Note: Descriptions are shown in the official language in which they were submitted.
1~1563~
The present invention relates to an analytical
method for the determination of nitrogen derived from nitrites '
or nitrates which are contained in slight amounts in aqueous
systems, such as natural bodies of water (e.g. sea water,
river water, lake or marsh water) and various waste waters,
and an apparatus therefor.
In view of the problems presented by environmental
pollution in large bodies of water, such as nutritional en-
richment, various studies have been carried out for the treat-
ment of waste water from industrial and sanitation installa-
tions. Furthermore, when testing the potability of water,
attention is paid to the presence of nitrogen compounds con-
tained in the water as an index for the safety of drinking
water. There has therefore been a need to develop a rapid,
accurate and inexpensive analytical method and apparatus for
the determination of nitrogen derived from nitrites or
nitrates contained in trace amounts in water.
A conventional analytical method is the Griess
method which comprises diazotizing nitrites contained in
water with sulfanilic acid, adding a-naphthylamine thereto,
and measuring the absorbance of the resulting diazo compound
of color. However, the sensitivity of this method is reduced
by the presence of oxidizing agents such as residual chlorine,
permanganates or hydrochlorates, and also reducing agents such
as sulfites, ferric compounds or sulfides, and further by
ammonium ions, urea, aliphatic primary amines or the like,
when they are present in large amounts in the system. Other
interfering substances are metal ions (e.g. silver ions,
bismuth ions, lead ions) which produce precipitates in the
presence of hydrochloric acid; and iron, gold and metavanadate
which produce precipitates in the presence of a-naphthylamine;
-- 1 --
9~
- 111563~
and further ions having a color (e.g. cobalt ions, nickel
ions, chromium ions, chromate ions, dichromate ions). In
order to obtain accurate analytical values, careful attention
must be paid to the influence of these co-existing substances
and the reaction used in the analysis, and further, persons
employing the analytical method must have a high level of
knowledge and skill. A semi-automatized form of the Griess
method is used in instrumental analysis, but this method is
also affected by co-existing substances as much as the analysis
which is carried out by hand.
It is well known that sulfamic acid is quantatively
reacted with nitrous acid to produce nitrogen gas and
sulfuric acid even at low temperatures, as shown by the fol-
lowing equation:
02NH2 + HN02 = H2504 + H20 + N2
Hence, a method for the determination of nitrous acid using
sulfamic acid as a standard is employed in Japanese Industrial
Standard (JIS~ and Japanese Pharmacopeia. However, according
to this method, it is impossible to determine nitrogen de-
rived from slight amounts of nitrites contained in wastewaters or natural bodies of water. No analytical method and
apparatus was therefore known for the simple, rapid and
practical determination of nitrogen derived from small amounts
of nitrites in which the above reaction is utilized.
In order to analyze nitrate ions in water, the
nitration of phenolic compounds is employed, e.g. methods
using phenoldisulfonic acid or sodium salicylate, which are
employed in the examination of service water. According to
these methods, nitrate ions are determined by measuring the
concentration of the colored products which are produced by
the nitration of phenol derivatives. However, these methods
~1563{)
are also affected by the presence of chlorine ions and nitrite
ions, and further, the water to be analyzed must be evaporated
to dryness on a water bath for nitration. Thus, these methods
are not necessarily easy to carry out, but they can be used
for determining nitrogen derived from nitrates in concentra-
tions of about 0.01 ppm, in the case of aqueous systems ¢on-
taining few interfering substances, such as tap water.
A brucine method is also used in the examination of
service water and also in JIS K-0102, which involves the oxi-
dation of organic compounds. This method comprises oxidizingbrucine with nitrate ions in the presence of conc. sulfuric
acid and measuring the concentration of the colored product,
in which the oxidized product shows a red color and thereafter
changes to a yellow color. However, this method is also
affected by chlorine ions and nitrite ions in just the same
way aR the methods using phenoldisulfonic acid or sodium
salicylate. Furthermore, when the aqueous systems to be
analyzed contain oxidative or reductive substances, they
must first be treated with a reducing or oxidizing agent,
respectively. Moreover, when the aqueous systems are turbid
or colored, they must first be treated with an aqueous sus-
pension of aluminum hydroxide and active carbon.
