What Is Chemical Sterilization?

Chemical fungicides are generally not used for routine cleaning of floors, walls, equipment, and furniture. However, it can be used in controlling disease outbreaks.

Chemical fungicide

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Chemical fungicides are generally not used for routine cleaning of floors, walls, equipment, and furniture. But when

pinyin

huà xué sh jn jì

chemical bactericide

Multiple chemicals can be used as

1. Chlorine (sodium hypochlorite)

Chlorine is a fast-acting oxidant and is a broad-spectrum chemical fungicide. It is generally sold as a bleach solution using sodium hypochlorite (NaOCl) solution, and can be diluted with water to a variety of effective chlorine concentrations when used.

Chlorine (especially when used as a bleach) is strongly alkaline and can attack metals. Organic matter (protein) can significantly reduce its activity. If high-concentration or used bleaching agents are stored in open containers, especially under high temperature conditions, chlorine gas will be released and its sterilization ability will be weakened. The frequency of replacement of the bleach working fluid should be determined based on the initial concentration of the bleach working fluid, the type (if no lid) of the container, the frequency and characteristics of use, and indoor conditions. In general, those bleach solutions that need to be immersed several times a day for materials containing high concentrations of organics should be replaced at least once a day, while those that are used less frequently can be maintained for a week.

The effective chlorine concentration of conventional laboratory disinfectants should be 1 g / L. A stronger solution containing 5 g / L of available chlorine is recommended to deal with spills of biohazardous substances and those containing large amounts of organic matter. Sodium hypochlorite solution as a household bleach contains 50 g / L of available chlorine, so a dilution of 1 to 50 or 1 to 10 is required to reach final concentrations of 1 g / L and 5 g / L. The sodium hypochlorite solution of industrial bleach contains nearly 120 g / L of available chlorine and must be diluted accordingly to achieve the above concentration.

Granules or tablets of calcium hypochlorite [Ca (ClO) 2] typically contain 70% of available chlorine. Granules or tablets are used to prepare solutions with a concentration of 1.4 g / L or 7.0 g / L, with effective chlorine concentrations of 1.0 g / L and 5 g / L, respectively.

It is not recommended to use bleach as a preservative, but it can be used as a general purpose disinfectant and for soaking non-metallic contaminated materials. In emergencies, drinking water can also be disinfected with a bleach with a final concentration of 1 to 2 mg / L of available chlorine.

Chlorine is highly toxic. Therefore, bleach should only be stored and used in a well-ventilated area. In addition, bleach cannot be mixed with acids to avoid the rapid release of chlorine. Many by-products of chlorine can be harmful to the human body and the environment. Abuse of chlorine-containing disinfectants, especially bleaching agents, should be avoided.

Sodium dichloroisocyanurate

The powder of sodium dichloroisocyanurate (NaDCC) contains 60% of available chlorine. Solutions prepared with NaDCC powders at a concentration of 1.7 g / L and 8.5 g / L will contain 1 g / L and 5 g / L of available chlorine, respectively. NaDCC tablets generally contain 1.5 g of available chlorine. Dissolving 1 or 4 tablets in 1 liter of water will give solutions with a concentration of about 1 g / L and 5 g / L, respectively. NaDCC storage of powders or tablets is convenient and safe. When blood or other biohazardous liquid overflows, you can use solid NaDCC and let it work for at least 10 minutes before removing it, and then further clean up the contaminated area.

Third, chloramine

Ketamine powder contains approximately 25% of available chlorine. Chloramine releases chlorine more slowly than hypochlorous acid, so if you want the same potency as hypochlorous acid, you need a higher initial concentration. On the other hand, organic matter does not affect chloramine solution as much as hypochlorous acid solution. It is recommended to use a concentration of 20 g / L in both "clean" and "pollution" situations.

The chloramine solution is virtually odorless. However, items immersed in chloramine must be thoroughly washed to remove residues of fillers added to the chloramine-T (sodium tosyl chloroformamide) powder.

