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equivalent,). A 1,000 mg/L solution of Cl 18 O 4
-
is prepared by dissolving
0.0123 g NaCl 18 O 4 in 10 mL of RW. The solution may be stored in an HDPE
screw-cap bottle (Sect. 6.3). The anhydrous NaCl 18 O 4 salt should be stored in a
desiccator to minimize absorption of water from the atmosphere. The
recommended holding time is one year.
7.2.1.1 INTERNAL STANDARD PRIMARY DILUTION STANDARD -
(IS–PDS) - 1.0 mg Cl 18 O 4- /L. Prepared gravimetrically, using an
analytical balance having +0.1 mg accuracy, by adding 0.1 g (100 µL) of
the IS-SSS to 99.9 g of RW in a 125-mL HDPE storage bottle.
Alternatively, this dilution may be done volumetrically. The
recommended holding time is one year.
7.2.1.2 INTERNAL STANDARD FORTIFICATION SOLUTION - (IS-FS) -
100 µg Cl 18 O 4- /L. Prepared by adding 10 mL of the IS-PDS to 90 mL of
RW in a 125-mL HDPE storage bottle. Alternatively, this dilution may
be done by weight using an analytical balance having +0.1 mg accuracy.
The recommended holding time is one year.
NOTE: A commercially prepared internal standard solution may be
used. (Dionex Corporation, Part No. 062923 or equivalent).
7.2.2 PERCHLORATE STOCK STANDARD SOLUTION (SSS) - 1,000 mg ClO 4- /L.
(NaClO 4 , anhydrous, 99% pure grade, or better, F.W.= 122.4, CASRN
7601-89-0, Sigma Aldrich Co., St. Louis, MO, Cat. No. S-1513, or equivalent).
A 1,000 mg/L solution of ClO 4
-
is prepared by dissolving 0.1231 g of NaClO 4 in
100 mL of RW. The solution may be stored in a HDPE screw-cap bottle
(Sect. 6.3). The anhydrous NaClO 4 salt should be stored in a desiccator to
minimize absorption of water from the atmosphere. The recommended holding
time is one year.
7.2.2.1 PERCHLORATE PRIMARY DILUTION STANDARD - (PDS) -
1.0 mg ClO 4- /L. Prepared gravimetrically using an analytical balance
having +0.1 mg accuracy, by adding 0.1 g (100 µL) of the SSS to 99.9 g
of RW in a 125-mL HDPE storage bottle. Alternatively, this dilution
may be done volumetrically. The recommended holding time is one
year.
7.2.2.2 PERCHLORATE FORTIFICATION SOLUTION - (FS) - 100 µg ClO 4- /L.
Prepared by adding 10 mL of the PDS to 90 mL of RW. The solution may
be stored in a 125-mL HDPE storage bottle. Alternatively, this dilution may
be done by weight using an analytical balance having +0.1 mg accuracy.
The recommended holding time is one year.
332.0-14