LaMotte SMART 2 - Manual (Page 230)

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: Boiler, cooling, and industrial water.
RANGE: 0.0–100.0 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 digestion.
Orthophosphate reacts in acidic conditions with ammonium
vanadomolybdate to form vanadomolybdophosphoric acid.
The resulting yellow color is proportional to the
concentration of orthophosphate.
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. Silica and arsenate
interfere only if the sample is heated. Arsenite, fluoride,
thorium, bismuth, molybdate, thiosulfate, and thiocyanate
cause negative interference. Ferrous iron concentrations
above 100 ppm will interfere.
Phosphorus, Total–HR 2/3 Smart2 TEST PROCEDURES 2.04