Aquasafe WSL50 Pro, Instruction Manual

Page: 43 / 193

SECTION 6: ASEPTIC PROCEDURES
Aseptic procedures are of paramount importance during microbiological
analysis, and extra
care must be taken when outside the central
laboratory, i.e. in the field. Everything must be kept clean and sterile,
particularly on the following surfaces:
Inner surface of the sampling cup
Inner surface of the graduated filter funnel
Filter membrane and absorbent pads
Upper surface of the sintered membrane support disc
Inside of the petri dishes
Support pad dispenser arm, and forceps
Before every use, rinse the filtration unit and sampling cup in clean water,
and dry by using clean tissue paper.
Pour approx. 1 mL of methanol into the sampling cup and swirl. (The
methanol can be stored in the plastic bottles provided)
Place the sample cup in a normal upright position, away from any
flammable substances.
Using a suitable means (cigarette lighter), ignite the methanol
– TAKE
CARE AROUND THE NAKED FLAME.
Allow the methanol to burn for a few seconds.
Whilst the methanol is still burning, invert the filtration unit and carefully
place inside the sample cup. Wait for at least 20 minutes to ensure that the
sample cup and filtration unit are sterile. Methanol burns anaerobically to
form formaldehyde gas, which reaches all areas of the filtration apparatus
and ensures a thorough sterilisation. Pour any residual methanol solution
away.
The above sterilisation procedures should be carried out
immediately before sampling, and after the filtration of each sample.
Reusable aluminium petri dishes must be sterilized, either by immersing in
boiling water, or flaming with methanol prior to use. After sterilisation,
ensure that the dishes are allowed to dry thoroughly before use. Other
methods of sterilisation can be employed, including autoclaving, or placing
the aluminium dishes in a conventional oven at 300°C for 30 minutes.
Once sterile, the petri dishes should be handled carefully to prevent
subsequent recontamination.