DelAgua OXFAM-DELAGUA, Руководство пользователя

Страница: 19 / 67

OXFAM-DELAGUA Water Testing Kit — Users Manual
18
3. Add the 38.1g of MLSB powder to the distilled water in the clean flask or
beaker and stir until the powder has dissolved. Gentle heat can be applied if
the powder is slow to dissolve. Add the remaining volume of distilled water
and continue stirring to thoroughly mix the broth.
The culture medium will be a bright red colour when dissolved.
Note: MLSB is a fine, but non-hazardous powder. However, the dust may irritate
the nose or upper respiratory tract if inhaled. Take care to avoid creating excess
dust when handling the powder and cover the nose and mouth with a cloth or dust
mask to reduce exposure. Spillages can be cleaned up using water and an absorbent
cloth.
4.
Pour a suitable volume of culture medium (approximately 50ml, but no less
than 40ml) into each of the 10 polypropylene bottles. This provides sufficient
medium in each bottle to carry out 16 tests; the maximum that can be
performed in one day using the Delagua kit.
5.
Replace the screw caps on the polypropylene bottles. Make sure the caps are
secure but do not tighten. Leaving the caps slightly loose prevents the bottles
from collapsing during sterilisation.
6.
If an autoclave is available, sterilise the bottles at 121°C (equivalent to 1 bar,
or 15 psi steam pressure) for 15 minutes. Tighten the caps carefully once the
medium has cooled.
7.
If you do not have access to an autoclave, then a household pressure cooker or
portable steriliser may be used. Place the bottles in a rack inside the cooker
(they may melt if placed directly on the base of the cooker), replace the lid and
heat to full pressure (about 1 bar or 15psi).
Once the cooker has reached full pressure allow steam to issue from the
release valve for 5 minutes, then time the 15 minutes sterilisation cycle using a
stopwatch or clock. At the end of the 15 minutes, switch off the heat and allow
the cooker to cool until it is comfortable to touch. Remove the media bottles
and tighten the caps.
8.
Label the bottles to indicate sterilised contents and the date and batch of
medium.