CA1054036A - Analytical method and apparatus for determination of total nitrogen and/or carbon contents in aqueous systems - Google Patents

Abstract

ANALYTICAL METHOD AND APPARATUS FOR DETERMINATION OF

TOTAL NITROGEN AND/OR CARBON CONTENTS IN AQUEOUS SYSTEMS

Abstract of the Disclosure:
An analytical method for determining rapidly and accurately the total nitrogen and/or carbon contents in aqueous systems containing nitrogenous and/or carbonaceous materials, which comprises introducing an aqueous solution containing nitrogenous and/or carbonaceous materials as a specimen to be analyzed together with a carrier gas into a reactor tube packed with a destructive oxidation catalyst and/or a reducing agent and/or an oxidizing agent and kept at certain elevated temperatures so as to decompose the nitrogenous and/or carbonaceous materials to nitrogen and/or carbon dioxide and measuring the amounts of nitrogen and/or carbon dioxide in the resulting gaseous mixture by the use of a thermal conductivity gas chromatograph, and an apparatus to be used for carrying out such method.

Description

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The present invention relates to an analytical method and apparatus for determining the total nitrogen and/or carbon contents in aqueous systems such as waste water.
With respect to environmental pollution problems, there has been hi~hly desired the appearance of an analy-tical method and apparatus for determining rapidly and accurately the total contents of nitrogen, carbon, phos-phorus, sulfur, etc. in aqueous systems by element, which lo may constitute the source of nutxitional enrichment or red water in waters.
For analyzing the total nitrogen content in aqueous systems, thexe are known the so-called wet chemi-cal methods, which however require an extremely long time for measurement. Further, in order to obtain accurate .
analytical values, considerable knowledge of the reactions applied to the analysis and the influences caused by co-existing components is necessary. Furthermore, the ~ -persons who carry out the analytical methods are requied to have high technical skill. There are also proposed some analytical methods using instruments such as a method for detection of ammonia produced from hydrogenative decomposi-tion of nitrogenous materials by coulometry, a method for ;~ ~`
detection of chemical fluorescence on the formation of nitrogen dioxide by the reaction of nitrogen monoxide derived from nitrogenous materials with ozone and a method for detection of nitrogen monoxide produced from nitro-genous materials by the use of an infrared analyzer.
On the other hand, as to the analysis of the total carbon content in aqueous systems, there are known a method

- 2 -i4036 wherein carbonaceous materials are decomposed in a carrier gas containing oxygen at high temperatures and the result-ing carbon dioxide is quantitatively determined (U.S. patent

3,296,~35), a method wherein carbonaceous materials are decomposed in a carrier gas containing no oxygen in the presence of a catalyst such as pallaclium at elevated temper-atures and the resulting carbon dioxide is determined quanti-tatively by means of an infrared analyzer (U.S. patent 3,530,292), etc. These methods are, however, disadvantage-ous in using an infrared analyzer, which is still expensive.Analytical me~hods using a gas chromatograph instead of an infrared analyzer have been proposed but they present problems in operation as well as safety problems, because the gas produced by decomposition is stored in a holder to achieve a uniform composition and is then subjected to analysis, or measurement is made by the use of a hydrogen flame ionization detector utilizing dangerous hydrogen gas.
Very few methods have been proposed for the simul-taneous determination of total nitrogen and carbon contents.
A typical one is based on the principle of an element analyzer for carbon, hydrogen and nitrogen and comprises subjecting carbonaceous materials to combustion in the presence' of oxygen and subjecting nitrogenous materials to reduction, followed by determination of the amounts of the resultant carbon dioxide and nitrogen using a gas chromatograph. However, this method requires a special and complicated device for the supply of oxygen gas. -A basic object of the present invention is to provide an analytical method for determination of the total nitrogen and/or carbon contents in aqueous systems contain-.. . . .