Fourth, chlorine dioxide

Chlorine dioxide is a highly effective rapid biocide, preservative and oxidant. It is often reported that it is active at concentrations lower than the chlorine concentration of the bleaching powder. Chlorine dioxide is unstable as a gas, it will decompose into chlorine (Cl2) and oxygen (O2) and exotherm. However, chlorine dioxide is soluble in water and stable in aqueous solutions. There are two ways to obtain chlorine dioxide: (1) When two separate components, hydrochloric acid (HCl) and sodium chlorite (NaClO2) are mixed, it can be generated; (2) order its stable state, and then activate at any time when needed generate.

In terms of oxidizing fungicides, chlorine dioxide is a highly selective oxidant. Ozone and chlorine are more reactive than chlorine dioxide and can oxidize most organics. However, chlorine dioxide only works with reducing sulfides, secondary amines, tertiary amines, and other strongly reducing and reactive organics. Therefore, compared with the use of chlorine and ozone, chlorine dioxide can obtain a more stable reaction product at a much lower content. In the case of more organic matter, due to its selectivity, using an appropriate amount of chlorine dioxide is more effective than ozone and chlorine.

Five, formaldehyde

At temperatures above 20 ° C, formaldehyde (HCHO) is a gas capable of killing all microorganisms and their spores. But formaldehyde has no killing activity on prions.

The onset of formaldehyde is relatively slow and requires a relative humidity of about 70%. The product on the market is paraformaldehydea solid polymer that is flaky or small, or formalina gaseous aqueous solution with a concentration of about 370 g / L (37%) , Which contains methanol (100 mL / L) as a stabilizer. Both forms of heating can generate gas for decontamination and disinfection of enclosed spaces such as biological safety cabinets and rooms. Formaldehyde (5% formalin solution) can be used as a liquid disinfectant.

Formaldehyde is suspected of being a carcinogen. It has a pungent odor and its gas can irritate the eyes and mucous membranes, so it must be stored and used in a fume hood or well-ventilated place. Must comply with national chemical safety regulations.

Six, glutaraldehyde

Like formaldehyde, glutaraldehyde [OHC (CH2) 3CHO] is also active against reproductive bacteria, spores, fungi, and lipid- or non-lipid-containing viruses. It is not corrosive and acts faster than formaldehyde, but it also takes several hours to kill bacterial spores.

The glutaraldehyde supplied is usually a solution with a concentration of about 20 g / L (2%). Most products need to be added to the bicarbonate mixture provided with the product for "activation" (to become alkaline) before use. The activated solution can be reused for 1 to 4 weeks depending on its formulation design, application type and frequency of use. The dipstick provided with some products is only a rough indication of the active glutaraldehyde level in the solution. If the glutaraldehyde solution becomes cloudy, it should be discarded.

Glutaraldehyde is toxic and irritating to the skin and mucous membranes and should be avoided. Must be used in a fume hood or well-ventilated area. It is not recommended to use its spray or solution to decontaminate environmental surfaces. National regulations for chemical safety must be observed.

Seven, phenolic compounds

Phenolic compounds are one of the earliest fungicides used. However, its use has recently been limited for security reasons. They are active against reproductive bacteria and lipid-containing viruses, and when properly formulated, they are also active against mycobacteria. They are not active against spores, and their activity against nonlipoviruses is uncertain. Many phenolic products are used to decontaminate environmental surfaces, and some (such as triclosan and chloroxylenol) are the most commonly used antibacterial agents.

Triclosan is often used as a hand washing product. It is primarily active against multiplying bacteria and is safe for the skin and mucous membranes. However, experimental studies have found that bacteria resistant to low concentrations of triclosan are also resistant to certain antibiotics. The significance of this discovery in this area is unclear.

Some phenolic compounds are sensitive to the hardness of water and may cause inactivation, so they must be diluted with distilled or deionized water.

It is not recommended to use phenolic compounds on food-contact surfaces and young children's playgrounds. They may be absorbed by the rubber and may penetrate the skin. Must comply with national chemical safety regulations.