Under these circumstances, the present inventors have
investigated new analytical methods for the determination of
nitrogen derived from nitrites or nitrates contained in
aqueous systems, and have found that nitrogen derived from
nitrites can be determined rapidly and accurately by reacting
the nitrites contained in the aqueous system to be analyzed
with an aqueous solution of sulfamic acid in a reactor,
removing the produced nitrogen gas from the aqueous system
with a carrier gas and measuring the nitrogen gas with a
-- 3 --
1~1563~
nitrogen gas detector. Furthermore, they have found that
nitrogen derived from nitrates contained in an aqueous system
can also be determined by first converting the nitrates to
nitrites by reduction and then following the above procedure.
Thus, according to the invention there is provided a method
for the determination of nitrogen derived from nitrites con-
tained in an aqueous system, which comprises reacting an
aqueous solution containing nitrites to be determined with an
aqueous solution of sulfamic acid in a reactor which is pro-
vided in a carrier gas stream removing the nitrogen gas thusproduced with the carrier gas from the aqueous system, and
measuring the nitrogen gas with a nitrogen gas detector.
An advantage of the present invention, at least in
preferred forms, is that it can provide an improved analytical
method for the determination of nitrogen derived from nitrites
which are contained in small amounts in aqueous systems.
Another advantage of the invention, at least in preferred forms,
is that it can provide an improved analytical method from the
determination of nitrogen derived from nitrates whi~h are con-
tained in a slight amount in aqueous systems.
When the nitrogen is contained in the aqueous systemin the form of nitrates, the nitrates can first be reduced
with a reducing agent to nitrites and thereafter the aqueous
~olution containing the resulting nitrites can be subjected
to the above procedure.
The aqueous solution of sulfamic acid used in the
present invention is usually an aqueous solution containing
0.1 to 15% by weight of sulfamic acid. The aqueous solution
should usually contain sulfamic acid in a larger amount than
that necessary for converting all nitrites contained in the
a~ueous system into nitrogen. The aqueous solution may
1~1563a)
contain sulfamic acid alone, but it is preferable that it
also contain a salt such as sodium chloride, by which the
nitrogen gas produced by the reaction is more rapidly turned
out from the aqueous system with the carrier gas.
The salt may be any water-soluble salt which is not
reacted with sulfamic acid, for example, chlorides, sulfates,
nitrates or phosphates of alkali metals (e~.g. sodium, potas-
sium), alkaline earth metals (e.g. magnesium, calcium), or
ammonium. Among them, chlorides, sulfates, nitrates or
phosphates of alkali metals or ammonium are preferred. The
concentration of the salt is not critical, but is usually in
the range of 0.1 to 30% by weight, preferably 0.5 to 10%
by weight. The salt may be added to the aqueous solution con-
taining nitrites or nitrates instead of being added to the
aqueous solution of sulfamic acid, or may be added to both
solutions.
The order of addition of the aqueous solution to
be analyzed and the aqueous solution of sulfamic acid into
the reactor is optional, but from the practical viewpoint, it
is preferable first to add a large amount of the aqueous
solution o sulfamic acid and thereafter to add the aqueous
sGlution to be analyzed, because in this manner a large number
of aqueous solutions can be analyzed without adding a new
solution of sulfamic acid.
Nitrates contained in the aqueous solution to be
analyzed are first reduced to nitrites by known methods as
described in JIS K-0102 or as employed in the examination of
drainage. Preferably, the nitrates are reduced by treating
them with zinc powder in a neutral or weakly alkaline range in
the presence of an ammonium compound. Suitable examples of
the ammonium compound are ammonium carbonate, ammonium acetate,
- 1~1563~
ammonium chloride, ammonium sulfate, ammonium citrate, or the
llke, which are used at a concentration of 0.1 to 0.5~ by
weight (as ammonium ions) based on the weight of nitrate;;ion.
