Page 132 - The Veterinary Laboratory and Field Manual 3rd Edition

The selection, use, maintenance and quality control of laboratory equipment and supplies 101

• Most plastics allow the transmission of The raw materials used in detergents (clean-
microwaves. However, as with any microwave ing agents, cleaners) are:
vessel, be sure it holds a microwave absorb-
ing material, such as water, before placing in • surfactants (tensides)
the oven. • acids
• alkalis (lyes)
StErILIzatIon • water-soluble and water-insoluble solvents
• If the plastic ware is to be sterilized by auto- • auxiliary ingredients.
claving always pre-check that the polymer can
withstand repeated exposure to temperatures Surfactants are the most important of these raw
of 121°C. materials.
• When autoclaving bottles always ensure the Aqueous detergents (as well as other aque-
caps are loosened or removed to prevent acci- ous liquids) are either neutral, acidic or alkaline.
dental collapse or deformation. Commercially available cleaning products can be
classified as follows:
dISPoSaL
• If the disposal of an item of plastic ware is • neutral detergents pH approx. 5–9
unavoidable, always follow local laws and • acidic detergents pH < 5
regulations. • alkaline detergents pH > 9
(use concentration)
• solvent detergents.
cleaning of laboratory ware
Detergents that cannot be clearly assigned to any
Cleaning means the removal of dirt or of any particular class.
other unwanted material (blood, food residues
and so on). This removes visible contami- • Neutral detergents, the principle ingredient
nants. The goal of cleaning is to assure visible of which is surfactants. Neutral detergents
cleanliness. are, in general, much weaker than alkaline
Cleaning has the task of mechanically remov- detergents (lyes), therefore alkaline deter-
ing bacteria and fungi or of depriving them of their gents should preferably be used to clean
source of nutrients. The number of germs (bio- surgical instruments.
burden) can be considerably reduced (50–90%) by • Acidic detergents remove lime and cement
cleaning thoroughly. residues (acetic acid, citric acid, phosphoric
Factors decisive for effective cleaning: acid), commonly are used as toilet cleaners,
with addition of surfactants and as cleaners
• chemical action for sanitary fittings.
• mechanical action • Alkaline detergents remove incrustations in
• time the kitchen as well as in industrial and hos-
• temperature. pital settings (caustic potash solution, soda
[sodium carbonate], ammonia and so on).
If one, for example, wants to use fewer chemi- They are used concentrated as oven cleaners
cals, then one must clean for longer or use and are stronger than neutral detergents.
greater mechanical action, which means having
to scrub harder.

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