Test Procedures
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
MDL:
0.07 mg/L
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 fi ltered 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), sulfi de (>90 ppm) and zinc (>80
ppm) will interfere.
PHOSPHORUS
, TOTAL, LOW RANGE
SMART Spectro 2 Test Procedures 05.02.16
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