Method 8000B. If the average exceeds 15% of
11.2 Method number 2: Disk solid-phase extrac-
the average from the initial calibration, a new ini-
tion
tial calibration must be obtained.
11.2.1
For each sample, place an Empore SDB-RPS
disk on the center of a 47-mm vacuum filter
11.0 PROCEDURE
apparatus and moisten with acetone so that the
11.1 Method number 1: Cartridge solid-phase
disk adheres to the filter base. Assemble the res-
extraction
ervoir and ascertain that the disk is centered so
11.1.1
that the water sample will pass through the disk,
For each sample, place an unused Waters Sep-
not around an edge.
Pak Vac Porapak RDX cartridge on a solid-phase
extraction manifold and clean and condition the
11.2.2
solid phase by eluting with 30 mL of acetonitrile
To condition each disk, follow manufacturer's
by gravity flow, followed by 50 mL of reagent-
directions for rinses with 10 mL each of acetone,
grade water at 10 mL per minute. Air must NOT
isopropanol, and methanol. For the final organic
pass through the cartridge between the acetoni-
solvent rinse, add a 20-mL aliquot of acetonitrile
trile and the reagent water. (Note: if air passes
and allow the acetonitrile to soak into the disks
through the cartridge, recondition the cartridge
for three minutes. Turn on the vacuum and allow
with acetonitrile followed by water.) Just before
most (but not all) of the acetonitrile to be pulled
the last of the reagent water is pulled through,
through the disk. Repeat with a second 20-mL al-
turn off the vacuum.
iquot of acetonitrile.
11.1.2
11.2.3
Measure up to a 1000-mL aliquot of each
Add a 50-mL aliquot of reagent-grade water to
water sample using a 1-L graduated cylinder or
the reservoir and turn the vacuum on once again,
volumetric flask. (Alternatively, mark the level of
pulling the water through the disk. Just before
sample on the sample bottle, then measure the
the last of the water is pulled through, repeat
sample volume by measuring the volume of
with a second 50-mL aliquot of reagent-grade
water required to refill the bottle after the sample
water. Just before the last of the water is pulled
is removed.) Pull the samples through the car-
through, turn the vacuum off. The disk must not
tridges at about 10 mL per minute by turning on
be allowed to dry between the acetonitrile and
and adjusting the vacuum.
water rinses. If air is accidentally pulled through
the disk, recondition the disk with acetonitrile
11.1.3
(11.2.2).
Once all the sample has been drawn through a
cartridge, draw air through the cartridge for 15
11.2.4
minutes in order to remove any excess water.
Fill the reservoir with a 250-mL aliquot of wa-
Turn the vacuum off. Remove any drops of water
ter sample, turn the vacuum on, and begin to
pull the sample through the disk. Refill the reser-
that may be clinging to the cartridge tip.
voir as needed. (Alternatively, a 1-L bottle may
be inverted onto the reservoir, and the sample
11.1.4
will flow from the bottle without overflowing
Elute the samples by passing a 4-mL aliquot of
the reservoir.) A 1-L sample should take less than
acetonitrile through each cartridge at about 1 mL
15 minutes, with resulting flow rates ranging
per minute (gravity flow) and collect the extract
from 70 to 100 mL per minute.
in a 5-mL graduated cylinder. Measure the actual
volume (0.1 mL) of the solvent extract.
11.2.5
11.1.5
Once all the sample has been drawn through
If the extract is turbid, filter through a Millex-
the disk, draw air through the disk for 20 minutes
SR filter unit.
in order to remove any excess water. Turn the
vacuum off. Remove any drops of water that may be
11.1.6
clinging to the tip of the funnel base.
Store extracts in a freezer until analysis.
27
Previous Page
