ES1281109U - DEVICE FOR DETECTION OF FORMALDEHYDE - Google Patents

Abstract

An "in situ" detection device for formaldehyde in the gas phase, comprising the reagents: - a primary beta-arylethylamine having alkoxy groups, hydroxyl groups or combinations of both in positions 3 and 4, - an amino acid glycine and - a reducing sugar arranged on a support of a material, selected from paper, a hydrophobic polymer, a hydrophilic polymer, metal, glass and plastic.

Description

Device for the detection of formaldehyde

TECHNICAL SECTOR

This invention falls within the technical field of substance analysis devices through the use of chemical indicators and by optical means, specifically the detection of formaldehyde by colorimetry or fluorescence.

STATE OF THE ART

Formaldehyde is one of the most important basic organic compounds in the chemical industry. The Spanish group ERCROS produces around 788,000 tons per year and BASF 500,000 tons per year. It is used in the production of various products, from medicines to melamine, bakelite, etc.

Given that the risk prevention regulations are increasingly restrictive in terms of the daily dose and the maximum levels of exposure to formaldehyde, there is a growing demand from the companies in which formaldehyde is used in the development of new sensors for the detection of this compound.

In recent years the use of chemodosimeters, chromogenic or fluorogenic for the detection of neutral species has undergone enormous development. The chemodosimetric approach in the design of detection systems has several advantages, selectivity being the most important.

In this chemodosimetric method, the probe must be designed in such a way that a chemical reaction with the analyte results in observable changes in its photophysical properties. These methods are based on a chemical reaction with the analyte that results in observable changes. To be useful in the detection process, the reaction must take place rapidly, it must be selectivity for the analyte under study, and it is important that it occurs under mild conditions.

Exposure to amounts of formaldehyde of 10 to 20 ppm is known to cause almost immediate irritation to the eyes and a sharp burning sensation in the nose and throat that may be associated with sneezing, coughing, and difficulty breathing deeply. Recovery from these transitory effects is rapid. However, exposure for 5 to 10 minutes at 50 to 100 ppm can cause serious permanent injury to the lower respiratory tract. Furthermore, it is well known that formaldehyde has a toxic effect on the nervous system and has characteristics carcinogenic. On the other hand, formaldehyde is a widely used chemical agent. It is generated, for example, from building materials such as pressed wood products (mainly from adhesive resins) or fibreboard or plywood. It is also used as an additive for permanent press, an ingredient in glues and a preservative in medical laboratories as an embalming liquid and a sterilizer. Formaldehyde is also a by-product of combustion (cigarette smoke, fuel-burning appliances, and kerosene heaters) and can therefore be found in significant concentrations and in a variety of environments.

The detection of formaldehyde is usually carried out using different techniques such as spectrophotometry, HPLC, laser-induced fluorescence spectroscopy, capillary electrophoresis, conductimetry, and enzyme-based biosensors. These methods, although they present extraordinarily low detection limits, involve expensive instrumentation and the need for experienced personnel to carry out the measurements. Furthermore, in the case of enzymatic reactions, there is an additional problem arising from the lack of stability of this type of sensor.

Unlike these, optical methods show certain advantages such as operational simplicity, portability or the possibility of real-time monitoring.

Detection of formaldehyde carried out so far using optical methods has been based on the use of slow reactions that require elevated temperature conditions to occur.

Derivatization reactions have also been used to convert the analyte into another compound that can be studied by different instrumental techniques. The use of simpler spectrophotometric techniques such as ultraviolet or fluorescence generally requires prior derivatization, as occurs in the chromotropic acid method (4,5-dihydroxynaphthalene-2,7-disulfonic acid). Document DE 19600762 describes a device for determining formaldehyde on the surface of furniture or on walls using chromotropic acid, therefore by means of a different reaction to the present invention, with which it presents other interferents, reaction rates and responses different from those used achieved with the device of the present invention.

Derivatizing agents such as 2,4-dinitrophenylhydrazine, phenylamines or diamines (such as p-phenylenediamine) have been used in other cases.

Brilliant cresyl blue, a trade name for a mixture of two aromatic amines, has also been used in the detection of formaldehyde. The major drawback of this reagent is that the compounds are aromatic amines with the consequent danger that this entails.

Other techniques are based on the use of the Hantzsch reaction which leads to obtaining a slightly colored compound. Based on the Hantzsch reaction, 4-amino-3-penten-2-one has been marketed under the name Fluoral P for the detection of formaldehyde, subjecting the compound to a series of modifications to facilitate its use. The study of the environmental impact of this compound has not been carried out so its contaminating potential is unknown.

