463A1 (en) | 1993-08-12 | 1994-08-04 | Formaldehyde detecting paper |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2129463A1 (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102172466A (en) * | 2011-04-02 | 2011-09-07 | 陈志朋 | Formaldehyde processing liquid for furniture |
| CN103969252A (en) * | 2013-01-30 | 2014-08-06 | 上海市上海中学 | Rose-variety flower extract-containing formaldehyde color-change indicator |
| CN113390864A (en) * | 2021-06-10 | 2021-09-14 | 宁波大学 | Multifunctional graphene quantum dot detection agent and application thereof |
| CN113984743A (en) * | 2021-09-30 | 2022-01-28 | 华南理工大学 | Formaldehyde detection test paper based on nano composite fiber and preparation method and application thereof |
-
1994
- 1994-08-04 CA CA 2129463 patent/CA2129463A1/en not_active Abandoned
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102172466A (en) * | 2011-04-02 | 2011-09-07 | 陈志朋 | Formaldehyde processing liquid for furniture |
| CN103969252A (en) * | 2013-01-30 | 2014-08-06 | 上海市上海中学 | Rose-variety flower extract-containing formaldehyde color-change indicator |
| CN113390864A (en) * | 2021-06-10 | 2021-09-14 | 宁波大学 | Multifunctional graphene quantum dot detection agent and application thereof |
| CN113390864B (en) * | 2021-06-10 | 2023-07-25 | 宁波大学 | Multifunctional graphene quantum dot detection agent and application thereof |
| CN113984743A (en) * | 2021-09-30 | 2022-01-28 | 华南理工大学 | Formaldehyde detection test paper based on nano composite fiber and preparation method and application thereof |
| CN113984743B (en) * | 2021-09-30 | 2022-08-16 | 华南理工大学 | Formaldehyde detection test paper based on nano composite fiber and preparation method and application thereof |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |