Systematic preparation of laboratory glassware
6
Cleaning and drying
The Miele system consists of the
following components:
● Washer disinfector
● Baskets and inserts for laboratory
equipment
Miele’s G 7883– G 7736 CD washer
disinfectors are single cabinet systems
in which the whole process takes place
(wash, rinse and disinfection if appli-
cable, followed by drying) in a closed
system. The cleaning process is car-
ried out with injectors using water ba-
sed agents. Programmable Profitronic
and MCU controls enable programmes
to incorporate specific process para-
meters (temperature, time, amount of
cleaning agents etc.) for the cleaning
task in hand. With the Multitronic Novo
plus controls specific process parame-
ters can also be changed in standard
cleaning programmes. The controls are
able to monitor and maintain the rele-
vant process parameters ensuring con-
sistent standards of cleanliness. Other
features and options, such as heating
for the process water, dispensers for
acidic, ph-neutral or alkaline cleaning
agents, high performance circulation
pumps, hot air drying units and auto-
matic mobile unit recognition enable
cleaning processes to be carried out
fully automatically.
Miele offer a wide range of mobile units
as well as baskets and inserts for
laboratory glassware processing.
There are injector jets for pipettes and
measuring flasks, conical and Erlen-
meyer flasks. Injector jets ensure
thorough internal cleaning, rinsing and
drying of laboratory glassware. Rotat-
ing spray arms ensure thorough exter-
nal cleaning and rinsing.
There are special inserts for holding
beakers, Petri dishes, wide necked
bottles and Erlenmeyer flasks and test
tubes securely. These can be placed in
the lower or upper basket. The spray
arms in the machine and in the upper
basket ensure excellent internal and
external cleaning and rinsing results.
Water preparation
Very often different quality water is re-
quired for different stages of a pro-
gramme, e.g. for the wash and the
rinse.
Usually the beginning of a wash pro-
gramme would use softened water
(pre-wash, main wash and first rinses).
Using softened water prevents lime-
scale building up in the machine as
well as unwanted side effects during
the cleaning process.
Fully demineralised purified water is
then used in the final rinsing stages.
This water quality ensures the very
best surface cleanliness of laboratory
glassware. However, to ensure this
level of cleanliness any contamination
must first be removed.
Cleaning agent
Cleaning agents can generally be split
into 3 groups.
● alkaline products
● pH neutral products
● acidic products
Alkaline cleaning agents are complex
mixtures and can contain substances
such as potassium or sodium hydroxi-
de, silicates, cabonates, polycarbona-
tes, complex compounds, tensides,
enzymes, oxidation agents etc. The
cleaning agent must be selected ac-
cording to application and type of
contamination on the equipment. For
instance cleaning agents without ten-
sides, but preferably with oxidation
agents should be used for equipment
used for plant and cell cultures. If
samples are being analysed for phos-
phorous or phosphates in a laboratory,
then the detergent should be phospha-
te or phosphonate free.
pH-neutral products generally contain
tensides, emulsifiers or enzymes. They
are occasionally used together with
alkaline cleaning agents.
Acidic products are based on citric or
phosphoric acid. They are often used
for neutralisation of laboratory equip-
ment after cleaning with an alkaline
agent. Sometimes it is necessary to
use a strong acidic cleaning agent, e.g.
to remove limescale deposits from
flasks used for water testing.
Cleaning programme
The wash programme consists of
separate stages of a process carried
out in the correct order using the
appropriate cleaning agents. To create
a suitable programme it is important to
know the physical and chemical pro-
perties of the type of contamination
being handled.
Many contaminants are water soluble
or can be dissolved using alkalines
(e.g. organic acids) or acids (e.g. amine
and some metal oxides).
Chemical changes can convert some
insoluble residues into soluble matter
(e.g. alkaline hydrolysis of animal fats
and oils into fatty acids and glycerine).
Other contaminants are virtually chemi-
cally inert and can only be broken
down or emulsified using high tempe-
ratures and tensides (e.g. paraffin wax).
In certain circumstances dispensing
the incorrect amount of cleaning agent,
or running a programme with the pro-
cess parameters set in the wrong order
can lead to unsatisfactory results (e.g.
running a hot pre-rinse on items conta-
minated blood will cause the blood to
coagulate).
Process assurance
The aim of all laboratories is to carry
out standardised processes which can
be validated. In order to validate pro-
cesses and working procedures these
must be reproducible and be suitable
for being documented. This requires a
high degree of process assurance.
The controls used on Miele washer
disinfectors can monitor validated pro-
cedures and working processes, e.g.
they can:
● control and monitor temperature and
time
● control the pressure of the recircula-
tion pump
● control and monitor the amount of
water used
● monitor level in the supply canisters
and control the amount of liquid
agents dispensed