Some colorimetric dosimeters are described in the literature that allow visual detection of formaldehyde through various chemical reactions with detection limits on the order of those of the method described in the present invention. Thus, amino-3-hydrazino-5-mercapto-1,2,4-triazole marketed as Purpald ® has frequently been used as chemodosimeters. This compound is used in conjunction with ZnO, KIO4, and agar. The Journal Environmental Technology article [1] discloses a formaldehyde detection procedure based on these reagents. Detection according to Journal Environmental Technology can be done with the naked eye, without the need to use any measuring instrument and there are devices that allow double detection. The disadvantage of the method disclosed in this article in relation to that used in the device of the present invention lies in its greater danger from both a personal and environmental point of view. On the one hand, the organic compound used is flammable even in the solid state, and on the other hand, potassium periodate is a strong oxidant that can react with numerous organic compounds.

The Pictet-Spengler reaction of primary catecholamines with formaldehyde followed by dehydrogenation to generate the corresponding 3,4-dihydroisoquinolines, has been used for the histochemical differentiation of biogenic monoamines (dopamine or norepinephrine) by fluorescence microscopy, as described in [ 2]. However, in this reference, the reaction only works in solution, unlike what happens in the present invention, since amines are not volatile and formaldehyde is the reagent that is available on the support for the detection of amines. There is also no information or suggestion about the possible use of the reaction for the detection of formaldehyde.

Document [3] describes a procedure for the detection of formaldehyde through the formation of polidopamine nanotubes from dopamine and using a ZnO standard. The detection limits reached are lower than 100 ppb. Although these sensors are prepared from dopamine, however, the detection is not done with the naked eye but requires instrumental methods. Document [3] also discloses the possibility of using SBA-15 mesoporous silica and other nanostructures such as ZIF in some substance detection procedures.

The method described in US4438206A comprises detecting formaldehyde in the presence of albumin, by fluorescence of the substance formed by reacting a solution containing formaldehyde with acetyl ketone. This method has a good sensitivity, but for its use it is necessary to prepare the reagent that will give rise to the color changes and also the measurements are always carried out in solution and there is no indication about its possible use in the gas phase.

US20040197225 A1 discloses a formaldehyde sensor containing silica gel as a support. The reaction on which it is based is the Hantzsch reaction using 4-amino-3-penten-2-one, different from that used in the present invention. Unlike what is disclosed in US20040197225A1, the present invention uses the Pictet-Spengler reaction and only needs a scanner to perform the quantification. Furthermore, the environmental impact of the 4-amino-3-penten-2-one used in US20040197225A1 has not yet been evaluated.

According to document US4511658 the detection limit reached is good but the use of amino-3-hydrazino-5-mercapto-1,2,4-triazole as an organic compound makes it more dangerous than the procedure that uses the present device invention.

The Pictet Spengler reaction on which the device of the invention is based, had been described for the detection of catecholamines with some adjustments to give stability. And although it has been disclosed - document [3] - the use of functionalized mesoporous silica, and ZnO nanotubes as support for formaldehyde detection reactions, there is no data on the possibility that the reaction could give rise to a device capable of to detect formaldehyde with the naked eye and to reach detection limits of 2 ppm as described in the present invention.

Other reactions for the detection of formaldehyde supported on silica have been found [3] but they present more than one stage, present instability and / or require different and more complex detection techniques. A document was found that discloses two-way formaldehyde detection based on a totally different and less environmentally friendly system.

Therefore, although the reaction used in the process of the present invention was known [2], and [3] discloses a sensor that is based on a similar supported reaction, the technical advantage of the present invention is that it has been achieved withstand the reaction in a material so that formaldehyde can be detected in two ways, resulting in a simple, environmentally friendly sensor that allows reading with the naked eye.

Taking into account the systems present in the market, the design of simple tests for the detection of formaldehyde with the appropriate selectivity and sensitivity and that are respectful with the environment is a necessary development.

In the present invention, detection is carried out with a device through a reaction known per se, but which occurs directly on the surface of a support such as silica and therefore does not require a solvent. The process is in one stage and is produced at room temperature and in short times, in respectful environmental conditions, easily and with good detection limits. Furthermore, the invention makes it possible to measure the amount of formaldehyde through two channels.

DESCRIPTION OF THE INVENTION

The present invention relates to an "in situ" detection device for formaldehyde in the gas phase.

In the gas phase formaldehyde detection device that allows to carry out:

a) a Pictet-Spengler reaction of a primary beta-arylethylamine having alkoxy groups, hydroxyl groups or combinations of both in positions 3 and 4, with formaldehyde

b) a dehydrogenation of the product obtained in said reaction in the presence of an amino acid and a reducing sugar,

so that a) and b) are produced in a single stage on an acidic support, in the absence of solvent,

c) and the detection of the final product.

