Hach DR/850 - Page 231

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3. Analyze each spiked sample, following all steps of the
Monochloramine and Free Ammonia procedure. The
ammonia nitrogen concentration should increase 0.02 mg/L
for each 0.1 mL of standard added.
4. If these increases do not occur, see Standard Additions
(Section 1 of the DR/890 Procedures Manual) for more
information.
Standard Solution Method
Prepare a 0.20 mg/L ammonia nitrogen standard by diluting
2.00 mL of the Ammonia Nitrogen Standard Solution, 10 mg/L,
to 100 mL with dilution water. Or, using the TenSette Pipet,
prepare a 0.20 mg/L ammonia nitrogen standard by diluting
0.4 mL of a Ammonia Nitrogen Voluette Standard Solution,
50 mg/L as NH
3
–N, to 100 mL with dilution water. Analyze the
standard solution, following all steps of the Monochloramine and
Free Ammonia procedure.
Method Performance
Monochloramine Test
Precision
In a single laboratory, using a monochloramine standard solution
of 2.10 mg/L Cl
2
and representative lots of reagent, a single
operator obtained a standard deviation of ± 0.12 mg/L Cl
2
.
Estimated Detection Limit
The estimated detection limit for Method 10171 is 0.05 mg/L Cl
2
.
Free Ammonia Test
Precision
In a single laboratory using a solution containing 1.80 mg/L Cl
2
plus 0.20 mg/L ammonia nitrogen (NH
3
–N) and two
representative lots of reagent with the DR/890, a single operator
obtained a standard deviation of ± 0.01 mg/L N for seven
replicates.
Estimated Detection Limit
The estimated detection limit for program 46 is 0.02 mg/L N.
For more information on the estimated detection limit, see
Section 1 of the DR/850 or DR/890 Procedure Manual.
Nitrogen, Free Ammonia and Chloramine (Mono), continued