The analytical method of the present invention comprises introducing an aqueous solution containing at least one of nitroyenous and carbonaceous materials as a specimen to be analyzed together with a carrier gas into a reactor tube packed with at least one of a destructive oxidation catalyst, a reducing agent and an oxidizing agent, maintaining this at an elevated temperature so as to decompose the nitrogenous material to nitrogen and the carbonaceous material to carbon dioxide and ~easuring the amounts of nitrogen and carbon dioxide present in the resulting gaseous mixture by the use of a thermal con-ductivity gas chromatograph. :
The above analytical method may be carried out by the use of an apparatus which comprises a reactor tube provided with an inlet and an outlet through which a carrier

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gas is passed and pac~ed with a destructive oxidation catalyst and/or a reducing agent and/or an oxidizing agent, a means for injecting a specimen to be analyzed into the reactor tube, a means for supplyinc3 an inert gas as the carrier gas into the reactor tube, a means for removal of moisture from the gaseous mixture produced in the reactor tube and a gas chromatograph provided with a thermal con-ductivity detectorO
A specimen to be analyzed, which is an aqueous solution containing nitrogenous and/or carbonaceous materials, is introduced from the injector means into the reactor tube, usually through the inlet for the carrier gas.
Examples of the inert gas as the carrier gas are helium, argon, etc. Preferred is helium, because it has a larger difference from nitrogen and carbon dioxide in thermal conductivity. When the determination of the total carbon content is intended, nitrogen may be also used as the carrier gas. In case of the determination of the total nitrogen content with or without the total carbon content, however, nitrogen can not be used as the carrier gas. The inert gas from the supply means is introduced into the reactor tube, usually at a flow rate of about 20 to 200 ml/min.
The reactor tube may be made of a heat and corro-sion resistant material such as quartz or ceramics ~e.g.
mullite). While no particular limitation exists on the size of the reactor tube, a typical example of practically utiliz-able reactor tubes is the one having an inner diameter of about 7 to 13 mm and an inner volume of about 20 to 50 ml.
The reactor tube is packed with a destructive i ' ~ . . ' ~LO~i4~36 oxidation catalyst and/or a reducing agent and/or an ~
oxidizin~ agent. When only the determination of the total nitrogen content is intended, the reactor tube may be packed with a destructive oxidation catalyst and a reducing agent.
In this case, the destructive oxidation catalyst is to be , posltioned on the side of the inlet and the reducing agent on the side of the outlet. When only the determination of the total carbon content is intended, the oxidizing agent alone or together with the destructive oxidation catalyst may be packed into the reactor tube. For accelerating the decomposition of carbonaceous materials and avoiding the pulverization of the oxidizing agent, it is usually preferred to use the oxidizing agent with the destructive oxidation which is positioned on the side of the inlet. In case of the determination of the total contents of nitrogen and carbon being aimed at, the destructive oxidization catalyst, the reducing agent and the oxidizing agent are packed in the reactor tube. Preferably, these materials may be arranged in the said order in the reactor tube from the inlet side to the outlet side.
The reactor tube is heated by a conventional heating means so as to maintain the zone packed with the destructive oxidation catalyst at a temperature of from ~
about 700 to 1200~C (preferably from about 700 to 100 b c ) ;;
and the zone(s) packed with the reducing agent and/or the oxidizing agent at a temperature of from about 300 to 700C.
When only the oxidizing agent (i.e. without the destructive oxidation catalyst and the reducing agent) is used as the packing material, it may be heated at a temperature of from about 700 to 1200C.

