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Disinfection

Methods designed for the disinfection/decontamination of culture waste, work surfaces and equipment represent important means for minimizing the risk of harm.

The major disinfectants fall into four groups and their relative merits can be summarized as follows:

Hypochlorites (e.g. Chloros, Presept)

• Good general purpose disinfectant
• Active against viruses
• Corrosive against metals and therefore should not be used on metal surfaces e.g. centrifuges
• Readily inactivated by organic matter and therefore should be made fresh daily
• Should be used at 1000ppm for general use surface disinfection, 2500ppm in discard waste pots for washing pipettes, and 10,000ppm for tissue culture waste and spillage

Phenolics (e.g. Sudol, Hycolin)

• Not active against viruses
• Remains active in the presence of organic matter

Alcohol (e.g. ethanol, isopropanol)

• Effective concentrations 70% for ethanol, 60-70% for isopropanol
• Their mode of activity is by dehydration and fixation
• Effective against bacteria. Ethanol is effective against most viruses but not nonenveloped viruses
• Isopropanol is not effective against viruses

Aldehydes (e.g. glutaraldehyde, formaldehyde)

• Aldehydes are irritants and their use should be limited due to problems of sensitization
• Glutaraldehyde may be used in situations where the use of hypochlorites is not suitable e.g. cleaning of centrifuge bowls or materials constructed of stainless steel that may be attacked or corroded by using hypochlorite solutions.

Waste Disposal

Any employer has a ‘duty of care’ to dispose of all biological waste safely in accordance with national legislative requirements. Given below is a list of ways in which tissue culture waste can be decontaminated and disposed of safely(especially the solid waste, such as flasks, centrifuge tubes, contaminated golves etc). One of the most important aspects of the management of all laboratory-generated waste is to dispose of waste regularly and not to allow the amounts to build up. The best approach is ‘little and often’. Different forms of waste require different treatment.

• Tissue culture waste (culture medium) - Inactivate overnight in a solution of hypochlorite (10,000ppm) prior to disposal to drain with an excess of water
• Contaminated pipettes should be placed in hypochlorite solution (2500ppm) overnight before disposal by autoclaving and incineration
• Solid waste, such as flasks, centrifuge tubes(such as 15ml Centrifuge Tube, 50ml Centrifuge Tube), contaminated gloves, tissues etc. should be placed inside heavy duty sacks for contaminated waste and autoclaved prior to incineration. These bags are available from Bibby Sterilin and Greiner.
• If at all possible waste should be incinerated rather than autoclaved

Source: Sigma-Aldrich