Silica
Silica
Page 4 of 6
Silica_PT_ULow_HTB_Eng_Ody.fm
Reagent Preparation
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. 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 as above.
If running a large number of samples, the variable-volume dispensers are
convenient. The dispensers are made of fluoropolymer plastic. Do not use a
dispenser with glass bottles or glass parts because it will contaminate the reagent
with silica.
Labware
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.
Cleaning the Pour-Thru Cell
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.
Accuracy Check
Standard Additions Method (Sample Spike)
1. After reading test results, leave the sample cell (unspiked sample) in the
instrument. Verify the chemical form.
2. Touch
Options. Touch Standard Additions. A summary of the standard
additions procedure will appear.
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