~05~36 As the destructive oxidation catalyst, there may be used the one comprising a-t least one metal belonging to Group Is or VIII in the periodic table. In view of the hish stability at elevated temperatures, the use of a platinum group meta] such as platinum or palladium is favor-able. The destructive oxidation catalyst may be employed in any conventional form which does not prevent the flow of a gaseous material (e.g. pellets, wires, gauzes). When desired, the destructive oxidation catalyst may be ~ metal deposited on a conventional carrier material (e.g. asbestos, alumina). The destructive oxidation catalyst heated at a temperature frorn about 700 to 1200C can decompose nitro-genous and carbonaceous materials in cooperation with the oxidizing action of water at such high temperature to produce lower molecular compounds, of which portions are further converted into nitrogen and carbon dioxide.
As the reducing agent, there may be used the one comprising at least one of copper, nickel, iron, cobalt and zinc. In view of the high reducing power, preferred are reduced copper or reduced nickel. The reducing agent may be ;~
employed in any conventional form (e.g. pellets, wires, gauzes). The reducing agent heated at a temperature of from -~
about 300 to 700C is effective in converting nitrogenous .~ j ., .
oxides present in the gaseous mixture coming through the -preceding zone of the destructive oxidation catalyst into nitrogen and also in eliminating oxygen in the said gaseous mixture. -As the oxidizing agent, there may be used the one comprising at least one of oxides of cobal-t, nickel, vanadium tungsten, silver and manganese. They may be used alone or `~
.

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in combinationO A -typical example of their mix~ure is hop-calite, i.e. a mixture of manganese oxide, copper oxide, cobalt oxide and silver oxide. In view of the high oxidi~
zincJ power at elevated temperatures, the use of oxides of cobalt is preferred. The oxidizing agent may be in any conventioanl form (e.g. pellets, wires, gauzes) and when heated at a temperature of from about 300 to 700C converts the incompletely oxidiæed carbonaceous compounds present in the gaseous mixture coming through the preceding zone of the destructive oxidation catalyst to the completely oxidized carbonaceous compound, i.e. carbon dioxide.
In the reactor tube, the nitrogenous and/or carbonaceous materials are decomposed to nitrogen and/or carbon dioxide. The gaseous mixture comprising these gaseous materials flows out from the reactor tube through the outlet and is led into the means for removal of mois-ture. As the means for removal of water, there may be employed any conventional one such as a tube packed with a dehydrating agent (e.g. magnesium perchlorate, phosphorus pentoxide, ion exchange resin) or an electronic cooler.
Then, the moisture-free gaseous mixture lS sent to the thermal conductivity gas chromatograph for detecting nitrogen and carbon dioxide, which may be any conventional one. Both a single column passage type and a double column passage type are utilizable. In the separation column, any conventional packing material for gas chromatography may be used, and specific examples are silica gel, activated car-bon, porous polymer beads, etc.
The analytical method and apparatus of the present invention will be hereinafter illustrated in details with ~' reference to the accompanying drawings in which~

-Figure 1 is a block diagram showing an embodiment of the invention for determining total nitrogen and carbon contents; and Figure 2 is a graph of nitrogen and carbon dioxide chromatogram peaks.
In Figure 1, an inert gas (e.g. helium) available as the carrier gas from a gas cylinder (1) flows through a conduit (2) and branches into two directions. In one direc tion, the gas is led at a constant flow rate through a pres-sure controller (4), a pressure gauge (6) and a conduit (25)into the reference side of a gas chromatograph. In the other direction, the gas runs at a constant flow rate through ' `
a pressure controller (3) and a pressure gauge (5) to a con-duit (7). Fxom conduit 7 it passes through valve (8), which has three flow paths and in Figure 1 is postioned for analy-zing, and through heated conduit 9 to reactor tube inlet (11).
A reactor tube (12) is provided with an inlet (11) ;~
and an outlet (18) for the carrier gas, and the inlet (11) also serves to introduce a specimen to be analyzed there-through. In the reactor tube (12), is a destructive oxida- ;
tion catalyst zone (13), a reducing agent zone (14) and an oxidizing agent zone (15). Furnaces (16j and (17) are provided for heating respectively the destructive'oxidation ~
catalyst zone and the zones of the reducing agent and of the ~ ;
oxidizing agent to maintain those zones at elevated temper-atures.
An aqueous solution containing nitrogenous and carbonaceous materials (usually about 10 to 100 ~1) as the specimen is introduced into the reactor tube (12) from the inlet (11) by the use of an appropriate supply means (10) such as a microsyringe or an automatic weighing injector.
The gaseous mixture formed in the reactor tube (12) is ~

