Hach DR/850 Procedures Manual page 367

PHOSPHORUS, REACTIVE,
Interferences
Sample Disposal Information
The following may interfere when present in concentrations
exceeding these listed below:
Substance
Aluminum
Arsenate
Chromium
Copper
Iron
Nickel
Silica
Silicate
Sulfide
Turbidity (large amounts)
Zinc
Highly buffered samples or
extreme sample pH
The PhosVer 3 Phosphate Reagent Powder Pillows should be
stored in a cool, dry environment.
Final samples will contain molybdenum. In addition, final
samples will have a pH less than 2 and are considered corrosive
(D002) by the Federal RCRA.
continued
Interference Level and Treatment
200 mg/L
Interferes at any level
100 mg/L
10 mg/L
100 mg/L
300 mg/L
50 mg/L
10 mg/L
6 mg/L. Sulfide interference may be removed by
oxidation with Bromine Water as follows:
1. Measure 25 mL of sample into a 50-mL beaker.
2. Swirling constantly, add Bromine Water drop-wise
until a permanent yellow color develops.
3. Swirling constantly, add Phenol Solution dropwise
until the yellow color just disappears. Proceed with
step 1.
May cause inconsistent results 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.
80 mg/L
May exceed the buffering capacity of the reagents and
require sample pretreatment; see pH Interferences
(Section 1).
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