Zinc powder is preferably used in an amount of 0.2 to 10~
by weight based on the weight of the nitrate ions. The re-
duction of nitrates with zinc powder is carried out by adding
an ammonium compound and zinc powder to the aqueous solution
containing nitrates and shaking the mixture for about 20
seconds or longer, preferably for about 20 to 180 seconds.
After reducing nitrates contained in the aqueous
solution to be analyzed, the resulting aqueous solution con-
taining nitrites thus produced is subjected to the determina-
tion of nitrogen of the present invention, by which the ni-
trogen derived from the nitrates can be determined.
Aqueous solutions to be analyzed usually contain
both nitrites andnitrates, and hence, when the aqueous solu-
tions are analyzed after reducing the nitrates as mentioned
above, the total nitrogen derived from the nitrites and
nitrates can be determined. On the other hand, when the
aqueous solutions are analyzed by reacting them with an aqueous
solution of sulfamic acid without first subjecting them to
the above reduction treatment, only the nitrogen derlved from
the nitrites is determined. Thus, the nitrogen derived from
the nitrates can be calculated by subtracting the amount of
nitrogen derived from the nitrites from the total amount of
nitrogen derived nitrites and nitrates.
The detection of the nitrogen gas can be carried out
by a thermal conductivity method, by mass spectrometry or by
discharge spectrometry.
When the nitrogen gas is detected by a gas chromato-
graph equipped with a thermal conductivity detector, a carrier
t 1~1563iD
gas such as helium, argon or hydrogen is used, and the sep-
arating column is packed with a filler of the type usually
used in the gas chromatography of inorganic gases, such;as
silica gel, active carbon, porous polymer beads, or molecular
sieves. In the case of mass spectrometry, hel~um, argon or
hydrogen is used as a carrier gas, and the nitrogen gas pro-
duced in the reaction zone is preferably,measured by mass
fragmentgraphy at m/e = 28. In case of a discharge spectro-
metry, argon is used as a carrier gas, and the nitrogen gas
produced in the reaction zone is passed through a detecting
cell and is discharged therein by applying a high electrical
voltage to the electrodes provided at both sides of the cell,
and a wavelength of 3371 A is isolated from the emission
spectrum with an optical filter and is detected with a photo-
multiplier. By this method, the nitrogen can be determined
with high sensitivity.
One embodiment of the analysis of the present in-
vention using a gas chromatograph equipped with a thermal con-
ductivity detector is illustrated with reference to the
accompanying drawings, in which:
Figures 1, 2 and 3 are schematic diagrams of embodi-
ments of the apparatus used in the present invention; and
Figures 4, 5, 6 and 7 are the calibration curves of
the solutions referred to in the Examples disclosed herein-
after, which show the relation between the peak height of the
nitrogen in the gas chromatogram and the amount of the
nitrogen derived from nitrites or nitrates.
As is shown in Figures 1, 2 and 3, a carrier gas
(e.g. helium or argon) from a device for supplying such a gas
(e.g. helium cannister or argon cannister) is divided into
two streams, and one of them is sent to a reference side of a
` ~lS63~)
gas chromatograph via a pressure controller 4 and the other one
is sent to a reaction tube 9 via a pressure controller 3 and
optionally a switching cock 7. The carrier gas flows at a rate
of 20 to 100 ml/minute. The reaction tube 9 is made of a
hard glass and the upper part above a glass filter 10 has an
inner diameter of 8 to 15 ~n and an inner volume of 5 to 20
cm3. In the upper part, a capil~ary tube 12 and a cock 13 are
provided and are used for removing the solution to be reacted
(i.e. an aqueous solution of sulfamic acid), the solution to
be analyzed, the reaction mixture and the washing liquid. The
glass filter 10 preferably has a grade of 2G or 3G (JIS R-
3503-1958) so that the reaction mixture does not pass through
when the carrier gas is passing upwardly therethrough and has
a thickness of 2 to 5 mm. At the top of the reaction tube 9,
an inlet 14 is provided for introducing the aqueous solution
of sulfamic acid and the solution to be analyzed. These sol-
utions are introduced into the reaction tube 9 from an inlet
14 by means of, for example, a microsyringe or an automatic
injector 15. The nitrogen gas produced in the reaction mix-
ture 11 is removed from the aqueous sys tm with the carriergas and passes through a splash removing tube 17 and is
optionally led to an oxidation-reduction tube 19. The splash
removing tube 17 is packed with a water-absorptive material
(e.g. gauze) which is impregnated with an indicator, and when
splashes of the reaction mixture are carried on the ca~rier
gas, the splash removing tube becomes colored.
