Hach DR2400 - Page 605

Phosphorus, Acid Hydrolyzable
Phosphorus, Acid Hydrolyzable
PhosphorusAcidHyd_TNT_Other_PHY_Eng_Ody.fm Page 3 of 6
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 samples immediately for best results. If prompt analysis is not possible,
preserve samples by filtering immediately and storing the sample at 4 °C (39 °F)
for up to 48 hours.
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.
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. Snap the neck off a Phosphate 2-mL Ampule Standard, 50-mg/L as PO
4
3–
.
Interfering Substance Interference Levels and Treatments
Aluminum Greater than 200 mg/L
Arsenate All levels
Chromium Greater than 100 mg/L
Copper Greater than 10 mg/L
Iron Greater than 100 mg/L
Nickel Greater than 300 mg/L
Silica Greater than 50 mg/L
Silicate Greater than 10 mg/L
Sulfide
Greater than 9 mg/L. Remove sulfide interference as follows:
1. Measure 25 mL of sample into a 50-mL beaker.
2. Swirling constantly, add Bromine Water (Cat. No. 2211-20) drop-wise until a permanent
yellow color appears.
3. Swirling constantly, add Phenol Solution (Cat. No. 2112-20) drop-wise just until the yellow
color disappears. Proceed with step 1.
Tu rb i di ty
Large amounts may cause inconsistent results in the test because the acid present in the
powder pillows may dissolve some of the suspended particles and because of variable
desorption of orthophosphate from the particles.
Zinc Greater than 80 mg/L
Highly buffered samples or
extreme sample pH
May exceed the buffering capacity of the reagents and require sample pretreatment.