More specifically, the invention relates to an "in situ" detection device for formaldehyde in the gas phase, comprising the reagents:

- a primary beta-arylethylamine having alkoxy groups, hydroxyl groups or combinations of both in positions 3 and 4,

- an amino acid glycine and

- a reducing sugar

arranged on a support of a material, selected from paper, a hydrophobic polymer, a hydrophilic polymer, metal, such as an aluminum plate, glass, plastic, preferably silica gel, in turn arranged on an aluminum plate.

The beta-arylethylamines that react with formaldehyde are those that have alkoxy groups in positions 3 and 4, in general or hydroxyl groups. They all cause fluorescent products, but the greatest fluorescence occurs when there is a hydroxyl in position 3.

The alkoxy groups can be, for example: ethoxy, methoxy, propoxy, butoxy, and are preferably methoxy groups.

The beta-arylethylamine can be, for example, a 3,4-dialkoxyarylethylamine or 4-alkoxy-3-hydroxyarylethylamine, 3,4-dihydroxyarylethylamine, and according to particular preferred embodiments it is a catecholamine or 3,4-dihydroxyarylethylamine, more preferably it is still 3,4-dihydroxyphenylethylamine or dopamine.

The aromatic ring may have additional substituents such as alkyl, alkoxy, hydroxyl, halogen groups, but is preferably a ring substituted only in the 3- and 4-positions with alkoxy or hydroxyl groups.

The alkyl chain of beta-arylethylamine can have substituents such as alkyl, alkoxy, hydroxyl, halogen groups, but preferably it does not have them or they are not very bulky substituents.

The dehydrogenation reaction generates the double bond in the heterocycle resulting from reaction i) and that reaction is what makes it fluorescent.

Final product detection can be colorimetric or fluorescent.

According to preferred embodiments, the invention refers to an "in situ" detection device for formaldehyde in the gas phase, comprising the reagents:

- dopamine

- the amino acid glycine and

- sucrose

arranged on a silica gel support, in turn arranged on an aluminum plate.

When catecholamine is dopamine, the reaction scheme is as follows:

The present invention relates to a formaldehyde in situ detection probe or device.

Therefore, the device comprises the reagents necessary to carry out the Pictet-Spengler reaction with formaldehyde on an acidic support, such as a silica support, and in the absence of solvent.

According to particular embodiments of the device, the support has the reagents arranged on a base material that can be, for example, an aluminum plate coated with the support, such as silica gel.

Color changes are observed with the naked eye and fluorescence changes are detected with a manual lamp that does not have to be attached to the device.

The device of the invention can be used for the in situ detection of formaldehyde in contaminated atmospheres.

The device is capable of acting as a passive colorimetric and fluorescent sensor for the detection of formaldehyde in real time.

The reagents are used in the approximate ratio of 20: 5: 1 of betaarylethylamine: amino acid: reducing sugar.

According to particular embodiments, the device comprises a mixture of three commercial products supported (dopamine, glycine and sucrose) on an aluminum plate coated with silica gel. The concentrations of these reagents are used in the 20: 5: 1 ratio of dopamine: glycine: sucrose. The signal generation mechanism is a direct, easy, reproducible cyclization reaction and allows a stable device to be obtained under normal conditions.

Under these conditions, the formaldehyde concentration can be determined down to levels below 2 ppm through a double path: color change and fluorescence emission, giving rise to devices with short reaction times and high sensitivity.

Preferred embodiments of the device comprise a test strip that contains the different components of the detection system for colorimetric detection.

The device offers a double measurement channel since it gives rise to changes in color, which allows detection in real time and with the naked eye, without the need to use any measuring instrument and changes in its fluorescent properties whose observation with the naked eye requires the use of an ultraviolet hand lamp.

The formaldehyde detection device can be used in the furniture industry. On the other hand, the device can not only serve to determine the emission of the boards but also as a personal protection system since the signal, being cumulative, can be used to determine the maximum time of permanence of the workers in a polluted environment. The device can also be used in the automotive industry, particularly for upholstery, or in hospitals.

The gas phase formaldehyde detection device can be used:

- As a portable formaldehyde sensor, for use in the furniture industry (a new European regulation is foreseen that strictly regulates the emission limits of formaldehyde from wooden boards)

- As a formaldehyde sensor in the healthcare environment where the values of this pollutant in the environment can exceed those established as occupational risk levels

- At the domestic level, it can be marketed to control contamination in these environments, mainly in environments where there are children or people with a special sensitivity to this compound.

The developed device presents the advantages of simplicity of operation, ease of reading, is portable and allows the design of single-use probes for the detection of formaldehyde in the gas phase selectively and with high sensitivity.