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~OS~36 carried with the carrîer gas through the outlet (18) and a conduit ~19) to a moisture removal means (20). The gaseous mixture after removal of the moisture is sent through a conduit (21), the valve (8) and a conduit (22) into a thermal conductivity gas chromatograph wherein separation columns (23) and (26) are packed with packing ma~erials. The signal obtained from a thermal conductivity-detector (24) is recorded on a recoder (30) through a sig-nal line (29).
Analysis may be made on the basis of the peak area or the peak height in the recorded chromatogram. The total nitrogen and carbon contents in the specimen can be directly recorded by a data analysis apparatus (31) such as a digital integrator. The valve (8) is adjustable to provide for separation of the gas chromatograph on the replacement of the materials packed in the reactor tube (12). When the valve (8) is changed from the position as indicated in Figure 1, the conduit (7) is connected to the conduit (22) so that the carrier gas flows directly into the gas chromatograph. The conduits (27) and (21) are respectively connected with the conduits (9) and (28), whereby communication to atmosphere is made. The conduit (9) is heated, for instance, at about 120C for preventing ;
the condensation of water resulting from the partial back current of the gaseous mixture on the injection of the ~-specimen.
Advantageously, the analytical method of the invention can determine the total nitrogen and/or carbon -contents in aqueous systems including nitrogenous and/or carbonaceous materials rapidly and accurately by the use of a simple apparatus without any high technical skill or experience or any special knowledge. Irrespective - 10 - .
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of the state of the nitorgenous and/or carbonaceous materials ! `
existing in aqueous systems and even in the presence of such high concentrations of salts as in sea water, the total nitrogen and/or carbon conten-ts can be determined. Also, the total organic carbon content can he readily determined by treatment oE the specimen with an inorganic acid such as hydrochloric acid for decarboxylation or by using an appara-tus for measurement of inorganic carbon in combination~
Since the apparatus of the invention is quite simple, it is easily maintained. Further it can be made automatic without any difficulty, and the continuous moni-toring of the total nitrogen and/or earbon contents in various aqueous systems beeoms possible.
Praetical and presently preferred embodiments of the invention are illustratively shown in the following Examples.
Example 1 T~e apparatus as shown in Figure 1 of the accompany-ing drawings was used.
In a mullite pipe of 10.5 mm in inner diameter and 30 em in length as the reaetor tube, eylindrical platinum guaze (60 mesh; 5 cm in length) as the destructive oxidation catalyst, reduced eopper wire (about 8 ml; 0.6 mm in dia- ~
metér; 5 mm in length) as the reducing agent and pelletized ~ ~ `
trieobalt tetroxide (about 6 ml; 10 to 24 mesh) as the ~ ;
oxidizing agent were eharged SQparating eaeh material from others with quartz cotton and also plaeing quartz eotton at the lowest part. The destruetive oxidation eatalyst zone '., '-',',: ' ~, ' . . ~ .

