REEVALUATION OF HIGH-TEMPERATURE COMBUSTION AND CHEMICAL OXIDATION MEASUREMENTS OF DISSOLVED ORGANIC-CARBON IN SEAWATER

Various commercial HTC analyzers are now being used in marine laboratories with inconsistent and less than uniform results. A small intercalibration exercise was held in Bermuda to compare results from several commercial HTC analyzers and the traditional wet chemical oxidation method. The exercise utilized a single low carbon water to determine the instrument blank, and a single set of standards was used for all analyses. Five Sargasso Sea water samples from the surface to 4,000 m and a dried extract of dissolved organic matter from a black-water river were used as the samples for comparison. Analyses by the four methods agreed within 15%, and the seawater values were similar to previously published values. The results demonstrate the importance of careful instrument blank determination and of accurate determination of the CO2 peak.