Phosphorus, Total
Phosphorus, Total
Page 4 of 6
PhosphorusTot_UniCell_APD_Eng_Ody.fm
For wastewater samples — If prompt analysis is impossible, preserve
samples
*
by adjusting the pH to 2 or less with Sulfuric Acid, 5.25 N
(Cat. No. 2449-00) and storing the sample at 4 °C for up to 28 days. The pH can
be checked using pH Paper (Cat. No. 391-33). 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 Standard Solution. Rinse again
with deionized water. Do not use detergents containing phosphate 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. See
3.2.2 Standard Additions for more information.
5. Snap the neck off a 10-mL Voluette
®
Ampule of Phosphate Standard Solution,
500-mg/L as PO
4
3–
.
6. Prepare three sample spikes. Fill three 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. Mix well.
7. Analyze each sample spike as described in the procedure above, starting with
the 0.1 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.
Standard Solution Method
1. Use a 10-mg/L PO
4
3–
standard solution listed under Optional Standards.
Perform the phosphate procedure as described.
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.
* See 40 CFR 136.3
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