When the aqueous solution to be analyzed contains
volatile organic substances, the organic substances vaporize,
and hence it is preferable to oxidize them in the oxidation-
reduction tube 19, as is shown in Figures 2 and 3, and thenthe resulting carbon dioxide is removed in an acidic gas-
-- 8 --
1~1563~)
removing tube 25. The oxidation-reduction tube 19 may be made
of quartz and is packed with an oxidizing agent (e.g. copper
oxide or cobalt oxide) and a reducing agent (e.g. reduced
copper or reduced nickel) and has an inner diameter of 8
to 15 mm and a length of 15 to 30 cm. The oxidation-reduction
tube 19 is preferably heated at 300 to 700C. with an electric
furnace 20. The gas passed through the oxidation-reduction
tube 19 is optionally further passed through a moisture-
removing tube 22 and a switching cock 7 and is led into the
acidic gas-removing tube 25, as is shown in Figure 3. The
moisture-removing tube 22 is provided in order to remove the
moisture which is produced by vaporization of the aqueous
solutions contained in the reaction system. The moisture-
removing tube 22 may be made of a glass and is packed with a
dehydrating agent such as magnesium perchlorate, hydroscopic
ion exchange resin, calcium chloride or silica gel. The
acidic gas-removing tube 25 may be made of a glass and packed
with soda asbestos or soda lime.
The gas ~assed through the acidic gas-removing
tube 25 is introduced into a gas chromatograph equipped with
a thermal conductivity detector 30. The gas chromatograph may
be any double column flow or single column flow type. Sep-
arating columns 28 and 29 are packed with a filler which is
usually used for gas chromatography of an inorganic gas,
such a6 silica gel, active carbon, polar polymer beads or
molecular sieves. The signals obtained in the thermal con-
ductivity detector 30 are sent to a recorder 32 through a
signal line 31 and are recorded therein.
In Figures 1, 2 and 3,the numerals 2, 5, 6, 8, 16,
30 18, 21, 23, 24, 26, 27 and 33 identify pipes for connecting
each of the various devices.
_ g _
1~15iE;3~
As is shown in Figure 3, the carrier gas divided
from the pipe 2 may optionally be led into a dissolved air-
removing tube 37 via a needle valve 34 and a capillary tube
35. Usually, water contains dissolved air which contains
about 15 ppm of nitrogen gas, and hence it is preferable to
remove the dissolved air from the aqueous solutions to be
subjected to the reaction by feeding the aqueous solution
to the dissolved air-removing tube and bubbling the solutions
with a carrier gas. Furthermore, in order to prevent further
dissolving of air, a septum 36 having fine pores for collect-
ing the reaction mixture is provided at the upper part of the
dissolved air-removing tube 37. The dissolved air may also
be removed by other conventional methods before introducing
the aqueous solutions into the reaction system of the present
invention, or may also be removed by bubbling the solutions
in the reaction tube with a carrier gas by blowing the carrier
gas into the reaction tube from the lower end thereof.
The present invention is illustrated by the
following Examples but is not limited thereto.
