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17.
Wipe the prepared
sample and place it into
the cell holder.
Interferences
Sample, Collection, Storage, and Preservation
Accuracy Check
NitrogenTot_UniCell_Other_PSD_Eng_Ody.fm
Read
18.
Touch
Read.
Results will appear in
mg/L N.
The ions listed in the table have been tested up to the given concentrations.
Cumulative effects and the influence of other ions have not been evaluated. Ions
may interfere when present in conditions exceeding those listed below:
Interfering Substance
COD
–
Cl
Analyze samples within 3 hours after collection for best results. Collect samples
in clean plastic or glass bottles. To preserve samples for longer periods, add 1 mL
of concentrated sulfuric acid per liter and store at 4 °C.
Warm the sample to room temperature before testing. Adjust the pH to 4–9 with
5.0 N Sodium Hydroxide. Do not use mercury compounds as preservatives.
Correct the test results for volume additions by dividing the total final volume
(acid + base + sample) by the initial sample volume and multiplying the result
by this factor. See Correcting for Volume Additions on page 29 in the
procedure manual.
Standard Additions Method
1. After reading test results, leave the sample cell (unspiked sample) in the
instrument. Verify that the units displayed are in mg/L.
2. Touch Options. Touch Standard Additions. A summary of the standard
additions procedure will appear.
3. Make sure that the standard concentration, sample volume, and additions
volumes on the screen match your values. If they don't, touch Edit, then edit
the values. If they match, touch OK to proceed. The unspiked sample
reading will appear in the top row.
Nitrogen, Total
No interference up to:
1000 mg/L
2000 mg/L
Nitrogen, Total
Page 3 of 6
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