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Silica
Sample Collection, Storage, and Preservation
Reagent Preparation
Labware
Cleaning the Pour-Thru Cell
Silica
Page 4 of 6
Use only plastic containers with tight-fitting closures. Do not use glass
containers; they will contaminate the sample with silica. Soak sampling
containers with a solution made of one part Molybdate 3 Reagent
(Cat. No. 1995-03) to 50 parts of high quality deionized water of low silica
concentration. Fill completely and let stand for several hours. Rinse thoroughly
with low-level silica water, drain and close. Repeat this cleaning periodically.
Allow the sample stream to flow for 1–2 minutes before collection. Do not adjust
the flow during the sampling period as this may introduce particulates. Rinse
the container well with sample before collecting the portion for analysis.
Analyze as soon as possible.
Amino Acid F Reagent Solution is available in either 100-mL bottles or a package
of 20 unit-dose ampules. The bottled reagent is stable for up to one year if the
bottle is kept closed when not in use. The ampuled reagent is sealed under argon
and is more stable with a shelf life greater than 1 year. Reduced sensitivity at
high concentrations (1000 µg/L) indicates reagent instability. Check the bottled
reagent on a routine basis by performing an analysis on a 1-mg/L Silica
Standard Solution (Cat. No. 1106-49). If the concentration is less than 950 µg/L,
use a fresh bottle of Amino Acid F Reagent Solution.
Prepare larger or smaller volumes of Amino Acid F Reagent by dissolving
Amino Acid F Reagent Powder in Amino Acid F Reagent Solvent at a ratio of
11 grams per 100 mL of reagent solvent. These reagents are available as the
Amino Acid F Reagent Package. This prepared solution has limited stability;
test routinely with the 1-mg/L Silica Standard Solution.
All containers used in this test must be cleansed thoroughly to remove any traces
of silica. Use plastic containers for all analysis and storage because glass can
contaminate the sample with silica. Small bottles or flasks with screw-type
closures work well.
Clean containers by normal means (do not use phosphate detergents), then rinse
with high quality deionized water of low-level silica concentration. Soak for
10 minutes with a 1:50 dilution of Molybdate 3 Reagent in low-level silica water.
Rinse repeatedly with either low-level silica water or the sample before use.
Keep containers tightly closed when not in use. Fill the Pour-Thru Cell with this
same mixture of Molybdate 3 and water, and let stand for several minutes before
use. Rinse with low-level silica water.
The Pour-Thru Cell may accumulate a buildup of colored products, especially if
the reacted solutions are allowed to stand in the cell for long periods after
measurement. Remove the color by rinsing with a 1:5 dilution of ammonium
hydroxide, followed by several deionized water rinses. Cover the Pour-Thru
Cell when it is not in use.
Silica_PTRL_ULow_HTB_Eng_Ody.fm
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