Page 101 - The Veterinary Laboratory and Field Manual 3rd Edition

70 Willy Schauwers

• Wipe down the inside of the unit with disin- glass or metal laboratory ware. Ovens come in a
fectant or soapy water as required or between range of sizes with a variety of shelving options.
batches of contents. An oven can be set to a specific temperature and
most models have a fan to ensure air circulation.
Generally, items should not be added to the oven
Quality assurance
until the desired temperature has been reached.
Record, on a daily basis, the minimum/maximum Let the oven cool down to at least 40°C before
temperature of the incubator on the tempera- removing sterilized items.
ture daily control worksheet. For this purpose,
use the form ‘FORM-SOP-LABORATORY- Quality assurance
EQUIP-05–01 Temperature registration min max
thermometer’. Check the temperature on a regular basis against
a certified thermometer. See ‘SOP-LABORATORY-
EQUIP-05 Temperature registration’ and
ovens ‘FORM-SOP-LABORATORY-EQUIP-05–06-
Compare temperature with certified thermometer’.
If the laboratory is fairly large, a small hot-air
oven (Figure 2.34) is useful for drying glassware
(a drying cabinet is even more suitable for dry- balances
ing glassware) and for dry-heat sterilization of
The sensitivity of balances commonly used in
veterinary diagnostic laboratories ranges from
0.1 g to 0.0001 g with a capacity of 50–2000 g.
A regional laboratory is likely to have two
types of balances. In a district laboratory, it
might be suitable to have a balance that can
operate on battery as well as mains. A double
pan balance for counter weighing, for example,
for centrifugation, and for more accurate weigh-
ing a single pan (Figure 2.35), digital read-out
electronic balance. The more sensitive electronic
analytical balances (Figure 2.36) are significantly
more expensive. Weighing procedures must be
carried out with care to obtain the correct weight
and to protect the instrument.

Use and maintenance

• The balance should be placed on a solid, level
stable surface away from draughts, vibration
and direct sunlight.
• Always zero (tare) the balance before com-
Figure 2.34 Oven. Photo: Willy Schauwers, mencing weighing.
Provincial Institute for Hygiene, Antwerp, Belgium. • Weigh chemicals at room temperature.

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