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Abstract:

Glutaraldehyde (Molecular Formula: C5H8O2 or OCH(CH2)3CHO) is a colorless oily, liquid with a sharp pungent smell. Glutaral is used as a bactericide, disinfector, tanning agent. And it also widely used in petroleum development, leather treatment, food, plastics, coatings, etc. You can also see it in ingredient lists in some products. But you should know there are some side effects of glutaral. For example, glutaraldehyde allergy, glutaraldehyde toxicity, and other hazards. Don’t worry about that. This page will show you the latest glutaral use guide and analytics in 2020.

Content Table

    1. What is the glutaraldehyde definition?
    2. Glutaraldehyde uses.
    3. What are the glutaraldehyde side effects?
    4. How should the glutaraldehyde be stored?
    5. Conclusion.
    6. Questions about glutaraldehyde reaction.

1. What is glutaraldehyde?

A water-soluble oil used as a disinfectant, tanning agent, and in resins. Glutaraldehyde is an organic compound with the formula CH2(CH2CHO)2. A colorless oily liquid with a sharp pungent odor.

2. Where does glutaraldehyde be used for?

2.1 Glutaraldehyde is used as an antimicrobial agent.

Glutaraldehyde is used as an antimicrobial agent. Glutaral is a useful antimicrobial agent. But it is dangerous and undesirable to take care of and is thermally unpredictable. Despite these disadvantages, glutaral is specified for use against microorganisms in cooling down towers of air-conditioning systems in buildings. And also to manage anaerobic sulfate-reducing microorganisms in oil wells.

It is declared that it supplies a bioavailable resource of carbon for greater plants. Those plants are not readily available to algae. Though not marketed therefore due to government guidelines, the biocidal effect of glutaral eliminates most algae at the focus of 0.5-5.0 ppm. This concentration is not hazardous to a lot of water animals and vegetations.

2.2 Glutaraldehyde is used as a disinfectant.

Glutaraldehyde mainly kills microorganisms through its two active aldehyde groups. Its activity is affected by pH and temperature. Under acidic conditions, glutaral monomers are hydrolyzed into monohydrate, dihydrate, cyclic semiacetal and acetal like polymers, which are in equilibrium with each other.

The glutaraldehyde used for disinfection is usually a 2% alkaline solution, and the acid solution needs to be activated (alkalized) before use.

Because there are only a few glutaraldehyde monomers in acidic aqueous solution, its biological activity is poor. However, the polymerization of glutaral is slow under acid condition, so the acid glutaral is relatively stable and can be stored for a long time.

Under acid conditions, more free aldehydes can be produced by increasing the temperature, so as to improve its biological activity.

Glutaral has high biological activity under the condition of pH 7.5-8.5. It can kill all microorganisms including spores. Glutaraldehyde can be polymerized into an unsaturated polymer of butyraldehyde type in alkaline condition, and then form a higher polymerization form. In the alkaline aqueous solution, the polymerization of glutaral is irreversible.

With the increase of polymer, its activity gradually weakened or disappeared. With the increase of pH, temperature and storage time, the polymerization of basic glutaraldehyde can be strengthened and its activity can be reduced. Therefore, the activity of basic glutaral is strong, but the validity period is generally only two weeks; the activity of acid glutaraldehyde is weak, but the validity period is longer, up to one month.

2.3 Glutaraldehyde is used as a fixative.

Glutaraldehyde as a fixative has a fast reaction speed. It is a good anterior fixative. But its penetration rate is slow. If necessary, it is better to use it with formaldehyde.

Glutaral is a strong fixative for protein. It can react with amino groups quickly and irreversibly. Like formaldehyde, an aldehyde group of glutaral reacts with an amino group. After dehydration, unstable Schiff bond compounds were formed.

When glutaraldehyde was used for immobilization, the immobilization effect of the small sample was ideal. For some samples with strong antigenicity, 4% paraformaldehyde and 0.05% ~ 0.5% glutaraldehyde can also be used for fixation.

The process of glutaral immobilizing protein through crosslinking will be accompanied by the release of hydrogen ions, which will reduce the pH value of the sample. In order to keep the pH value stable at the best level, sufficient buffer should be added into the fixative of glutaral.

