Optimization of a TOC/DOC analyzer with nM precision

Marine dissolved organic carbon (DOC) represents a large and dynamic reservoir of reduced carbon (662 x 10¹⁵g C) that is comparable in size to the Earth’s reservoir of atmospheric CO_2. Measurements of DOC concentration in seawater have dramatically improved since the mid 1990s with the use of standard high temperature combustion (HTC) techniques, but these measurements are still subject to shore-based analyses, high blank variability, and micromolar resolution (CV ~3%). At present, the analytical precision of HTC methods is insufficient to address more specific studies tracing DOC uptake and respiration, conservative mixing of water masses, photochemical oxidation, and photosynthesis. To overcome these challenges, we developed a prototype TOC/DOC analyzer capable of nanomolar precision and improved seaworthiness that utilizes a flow-through system combining UV and wet chemical oxidation. We show progress in the optimization of this novel instrument that, unlike current HTC methods, has potential application for shipboard analyses (both discrete samples and underway), detection of mineralization processes in situ, and deployment in autonomous monitoring systems.