Plastics Cleaning, Sterilization, Microwaving

PLASTICS ... Cleaning, sterilization, microwaving

Cleaning.
To retain the quality of plastic labware, first wash in a mild, non-alkaline detergent. Next, rinse the labware thoroughly with tap water and a final rinse with distilled water to eliminate all traces of residue. Polycarbonate items should not be exposed to strong alkaline cleaning agents. These agents will cause crazing and cracking of the polycarbonate surface. To avoid damage to plastic products, do not utilize abrasive materials such as cleansers or scouring pads. Laboratory washing machines are a convenient method of cleaning most types of plastics with the exception of low-density polyethylene, acrylic and polystyrene. Items manufactured of these plastics are adversely affected by the heat involved. In addition, the strength of polycarbonate will be weakened by repeated exposure to washers. Therefore, polycarbonate labware utilized in high stress situations should be washed by hand to ensure effective performance. When laboratory washing machines are used, water temperature should be set at 135°F (57°C) maximum. If ultrasonic cleaners are employed, avoid direct contact with transducer diaphragm. When special cleaning is necessary, such as the removal of grease or oil, organic solvents (e.g., acetone, alcohols) may be applied. Use with caution. More than brief exposure may affect the polyolefins. Rinse again thoroughly before use. For PSF, PS or PVC, only an alcohol based solution should be administered. Do not use organic solvents when cleaning acrylics. To remove organic matter from plastic labware, sodium hypochlorite solutions (bleaches) are suggested. A cleaning agent made of chromic acid, though effective, will eventually cause plastic to become brittle.

Sterilization.
Always clean items and rinse in distilled water thoroughly prior to autoclaving. To avoid pressure build up, set closures upon containers loosely without threading. Carboys and spigots should be autoclaved empty to prevent leakage. Autoclave at 121°C for 20 minutes to assure sterility. Ethylene-oxide or chemical disinfectants are recommended for PVC. Chemical disinfectants such as benzalkonium chloride, formalin, ethanol, iodophor and quaternary ammonium compounds may be used. When choosing ethylene-oxide (ETO) gas sterilization, a seven to fourteen day quarantine period is necessary for the assurance of no ETO residue.

Microwaving.
All plastic materials allow transmission of microwaves. However, the heat resistance of the plastic material must be taken into account since the contents of the container in a microwave oven may exceed the plastic's heat resistance.