55
Metals Method
Note: If analyzing aliquots smaller than 0.5 mL, pH adjustment is not necessary.
1. Pipet the appropriate analysis volume into the appropriate mixing
graduate cylinder. See Sample and Analysis Volume Tables for Oils
following the specific digestion to determine the analysis volume.
Note: Some methods require pipetting into a volumetric flask or a regular
graduated cylinder.
2. Dilute to about 20 mL with deionized water.
9.
If analyzing for
aluminum, nickel or
iron, continue to Step
10. If analyzing for other
substances, dilute to the
100-mL mark with
deionized water; Skip
Step 10 and go to
Step 11.
10. Turn the
temperature dial to a
heat setting of 204 ° C
(400°F). Add 150 mL of
water to a 400-mL
beaker. Place the beaker
on the heater. Place the
flask in the beaker and
boil for15 minutes. Cool
to room temperature and
dilute
to the mark with
demineralized water.
Invert several times
to mix.
Note: When using a
Digesdahl Digestion
Apparatus system without
temperature control dials,
reset to a lower setting that
gently boils the water.
11. Ifthesampleis
visibly turbidity, filter or
wait until the turbidity
settles, and the upper
portion of the sample is
clear.
Filter as follows:
a)
Place a filter paper into
the filter holder with
wrinkled surface upward.
b) Place the filter holder
assembly in the filtering
flask and wet the filter
with demineralized water
to ensure adhesion to
the holder.
c) While applying a
vacuum to the filtering
flask, transfer the sample to
the filtering apparatus.
d) Slowly release the
vacuum from the filtering
flask and transfer to
another container.
12. Continue the
analysis using the
appropriate procedure
below.
DIGESTION PROCEDURE FOR OILS, continued
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