Glutaraldehyde can fix DNA and RNA in tissues and cells by fixing nucleoprotein and can preserve glycogen. It can also immobilize lipids associated with proteins or containing amino and imino groups. However, only using glutaral fixed sample can not prevent the subsequent dehydration, infiltration and embedding process of sample lipids extraction. Therefore, the effect of cell membrane fixation is not ideal.

Glutaraldehyde does not completely destroy the semipermeable properties of the cell membrane during the fixation process. Therefore, it is necessary to select a suitable osmotic pressure of the fixing liquid to avoid the false appearance of fixation. However, it is difficult to find universal osmotic pressure because of the variety of fixed cells and buffers.

The principle of glutaraldehyde fixing is forming intermolecular cross-links. Thereby affecting the protein conformation to fix it. Glutaraldehyde fixing has the advantages of strong penetrability and good preservation of the fine structure. But glutaraldehyde fixing had some effect on that antigenicity. Therefore, glutaraldehyde is often used as a fixative for immunoelectron microscopy in combination with other fixatives. For scanning electron microscopy, glutaraldehyde fixation usually takes 1 to 4 hours.

In practical operation, 1.0% – 2.5% glutaraldehyde (using 0.1M phosphate buffer or 0.1M dimethyl arsenate buffer) can provide ideal fixation effect in general. In general, the fixed solution is not specially adjusted for osmotic pressure unless the illusion caused by obvious osmotic pressure is observed. (It needs to be prepared separately, and the purchase is generally 25% glutaraldehyde solution.)

2.5 glutaraldehyde fixative is composed of glutaral, phosphate, deionized water, etc. The pH range is between 7.2-7.4. The glutaraldehyde fixative has a good fixation effect on the fine structure of cell nucleus and cytoplasm. 2.5% glutaraldehyde fixative is often used for the fixation of electron microscope specimens.

The sample fixed before glutaral is not easy to become brittle and can be fixed for a long time (but it is better not to exceed a week), so it is suitable for taking materials far away from the laboratory or field. However, glutaral will produce a series of reactions by itself in the dilute solution, so the fixative should be prepared as fresh as possible.

As a medication, the glutaraldehyde 10 solution is used to treat plantar warts. For this purpose, a 10% w/v solution is used. It dries the skin, facilitating the physical removal of the wart.

The technique is to apply the 10% glutaraldehyde solution buffered to warts twice daily. Since this glutaraldehyde 10 solution is fixative, the outer layers of the wart become hardened in several days, and also the skin around the wart becomes tan or brown. The physician or nurse instructs the patient or a parent to pare the wart using a small blade.

Click here to know more details about Glutaraldehyde Fixative for Electron Microscopy. You can search “glutaraldehyde fixation protocol” on google to get more details.

2.4 Glutaraldehyde is used for industrial water treatment.

  • It has a highly effective and algae-killing effect, glutaraldehyde can penetrate into the cell wall of microorganisms, and produce a chemical cross-linking effect with microbial proteins, causing the microbial eggs to solidify, prevent their metabolism, and inhibit the reproduction of bacteria.
  • The glutaral aqueous solution itself will be biodegraded and decomposed due to its own destruction. Therefore, it will not cause new pollution to the water, nor will it cause environmental pollution.
  • The toxicity of the glutaraldehyde aqueous solution is very low. 2% glutaral water ficus solution-(equivalent to a concentration of 20,000 ppm), its LD50 (orally administered to rats) is 12.6 mL/kg, which is close to the level of non-toxic chemicals. In general, the concentration used in actual water treatment is 50 to 200 ppm, and it has almost no toxicity when used in this range.
  • It can be used in a wide range of pH and temperature.
  • It can be completely mutually compatible with water in any proportion.
  • Water-soluble glutaraldehyde will not cause corrosion to the equipment.
  • After glutaral is added to the circulating water, the water quality remains colorless, ambiguous, and odorless.
  • Glutaral reacts with ammonia, ammonium salts and primary amine compounds, and thus loses its antibacterial ability. Therefore, if these amine compounds are contained in the circulating water, they must be disposed of in advance. However, it contains a small number of amine compounds and generally does not affect the bacteriostatic ability of glutaraldehyde.

2.5 Glutaraldehyde is a component of leather tanning solutions.

Under mild alkaline conditions, a selective aldol condensation reaction of glutaraldehyde and formaldehyde can produce a new type of tanning solution. Spectral and chemical analysis results show that the main chemical component of the reaction product is hydroxymethyl glutaral.