Example 1
Nitrogen derived from nitrites was determined
by using an apparatus as shown in Figure 1. The reaction
tube had an inner diameter of 13 mm and an inner volume
of 12 ml, and contained a 3G glass filter having a
thickness of 2 mm. An aqueous solution (3 ml) containing
5 ~ by weight of sulfamic acid and 5 % by weight of
sodium chloride was added to the reaction tube. The
moisture-removing tube had an inner diameter of 8 mm
and a length of 150 mm and was packed with 10 - 20 mesh
magnesium perchlorate, and the acidic gas-removing tube
had an inner diameter of 8 mm and a length of 70 mm and
-- 10 --
- ~lS630
was packed with 20 - 40 mesh soda asbestos. A stainless
steel column having an inner diameter of 3 mm and a
length of 50 cm was used as the separating column of
the gas chromatograph, which was packed with 60 - 80
mesh active carbon. Under the conditions of a column
temperature of 50C, a temperature of the thermal
conductivity detector of 60C and an electric current
of the bridge of 180 mA, a carrier gas (helium) was
flowed at a rate of 60 ml/minute. An aqueous solution
of sodium nitrite having an appropriate concentration
was prepared and the dissolved air was turned out with
helium gas, and the aqueous solution (100 ~1~ thus
obtained was introduced into the reaction tube by means
of a microsyringe, and then a calibration curve was
drawn. The chromatogram was obtained in about 2 minutes.
A relation between the peak height Oc the spectrum
~nitrogen) and the concentration of nitrogen derived
from nitrites contained in the test solution showed
a good straight line as shown in Figure 4.
Based upon the calibration curve obtained
above, test solutions having various concentrations of
nitrites were tested and the concentration of nitrogen
derived from nitrites was measured. The results are
shown in the following Table 1.
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P~ ~ Ln ~ ~ cn o ~ ~ ~
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z ~ ~a
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Ln o ~r o ~ o Ln ~ a~
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0~ Z ~ ~ ~ o ~ ~ ~ o ~ ~
~ ~ ~ ~ ~ Ln CO ~ ~ ~
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æ ~
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Z ~ O ~ o o o o o o o Ln
U~ Q~ o o o Ln o o o o
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u~ o ~ o~o 0~o o\ 0o 0\o
u~ ~ ~ ~ ~ ~ ~
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E~ 0~ Z Z Z Z Z Z Z Z
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-- 12 --
1~1563~
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-- 13 --
1~15~3~)
Example 2
Nitrogen derived from nitrites was deter~ined
by using an apparatus as shown in Figure 2. The reaction
tube was made of a hard glass and had an inner diameter
of 13 mm and an inner volume of 12 ml and contained a
3G glass filter having a thickness of 2 mm. The moisture-
removing tube had an inner diameter of 8 mm and a
length of 150 mm and was packed with 10 - 20 mesh magnesium
perchlorate, and the acidic gas-removing tube had an
inner diameter of 8 mm and a length of 70 mm and was
packed with 20 - 40 mesh soda asbestos. The oxidation
tube had an inner diameter of 10 mm and a length of 200
mm and was packed with linear copper oxide having a
diameter of 0.6 mm and a length of 2 - 4 mm, and at
both sides of the oxidation tube, quartz was packed in
a length of about 2 cm. A stainless steel column having
an inner diameter of 3 mm and a length of 1 m was used
as the separating column of the gas chromatograph and
was packed with 60 - 80 mesh active carbon. A carrier
gas (helium) was flowed at a rate of 60 ml/minute. The
determination was carried out under the conditions of'
a column temperature of 50C, a temperature of the
thermal conductivity detector of 60C, an electric
current of the bridge of 180 mA and a full scale of the
recorder of 1 mV. The aqueous solution to be reacted
was a 5 ~ by weight aqueous solution of sulfamic acid.
Aqueous solutions (3 ml) having various concentrations
of sodium nitrite were each collected in a syringe and
were introduced into the reaction tube and were allowed
to stand for about 4 minutes in order to turn out the
- 14 -
_, . .
