Phosphorus, Total
Phosphorus, Total
PhosphorusTot_TNT_High_MOL_Eng_Ody.fm Page 5 of 6
3. Touch On. Touch Adjust to accept the displayed concentration (the value
depends on the selected chemical form). If an alternate concentration is used,
touch the number in the box to enter the actual concentration, then touch
OK.
Touch
Adjust.
For more information, see Section 3.2.4 Adjusting the Standard Curve on page 40.
Method Performance
Precision
Standard: 50 mg/L PO
4
3–
See Section 3.4.3 Precision on page 44 for more information, or if the standard
concentration did not fall within the specified range.
Sensitivity
See Section 3.4.5 Sensitivity on page 44 for more information.
Summary of Method
Phosphates present in organic and condensed inorganic forms (meta-, pyro-, or
other polyphosphates) must be converted to reactive orthophosphate before
analysis. Pretreatment of the sample with acid and heat provides the conditions
for hydrolysis of the condensed inorganic forms. Organic phosphates are
converted to orthophosphates by heating with acid and persulfate.
Orthophosphate reacts with molybdate in an acid medium to produce a mixed
phosphate/molybdate complex. In the presence of vanadium, yellow
molybdovanadophosphoric acid forms. The intensity of the yellow color is
proportional to the phosphate concentration. Test results are measured
at 420 nm.
Program 95% Confidence Limits of Distribution
541 49.5–50.5 mg/L PO
4
3–
Portion of Curve ∆Abs ∆Concentration
Entire range 0.010 1.0 mg/L PO
4
3–
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