APPARATUS FOR MEASURING THE TOTAL ORGANIC CARBON AND NITROGEN CONTENT OF WATER

The invention relates to an apparatus for measuring the total organic carbon (TOC) and nitrogen (TN) content of water. The TOC value is correctly determined as the sum of the liquid, dissolved and solid substances in a sample of water. The apparatus comprises an NDIR gas analyser for simultaneously measuring the concentration of the gas components CO2 and NO with a phase separator T, a thermal reactor OX, a condenser K and two amplifiers A1 and A2 for the pneumatic signals of the receivers E1 and E2 having an indicator for the measured concentrations TOC and TN. In the phase separator T, the sample is split up into a gaseous and a liquid part. The gaseous part, which essentially contains the inorganic carbon component, the TIC component, in the form of CO2 gas, is cooled in a condenser to such an extent that a substantial component of its water-vapour content precipitates in the condenser as a result of condensation. The dried gaseous part is fed as a reference gas through the reference cells. This measure serves to compensate for the TIC component of the sample and to compensate for the unavoidable water-vapour cross-sensitivity in the measurement of the CO2 and the NO concentration. The gaseous part emerging from the reference cells is again added to the liquid part of the sample in full and is oxidised along with the latter in a thermal reactor. The gas sample produced in this process is loaded with water vapour at the same temperature as the reference gas V using the condenser K and is fed to the measuring chambers of the cells as test gas M, the test gas M containing the total carbon dioxide component and the total nitrogen oxide component of the gas sample.