Methodological investigations on DOC determinations by the HTCO method

Results are presented on the function and use of the catalyst in the commonly employed high-temperature catalytic oxidation (HTCO) method for determination of organic carbon concentrations, The instrument used was a Shimadzu TOC 5000 analyzer with a 0.5% platinum-coated aluminum oxide catalyst, Some basic considerations on gas flow rates and volumes of the catalyst kiln, together with experiments using carrier gas with and without oxygen, led to the conclusion that O-2 is unlikely as the source of reacted oxygen in the HTCO oxidation of organic carbon. Results from injections of C-14-labelled organic material showed that no residual carbon remains on the catalyst surface after a large number of injections, This indicates that the oxidation of organic carbon to gaseous compounds is complete and the catalyst is not a source of carry over signal between injections. The blank signal from injection of water probably originates from carbonaceous compounds contained in the catalyst particles. A series of salt water injections (salinity 34.4) showed that > 2500 injections can be made without deterioration of catalyst performance.