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was kept at 950C, and the reducing agent zone and the oxidizing agent zone were maintained at 500C. In a stain-less steel column of 1 m in length as the separation column in the gas chromatograph, silica gel (60 to 80 mesh) was charged, and the temperature of the column was set at 80C.
The temperature of the thermal conductivity detector was kept at 100C. Helium as the carrier gas was flowed ~t a rate of 60 ml/min.
An aqueous solution containing sodium nitrate and potassium hydrogen phthalate (20 ~1) was introduced into the reactor tube by the aid of a microsyringe, and calibration curves were prepared by plotting the relationships of the peak areas of nitrogen and carbon dioxide on the chromato-gram with the total nitrogen and carbon contents on a graph as shown in Figure 2 of the accompanving drawings wherein the marks (o) and (x) indicate respectively the ones of nitrogen and o~ carbon.
Using the calibration curves thus obtained, the total nitrogen and carbon contents in aqueous solutions of ~ ~
various nitrogenous and carbonaceous materials were measured. ~ ~`
The results are shown in Table 1 wherein each value is the average in four repetitions.
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Table 1 Test compound Known total ¦ Measured total content (ppm) I content (ppm) .
N ¦ C ¦N C
L-Methionine 93 400 193 900 4-Aminoantipyrine127 400 ~128 401 Glyci.ne 100 172 102 174 ~:
Hexamethylene- 50 64 52 65 :~
tetramine : :
Polyvinyl alcohol _ 55 _ 57 . Urea 200 86 201 87 Sodium thiocyanate 165 142 160 145 Sodium hydrogen _ 200 _ 200 carbonate .
Ammonium chloride . 500 _ 502 _ . .
Pyridine + 3~ NaCl 86 371 86 372 ~ .
Glycine + 3% Na2SO4 200 343 202 339 ~
Aniline + 3% NaCl ¦ 77 397 77 396 : ;
Example 2 :
.
The total nitrogen and carbon contents in aqueous `~
solutions of various nitrogenous and carbonaceous materials were measured in the same manner as in Example L but using .
~ 0.1 ~ p~lladium deposited on alumina (particle size, 20 to ~ :
40 mesh; about 4 ml) in place of platinum gauze.
The results are shown in Table 2.
Table 2 ,~
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Test compound Known total ¦ Measured total ~ :
. content (ppm) ~ content (ppm) Aniline _ _ _ 198 39 19 Pyridine 86 371 ~ 84 372 NaHCO3+ 3% NaCl _ 500 _ 502 -Urea + 3% NaCl200 86 201 85 - ~ : . -.. . - . . . . .. ..
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~(~5~a336 _xample 3 The total nitrogen contents in aqueous solutions of various nitrogenous materials were determined in the same manner as in E~xample 1 but using the reactor tube wherein the oxidizing agent was eliminated.
The results are shown in Table 3.
Table 3 ~ .
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Test compound Total N content (ppm) Known ¦ Measured Sodium nitrite100 98 Sodium azide 100 102 Sulfamic acid 60 61 mmonium sulfate200 199 .: , _ ._ Example 4 In a mullite pipe of 7 mm in inner diameter and 30 cm in length as the reactor tube, cylindrical platinum gauze (60 mesh; 1 cm in length) as the destructive oxidation catalyst and pelletized tricobalt tetroxide (about 6 ml; 10 to 24 mesh) as the oxidizing agent were charged separating ~
each material from others with quartz cotton and also ~ ~ -placing quartz cotton at the lowest part. The destructive oxidation catalyst zone was kept at 950C, and the lxidizing agent zone was maintained at 500C. In a stainless steel ~-column of 1 m in length as the separation column in the gas chromatograph, silica gel (60 to 80 mesh) was charged, and the temperature of the column was set at 80C. The temper~
ature of the thermal conductivity detector was kept at 80C.

Helium as the carrier gas was flowed at a rate of 60 ml/min. -;
. Using the calibration curve prepared by the use of an aqueous solution containing potassium hydrogen phthalate, ., . :

~lO54036 the total carbon contents in aqueous solutions of various carbonaceous materials were measured. The injected amount of the specimen was 20 ~1.
The results are shown in Table 4.
Tab].e ~ :

