41
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
Aqueous Liquids following this procedure to determine the
analysis volume.
Note: Some methods require pipetting into a volumetric flask or a regular
graduate cylinder.
9. Dilute the digest to
approximately 70 mL
with deionized water.
Note: Add deionized water
slowly at first. Cool the
flask if necessary
for handling.
10. If analyzing for
aluminum, nickel or
iron, continue to Step 11.
If analyzing for other
substances, dilute to the
100-mL mark with
deionized water; skip
Step 11 and go to
Step 12.
11. 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 for 15 minutes. Air
cool to room
temperature and dilute to
the 100-mL mark with
deionized water. Invert
several times to mix.
12. Ifthesamplehas
visible 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
deionized 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.
Continue with the
analysis using the
appropriate procedure
below.
DIGESTION PROCEDURE FOR AQUEOUS LIQUIDS, continued
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