and ammonium) methods are based on colorimetric principles,
measuring the absorption of specific wavelengths after addition of
chemicals reacting with the N containing molecule [1]. In
(NO 3
À + NO 2
À
) analysis, nitrate is reduced to nitrite and all nitrite
in the sample is reacted with an aromatic amine, which is then
coupled with another aromatic amine to form an azo dye. The
reduction of nitrate to nitrite here is performed with an acidic
vanadium chloride reagent [2]. Ammonium analysis is based on
the formation of indophenol by phenol and hypochlorite in the
presence of sodium nitroprusside. The method records also unionized ammonia (NH 3 ). Dissolved organic nitrogen (DON) can
be derived from high temperature (>700
C) catalytic oxidation of
a filtered and acidified sample [1]. The sample is sparged with
synthetic air and non-purgeable dissolved nitrogen compounds
are then combusted and converted to nitrogen monoxide (NO),
which is cooled and detected by gas phase chemiluminescence [3]
resulting total dissolved nitrogen (TDN). DON is calculated as a
difference between TDN and DIN, where DIN is the sum of all
dissolved inorganic nitrogen species. TDN can be determined
together with total dissolved carbon (DOC), which is presented
in a separate chapter. The particulate organic nitrogen (PON) is
measured simultaneously with particulate organic carbon (POC)
after combustion. In this technique, the sample placed on a filter is
combusted at very high temperature (~1000
C) in a combustion
tube filled with an oxidation catalyst and oxides of N are reduced to
N 2 in reduction tube and determined by CN analyzer or a mass
spectrometer [1].
2 Materials
Use only analytical grade reagents.
2.1 Dissolved
Inorganic Nitrogen
1. Ammonium chloride (NH 4 Cl).
2. Concentrated hydrochloric acid (37% HCl).
3. Disodium nitroprusside dihydrate (Na 2 Fe(CN) 5 NO·2H 2 O).
4. N-(1-naphtyl)-ethylenediamine
dihydrochloride
(C 10 H 7 NHCH 2 ·CH 2 ·NH 2 ·2HCl).
5. Phenol (C 6 H 5 OH).
6. Potassium nitrate (KNO 3 ).
7. Sodium hydroxide (NaOH).
8. Sulfanilamide (NH 2 ·C 6 H 6 ·SO 2 ·NH 2 ).
9. Dichloroisocyanuric acid (Trione).
10. Tri-sodium citrate dihydrate (C 6 H 5 Na 3 O 7 ·2H 2 O).
11. Vanadium chloride (VCl 3 ).
12. Ultrapure water (e.g., Milli-Q).
72
Jaana Koistinen et al.
measuring the absorption of specific wavelengths after addition of
chemicals reacting with the N containing molecule [1]. In
(NO 3
À + NO 2
À
) analysis, nitrate is reduced to nitrite and all nitrite
in the sample is reacted with an aromatic amine, which is then
coupled with another aromatic amine to form an azo dye. The
reduction of nitrate to nitrite here is performed with an acidic
vanadium chloride reagent [2]. Ammonium analysis is based on
the formation of indophenol by phenol and hypochlorite in the
presence of sodium nitroprusside. The method records also unionized ammonia (NH 3 ). Dissolved organic nitrogen (DON) can
be derived from high temperature (>700
C) catalytic oxidation of
a filtered and acidified sample [1]. The sample is sparged with
synthetic air and non-purgeable dissolved nitrogen compounds
are then combusted and converted to nitrogen monoxide (NO),
which is cooled and detected by gas phase chemiluminescence [3]
resulting total dissolved nitrogen (TDN). DON is calculated as a
difference between TDN and DIN, where DIN is the sum of all
dissolved inorganic nitrogen species. TDN can be determined
together with total dissolved carbon (DOC), which is presented
in a separate chapter. The particulate organic nitrogen (PON) is
measured simultaneously with particulate organic carbon (POC)
after combustion. In this technique, the sample placed on a filter is
combusted at very high temperature (~1000
C) in a combustion
tube filled with an oxidation catalyst and oxides of N are reduced to
N 2 in reduction tube and determined by CN analyzer or a mass
spectrometer [1].
2 Materials
Use only analytical grade reagents.
2.1 Dissolved
Inorganic Nitrogen
1. Ammonium chloride (NH 4 Cl).
2. Concentrated hydrochloric acid (37% HCl).
3. Disodium nitroprusside dihydrate (Na 2 Fe(CN) 5 NO·2H 2 O).
4. N-(1-naphtyl)-ethylenediamine
dihydrochloride
(C 10 H 7 NHCH 2 ·CH 2 ·NH 2 ·2HCl).
5. Phenol (C 6 H 5 OH).
6. Potassium nitrate (KNO 3 ).
7. Sodium hydroxide (NaOH).
8. Sulfanilamide (NH 2 ·C 6 H 6 ·SO 2 ·NH 2 ).
9. Dichloroisocyanuric acid (Trione).
10. Tri-sodium citrate dihydrate (C 6 H 5 Na 3 O 7 ·2H 2 O).
11. Vanadium chloride (VCl 3 ).
12. Ultrapure water (e.g., Milli-Q).
72
Jaana Koistinen et al.