27
• The instrument directly displays concentration in
mg/L of ammonia
nitrogen
(NH
3
-N) on the Liquid Crystal Display.
• To convert the reading to mg/L of ammonia (NH
3
), multiply by a
factor of 1.214.
INTERFERENCES
Interference may be caused by:
• Organic compounds like: chloramines, various aliphatic and aromatic
amines, glycine or urea above 100 ppm N (positive error).
To eliminate these interferences distillation is required.
• Organic compounds like: aldehydes, alcohols (e.g. ethanol) or
acetone above 1 % (negative error).
To eliminate these interferences distillation is required.
• Sulfide: may cause turbidity.
Ammonia HR
54
•
Choose a homogeneous sample. Samples containing settleable solids
need to be homogenized with a blender.
•
Preheat the Hanna Reactor C 9800 to 150 °C (302°F). For correct
use of the reactor follow Reactor Instruction Manual.
Use of the optional HI 740217 safety shield is strongly recommended.
Do not use an oven or microwave because leaking samples can
generate a corrosive and possibly explosive atmosphere.
• Remove the cap from two Reagent Vials.
• Add exactly 0.2 mL of sample to one vial (sample vial), and 0.2
mL of deionized water to the other vial (blank vial), while keeping
the vials at a 45-degree angle. Replace the cap tightly and mix
by inverting each vial a couple of times.
Warning
: as the vials become very hot during mixing, be careful
in handling them.
•
Insert the vials into the reactor and
heat them for 2 hours at 150°C.
•
At the end of the digestion period
switch off the reactor. Wait for twenty
minutes to allow the vials to cool to
about 120°C.
• Invert each vial several times while
still warm, then place them in the test
tube rack.
Warning
: as the vials are still hot, be
careful in handling them.•
Leave the vials in the tube rack to cool
to room temperature. Do not shake or
invert them anymore otherwise the
samples may become turbid.
COD HR