Test compound . Total C content (ppm) . Known Measured _ _ o-Cresol . 47 48 . m-Cresol 109 108 Glucose 100 98 Benzoic acid 69 70 . ~ -Sodium ~-naphthalene- 51 52 sulfonate :
m-Toluidine 248 246 ..
Aniline 623 638 : :
Pyridine 742 745 . .
: Example 5 :::-In a quartz pipe of 7 mm in inner diameter and 20 ~ ~ }
cm in length as the reactor tube, cobalt oxide (about 3 ml) ~ -as the oxidizing agent was charged, and the temperature was ~ -:
kept at 800C. In a stainless steel column of 2.5 m in length as the separation column in the gas chromatograph, silica gel (60 to 80 mesh) was charged, and the temperature : of the column was maintained at 80C. The t.emperature of - ; -.
the thermal conductivity detector was set at 80C. Helium ;: as the carrier gas was flowed at a rate of 40 ml/min.
Using the calibration curve prepared by the use of an aqueous solution containing potassium hydrogen phthalate, the total carbon contents in aqueous solutions of various carbonaceous.materials were measured. The injected amount ~ :~
of the specimen was 20 ~
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-lQ54~36 The results are shown in Table 5.
Table 5 Test compound Total C content (ppm) :, _ _ : Known Measured _.
Benzoic acid 100 107 Urea 100. 94 :
Alanine 100 96 Hippuric acid 104 105 :.
Glucose 105 109 :~
Sodium ~-naphthalene g8 97 sulfonate ': '. . ' :.
Example 6 . The total carbon content in an aqueous solution of ; potassium hydrogen phthalate and sodium hydrogen carbonate was measured in the same manner as in Example 5 but using as ~ -the oxidizing agent(s) manganese oxide (about 3 ml) (Case A), 5 % palladium deposited on asbestos (about 1 ml) and cobalt oxide (about 3 ml) (Case B) or pelletized silver ~; (about 1 ml) and cobalt oxide (about 3 ml) (Case C).
The results are shown in Table 6.
Table 6 , _ ; .. ..
. Test compound Total C content (ppm) ~ :
. _ .
. Known Measured Potassium hydrogen 162166 165 171 phthalate 810 799 816 832 Sodium hydrogen 100 109 97 104 -carbonate 500 ) _ :~

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Claims (24)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An analytical method for determination of the total content of nitrogen, carbon or both nitrogen and carbon in an aqueous solution containing at least one of nitrogenous and carbonaceous materials as a specimen, which comprises introducing the aqueous solution with an inert gas containing substantially no nitrogen or carbon dioxide as a carrier gas into a reactor tube packed with at least one of a destructive oxidation catalyst, a reducing agent and an oxidizing agent, maintaining this at elevated temperatures so as to decompose any nitrogenous material to nitrogen and carbonaceous material to carbon dioxide and measuring the amounts of any nitrogen and carbon dioxide in the resulting gaseous mixture from the reactor tube by the use of a thermal conductivity gas chromatograph.

2. The method according to claim 1, wherein the reactor tube is packed with a destructive oxidation catalyst, a reducing agent and an oxidizing agent.

3. The method according to claim 2, wherein the destructive oxidation catalyst, the reducing agent and the oxidizing agent are heated at 700 to 1200°C, at 300 to 700°C
and at 300 to 700°C, respectively.

4. The method according to claim 1, wherein the reactor tube is packed with a destructive oxidation catalyst and a reducing agent.

5. The method according to claim 4, wherein the destructive oxidation catalyst and the reducing agent are heated at 700 to 1200°C and at 300 to 700°C, respectively.

6. The method according to claim 1, wherein the reactor tube is packed with a destructive oxidation catalyst and an oxidizing agent.

7. The method according to claim 6, wherein the destructive oxidation catalyst and the oxidizing agent are heated at 700 to 1200°C and at 300 to 700°C, respectively.

8. The method according to claim 6, wherein the destructive oxidation catalyst and the oxidizing agent are heated at 700 to 1200°C.

9. The method according to claim 1, wherein the reactor tube is packed with an oxidizing agent.

10. The method according to claim 9, wherein the oxidizing agent is heated at 700 to 1200°C.

11. The method according to claim 1, wherein the destructive oxidation catalyst comprises at least one metal selected from the group consisting of metals belonging to Group IB or VIII in the periodic table.

12. The method according to claim 11, wherein the metal is platinum or palladium.

13. The method according to claim 1, wherein the reducing agent comprises at least one metal selected from the group consisting of copper, nickel, iron, cobalt and zinc.

14. The method according to claim 13, wherein the metal is reduced copper or reduced nickel.

15. The method according to claim 1, wherein the oxidizing agent comprises at least one oxide selected from the group consisting of oxides of cobalt, nickel, vanadium, tungsten, silver and manganese.

