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What is ethylene oxide sterilization

- Feb 13, 2019 -

Ethylene oxide (EO) has been used in disinfection and sterilization for a long time, and it is the only reliable chemical gas sterilizing agent recognized worldwide. In the past, ethylene oxide was mainly used for industrial scale disinfection and sterilization. With the development of modern industrial technology and automation and intelligent technology, ethylene oxide sterilization technology can be safely used in medical institutions for fear of heat and humidity. Sterilization of precision medical devices.


1、The characteristics of ethylene oxide

Ethylene oxide is the second generation of chemical disinfectant after formaldehyde. It is still one of the best cold disinfectants. It is also the current four low temperature sterilization technology (low temperature plasma, low temperature formaldehyde vapor, ethylene oxide). , glutaraldehyde) is the most important member.


Ethylene oxide is a simple epoxy compound which is a non-specific alkyl compound having a molecular formula of C2H4O and a structural formula of -CH2-CH2-O- with a molecular weight of 44.06. The specific gravity was 0.884 at 4 ° C, the boiling point was 10.8, and the freezing point was 111.30%. At normal temperature and pressure, ethylene oxide is a colorless gas, heavier than air, and has a density of 1.52. It has an aromatic etheric taste and a odor threshold of 760-1064 mg/L.


When the temperature is lower than 10.8 ° C, the gas liquefies, is a colorless transparent liquid at low temperature, can be mixed with water in any proportion, and can be dissolved in common organic solvents and greases, the gas can be some solids (such as rubber, plastic) Etc.) absorption. Ethylene oxide liquid itself is a good organic solvent, which can dissolve some plastics and should be noticed during the disinfection process. The vapor pressure of ethylene oxide is relatively large, so the penetration of the disinfecting article is strong, and the diffusibility can penetrate the micropores to reach the deep part of the article, which is beneficial to sterilization and preservation of articles.


Ethylene oxide is flammable and explosive. When the air contains 3% to 80% of ethylene oxide, it forms an explosive gas. It burns or explodes in the event of an open flame. The concentration of ethylene oxide commonly used in disinfection and sterilization is 400-800 mg/L, which is in the range of flammable and explosive concentrations in air. Therefore, attention should be paid during use.


Ethylene oxide and an inert gas such as carbon dioxide are mixed in a ratio of 1:9 to form an explosion-proof mixture, which is safer for sterilization and sterilization. Ethylene oxide can be polymerized, but in general, the polymerization is slow, and polymerization occurs mainly in a liquid state. In a mixture of ethylene oxide and carbon dioxide or a hydrocarbon of fluorine, the polymerization is slower and the solid polymer is less likely to explode.


2、The principle of ethylene oxide sterilization

1, alkylation

The mechanism of action of ethylene oxide to kill various microorganisms is mainly alkylation. The sites of action are the sulfhydryl groups (-SH), amino groups (-NH2), hydroxyl groups (-COOH) in protein and nucleic acid molecules. Hydroxy (-OH) and the like, ethylene oxide can cause alkylation of these groups, causing the biological macromolecules of the microorganisms to be inactivated, thereby killing the microorganisms.


2. Inhibition of biological enzyme activity

Ethylene oxide can inhibit the activity of various enzymes of microorganisms, such as phosphate dehydrogenase, cholinesterase and other oxidases, which hinders the completion of the normal metabolic process of microorganisms and causes their death.


3. Killing of microorganisms

Ethylene oxide liquids and gases have strong microbicidal effects. In contrast, gas has a stronger microbicidal action, and gas is generally used for sterilization.


Ethylene oxide is a high-efficiency broad-spectrum sterilizing agent, which has strong killing and inactivating effects on bacterial propagules, fungi and viruses. In the case where ethylene oxide is in contact with microorganisms, but the microorganisms contain sufficient moisture, the action of ethylene oxide and microorganisms is a typical first-order reaction, inactivating the dose of purely cultured microorganisms, and the reaction curve is in a semi-logarithmic value. It is a straight line.


This rule applies to all microorganisms. Different types of microorganisms have different resistance to ethylene oxide, but the difference is not significant. The resistance of bacterial spores to ethylene oxide is only 2 times stronger than that of propagules. No genetic determination is found. A microorganism that is highly resistant to ethylene oxide. Bacterial spores are more resistant to ethylene oxide, and Bacillus subtilis var. black spores are the strongest.