Tt_
l~lS6~
. .
dissolved air. An aqueous solution of sulfamic acid
(100 ~ rom which dissolved air was turned out with
helium gas, was introduced into the reaction tube with
a microsyringe. The produced nitrogen gas was recorded
with a chromatogram. After the reaction, the test solution
was taken out from the system by opéning the needle valve,
and the reaction tube was washed by introducing therein
distilled water or an aqueous solution to be analyzed
(4 ml) with a syringe. The chromatogram was obtained
in about 2 minutes after introduction of the aqueous
solution of sulfamic acid. A relation between the peak
height of the spectrum (nitrogen) and the concentration
of nitrogen derived from nitrites showed a good straight
line as shown in Figure 5. The test results obtained
by using the calibration curve are shown in Table 2.
Table 2
~mount of NO2 ~ N Found amount f NO2 ~ N (ppm~
~dded to the test
solution No. 1 No. 2 No. 3 Average
0.300 0.287 0.303 0.306 0.299 :
0.200 0.207 0.194 0.199 0.200
0.100 0.102 0.097 0.111 0.103
0.050 0.046 0.049 0.052 0.049
O . 010 O . 009 O . 009 O . 010 û . 009
0.005 0.004 0.006 0.004 0.005
Example 3
Nitrogen derived from nitrates was determined by
using an apparatus as shown in Figure 3. The reaction tube
was made of a hard glass and had an inner diameter of 13
mm and an inner volume of 12 cm3 and contained a 2G glass
-- 15 --
111563~
.
filter having a thickness of 2 mm. An aqueous solution
(3 ml) contair.ing 3 % by weight of sodium chloride-and
10 ~ by weight of sulfamic acid was introduced into
the reaction tube. The moisture-removing tube had an
inner diameter of 9 mm and a length of 150 mm and was
packed with an equal amount of 20 - 40 mesh magnesium
perchlorate and 20 - 40 mesh hydroscopic sulfonic acid
type ion exchange resin, and the oxidation-reduction
tube had an inner diameter of 10 mm and a length of
200 mm and was packed with 80 mm of a linear copper
oxide having a diameter of 0.6 mm and a length of 2 - 4
mm, and 80 mm of a linear reduced copper having a diameter
of 0.6 mm and a length of 2 - 4 mm, in this order, and
at the both sides of the oxidation-reduction tube, quart~
wool was packed in a length of 20 mm and was heated at
500C with an electrical furnace. The glass-made splash
removing tube had an inner diameter of 9 mm and a length
of 70 mm and was packed with a gauze which was impregnated
with a dye, Congo Red, and the acidic gas-removing tube
had an inner diameter of 9 mm and a length of 70 mm and
was packed with 20 - 40 mesh soda asbestos. A stainless
steel column having an inner diameter of 3 mm and a length
of 1 m was used as the separating column of a gas
chromatograph and was packed with 60 - 80 mesh active
carbon. A carrier gas (helium) was f lowed at a rate
of 60 ml/minute. The determination was carried out
under the conditions of a column temperature of 60C,
a temperature of the thermal conductivity detector of
60C and an electric current of a bridge of 160 mA.
Aqueous solutions containing various concentration
- 16 -
r
1563~
of sodium nitrate (20 ppm, 10 ppm and 5 ppm as nitrogen
derived from the nitrate) were prepared by using g~aranteed
sodium nitrate reagent and each 25 ml thexeof was collected
in a 50 ml test tube, to which was added an aqueous solution
of an ammonium compound (30 ~ by weight ammonium carbonate
solution, 0.65 ml; 26 % by weight ammonium chloride solution,
1.0 ml; 50 % by weight ammonium acetate solution, 0.6 ml;
30 ~ by weight ammonium sulfate solution, 1.0 ml; or
30 % by weight ammonium citrate solution, 2.0 ml~, and
thereto was further added zinc powder tO.2 - 0.3 g).
The test tube was sealed and shaken for 1 minute.
