Phosphorus, Reactive (Orthophosphate)
Phosphorus, Reactive (Orthophosphate)
PhosphorusReac_AccuVac_Other_MOL_Eng_Ody.fm Page 5 of 6
View: Fit
, then select Ideal Line and touch OK to view the relationship between
the sample spikes and the “Ideal Line” of 100% recovery.
See Section 3.2.2 Standard Additions on page 32 for more information.
Standard Solution Method
1. Use a 10-mg/L phosphate standard solution in place of the sample. Perform
the molybdovanadate procedure as described above.
2. To adjust the calibration curve using the reading obtained with the
10-mg/L PO
4
3–
Phosphate Standard Solution, touch Options on the current
program menu. Touch
Standard Adjust.
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: 10.0 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
In the molybdovanadate method, orthophosphate reacts with molybdate in an
acid medium to produce a mixed phosphate/molybdate complex. In the
presence of vanadium, yellow molybdovanadophosphoric acid is formed. The
intensity of the yellow color is proportional to the phosphate concentration. Test
results are measured at 430 nm.
Program 95% Confidence Limits of Distribution
480 9.8–10.2 mg/L PO
4
3–
482 9.7–10.3 mg/L PO
4
3–
Portion of Curve ∆Abs
∆Concentration
Program 480
∆Concentration
Program 482
0.0 mg/L PO
4
3–
0.010 0.3 mg/L PO
4
3–
0.3 mg/L PO
4
3–
45.0 mg/L PO
4
3–
0.010 0.4 mg/L PO
4
3–
0.4 mg/L PO
4
3–
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