D7321_11 V2
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Thoroughly clean the outside
of the sample container
in the region of
the cap by wiping it
with a damp, lint-free cloth.
Shake the container
vigorously for about 1 minute.
Remove the cap, and remove
any external contaminant that
may be present in the threads.
Complete assembly
of the receiving
flask, pre-weighed filter,
and funnel as a unit.
See figure 1 of the
written standard.
To minimize operator
exposure to fumes,
the filtering procedure should
be performed in a fume hood.
Important-- the entire contents
of the sample container
shall be filtered through
the glass fiber filter
to ensure a correct measure of
the particulate contamination
in the sample.
Some fuels may filter
reasonably rapidly
during transfer of the
total contents of the sample
container through a
single glass fiber filter.
However, some fuels, due
to the quantity or nature
of the particulates, or
both, may plug the filters
during filtration
and require use
of multiple successive
filtrations.
To facilitate the latter,
it is advisable to use
smaller, cleaned graduated
transfer cylinders of 100
milliliter capacity.
Pour fuel from the
sample container
to the graduated cylinder,
start the vacuum,
and then transfer 100
milliliters of fuel
to the filter funnel.
Continue transferring
100-milliliter increments
of fuel to the filter funnel.
When all the fuel from
the sample container
has been filtered
or if filtration
slows so that 100
milliliters of sample
requires greater than 10
minutes for complete filtration,
then remove the
filter support, filter
funnel from the receiving flask,
and pour the filtered fuel
into a clean graduated cylinder,
and record the volume of fuel
in milliliters that
was filtered-- v sub f.
Keep the fuel sample
filtrate separate from
the solvent washings filtrate.
This allows the fuel to be
used for additional analyses.
If all the fuel
has been filtered,
thoroughly rinse
the sample container
and the graduated cylinder
with one or more portions
of filtered flushing
fluid, and pour the rinses
into the funnel, and proceed to
11.6 of the written standard.
If all the fuel has
not been filtered,
then proceed to 11.6 and
11.8 of the written standard,
and then repeat from 11.1
of the written standard.
Wash down the
inside of the funnel
and the outside of the
joint between the funnel
and the filter base filtered
with flushing fluid.
Use two washes with
approximately 50 milliliters
each of washing flushing fluid.
With the vacuum applied,
carefully separate the funnel
from the filter base.
Wash the periphery of
the glass fiber filter
by directing a gentle
stream of filtered flushing
fluid from the
edge to the center,
exercising care not to
wash any of the particulate
from the surface of
the glass fiber filter.
The volume of the
solvent required
is recommended to be
approximately 50 milliliters.
However, the rate of filtration
may dictate the solvent volume.
Take care not to wash
particles from the filter,
particularly at the stage when
the funnel has been removed.
The volume of the solvent
used to wash the filter
should be sufficient to rinse
any particles onto the filter
paper.
A final wash of
approximately 20 milliliters
of methanol or isopropanol,
[? propintanol, ?]
is applied with the use of a
pipette to remove trace of fuel
while taking care to minimize
the risk of dislodging
any particles on the filter.
A Pasteur pipette has been found
suitable for the final wash.
Maintain vacuum after the
final washing for 10 seconds
to 15 seconds to remove
excess filtered flushing fluid
from the glass fiber filter.
Using clean forceps, carefully
remove the glass fiber filter
from the filter base, and place
it on clean glass support rods
or watch glass in a
clean, covered Petri dish.
Dry and reweigh the
glass fiber filter
as described in 10.5 of
the written standard,
taking care not to disturb
the particulate on the surface
of the glass fiber filter.
Record the glass fiber filter
mass to the nearest 0.0001 gram
for each filtration.
If after removing the
filter from the drying oven
the filter is observed
to have discoloration
on the filter indicating
fuel on the outer edges,
gently rinse the filter
with more solvent,
rinsing gently from
the outer edges inward
so as to not disturb any
particulate matter filtered
and repeat 11.8.