Hach DR/850, Procedures Manual, Page: 228 / 460

228
Sampling and Storage
Collect samples in clean glass bottles. Most reliable results are
obtained when samples are analyzed as soon as possible after
collection.
Color Development Time
Test results are strongly influenced by sample temperature. Both
reaction periods in the procedure are the same and depend on
the temperature of the sample.
The reaction periods indicated
in the procedure are for a sample temperature of 18–20 °C (68–73
°F). Adjust both reaction periods according to Table 3.
Interferences
This method is intended for finished, chloraminated drinking
water samples that have a measurable combined (total) chlorine
disinfectant residual. Samples where the disinfectant residual has
disappeared and samples which exhibit a chlorine demand may
produce low ammonia test results. Blanks and ammonia standards
analyzed without a disinfectant residual must be prepared using
high quality, reagent grade water.
The following do not interfere in free ammonia determination
when at or below the stated concentration.
Table 3 Reaction Period
Sample Temperature
Reaction Periods
(Minutes)
° C ° F
5 40 10
7 42 9
9 48 8
10 50 8
12 54 7
14 58 7
16 61 6
18 68 5
20 73 5
23 75 2.5
25 77 2
>25 >77 2
Nitrogen, Free Ammonia and Chloramine (Mono), continued