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Interferences
Interfering Substance
Chlorine
Hardness
Iron
Seawater
Sulfide
Glycine, various aliphatic and
aromatic amines, organic
chloramines, acetone,
aldehydes and alcohols
Sample Collection, Storage, and Preservation
Accuracy Check
NitrogenAmm_None_Other_NES_Eng_Ody.fm
Remove residual chlorine by adding 2 drops of sodium arsenite for each mg/L Cl from a 250 mL
sample. Sodium thiosulfate can be used in place of sodium arsenite. See Sample Collection,
Storage, and Preservation below.
A solution containing a mixture of 500 mg/L CaCO
interfere. If the hardness concentration exceeds these concentrations, add extra
Mineral Stabilizer.
Interferes at all levels by causing turbidity with Nessler Reagent.
May be analyzed by adding of 1.0 mL (27 drops) of Mineral Stabilizer to the sample before
analysis. This complexes the high magnesium concentrations found in sea water, but the
sensitivity of the test is reduced by 30 percent due to the high chloride concentration. For best
results, perform a calibration, using standards spiked to the equivalent chloride concentration, or
distill the sample as described below.
Interferes at all levels by causing turbidity with Nessler Reagent.
May cause greenish or other off colors or turbidity. Distill the sample if these compounds
are present.
Collect samples in clean glass or plastic bottles. If chlorine is present, add one
drop of 0.1 N Sodium Thiosulfate (Cat. No. 323-32) for each 0.3 mg/L Cl
1-liter sample. Preserve the sample by reducing the pH to 2 or less with sulfuric
acid (at least 2 mL). Store at 4 °C (39 °F) or less. Preserved samples may be stored
up to 28 days. Warm samples to room temperature and neutralize with 5 N
Sodium Hydroxide (Cat. No. 2450-32) before analysis. Correct the test result for
volume additions; see Section 3.1.3 Correcting for Volume Additions on page 29.
Standard Additions Method (Sample Spike)
1. After reading test results, leave the sample cell (unspiked sample) in the
instrument.
2. Touch
. Touch
Options
additions procedure will appear.
3. Touch
to accept the default values for standard concentration, sample
OK
volume, and spike volumes. Touch
are accepted, the unspiked sample reading will appear in the top row. See
Standard Additions in the instrument manual for more information.
4. Snap the neck off a Nitrogen Ammonia Voluette
50-mg/L NH
–N.
3
5. Prepare three sample spikes. Fill three mixing cylinders (Cat. No. 1896-40)
with 25 mL of sample. Use the TenSette
and 0.3 mL of the 50 mg/L 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
. Each addition should reflect approximately 100% recovery.
Read
Interference Levels and Treatments
and 500 mg/L Mg as CaCO
3
. A summary of the standard
Standard Additions
to change these values. After values
Edit
®
Pipet to add 0.1 mL, 0.2 mL,
Nitrogen, Ammonia
does not
3
2
®
Ampule Standard,
Nitrogen, Ammonia
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