Page 135 - The Veterinary Laboratory and Field Manual 3rd Edition

104 Willy Schauwers

• Immersion method: for the immersion ucts are susceptible to attack by alkalis and a
method, labware is soaked in the cleaning neutral detergent is recommended.
solution for 20 to 30 min at room tempera- • If using an automatic laboratory washing
ture, then rinsed with tap water, and finally machine to wash plastic volumetric ware,
with distilled water. Only for stubborn resi- such as measuring cylinders, employ a wash
dues should the soaking time be extended temperature below 60°C. High temperatures
and the temperature increased. can affect volumetric accuracy.
• Ultrasonic bath: both glass and plastic lab- • Ultrasonic baths may be used for cleaning
ware may be cleaned in an ultrasonic bath. plastic ware. However, do take care that the
However, direct contact with the sonic mem- products do not directly touch the transducer
branes must be avoided. membrane.
• Machine cleaning: machine cleaning with a
laboratory washing machine is gentler to lab- Cleaning in trace analysis: To minimize metallic
ware than cleaning in an immersion bath. The traces, laboratory equipment is placed into 1N
labware is only exposed to the cleaning solu- HCl or 1N HNO at room temperature for not
3
tion for the relatively short flushing periods more than 6 h (glass laboratory equipment can
when sprayed by the jet or ejector nozzles. be boiled for 1 h in 1N HNO ). It is then rinsed
3
Lightweight objects will not be tossed and with distilled water. To minimize organic con-
damaged by the jet if they are secured in tamination, laboratory equipment can first be
washing nets. Labware is protected against cleaned with alkalis, or a solvent such as alcohol.
scratching when the wire baskets in the There is extra material on the website detail-
washing machine are plastic coated. ing the cleaning of:

Plastic labware items generally have smooth, • new glassware
non-wetting surfaces and can usually be cleaned • dirty glassware
effortlessly under low alkalinity conditions. • pipettes
Polystyrene or polycarbonate labware, for • dirty slides.
example, centrifuge tubes, must only be cleaned
manually with neutral detergents. Prolonged
exposure even to low alkaline detergents will disinfection and sterilisation of
impair their strength. The chemical resistance laboratory ware
of these plastics should be verified in each
case. Disinfection kills the disease-causing (pathogenic)
bacteria. Bacterial spores are not killed. However,
in many cases disinfection suffices. Disinfection
Washing and cleaning
means that one can no longer contract infection
• Most laboratory plastic ware is readily cleaned from the disinfected objects (dis-infection).
in warm water with a detergent and soft cloth The goal of disinfection is to kill germs and
or sponge. Avoid using abrasive cleaners or reduce the number of germs such that the disin-
scouring pads which can result in surfaces fected objects can no longer transmit infection.
becoming scratched. Sterilization means the killing of all micro-
• A low or non-alkaline detergent is suitable organisms, including bacterial spores. The goal
for cleaning most plastic ware. Note however of sterilization is to assure absolute absence of
that polystyrene and polycarbonate prod- organisms.

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