A device for measuring the total organic carbon content (TOC) of a sample fluid comprises a measuring cell (2) defining a volume (3) for containing a sample fluid and an excimer lamp (20) arranged to cause an oxidation reaction of the sample fluid by emitting radiation onto the sample fluid in the volume (3). A pair of electrodes is arranged to measure the conductivity of the sample fluid during the oxidation reaction and at least one temperature senor (31) is arranged on the measuring cell (2) to measure a temperature that is related to the sample fluid. The total organic carbon content (TOC) of the sample fluid is determined on the basis of the measured conductivity compensated by the temperature related to the sample fluid.