Sterilization:
Sterilization may be defined as the complete
destruction of all organisms, or their removal from materials by means of heat
,chemicals, irradiation or filtration methods.
Heat: The usual methods employed for the
sterilization of laboratory materials which involves :
1- hot air sterilizer (oven): this is used for sterilizing all
kinds of laboratory glassware, such as test tubes, pipettes, Petri dishes, and
flasks, it may be used to sterilize other laboratory materials and equipment
that are not burned by the high temperature of the sterilizer and this is
operated at temperature of 160 to 180 °C for a period 1½ hr.
2- wet air sterilizer (autoclave): this is used to sterilize
most type of solid and liquid media with and without carbohydrate, gelatin
media, distilled water, normal saline, rubber tubing and gloves. The autoclave
is operated usually at 15 Ib. steam pressure for a period of 15 min., which
corresponds to temperature of 121°C.
Filtration : some solution cannot be sterilized
by heat without being greatly altered in their physical and chemical
properties. Serum , antibiotics, enzymes and other preparation containing heat
–sensitive compounds are best sterilized by process of filtration. The type of
filters employed for this purpose include: Berkefeld Filters, Fritted – glass
Filters and Porcelain or Chamberland Filters.
Chemical sterilization: Chemicals are
also used for sterilization. heating, it is not always appropriate, because it
will damage heat-sensitive materials such as biological materials, fiber optics, electronics, and many plastics.
Ethylene oxide:
(EO or EtO) gas is commonly used to sterilize objects sensitive to temperatures
greater than 60°Csuch as plastics
Ozone: is used
in industrial settings to sterilize water and air, as well as a disinfectant for
surfaces.
Radiation sterilization: Gamma rays are
commonly used for sterilization of disposable medical equipment, such as
syringes, needles
Ultraviolet lightirradiation (UV, from a germicidal lamp)
is useful only for sterilization of surfaces and some transparent objects.