Hach DR2400 - Page 628

Phosphorus, Reactive (Orthophosphate)
Phosphorus, Reactive (Orthophosphate)
Page 4 of 6
PhosphorusReac_AccuVac_Other_MOL_Eng_Ody.fm
The following do not interfere in concentrations up to 1000 mg/L:
Sample Collection, Storage and Preservation
Collect samples in clean plastic or glass bottles that have been cleaned with
1:1 Hydrochloric Acid Solution (Cat. No. 884-49) and rinsed with deionized
water. Do not use a commercial detergent because the phosphate content will
contaminate the sample.
Analyze samples as soon as possible for best results. If samples cannot be
analyzed promptly, store the sample for up to 48 hours at 4 °C (39 °F) or below.
Warm to room temperature before analyzing.
Accuracy Check
Standard Additions Method (Sample Spike)
1. After reading test results, leave the sample cell (unspiked sample) in the
instrument. Verify the chemical form.
2. Touch
Options. Touch Standard Additions. A summary of the standard
additions procedure will appear.
3. 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
Standard Additions in the instrument manual for more information.
4. Snap the neck off a Phosphate 2-mL Ampule Standard, 500-mg/L PO
4
3–
.
5. Prepare three sample spikes. Fill three mixing cylinders (Cat. No. 1896-40)
with 25 mL of sample. Use the TenSette
®
Pipet to add 0.1 mL, 0.2 mL, and
0.3 mL of standard, respectively, to each sample and mix thoroughly.
6. 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.
7. After completing the sequence, touch
Graph to view the best-fit line through
the standard additions data points, accounting for matrix interferences. Touch
Table 2 Non-Interfering Substances
Pyrophosphate Tetraborate selenate Benzoate
Citrate Lactate Formate
Oxalate Tartrate Salicylate
Al
3+
Fe
3+
Mg
2+
Ca
2+
Ba
2+
Sr
2+
Li
+
Na
+
K
+
NH
4+
Cd
2+
Mn
2+
NO
3
–
NO
2
–
SO
4
2–
SO
3
2–
Pb
2+
Hg
+
Hg
2+
Sn
2+
Cu
2+
Ni
2+
Ag
+
U
4+
Zr
4+
AsO
3
–
Br
–
CO
3
2–
ClO
4
–
CN
–
IO
3
–
SiO
4
4–