Hach DR2400 - Page 489

Nitrogen, Ammonium
Nitrogen, Ammonium
NitrogenAmm_UniCell_SAL_Eng_Ody.fm Page 3 of 4
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. Enter 1286 mg/L NH
4
+
(1000-mg/L NH
3
–N) as the standard concentration.
4. Touch
OK to accept the default values for 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.
5. Prepare three sample spikes. Fill three 100-mL mixing cylinders
(Cat. No. 20886-42) with 100 mL of sample. Use a pipet to add 0.2 mL, 0.4 mL,
and 0.6 mL of (1286 mg/L NH
4
+
) 1000-mg/L NH
3
–N standard, respectively,
to each sample and mix 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 25-mg/L nitrogen ammonia standard solution by pipetting 25.00 mL
of 1000-mg/L Ammonia Nitrogen standard into a 1000-mL Class A volumetric
flask. Dilute to the mark with deionized water.
Note: Make sure the selected chemical form is NH
4
+
–N.
Method Performance
Precision
Standard: 25 mg/L NH
4
+
–N
See Section 3.4.3 Precision on page 44 for more information, or if the standard
concentration did not fall within the specified range.
Sensitivity
See Section 3.4.5 Sensitivity on page 44 for more information.
Program 95% Confidence Limits of Distribution
801 24.7–25.3 mg/L NH
4
+
–N
Program Portion of Curve ∆Abs ∆Concentration
801 Entire range 0.010 0.2 mg/L NH
4
+
–N