Results from experiments conducted at NIH indicate that a combination of 60% ethanol with 0.01N HCl (pH 4) remarkably improved cidal action against poliovirus and adenovirus.

Phenol and Phenol Derivatives

Phenol based disinfectants come in various concentrations ranging mostly from 5% to 10 %. These derivatives including phenol have an odor, which can be somewhat unpleasant. Phenol itself is toxic and appropriate personal protective equipment is necessary during application. The phenolic disinfectants are used frequently for disinfection of contaminated surfaces (e.g., walls, floors, bench tops). They effectively kill bacteria including Mycobacterium tuberculosis, fungi and lipid-containing viruses. They are not active against spores or non-lipid viruses.

These are recommended for the killing of vegetative bacteria, including

Mycobacterium tuberculosis, fungi and lipidcontaining viruses (0.52.0%).  They are ineffective against spores and most nonlipidcontaining viruses.

• Low solubility in water unless combined with detergent.
• Stable in storage.
• Germicidal against Gramnegative and Grampositive organisms and tubercle bacilli.
• Less adversely affected by organic matter than other common germicides.
• Effective over relatively large pH range.
• Limited sporicidal activity.
• Prolonged contact deteriorates rubber.
• Can cause skin and eye irritation.
• Not for use on food contact surfaces.
• Many active against lipophilic viruses.

Quaternary Ammonium Compounds (Quats)

Quats are cationic detergents with strong surface activity. They are acceptable for general-use disinfectants and are active against Gram-positive bacteria and lipid-containing viruses. They are less active against Gram-negative bacteria and are not active against non-lipid-containing viruses and bacterial spores.

Quats are easily inactivated by organic materials, anionic detergents or salts of metals found in water. If Quats are mixed with phenols, they are very effective disinfectants as well as cleaners. Quats are relatively nontoxic and can be used for decontamination of food equipment and for general cleaning.

• Stable in storage.
• No odor but act as deodorizers.
• Use dilution usually nonirritating to skin but prolonged skin or eye contact should be avoided.
• Effective at temperatures up to 212°F.
• Effective against must bacteria and fungi.  Bacteriostatic and fungistatic in high dilutions.
• Generally ineffective against tubercle bacilli, spores, and hydrophilic viruses.
• More effective in alkaline than acid solutions.
• Neutralized by soap and anionic detergents.
• Effectiveness reduced by organic material.
• Have builtin detergency properties.
• Some active against lipophilic viruses.

Halogens (Chlorine and Iodine)

Chlorine-containing solutions have broad spectrum activity. Sodium hypochlorite is the most common base for chlorine disinfectants. Low concentrations of available chlorine (2 to 500 ppm) are active against vegetative bacteria, fungi, most viruses.  Effectiveness increases with concentration of available chlorine.  Rapid sporicidal action can be obtained at about 2500ppm.  The corrosive nature of many of these compounds (especially hypochlorites) and their decay rates limits their use. Common household bleach (5% available chlorine) can be diluted 1/10 to 1/100 with water to yield a satisfactory disinfectant solution. Diluted solutions may be kept for extended periods if kept in a closed container and protected from light. However, it is recommended to use freshly prepared solutions for spill clean-up purposes. Chlorine -containing disinfectants are inactivated by excess organic materials.

They are also strong oxidizers and very  corrosive. Always use appropriate personal protective equipment when using these compounds. At high concentrations and extended contact time, hypochlorite solutions are considered cold sterilants since they inactivate bacterial spores.

These are recommended for certain disinfecting procedures provided the available chlorine needed is considered (i.e., hypochlorites are rapidly inactivated by extraneous organic matter. Available chlorine must be able to exceed chlorine demands).

• Very active.
• Provides cidal action against a wide variety of Gramnegative and Grampositive bacteria and against many viruses.
• Solution of 2000 ppm available chlorine commonly used in laboratory as a soak for contaminated equipment.
• Neutralized rapidly in the presence of organic matter.

A one percent hypochlorite solution is recommended for destruction of the Hepatitis B antigen.

Iodophors

Iodine has similar properties to chlorine. Iodophors (organically bound iodine) are recommended disinfectants. They are most often used as antiseptics and in surgical soaps and are relatively nontoxic to humans. Although these show poor activity against bacterial spores, they are recommended for general use (70 to 150 ppm total iodine).  They are effective against vegetative bacteria, fungi and viruses.

• Combine iodine with nonionic detergent.
• Rapid biocidal action.
• Effective against Grampositive and Gramnegative organisms, and tubercle bacilli.
• Most effective in acid solutions.
• Vaporized at 120°F to 125°F  should not be used in hot water.
• Effectiveness reduced by organic matter (but not as much as with hypochlorites).
• Stable in storage if kept cool and tightly covered.
• Iodophors are relatively harmless to man.
• Iodophors have a builtin indicator.  If the solution is brown or yellow, it is still active.
• Iodophors can be readily inactivated and iodophor stains can be readily removed with solutions of sodium thiosulfate.
• Tarnish silver, silverplate, and copper.

For optimal cidal activity, dilute with warm, acidic water.  Resulting solutions are less stable but have a higher biocidal activity.

Formalin

Formalin is 37% solution of formaldehyde in water. Dilution of formalin to 5% results in an effective disinfectant. Formaldehyde is a human carcinogen and creates respiratory problems at low levels of concentration.

Formaldehyde Solutions  At a concentration of 8% formaldehyde exhibits good activity against vegetative bacteria, spores, and viruses.

FormaldehydeAlcohol  Solutions of 8% formaldehyde in 70% alcohol are considered very good for disinfection purposes because of their effectiveness against vegetative bacteria, fungi, spores and viruses.  For many applications, this is the disinfectant of choice.

Activated Gluteraldehyde  Two percent solutions exhibit good activity against vegetative bacteria, spores, and viruses.  Its use, however, must be limited and controlled because of its toxic properties and the damage to eyes.  Limited stability after activation (for alkaline gluteraldehyde).

Vapors and Gases

A variety of vapors and gases possess germicidal properties. The most commonly used are formaldehyde and ethylene oxide. Applied in closed systems under controlled conditions (e.g., humidity) these gases achieve sterility.

Formaldehyde gas is primarily used in the decontamination of spaces or biological containment equipment like biological safety cabinets. Formaldehyde is a toxic substance and a suspected human carcinogen. Considerable caution must be exercised in handling, storing, and using formaldehyde.

Ethylene oxide is used in gas sterilizers under controlled conditions. Ethylene oxide is also a human carcinogen and monitoring is necessary during its use.

Radiation

Gamma and X-ray are two principal types of ionizing radiation used in sterilization. Their application is mainly centered on the sterilization of prepackaged medical devices.