52-110
PHOSPHORUS REACTIVE, continued
SAMPLING AND STORAGE
Collect samples in plastic or glass bottles that have been acid cleaned
with 1:1 Hydrochloric Acid Solution and rinsed with demineralized
water. Do not use commercial detergents containing phosphate for
cleaning glassware used in this test.
Analyze samples immediately after collection for best results. If prompt
analysis is impossible, preserve samples up to 24 hours by storing at
4 °C. For longer storage periods, add 4.0 mL of mercuric chloride to
each liter of sample and mix. Use of mercuric chloride is discouraged
due to health and environmental concerns. Samples preserve with
mercuric chloride must have a sodium chloride level of 50 mg/L or
higher to prevent mercury interference in the test. Spike samples low in
chloride with a sodium chloride solution (5 mL of 10,246 mg/L sodium
chloride solution per liter of sample).
ACCURACY CHECK
Standard Addition Method
a) Snap the neck of a Phosphate Voluette Ampule Standard, 500 mg/L
PO
4
3-
.
b) Use the TenSette Pipet to add 0.1 mL, 0.2 mL and 0.3 mL,
respectively, to three 25-mL aliquots of a water samples. Mix well.
c) Analyze each sample as described in the procedure. Compare the
results with the original test sample. Each 0.1-mL addition should
increase the orthophosphate (PO
4
3-
)
2.0 mg/L for stored program 485.
When using store program 487, the increase should be 0.65 mg/L P for
each 0.1-mL addition of standard.
d) If these increases do not occur, see Standard Additions (Section I) for
more information.
Standard Solution Method
Prepare a 10.0-mg/L PO
4
3-
(3.3 mg/L P) standard solution by pipetting
10.0 mL of Phosphate Standard Solution, 50 mg/L as PO
4
3-
, into a
50-mL volumetric flask. Dilute to volume with demineralized water.
Or, prepare a 10.0-mg/L PO
4
3-
(3.3 mg/L P) standard solution by using
the TenSette Pipet to add 1.00 mL of Phosphate Voluette Ampule
Standard, 500 mg/L PO
4
3-
, into a 50-mL volumetric flask. Dilute to
volume with demineralized water.
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