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 laborato ries with inconsistent and less than uniform results. A small intercal ibration exercise was held in Bermuda to compare results from several commercial HTC analyzers and the traditional wet chemical oxidation me thod. The exercise utilized a single low carbon water to determine the instrument blank, and a single set of standards was used for all anal yses. 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 w ere used as the samples for comparison. Analyses by the four methods a greed within 15%, and the seawater values were similar to previously p ublished values. The results demonstrate the importance of careful ins trument blank determination and of accurate determination of the CO2 p eak.