Hach DR2400 - Page 518

Nitrogen, Total Inorganic
Nitrogen, Total Inorganic
Page 4 of 6
NitrogenTI_TNT_Other_TTR_Eng_Ody.fm
Sample Collection, Preservation, and Storage
Collect samples in clean plastic or glass bottles. Best results are obtained with
immediate analysis. If chlorine is known to be present, add one drop of 0.1 N
Sodium Thiosulfate (Cat. No. 323-32) for each 0.3 mg/L Cl
2
in a one-liter sample.
Preserve the sample by reducing the pH to 2 or less with concentrated (at least
2 mL) Hydrochloric Acid (Cat. No. 134-49). Store at 4 °C (39 °F) or less. Preserved
samples may be stored up to 28 days. Warm samples to room temperature.
Neutralize with 5 N Sodium Hydroxide (Cat. No. 2450-26) before analysis.
Correct the test result for volume additions. See Section 3.1.3 Correcting for Volume
Additions on page 29.
Accuracy Check
Standard Additions Method
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 the
instrument manual for more information.
4. Snap the neck off a fresh HR Nitrate Nitrogen PourRite Ampule Standard,
500-mg/L NO
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 0.1 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
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
To check accuracy, use a 10.0-mg/L Nitrate Nitrogen Standard Solution.
Alternatively, prepare this by diluting 1 mL of solution from a Nitrate Nitrogen
Voluette
®
Ampule Standard, 500-mg/L NO
3
–
–N, to 50 mL with deionized water.
The result should be 9–10 mg/L N.