16. The method according to claim 15, wherein the oxide is an oxide of cobalt.

17. An analytical method for determination of the total nitrogen and carbon contents in an aqueous solution containing nitrogenous and carbonaceous materials as a specimen, which comprises introducing the aqueous solution with an inert gas containing substantially no nitrogen and carbon dioxide as a carrier gas into a reactor tube packed with a destructive oxidation catalyst, a reducing agent and an oxidizing agent so as to decompose the nitrogenous and carbonaceous materials respectively to nitrogen and carbon dioxide and measuring the amounts of nitrogen and carbon dioxide in the resulting gaseous mixture from the reactor tube by the use of a thermal conductivity gas chromatograph, the destructive oxidation catalyst, the reducing agent and the oxidizing agent being heated at 700 to 1200°C, at 300 to 700°C and at 300 to 700°C, respectively.

18. The method according to claim 17, wherein the inert gas is helium.

19. The method according to claim 17, wherein the reactor tube is packed with the destructive oxidation catalyst, the reducing agent and the oxidizing agent in this order.

20. An analytical method for determination of the total nitrogen content in an aqueous solution containing nitrogenous materials as a specimen, which comprises introduc-ing the aqueous solution with an inert gas containing substantially no nitrogen as a carrier gas into a reactor tube packed with a destructive oxidation catalyst and a reducing agent so as to decompose the nitrogenous materials to nitrogen and measuring the amount of nitrogen in the resulting gaseous mixture from the reactor tube by the use of a thermal conductivity gas chromatograph, the destructive oxidation catalyst and the reducing agent being heated at 700 to 1200°C and at 300 to 700°C, respectively.

21. An analytical method for determination of the total carbon content in an aqueous solution containing carbonaceous materials as a specimen, which comprises introducing the aqueous solution with an inert gas contain-ing substantially no carbon dioxide as a carrier gas into a reactor tube packed with a destructive oxidation catalyst and an oxidizing agent so as to decompose the carbonaceous materials to carbon dioxide and measuring the amount of carbon dioxide in the resulting gaseous mixture from the reactor tube by the use of a thermal conductivity gas chromatograph, the destructive oxidation catalyst and the oxidizing agent being heated at 700 to 1200°C and at 300 to 700°C, respectively.

22. An analytical method for determination of the total carbon content in an aqueous solution containing carbonaceous materials as a specimen, which comprises introducing the aqueous solution with an inert gas contain-ing substantially no carbon dioxide as a carrier gas into a reactor tube packed with a destructive oxidation catalyst and an oxidizing agent so as to decompose the carbonaceous materials to carbon dioxide and measuring the amount of carbon dioxide in the resulting gaseous mixture from the reactor tube by the use of a thermal conductivity gas chromatograph, the destructive oxidation catalyst and the oxidizing agent being heated at 700 to 1200°C.

23. An analytical method for determination of the total carbon content in an aqueous solution containing carbonaceous materials as a specimen, which comprises introducing the aqueous solution with an inert gas contain-ing substantially no carbon dioxide as a carrier gas into a reactor tube packed with an oxidizing agent so as to decompose the carbonaceous materials to carbon dioxide and measuring the amount of carbon dioxide in the resulting gaseous mixture from the reactor tube by the use of a thermal conductivity gas chromatograph, the oxidizing agent being heated at 700 to 1200°C.

24. An analytical apparatus for determination of the total nitrogen and carbon contents in an aqueous solu-tion containing at least one of nitrogenous and carbona-ceous materials as a specimen, which comprises a means for supplying an inert gas containing substantially no nitrogen and carbon dioxide, a reactor tube provided with an inlet and an outlet through which the inert gas is passed and packed with at least one of a destructive oxidation cata-lyst, a reducing agent and an oxidizing agent, an injection means for introduction of the specimen into the reactor tube, a means for removal of moisture from the gaseous mixture produced in the reactor tube and a gas chromato-graph provided with a thermal conductivity detector, said means, said reactor tube and said gas chromatograph being connected with conduits.