An analytical apparatus for determination of the total nitrogen and/or carbon contents in an aqueous solution containing nitrogenous and/or carbonaceous materials as a specimen, which comprises a reactor tube provided with an inlet and an outlet, said reactor tube being packed with a destructive oxidation catalyst and/or a reducing agent and/or an oxidizing agent, supply means for introducing an inert gas containing substantially no nitrogen and/or carbon dioxide into the inlet of the reactor tube, an injection means for introducing the specimen to be analyzed into the inlet of the reactor tube, moisture removal means for removing moisture from the gaseous mixture produced in the reaction tube, said moisture removal means being disposed downstream from the outlet of the reactor tube, a gas chromatograph provided with a thermal conductivity detector, and disposed downstream of said moisture removal means, and conduit means for providing connection between the reactor tube, the moisture removal means and said gas chromatograph.