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USER MANUAL
5. Filter Washing
5.1
When the filtration is complete and the upper filter medium appears dry, continue the
steam and vacuum for a further 5 min. Discontinue the steam supply and cool the apparatus
by
passing tap water through the coils. Wash the filtration unit carefully with two portions of 25 ±1
mL of the wash solvent from a syringe or graduated wash bottle with a fine nozzle, taking care
to remove any adhered sample from the wall of the upper part of the apparatus. Carefully
remove the top portion of the filtration unit and wash the rim of the filter with a further 10 ±0.5
mL of the wash solvent in a similar manner. Finally wash the whole of the filter medium
area with 10 ±0.5 mL of
n
-heptane.
NOTE 5—
If the sample filters very rapidly, the vacuum should be released before the first
solvent washing, to ensure complete coverage of the filter medium area by
solvent. The vacuum should then be gently reapplied for the subsequent
operations.
6. Apparatus Disassembly
6.1
After the filter medium appears dry, discontinue the vacuum supply. Using the forceps,
carefully remove each filter medium separately and transfer them to the oven at 110°C.
Dry for 20 min and quickly transfer them to the same numbered weighing bottles as used in 2.
Allow them to cool in the cooling vessel to room temperature (5 to 10 min) and reweigh them
(against tare) to the nearest 0.0001 g.
7. Calculation
7.1
Calculate the mass percentage of total sediment to the nearest 0.01% m/m using the
following equation:
S=
(
M
5 -
M
4) - (
M
3 -
M
2) / 10
M
1
where:
S
= total sediment, % m/m,
M
1 = mass of sample, g,
M
2 = mass of lower filter medium before filtration, mg,
M
3 = mass of lower filter medium after filtration, mg,
M
4 = mass of upper filter medium before filtration, mg, and
M
5 = mass of upper filter medium after filtration, mg.
Summary of Contents for K4831X
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