Nitrogen, Ammonia
Nitrogen, Ammonia
NitrogenAmm_PP_Other_SAL_Eng_Ody.fm Page 3 of 4
For longer storage, adjust the pH to 2 or less with concentrated (about 2 mL per
liter) Sulfuric Acid (Cat. No. 979-49). Store samples at 4 °C or less. Samples
preserved in this manner can be stored up to 28 days. Just before testing the
stored sample, warm to room temperature and neutralize with 5.0 N Sodium
Hydroxide Standard Solution (Cat. No. 2450-26). Correct the test result for
volume additions; see Section 3.1.3 Correcting for Volume Additions on page 29.
Accuracy Check
Standard Additions Method (Sample Spike)
1. After reading test results, leave the sample cell (unspiked sample) in the
instrument.
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. Open an Ammonia Nitrogen Standard Solution, 10-mg/L as NH
3
–N.
5. Prepare three sample spikes. Fill three mixing cylinders (Cat. No. 1896-40)
with 25 mL of sample.Use the TenSette
®
Pipet to add 0.2 mL, 0.4 mL and
0.6 mL of standard, respectively to the cylinders and mix each thoroughly.
6. 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.
7. 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
Prepare a 0.20 mg/L ammonia nitrogen standard as follows:
1. Diluting 2.00 mL of the Ammonia Nitrogen Standard Solution, 10-mg/L, to
100 mL with deionized water. Or, use the TenSette
®
Pipet to prepare a
0.20 mg/L ammonia nitrogen standard by diluting 0.4 mL of a Ammonia
Nitrogen Voluette
®
Standard Solution, 50-mg/L as NH
3
–N, to 100 mL with
deionized water.
2. To adjust the calibration curve using the reading obtained with the
0.20-mg/L standard solution, touch
Options on the current program menu.
Touch
Standard Adjust.
3. Touch
On. Touch Adjust to accept the displayed concentration. If an alternate
concentration is used, touch the number in the box to enter the actual
concentration, then touch
OK. Touch Adjust.
See Section 3.2.4 Adjusting the Standard Curve on page 40 for more information.
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