Chemical Disinfectants
Page Contents
Disinfection | Choosing a Disinfectant | Preparing
Working Dilutions | Activity of Different Types
of Disinfectants (Table)
Common Disinfectants including: Chlorine Compounds, Alcohols, Iodine, Formaldehyde, Glutaraldehyde, Chlorhexidine, Hydrogen
Peroxide, Phenolics, Quaternary Ammonium Compounds
Disinfection
Decontamination of laboratory benches, furniture, equipment and other materials requires the use of chemical disinfectants. Their activity is related to the following factors:
- concentration
- pH
- contact time
- humidity
- temperature
- presence of organic matter
Choosing a Disinfectant
Microorganisms present a range of resistances to chemical disinfectants and no single disinfectant is effective in all situations. Consider the following points when selecting a disinfectant:
- type of microorganisms, numbers and presence of spores
- physical situation (surface type, suspension, etc.)
- contact available between disinfectant and microorganisms
- possible interaction between disinfectant and materials
- contact time allowable
- concentration
Preparing Working Dilutions
Follow the manufacturer's recommendations for dilution of concentrated disinfectant.
- Prepare fresh dilutions daily
- Use clean, dry containers
- Use clean water for dilutions
| Toxicity Against | Disinfectant | |||||
|---|---|---|---|---|---|---|
| Phenolic Compounds | Hypochlorites | Alcohols | Formaldehyde | Glutaral | Iodophors | |
| Fungi | good | slight | nil | good | good | good |
| Bacteria (gram +/-) | good | good | good | good | good | good |
| Mycobacteria | fair | fair | good | good | good | good |
| Spores | nil | fair | nil | good (<40ºC) | good (<20ºC) | slight |
| Lipid Viruses | slight | slight | slight | slight | slight | slight |
| Non-Lipid Viruses | variable | slight | variable | slight | slight | slight |
| Skin | slight | slight | nil | slight | slight | slight |
| Eyes | slight | slight | slight | slight | slight | slight |
| Lungs | nil | slight | nil | slight | slight | nil |
Common Disinfectants
Chlorine Compounds
Generally used in the form of sodium hypochlorite.
- Effective against a wide variety of microorganisms (vegetative bacteria and viruses). Preferred disinfectant for HIV and hepatitis viruses.
- Use at 0.1% as a general disinfectant.
- Less suitable in the presence of organic matter (such as blood). Concentration must be increased to retain action (0.5%).
- Effective between a pH range of 6-8.
- Strength decreases on standing (make fresh solutions daily).
- High concentrations corrode metal surfaces, and bleach and damage fabrics.
Alcohols
Ethanol (80% v/v ethyl alcohol) or 2-propanol (60-70% v/v iso-propyl alcohol) solutions are used to disinfect skin and decontaminate clean surfaces.
- Effective against fungi, vegetative bacteria, Mycobacterium species and some lipid-containing viruses.
- Not effective against spores.
- Most effective at 70% in water.
- May swell rubber or harden plastics.
- Do not use near flames due to flammability.
Iodine
Iodine vapour is highly toxic and is absorbed through the skin
Iodine is used in aqueous or alcoholic solution.
- Rapidly effective against most microorganisms.
- Usually diluted to 1% w/v free iodine, optimum pH neutral to acid.
- Not suitable in the presence of organic matter.
- Stains skin and may cause irritation.
- Dilute in alcohol for washing hands, or use as a sporicide.
- Prepare dilutions daily.
- Most commonly used for skin disinfection and decontaminating clean surfaces.
- Decomposes when heated above 40ºC.
- Do not use on aluminium or copper.
Formaldehyde
Precautions are required when handling formaldehyde (refer Australian Standard 2508.6.026)
Formalin is 37% w/v formaldehyde gas in water.
- Active against most microorganisms.
- 13% v/v formalin is a good decontaminant (but has an irritating odour).
- 8% v/v formalin in 80% v/v alcohol is effective against vegetative bacteria, spores and viruses.
- Does not corrode stainless steel.
- Use to disinfect equipment such as centrifuges or biosafety cabinets.
- Formaldehyde can be used to disinfect rooms, cubicles and safety cabinets: THIS PROCEDURE MUST BE PERFORMED BY NATA ACCREDITED PERSONNEL ONLY.
- Generated by heating paraformaldehyde suspended in silicone oil to 160ºC.
- Use 5 grams formaldehyde per cubic metre of space to be decontaminated.
- Requires relative humidity between 70% and 90% (humidity can be raised by evaporating water into the room).
- Formaldehyde can react with free chlorine to produce toxic gas. Remove hypochlorite solutions and hydrochloric acid from spaces to be decontaminated.
- Neutralise with ammonia following decontamination.
Glutaraldehyde
Glutaraldehyde is known to cause dermatitis and asthma
Glutaraldehyde is commercially available as 2% w/v aqueous solution which must be made alkaline to "activate" (e.g. by addition of 0.3% sodium bicarbonate).
- Active against vegetative bacteria, spores, fungi and many viruses.
- Less irritating than formaldehyde, but may cause dermatitis. Wear protective gloves when handling materials which have been immersed in glutaraldehyde.
- Discard if turbid.
- Also available in stable glycocomplexed form which does not require addition of alkaline buffer.
Chorohexidine
Chlorhexidine as chlorhexidine gluconate is dissolved in 70% alcohol.
- Use as antiseptic. Apply alcoholic chlorhexidine to the skin in the event of accidental contamination.
- Effective against Gram-positive organisms and HIV.
- Not recommended as a general disinfectant.
- Not active against sporulating bacteria or non-lipid-containing viruses.
- Active in ph range 5.5 - 8.0.
- Incompatible with soap and anionic detergents.
Hydrogen Peroxide
A concentration of 3% w/v generally used for disinfection.
- Active against a range of microorganisms.
- Fungi, spores and enteric viruses require higher concentration.
- No toxic end-products of decomposition.
- Do not use on aluminium, copper, zinc or brass.
Phenolics
Synthetic phenolics (clear soluble fluids) can be used as general disinfectants in the laboratory.
- Active against bacteria and lipid-containing viruses.
- Not active against spores and non-lipid-containing viruses.
- Active in presence of organic matter.
- Use for disinfecting floors, walls, benches and other furniture.
Quaternary Ammonium Compounds
Quaternary ammonium compounds are positively charged (cationic) surface-active disinfectants.
- Effective against Gram-positive bacteria and lipid-containing viruses.
- Not recommended as general disinfectants (they have a narrow antibacterial spectrum).
- Inactivated by proteins, soap and anionic detergents.