Phosphorus, Reactive (Orthophosphate)
Phosphorus, Reactive (Orthophosphate)
PhosphorusReac_UniCell_Asc_Eng_Ody.fm Page 3 of 4
Sample Collection, Storage, and Preservation
Analyze samples within 3 hours after collection for best results. Store in a cool
dry place in plastic or glass bottles that have been acid cleaned with
1:1 Hydrochloric Acid Solution and rinsed with deionized water. Do not use
commercial detergents containing phosphate for cleaning glassware used in
this test.
If prompt analysis is impossible, preserve samples up to 48 hours by filtering
immediately and storing at 4 °C (39 °F). Do not use mercury compounds as
preservatives. Warm samples to room temperature before analysis.
Accuracy Check
Standard Additions Method (Sample Spike)
1. Clean glassware with 1:1 Hydrochloric Acid Solution. Rinse again with
deionized water. Do not use phosphate detergents to clean glassware.
2. After reading test results, leave the sample cell (unspiked sample) in the
instrument. Verify the chemical form.
3. Touch
Options. Touch Standard Additions. A summary of the standard
additions procedure will appear.
4. Touch
OK to accept the default values for standard concentration, sample
volume, and spike volumes. Touch
Edit to change these values. After values
are accepted, the unspiked sample reading will appear in the top row.
5. Snap the neck off a 10-mL Voluette
®
Ampule of Phosphate Standard,
500 mg/L as PO
4
3–
.
6. Prepare three sample spikes. Fill three 100-mL mixing cylinders with 100 mL
of sample. Use a pipet to add 0.2 mL, 0.4 mL, and 0.6 mL of standard,
respectively to each cylinder and mix thoroughly.
7. Analyze each sample spike as described in the procedure above, starting with
the 0.2-mL sample spike. Accept each standard additions reading by touching
Read. Each addition should reflect approximately 100% recovery.
8. After completing the sequence, touch
Graph to view the best-fit line through
the standard additions data points, accounting for matrix interferences. Touch
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.
SiO
2
50 mg/L
Hg
2+
40 mg/L
Sn
2+
25 mg/L
Pb
2+
20 mg/L
Ag
+
,
Cr
3+
10 mg/L
Cr
6+
1 mg/L
(continued)
Interfering Substance No interference up to:
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