In addition, dehydration reactions can occur between the resulting product molecules, between the reaction product and the hydrated formaldehyde, and between the glutaraldehyde molecules, forming an ether linkage. The oligomer and monomer thus formed form an equilibrium in an aqueous solution.

The most suitable tanning effect is to maintain the pH value at 6.5-8. Using this product can produce pure white and lightfast leather. The modified product of 2 mol formaldehyde and glutaraldehyde can be further modified into an alkyd tanning solution.

A hydrogen-containing organic acid and formaldehyde were used as modifiers to modify glutaral to obtain a new type of alkyd tanning solution. The tanning solution is used for retaining grey leather so that the finished leather retains the characteristics of light, soft and thin tanned leather. It also makes the leather more compact and plump, with higher mechanical strength. The new aldehyde acid tanning solution has obvious effects on fixing tannin, improving the absorption and crosslinking of chromium.

Modified glutaral is used for mild tanning. It can not only make the leather have good light fastness, but also make the leather soft and plump. Although the fullness produced by it is not exactly the same as that produced by glutaral in general, the effects of modified glutaraldehyde on graininess, softness, and colorability are very superior.

In addition to these uses mentioned above, glutaraldehyde is frequently used in biochemistry applications as an amine-reactive homobifunctional crosslinker. A later article will explain glutaral as a crosslinking agent in detail.

2.6 2% Glutaraldehyde solution preparation

How to prepare 2% glutaraldehyde solution? If an aqueous solution is prepared, the mass fraction conversion can be performed. Because the 50% glutaraldehyde solution is actually 50% glutaraldehyde and 50% water. If you need to make 100 ml of 2% glutaraldehyde in water, you can take 4 ml of glutaraldehyde in water and add 96 ml of water.

Glutaraldehyde for disinfection is usually a 2% alkaline solution. Acidic solutions need to be activated (basified) before use. Glutaraldehyde is unstable under alkaline conditions and is easy to polymerize into polymers. Solutions with pH ≥ 8 generally lose activity within 4 weeks. The activated alkaline glutaraldehyde should not be used for more than two weeks.  The remaining dosage forms can be stored for 4 weeks.

2% acid glutaraldehyde is corrosive to metals. 2% neutral glutaraldehyde is corrosive to carbon steel products such as surgical blades. Before use, 0.5% sodium nitrite should be added to prevent rust.

You can search on google to get more details about glutaraldehyde disinfectant formulation.

3. What hazards does glutaraldehyde have?

3.1 Health hazards

Harmful by inhalation, ingestion or percutaneous absorption. It has a strong irritating effect on eyes, skin and mucous membranes. Inhalation can cause inflammation of the throat, bronchus, chemical pneumonia, and pulmonary edema. This product can cause allergic reactions.

3.2 Environmental hazards

It is harmful to the environment and can cause pollution to water bodies.

3.3 Explosion hazard

This product is flammable and highly irritating.

3.4 Hazardous characteristics

Combustible in case of open flames and high heat. Contact with strong oxidants can cause chemical reactions. Its vapor is heavier than air, and can spread to a relatively low place at a lower place, and will burn when encountering a fire source. It is easy to self-polymerize, and the polymerization reaction increases sharply as the temperature rises. In the case of high heat, the internal pressure of the container will increase, and there is a danger of cracking and explosion.

3.5 Occupational protection

Glutaral can cause local skin and mucous membrane irritation and has been reported to cause allergic contact dermatitis, asthma, epistaxis, rhinitis and so on. Therefore, when contacting the glutaraldehyde solution, wear thick rubber gloves and eye protection to prevent liquid from splashing into the eyes.

In order to reduce the concentration of glutaral in the indoor air, the room must be well ventilated. A partial exhaust hood should be provided above the glutaral container. The solution must be prepared in time to prevent the evaporation of glutaraldehyde when preparing and putting in and taking out items.

Special people such as nurses who frequently come into contact with glutaral will produce glutaraldehyde allergy in the short term, which is more harmful to visual organs and respiratory tract. Working in this environment for a long time can easily lead to occupational asthma.

4. Glutaraldehyde disposal and storage.

Sealed in a cool, dry place and refrigerated. Or sealed with argon at 0°C and protected from light. Ensure that there is good ventilation in the workplace. Store away from oxidants.

