Abstract
An apparatus for measuring the concentration of total organic carbon in water with a PCO2 electrode as a sensor was constructed and its feasibility was studied. The oxygen carrier gas (approximately 300 ml/min) is used instead of air, because nitrogen in air is converted into NOx which interferes with the PCO2 measurement. The sample combustion chamber is maintained at 800°C, whereas the oxidation chamber is operated at 600°C. Two ml of aqueous sample is injected onto a platinum boat in the combustion chamber with a roller pump and evaporated gradually. Carbonaceous materials are oxidized to carbon dioxide with a Pt-Rh catalyst on alumina. Water vapor is removed at room temperature by a cooling trap, and the carbon dioxide is absorbed in 2 ml of 0.5 M NaOH solution. The solution is acidified with 1 ml of 2 M HCl and introduced into a cell, where the potential of a PCO2 electrode is measured. The content of total organic carbon in the sample was calculated from a calibration curve obtained with the standard solution in the same manner. The time required for an analysis is about 8 min, and the precision is about ±20%.
