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NITRITE, LR,
continued
SAMPLING AND STORAGE
Collect samples in clean plastic or glass bottles.
Store at 4 °C (39 °F) or lower if the sample is to be analyzed within 24 to
48 hours. Warm to room temperature before running the test.
For longer storage periods, add 4.0 mL of Mercuric Chloride Solution*
for each liter of sample taken and mix. Sample refrigeration is still
required. This storage method may not be used when reporting
results to regulatory agencies. Do not use acid preservatives.
*Use of mercuric chloride is not recommended due to environmental and health concerns.
ACCURACY CHECK
Standard Solution Method
Prepare a nitrite nitrogen standard solution by dissolving 0.493 grams of
sodium nitrite, ACS, in 1000 mL of nitrite-free demineralized water to
-
give a 100 mg/L nitrite nitrogen (NO
-N) standard solution. This
2
solution is not stable and should be prepared daily. Use a TenSette Pipet
to dilute 1.00 mL of the stock solution to 1000 mL with nitrite-free
-
demineralized water to give a 0.10 mg/L (NO
-N) nitrite nitrogen
2
standard solution. Prepare this solution immediately before use.
STATISTICAL EVALUATION
A single operator repetitively tested samples of two laboratory prepared
solutions, using one DR/700, matched sample cells and two representative
-
lots of testing reagents. Testing 0.091 mg/L NO
-N concentration
2
samples the standard deviation was ±0.0010 mg/L NO
-
-N.
2
Testing zero concentration samples, the limit of detection was 0.0038 mg/L
-
NO
-N. The limit of detection was calculated as three times the standard
2
deviation when testing zero concentration samples (Adapted from
Analytical Chemistry, 1980, 52, 2242-2249).
Using two representative lots of AccuVacs, the standard deviation was
±0.0016 mg/L NO
-
-
-N and the limit of detection was 0.0089 mg/L NO
-N.
2
2
INTERFERENCES
Strong oxidizing and reducing substances interfere. Cupric and ferrous
ions cause low results. Ferric, mercurous, silver, bismuth, antimonous,
lead, auric, chloroplatinate and metavanadate ions interfere by causing
precipitation.
50-48
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