Measuring apparatus and method for determining the total organic carbon of a dissolved sample

A method for determining a total organic carbon content of a sample dissolved in a liquid medium, the method comprising:

• providing a measuring apparatus comprising:
• a reactor block made of an electrically conductive and corrosion-resistant material and configured as a housing which includes a housing wall, which includes an inlet into and an outlet out of the reactor block,
• wherein the housing wall encloses a flow chamber configured to enable digestion of the sample as to enable determining the total organic carbon of the sample, wherein a light source is arranged in the flow chamber as to enable a flow of the sample around a luminous section of the light source as to irradiate the sample with light from the light source, and
• at least one conductivity measurement device disposed in the reactor block and comprising:
• an external electrode, wherein the reactor block is configured as the external electrode of the at least one conductivity measurement device;
• a first internal electrode disposed within a first conductivity measuring cell defined within the reactor block upstream of the flow chamber relative to the flow of the sample;
• a second internal electrode disposed within a second conductivity measuring cell defined within the reactor block downstream of the flow chamber;
• and
• a control and evaluation unit configured to determine the content of total organic carbon in the sample based on conductivities detected by the at least one conductivity measurement device, wherein the housing wall further defines a first connecting channel configured to supply the sample from the inlet to the at least one conductivity measurement device;
• introducing the sample through the inlet of the reactor block into the first connecting channel in which the sample is heated to a reactor temperature;
• conveying the sample into the first conductivity measuring cell and performing a first measurement of conductivity of the sample using the control and evaluation unit;
• supplying the sample from the first conductivity measuring cell into the flow chamber in which the sample flows around the light source in an annular gap between an inner wall of the flow chamber and an outer surface of the light source or of a sealing device in which the light source is disposed, whereby radiation of the light source effects digestion of the sample, resulting in formation of carbon dioxide;
• conveying the sample from the flow chamber into the second conductivity measuring cell and performing a second measurement of conductivity of the sample using the control and evaluation unit;
• discharging the sample from the second conductivity measuring cell through the outlet of the reactor block;
• and
• determining the total organic carbon content of the sample using the first and second measurements of conductivity.