Hach DR2400 - Page 668

Phosphorus, Total
Phosphorus, Total
Page 4 of 6
PhosphorusTot_TNT_Other_PAP_Eng_Ody.fm
Interferences
Sample Collection, Storage, and Preservation
Collect samples in plastic or glass bottles that have been acid washed with
1:1 Hydrochloric Acid Solution (Cat. No. 884-49) and rinsed with deionized
water. Do not use commercial detergents containing phosphate for cleaning
glassware used in this test.
Analyze the samples immediately for the most reliable results. If prompt
analysis is not possible, samples may be preserved up to 28 days by adjusting
the pH to 2 or less with concentrated Sulfuric Acid (about 2 mL per liter)
(Cat. No. 979-49) and storing at 4 °C. Warm the sample to room temperature
and neutralize with 5.0 N Sodium Hydroxide (Cat. No. 2450-53) before analysis.
Correct for volume additions: see Section 3.1.3 Correcting for Volume Additions on
page 29.
Accuracy Check
Standard Additions Method (Sample Spike)
1. Clean glassware with 1:1 Hydrochloric Acid Standard Solution. Rinse again
with deionized water. Do not use phosphate detergents to clean glassware.
2. After reading test results, leave the sample cell (unspiked sample) in the
instrument. Verify the chemical form.
3. Touch
Options. Touch Standard Additions. A summary of the standard
additions procedure will appear.
4. 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
Section 3.2.2 Standard Additions on page 32 for more information.
5. Open a Phosphate 10-mL Ampule Standard, 50-mg/L as PO
4
3–
.
Interfering Substance Interference Levels and Treatments
Aluminum Greater than 200 mg/L
Arsenate Interferes at any level
Chromium Greater than 100 mg/L
Copper Greater than 10 mg/L
Iron Greater than 100 mg/L
Nickel Greater than 300 mg/L
pH, excess buffering
Highly buffered samples or extreme sample pH may exceed the buffering capacity of the
reagents and require sample pretreatment.
Silica Greater than 50 mg/L
Silicate Greater than 10 mg/L
Sulfide Greater than 90 mg/L
Turbidity (large amounts)
or color
May cause inconsistent results because the acid in the powder pillow may dissolve some of the
suspended particles and because of variable desorption of orthophosphate from the particles.
Zinc Greater than 80 mg/L