A method and an apparatus is provided for the determination of the content of organic carbon (TOC) of liquids, in particular ultra-pure water, wherein a liquid sample under investigation is located in a reaction chamber and carbon present in the liquid is statically oxidized to mainly carbon dioxide. After oxidation of the carbon, the sample quantity is transferred to a measuring cell, connected to the reaction chamber by liquid entering the reaction chamber from the outside the reaction chamber, where (i.e. in the measuring cell) the carbon concentration of the sample, which is proportional to the carbon content, is dynamically registered as the sample flows through the measuring cell.