Immediately, the mixture was filtered with a filter
paper (No. 5, C grade) and about 0.6 ml thereof was
added to a dissolved air-removing tube having an inner
diameter of 15 mm and a length of 7 cm and therein`dissolved
air was turned out with helium gas. The solution thus
obtained (100 ~1) was introduced into the reaction tube
with a microsyringe, and a calibration curve was drawn.
The chromatogram was obtained in about 2 minutes. A
relation between the peak height of the spectrum (nitrogen)
and the concentration of nitrogen derived from nitrate was
obtained for each ammonium compound. The relation showed
a good straight line in all solutions as shown in Figure
6.
By using the data of sodium nitrate as a
standard, various test solutions containing nitrate ion,
which was previously reduced with ammonium carbonate and
zinc powder into nitrite ion, were reacted with a 10 %
by weight aqueous sulfamic acid solution or a 3 to 10
% hy weight aqueous sulfamic acid solution containing
- 17 -
.
1~1563~
,:
various salts, and the concentration of nitrogen
derived from nitrates was measured based upon the `
calibration curve. The results are shown in Table 3.
- 18 -
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1~1563~)
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tdU 1~ o ~ ~ ~4 X ~ ~ ~ X
E-l
UO~ U
O Z ~:;
rl tt~ ~
0 ~ ~ + +
~ ~:
C) U~ h O v~
0 ~0 0 U~ ~
I O t~ O ¦ ~ ~ _ i
-- 20 --
1~1563~)
Example 4
Nitrogen derived from nitrates was determined
by using an apparatus as shown in Figure 3.
A test solution containing a slight amount of
nitrate ion (25 ml) was collected in a test tube and
thereto were added a 26 % by weight aqueous ammoniu~
chloride solution (1.0 ml) and zinc powder (0.25 g~ and
the mixture was shaken for 1 minute. After the mixture
(about 10 ml) was filtered with a filter paper ~o. 5,
C grade), the filtrate (about 3 ml~ was immediately
introduced into the reaction tube with a 5 ml syringe
and was allowed to stand for about 4 minutes in order
to turn out the dissolved air. To the reaction tube
was added a 10 % by weight aqueous sulfamic acid
solution (100 ~1) containing 3 % by weight of sodium
chloride, from which dissolved air was previously
turned out, by means of a microsyringe. The chromatogram
of the produced nitrogen gas was recorded. Other
conditions than the above were the same as in Example 3.
After the reaction, the test solution was taken out by
opening the cock, and the reaction tube was washed with
distilled water or ion exchange water (4 ml) and the
washing water was taken out likewise. Thereafter, the
next test solution was introduced into the reaction
tube and followed by the above procedure. The chromatogram
was obtained in about 2 minutes after introduction of
the aqueous solution to be reacted. A relation between
the peak height of the spectrum (nitrogen) and the
concentration of nitrogen derived from nitrates had a
good straight line as shown in Figure 7.
, , . _ . . _ . .
l~S63~
By using the data of sodium nitrate as a
standard, various tes~ solutions containing nitratè
ion were tested and the concentration of nitrogen
derived from nitrates was measured based on the
calibration curve. The results are shown in Table 4.
Table 4
Components of Amount of Found amount of NO - N
aqueous solution _ (ppm) 3
to be analyzed
added to the No. 1 No. 2 Average .
test solution
(ppm) ~ ~
NH4NO3 0.500~ 0.491 0.497 0.494
NH4NO3 + 3%NaCl 0.500 0.505 0.502 0.504
KNO3 0.2000.200 0.19 a 0.195
.KNO3 + 1%Na2SO4 0.200 0.203 0.197 0.200
I~NH4NO3 0.0500.046 0.048 0.047
NH4MO3 + 3~NaCl 0.050 0.052 0.049 0.050
,IKNO3 0.0200.018 0.020 0.019
KNO3 + 1%Na2SO4 0.020 0.021 0.021 0.021
',KNO3 i 0.0100.008 0.009 0.008
!IKNO3 + 3%NaCl ~ 0.010 ~ 0.011 0.010 0.010 :
- 22 -
