Hach DR2400 - Page 729

Silver
Silver
Silver_PP_Other_CLR_Eng_Ody.fm Page 3 of 6
Sample Collection, Storage, and Preservation
Collect samples in acid-cleaned glass or plastic bottles. Using pH paper,
adjust the pH to 2 or less with Concentrated Nitric Acid (Cat. No. 152-49)
(about 2 mL/liter). Store preserved samples at room temperature for up to 6
months. If the sample contains particulates or only dissolved metal content is
being determined, filter through a 0.45 mm filter at collection. After filtration,
adjust the pH to 2 or less as described above.
Before analysis, adjust the pH to 9–10 with 5.0 N Sodium Hydroxide
(Cat. No. 2450-32). (See step 13–step 14 of the Digestion procedure on page 4.) Do
not use a pH meter because of silver contamination from the electrode. Correct
for volume additions; see Section 3.1.3 Correcting for Volume Additions on page 29.
Accuracy Check
Standard Additions Method (Sample Spike)
1. After reading test results, leave the sample cell (unspiked sample) in the
instrument.
2. Touch
Options. Touch Standard Additions. A summary of the standard
additions procedure will appear.
3. Touch
OK to accept the default values for standard concentration, sample
volume, and spike volumes. Touch
Edit to change these values. After values
are accepted, the unspiked sample reading will appear in the top row. See
Standard Additions in the instrument manual for more information.
4. Add 5.00 mL of 1000 mg/L Silver Standard Solution to a 100-mL volumetric
Class A flask. Dilute to volume with deionized water. This is a 50.0 mg/L
standard solution.
5. Prepare three sample spikes. Fill three mixing cylinders (Cat. No. 1896-41)
with 50-mL of sample. Use the TenSette
®
Pipet to add 0.1 mL, 0.2 mL, and
0.3 mL of standard, respectively, to each sample and mix thoroughly.
6. Analyze each sample spike as described in the procedure above, starting with
the 0.1 mL sample spike. Accept each standard additions reading by touching
Read. Each addition should reflect approximately 100% recovery.
7. After completing the sequence, touch
Graph to view the best-fit line through
the standard additions data points, accounting for matrix interferences. Touch
View: Fit, then select Ideal Line and touch OK to view the relationship between
the sample spikes and the “Ideal Line” of 100% recovery.
See Section 3.2.2 Standard Additions on page 32 for more information.
Manganese Negative interference above 19 mg/L
Magnesium Positive interference above 2000 mg/L
Mercury Positive interference above 2 mg/L
Nickel Negative interference above 19 mg/L
Zinc Negative interference above 70 mg/L
(continued)
Interfering Substance Interference Levels and Treatments