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Iron, Total,
continued
Sampling and Storage
Collect samples in acid-washed glass or plastic bottles. Adjust the sample pH to 2
or less with Nitric Acid (about 2 mL per L). Store samples preserved in this manner
up to 6 months at room temperature. If reporting only dissolved iron, filter the
sample immediately after collection and before addition of nitric acid.
Before testing, adjust the pH of the stored sample to between 3 and 4 with 5.0 N
Sodium Hydroxide Standard Solution. Do not exceed pH 5 as iron may precipitate.
Accuracy Check
Standard Additions Method
1. Using a graduated cylinder, measure 25.0 mL of sample into each of three
50-mL beakers.
2. Snap the neck off an Iron Standard Solution Voluette™ Ampule, 25 mg/L Fe.
3. Use a TenSette
the three 50-mL beakers. Swirl to mix.
4. Analyze each standard addition sample as described in the procedure. The iron
concentration should increase by 0.1 mg/L for each 0.1 mL of standard added.
®
Pipet to add 0.1, 0.2, and 0.3 mL of standard, respectively, to
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