Eight, quaternary ammonium salts

Most of the quaternary ammonium compounds are mixed and often used in combination with other fungicides such as alcohols. Quaternary ammonium salts have good activity against reproductive bacteria and lipid-containing viruses. Certain types (such as benzalkonium chloride) are also used as preservatives.

The bactericidal effect of some quaternary ammonium salt compounds will be significantly affected by organic matter, water hardness and anionic detergents. Therefore, when using quaternary ammonium salt compounds for disinfection, it is necessary to carefully choose the type used for pre-cleaning. Some potentially harmful bacteria can grow in solutions of quaternary ammonium compounds. Due to their low biodegradability, these compounds may also accumulate in the environment.

Nine, ethanol

Ethanol (C2H5OH) and isopropanol [(CH3) 2CHOH] have similar sterilization properties. They are active against multiplying bacteria, fungi, and lipoviruses, but cannot inactivate spores, and their effects on nonlipoviruses are uncertain. The most effective concentration of its aqueous solution is about 70% (v / v); higher or lower concentrations are not suitable for sterilization. The main advantage of alcoholic solutions is that the articles do not leave any residue after processing.

Mixing ethanol with other reagents is more effective than using it alone, such as 70% (v / v) ethanol and 100 g / L formaldehyde, and ethanol with 2 g / L available chlorine. 70% (v / v) ethanol solution can be used to disinfect skin, laboratory benches and work benches of biological safety cabinets, as well as soak small surgical instruments. Because ethanol can dry the skin, it is often mixed with a lubricant. In situations where it is not convenient or possible to wash your hands thoroughly, it is recommended to use alcohol-based hand sanitizers to disinfect slightly contaminated hands. But it must be remembered that ethanol is not effective for spores and cannot kill all types of non-lipid viruses.

Ethanol is volatile and flammable and should not be used near open flames. The working fluid should be stored in a suitable container to avoid alcohol volatilization. Ethanol can harden rubber and dissolve certain gums. In order to avoid the use of ethanol for other non-sterile purposes, it is important to specifically inventory and store the ethanol in the laboratory. Bottles containing ethanol solutions must be clearly marked to avoid accidental autoclaving.

Ten, iodine and iodophor

This type of disinfectant has a similar effect to chlorine, except that organic matter has a slightly weaker inhibitory effect on them. Iodine can stain fibers and environmental surfaces and is generally not suitable as a disinfectant. However, iodophor and iodine are good antibacterial agents. Polyvidone iodine is a safe and reliable surgical hand wipe and antibacterial skin before surgery. Iodine antibacterials are generally not suitable for disinfection of medical / dental instruments. Iodine cannot be used on aluminum or copper.

Iodine is toxic. Products containing organic iodine must be stored at 4-10 ° C to prevent potentially harmful bacteria from growing inside.

Eleven, hydrogen peroxide and peracetic acid

Like chlorine, hydrogen peroxide (H2O2) and peroxyacetic acid (CH3COOOH) are strong oxidants and are broad-spectrum fungicides. They are safer for people and the environment than chlorine.

Hydrogen peroxide is usually supplied as a 3% solution that can be used immediately, or a 30% aqueous solution that is diluted by 5-10 times the volume with sterile water. However, the solution containing 3 to 6% hydrogen peroxide alone has a slow and limited bactericidal effect. Existing products contain other ingredients to stabilize hydrogen peroxide, accelerate its bactericidal effect and reduce its corrosiveness.

Hydrogen peroxide can be used to decontaminate the working table of the laboratory bench and the biological safety cabinet. Higher concentration solutions are suitable for decontamination of heat-sensitive medical and dental equipment. Special equipment is required to sterilize heat-sensitive medical / dental instruments using hydrogen peroxide or peracetic acid fumigation.

Hydrogen peroxide and peracetic acid can corrode metals such as aluminum, copper, brass, and zinc. They can also discolor fibers, hair, skin, and mucous membranes.

Items treated with them must be thoroughly rinsed before they come into contact with eyes and mucous membranes. They should be stored away from heat and light.

(Extracted from the Laboratory Biosafety Manual (Third Edition), published by the World Health Organization)