Nitrogen, Total
Nitrogen, Total
Page 4 of 6
NitrogenTot_UniCell_Other_PSD_Eng_Ody.fm
4. Prepare three sample spikes by filling three mixing cylinders with 50 mL of
sample. Use a pipet to add 0.2, 0.4, and 0.6 mL of 1000-mg/L NO
3
–N
Standard, respectively, to each sample and mix thoroughly.
5. 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. The
nitrogen concentration should increase by approximately 4, 8, and
12 mg/L N, respectively.
6. 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. Prepare a 20.0-mg/L NO
3
–N standard solution by pipetting 2.00 mL of
1000-mg/L NO
3
–N into a 100-mL volumetric flask. Dilute to the mark with
deionized water. Stopper and invert to mix.
2. To adjust the calibration curve using the reading obtained with the
20.0-mg/L N 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.
See Section 3.2.4 Adjusting the Standard Curve on page 40 for more information.
Method Performance
Precision
Standard: 20.0 mg/L NO
3
–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
800 15.2–24.8 mg/L N
Program Portion of Curve ∆Abs ∆Concentration
800 Entire range 0.010 0.6 mg/L N
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