5. Conclusion

Glutaraldehyde is thought of as the third milestone in the history of the development of chemical disinfectants after formaldehyde and ethylene oxide disinfection. Each coin has two sides. Glutaral has a wide range of applications, but health protection should be paid attention to in the process of use.

6. Questions about glutaraldehyde reaction.

6.1 Conditions for using glutaraldehyde as a cross-linking agent.

Q: I want to cross-link CMC and PVA with glutaraldehyde. Are there any conditions that need to be controlled? For example, pH, temperature, or other.

A: Never done this. But cross-linking with the amino group, the reaction is relatively good under the condition of pH 7.5~8.5, this is basic glutaraldehyde.

6.2 Help! PVA membrane, glutaraldehyde as a cross-linking agent.

Q: Add 2ml glutaraldehyde (25%) to the 10% PVA solution as a cross-linking agent. After drying to form a film. Place it in water. Soluble in water. But increase the amount of glutaraldehyde to 4ml. PVA solution is easily frozen. Is this what is the reason?

A: This result is cross-linked into a gel. It may be that the amount of glutaraldehyde is added more. Lead to excessive cross-linking, this is the phenomenon of excessive cross-linking. Also, PVA can absorb water even after cross-linking. However, it should not be completely soluble in water. It may be that your PVA molecular chain is short and the cross-linking is not tight, and the hydroxyl groups contained are not completely reacted.

6.3 Can glutaraldehyde replace aluminum glycine as a crosslinking agent?

Q: I am making a mask recently. It comes from a matrix material like a gel. I found that the cross-linking agent used in the literature is called aluminum glycinate or composite aluminum salt. But the price is expensive. Can I use glutaraldehyde as a cross-linking agent instead?

A: It depends on what your polymer matrix is. Some can be cross-linked with glutaraldehyde, such as polyvinyl alcohol. Be careful. When the laboratory designed the hydrogel for the epidermis, it was found that glutaraldehyde irritates the skin of many people. It can cause skin irritation, redness, and occasional itching. So in the future, it was changed to glyoxylate as a cross-linking agent.

6.4 What factors can effect glutaraldehyde solution change?

(1) Solution concentration and reaction time.

(2) pH value of solution.

(3) Temperature.

(4) Organics.

(5) The synergism of nonionic surfactants and other physical and chemical factors.

6.5 About glutaraldehyde autofluorescence.

Autofluorescence is a general term for the background fluorescence signal produced in the process of immunofluorescence detection, which is unrelated to the target signal. Glutaraldehyde used in tissue fixation produces a large amount of autofluorescence. This can seriously affect the discrimination of the signal of interest.

The mechanism for the significant increase in autofluorescence resulting from tissue fixation is not known. Glutaraldehyde can stabilize the tissue structure by forming covalent crosslinks. Due to the variety of protein side chains reacting with aldehydes, the reaction kinetics, reversibility and the complex chemical properties of crosslinkers, the chemical structures of crosslinks are different. This may also be one of the main reasons for the unclear autofluorescence mechanism.

6.6 About paraformaldehyde cross linking.

Q: If we use Paraformaldehyde (PFA) to store samples, will it be over-crosslinked?

A: No. Paraformaldehyde itself is not a crosslinking agent. It can only be crosslinked after being decomposed into formaldehyde under heating or alkaline conditions.

6.7 Is glutaraldehyde toxic?

Health hazards: Harmful by inhalation, ingestion, or percutaneous absorption. Environmental hazard: It is harmful to the environment and may cause pollution to the water.

6.8 What is Glutaraldehyde storage conditions?

The glutaraldehyde is preferably stored at an acidic pH of 3 to 5, and a stabilizer can also be added.

The glutaraldehyde solution is stable under normal storage conditions. If the water in the aqueous solution of glutaraldehyde evaporates, the residual material will rapidly polymerize through a harmless chemical reaction and produce a flammable residue.

If a concentrated solution of glutaraldehyde is contaminated with strongly acidic or basic impurities, it will undergo an aldol condensation reaction and cause exothermic polymerization of the glutaraldehyde in the solution. When this occurs, it is recommended that sufficient water be added to dilute the solution.

6.9 What is the Glutaraldehyde storage temperature?

Glutaraldehyde is easy to self-aggregate, and the higher the temperature, the more intense the aggregation. If the temperature is too high, it may explode, so it should be stored at a low temperature. Glutaraldehyde is stored at 2-8 ° C, preferably filled with argon.

 

 


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