LaMotte SMART 2 - Manual (Page 226)

Phosphorus in natural waters and wastewaters occurs almost exclusively in the
form of orthophosphates, condensed phosphates (pyro-, meta- and other
polyphosphates) and organically bound phosphates. Phosphates may be added
in small amounts to water supplies during treatment. Larger amounts are
introduced to water used for cleaning or laundering as components of
commercial cleaning preparations. Phosphates are used to treat boiler water
and are components of agricultural and residential fertilizers. Phosphorus is an
important nutrient for aquatic plants. The amount found in natural water is
generally not more than 0.1 mg/L unless the water has become polluted from
wastewater sources or excessive drainage from agricultural areas.
APPLICATION: Drinking, surface and saline waters; domestic and industrial
waste water.
RANGE: 0.00 –3.50 mg/L Total Phosphorus as Phosphate
METHOD: Pretreatment of the sample with heat and acid provides
conditions for the hydrolysis of condensed inorganic
phosphates. Heat, acid and persulfate convert the organic
phosphates to orthophosphate during the digestion.
Ammonium molybdate and antimony potassium tartrate
react in a filtered acid medium with dilute solutions of
phosphate to form an antimony-phosphomolybdate
complex. This complex is reduced to an intense blue colored
complex by ascorbic acid. The color is proportional to the
amount of phosphate present.
SAMPLE
HANDLING &
PRESERVATION: Rinse sample bottle with 1:1 hydrochloric acid followed by
deionized water. Do not use phosphate detergents. If the
sample can not be analyzed immediately, the sample should
be preserved by adjusting the pH to 2 or less with
concentrated sulfuric acid and refrigerated at 4°C. Warm the
sample to room temperature and neutralize with 5.0 N
sodium hydroxide before analyzing.
INTERFERENCES: Large amounts of turbidity may interfere. Aluminum (200
ppm), Arsenate (any level), Chromium (100 ppm), Copper
(10 ppm), Iron (100 ppm), Nickel (300 ppm), Silica (50
ppm), Silicate (10 ppm), Sulfide (90 ppm) and Zinc (80
ppm) will interfere.
Phosphorus, Total–LR 2/3 Smart2 TEST PROCEDURES 11.04