The advantages of the device of the invention are:

- the device can be used both for personal protection and for pollution control in workplaces by controlling the device by computer or by means of mobile phone applications,

- the compounds used in the process are all low-polluting and detection is carried out at room temperature and after short exposure times,

- it does not require waste management, given the non-polluting nature of the components used that are respectful with the environment since all the components are part of biological organisms and are harmless for fauna and flora,

- it is simple and cheap, and gas phase formaldehyde can be detected in real time,

- gas phase detection allows a cumulative measurement to be carried out;

- the measurement can be done through two channels: color and fluorescence, which gives the method robustness and greater sensitivity,

- the detection limits are below the values established in the different regulations.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1. Shows the changes in the UV spectrum after the addition of formaldehyde (0.9 equivalents).

Figure 2. Shows the fluorescence spectrum of a sensor and the same sensor in the presence of 4 equivalents of formaldehyde (Aexc = 420 nm).

Figure 3. Shows sensors supported on silica gel in the presence of increasing amounts of formaldehyde in the gas phase.

Figure 4. Response of the device in the presence of increasing amounts of formaldehyde gas.

EXAMPLES

Example 1

Device for the detection of formaldehyde in gas phase

Device Preparation

100 mg of dopamine, 25 mg of sucrose and 5 mg of glycine are dissolved in deionized water. Once all the reagents have been dissolved and with the solution homogenized, a silica gel plate is immersed inside said solution. The silica gel plate is then allowed to air dry and is ready to use once dry. If in Instead of using deionized water, a phosphate buffer at pH 7.5 is used, the results are practically the same.

The concentrations used in the example are the minimum to reach that detection limit. At lower concentrations the change would not be seen with those analyte values. Higher concentrations can be used while maintaining the ratio of the components but would make detection more expensive, therefore studies have been done at the indicated concentrations.

Conservation

Storing the silica gel plates exposed to environmental conditions (air, light, etc.) they maintain their sensory activity for 2 days. If they are kept protected from sunlight and in a dry and clean environment, the number of working days for their use increases considerably.

Detection experiment

In a round bottom flask, the formaldehyde source (formalin, melanin board etc.) is placed at the bottom, and suspended a few centimeters above the source the silica gel plate is placed (by means of a thread or any other method), it is heated to 60 ° C whereby the formaldehyde passes into the gas phase and comes into contact with the sensor supported on the silica gel plate located a few centimeters above, giving rise to a color change that reveals the presence of gas. The round bottom flask can be substituted for any other container. The LOD (limit of detection) in the gas phase was less than 1.08 | jg / L. This value is below the limit of 2 ppm for 15 minutes accepted by OSHA (Occupational Safety and Health Administration of USA).

Example 2.

Example of device response to increasing formaldehyde values

The evaluation of the response of the sensor against gaseous formaldehyde patterns was carried out as follows: In 100 mL round bottom flasks, the probe is suspended in such a way that it does not touch the wall of the container. Known increasing amounts of formaldehyde dissolved in water are placed inside each flask and the flasks are sealed. The flasks are heated to 60 ° C to cause the passage of the aldehyde to the gas phase and the heating is maintained for 5 hours to guarantee the total release of the analyte.

BIBLIOGRAPHY

[1] Journal Environmental Technology, Volume 37, 2016 - Number 13 Colorimetric monitoring of formaldehyde in indoor environment using built-in camera on mobile phone, Yoshika Sekine, Risa Katori, Yuko Tsuda & Takio Kitahara,

[2] Acta Chemica Scandinavica 1966, 20, 2755-2762, Gosta Jonsson

[3] Journal of Material Chemistry 2016, 4, 3487; Polydopamine nanotubes: bio-inspired synthesis, formaldehyde sensing properties and thermodynamic investigation; Dong Yan, Pengcheng Xu, Qun Xiang, Hongru Mou, Jiaqiang Xu, Weijia Wen, Xinxin Lic, and Yuan Zhang.

Claims (7)

1. An "in situ" detection device for formaldehyde in the gas phase, comprising the reagents: - a primary beta-arylethylamine having alkoxy groups, hydroxyl groups or combinations of both in positions 3 and 4, - an amino acid glycine and - a reducing sugar arranged on a support of a material, selected from paper, a hydrophobic polymer, a hydrophilic polymer, metal, glass and plastic. 2. A device according to claim 1, characterized in that the beta-arylamine is a catecholamine. 3. A device according to claim 2, characterized in that the beta-arylamine is dopamine. 4. A device according to claim 1, characterized in that the reducing sugar is sucrose. 5. A device according to claim 1, in that the amino acid is glycine. 6. A device according to claim 1 characterized in that it comprises the reagents: - dopamine - the amino acid glycine and - sucrose arranged on a silica gel support, in turn arranged on an aluminum plate. A device according to claim 1, characterized in that the reagents are used in the 20: 5: 1 ratio of dopamine: glycine: sucrose.