Test Procedures
Nitrogen is essential for plant growth, but the presence of excessive amounts in water
supplies presents a major pollution problem. Nitrogen compounds may enter water as
nitrates or be converted to nitrates from agricultural fertilizers, sewage, industrial and
packing house wastes, drainage from livestock feeding areas, farm manures and legumes.
Nitrates in large amounts can cause “blue babies” (methemoglobinemia) in infants less
than six months of age. Nitrate concentration is an important factor to be considered in
livestock products, where, in addition to causing methemoglobinemia, it is responsible
for many other problems. Nitrates in conjunction with phosphate stimulate the growth of
algae with all of the related diffi
culties associated with excessive algae growth.
U.S. Public Health Service Drinking Water Standards state that 10 ppm nitrate nitrogen
should not be exceeded. To the sanitary and industrial engineer, concentrations of less
than 1 ppm are acceptable.
APPLICATION:
Drinking, surface, saline, domestic and industrial waters.
RANGE:
0–25 mg/L Total Nitrogen
MDL:
2 mg/L
METHOD:
All forms of nitrogen are converted to nitrate by an alkaline
persulfate digestion. Interference from halogen oxides is
eliminated by the addition of sodium metabisulfi te. Nitrate in
acid reacts with chromotropic acid to form a yellow color in
proportion to the amount of nitrate in the treated sample.
SAMPLE HANDLING &
PRESERVATION:
If the sample can not be analyzed immediately, the sample
should be preserved by adjusting the pH to 2 or less with
concentrated sulfuric acid and refrigerated at 4°C. Warm
the sample to room temperature and neutralize with 5.0 N
sodium hydroxide before analyzing.
INTERFERENCES:
Bromide (>60 ppm) and chloride (>1000 ppm) will have a
positive interference.
NITROGEN
, TOTAL
SMART Spectro 2 Test Procedures 05.02.16
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