Page 133 - The Veterinary Laboratory and Field Manual 3rd Edition

102 Willy Schauwers

Use of detergents for cleaning throughout the laboratory. Since untrained
glassware workers are often employed in the glassware/
plastic ware washing sections of laboratories
The use of biological detergents for cleaning and are sometimes not well supervised, poor
glassware in laboratories is essential. These results can often be traced back to this section
detergents are available in either liquid or pow- of the laboratory. For example, traces of soap and
der form. Detergents possess the following poor sterilization techniques will affect chemical
advantages over soaps.
analysis, haematological, serological and many
• Their action is unaffected by the temperature microbiological assays.
of the water.
• They are equally efficient in either slightly General precautions
alkaline or slightly acid water.
• They do not coagulate proteins. • Careful handling and storage should be used
to avoid damaging glassware.
The main disadvantage of detergents is that the • Inspect the glassware before each use and dis-
slightest trace on labware causes contamina- card if scratched on inner surfaces, chipped,
tion of samples and can result in haemolysis of cracked or damaged in any way.
blood. It is therefore extremely important in a • Use only plastic core brushes that have soft
washing procedure to ensure that all detergent non-abrasive bristles or soft, clean sponges/
is removed by thorough rinsing in changes of rags. Use brushes to clean inside of deep
deionized water. Usually 20 ml of liquid soap per glassware.
1 l of water can be used for cleaning glassware. • Rubber sink and counter mats can help
Good laboratory technique demands clean reduce the chance of breakage and resultant
labware, because the most carefully executed injury.
piece of work may give an erroneous result if • Do not overload sinks or soaking bins.
dirty glassware is used. In all instances, glassware • Do not place metal or other hard objects, such
must be physically clean; it must be chemically as spatulas, glass stirring rods or brushes
clean; and in many cases, it must be bacterio- with metal parts, inside the glassware. This
logically clean or sterile. All labware must be will scratch the glass and cause eventual
absolutely grease-free. The safest criterion of breakage and injury.
cleanliness is uniform wetting of the surface by • Never use strong alkaline products and
distilled water. This is especially important in hydrofluoric acid as cleaning agents. These
glassware used for measuring the volume of liq- materials dissolve glass, leading to damage
uids. Grease and other contaminating materials and eventual breakage.
will prevent the glass from becoming uniformly • Do not use any abrasive cleansers, as these
wetted. This in turn will alter the volume of resi- will scratch the glass and cause eventual
due adhering to the walls of the glass container breakage and possible injury. Scouring pads
and thus affect the volume of liquid delivered. will scratch glass and should not be used.
Furthermore, for pipettes and burets, the menis- • Do not use heat as a method to remove carbon
cus will be distorted and the correct adjustments residues. Heating glassware to temperatures
cannot be made. The presence of small amounts > 400°C will cause permanent stresses in the
of impurities may also alter the meniscus. glass and eventual breakage.
Insufficient cleaning and sterilization of • Use proper drying racks for cleaned glass-
glassware will lead to erroneous test results ware.

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