Analytical method and apparatus for the determination of total nitrogen contents in aqueous systems

Claim 2

An analytical method for the determination of the total nitrogen content in an aqueous system, which comprises: (1) introducing a sample aqueous solution together with an inert gas, containing substantially no nitrogen, and carbon monoxide as a carrier gas through a reaction tube, which is packed with a decomposition catalyst, and which is maintained at a temperature of 700° to 1200° C.; (2) passing the resulting gaseous mixture through a condenser, thereby condensing and removing water contained in the gaseous mixture; (3) passing the gaseous mixture through a moisture-absorbing tube; (4) passing the resulting gas through a low temperature reaction tube, which is packed with an oxidizing agent or a reducing agent or both and which is maintained at a temperature of 300° to 700° C.; (5) passing the obtained gas mixture through a carbon dioxide-absorbing tube; (6) sending the gas mixture coming out of the carbon dioxide-absorbing tube to a mass spectrometer; and (7) measuring the nitrogen content of the gas mixture with the mass spectrometer.

Claim 3

The method according to claim 1, wherein said inert gas is helium or argon and said decomposition catalyst comprises platinum or palladium.

Claim 4

The method according to claim 1, wherein said oxidizing agent is copper oxide or cobalt oxide and said reducing agent is reduced copper or reduced nickel.

Claim 5

An analytical apparatus for the determination of the total nitrogen content in an aqueous system comprising: a decomposition tube packed with a decomposition catalyst; a supply means for introducing an inert carrier gas into the inlet of the decomposition tube; an injection means for introducing the sample to be analyzed into the decomposition tube; a heating means for maintaining the decomposition tube at a temperature of 700° to 1200° C.; a condenser means for condensing and removing water from the gaseous mixture produced in the decomposition tube, said condenser means being disposed downstream from the outlet of the decomposition tube; a moisture-absorbing tube packed with a moisture absorber which is disposed downstream from the outlet of the condenser means; a lower temperature reaction tube packed with an oxidizing agent and/or a reducing agent, and disposed downstream from the outlet of the moisture-absorbing tube; a heating means for maintaining the lower temperature reaction tube at a temperature of 300° to 700° C.; a carbon dioxide-absorbing tube packed with a carbon dioxide absorber and disposed downstream from the outlet of the lower temperature reaction tube; a mass spectrometer disposed downstream from the outlet of the carbon dioxide-absorbing tube; a data processing means for determining the total nitrogen content of the sample from mass spectrographic data derived from the mass spectrometer; and conduit means for providing a connection between the decomposition tube, the condenser means, the moisture absorbing tube, the lower temperature reaction tube, the carbon dioxide-absorbing tube and the mass spectrometer.

Claim 6

An analytical apparatus for the determination of the total nitrogen content in an aqueous system comprising: a decomposition tube packed with a decomposition catalyst; a supply means for introducing an inert carrier gas into the inlet of the decomposition tube; an injection means for introducing the sample to be analyzed into the decomposition tube; a heating means for maintaining the decomposition tube at a temperature of 700° to 1200° C.; a condenser means for condensing and removing water from the gaseous mixture produced in the decomposition tube, said condenser means being disposed downstream from the outlet of the decomposition tube; a moisture-absorbing tube packed with a moisture absorber which is disposed downstream from the outlet of the condenser means; a lower temperature reaction tube packed with an oxidizing agent and/or a reducing agent, and disposed downstream from the outlet of the moisture-absorbing tube; a heating means for maintaining the lower temperature reaction tube at a temperature of 300° to 700° C.; a carbon dioxide-absorbing tube packed with a carbon dioxide absorber and disposed downstream from the outlet of the lower temperature reaction tube; a mass spectrometer disposed downstream from the outlet of the carbon dioxide-absorbing tube; a data processing means for determining the total nitrogen content of the sample from mass spectrographic data derived from the mass spectrometer; and conduit means for providing a connection between the decomposition tube, the condenser means, the moisture absorbing tube, the lower temperature reaction tube, the carbon dioxide-absorbing tube and the mass spectrometer.