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Cleaning Solution Containers
Great care should be taken to ensure that reagent and
standard
solution
containers
whenever their contents are changed, as algal growth can also
occur in them. Under normal circumstances thorough rinsing
of the containers with high purity water may be adequate.
However, if there is any evidence of algal growth, the
containers should be rinsed with sodium hypochlorite solution
(containing about 0.1% available chlorine) and thoroughly
flushed out with water afterwards. A bottle brush may be useful
to remove stubborn deposits.
It is advisable when changing standard or reagent solutions to
replace the container and remove the empty/used one for
thorough cleaning.
Note. It must be emphasised that containers which are to
be used for ammonia standard solutions must be very
thoroughly washed out after chlorine treatment because
any residual chlorine will react with ammonia and hence
change the standard concentration. In addition to
thorough washing with water, it is suggested that the
containers are rinsed with a portion of the ammonia
standard before finally filling.
8.2.6 Consumables Spares Kit
If one is not supplied, it should be ordered before the end of the
first year of operation. This kit includes all the components
which are recommended for replacement annually (see
Section 10). This annual refurbishment ensures a high level of
reliability from the monitor over a period of many years.
Another kit should be ordered when the old one is used so that
all the items are available throughout the following year's
operation. The consumable spares kit is in addition to the
electrode spares kit.
The kit contains the following:
•
one set of pump tubing
•
one set of pump capstans
•
a complete set of plumbing tubing
•
sundry items – 'O' rings, tube connectors, pump tube
bungs and fuses
•
plastic syringe and bottle brush – for cleaning pipework,
valves, flowcell and constant-head unit.
are
thoroughly
cleaned
8.2.7 Assembling/Refurbishing the Probe
The ammonia probe is a gas sensing combination electrode
assembly. It is supplied in kit form and must be assembled or
refurbished using one of the appropriate procedures below:
Refurbishing
a) Dismantle the probe and rinse off the filling solution with
dimineralised water.
b) Remove the membrane from the end cap and retain the
sealing washer; use a new washer if it is damaged.
c) Proceed from step c) in Assembling the Probe below.
Assembling the Probe
a) Unscrew the end cap from the probe body. Rinse the probe
body with distilled or de-ionised water. Allow to drain.
b) Remove the teat from the glass electrode. Rinse the
electrode with distilled or de-ionised water. Dry with a
paper tissue.
c) Screw the glass electrode into the body until the tip of the
electrode is flush with the end face of the probe. Note the
number on the electrode cap in line with the mark on the
body. Unscrew the electrode cap four full turns.
d) Drop a membrane (coloured white) into the end cap and
place the sealing washer centrally upon it.
e) Screw the end cap firmly onto the body, taking care not to
wrinkle the membrane. Ensure that the body seal and the
membrane sealing washer are both under compression.
f) Holding the probe upright, inject the filling solution
provided through the filling hole until there is a 50 to 60 mm
depth of solution inside so that the reference element is
immersed in the solution. Wipe any excess filling solution
from the body.
g) Tap the end of the probe with the finger to dislodge any air
bubbles which have been trapped between the end of the
glass electrode and the membrane. Screw the glass
electrode down four turns to the flush position again and
then a further 1.0 ±0.1 turns. The tip of the electrode should
now be pressing against the membrane. In some
circumstances, particularly if the electrode response is
sluggish, the screw may be given a further 0.2 to 0.3 turn.
Beware of overtightening, which can puncture the
membrane.
h) Push the probe cap onto the top of the probe body so that
it covers the filling hole.
Note. A newly assembled probe should be run on sample
for 2 to 4 hours before a calibration is attempted.
8 MAINTENANCE...
31
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