Estimation of dissolved organic carbon (DOC) concentrations in nanoliter samples using UV spectroscopy.

A simple analytical system has been developed and tested for estimating dissolved organic carbon (DOC) concentrations in nanoliter samples of sediment porewaters. The system consists of a loop injector that introduces 200 nL of sample directly into the capillary tubing connected to a scanning UV-VIS detector equipped with a 35-nanoliter capillary flowcell. Analysis of DOC by spectroscopic and high-temperature catalytic oxidation (HTCO) methods on the same samples showed a strong linear correlation between UV absorbance at 254 nm and HTCO-DOC concentration, allowing the DOC quantification. The simplicity and the robustness of the UV system allow DOC measurements in the field at a rate of 30 samples/h. We have used the UV system successfully for determining high-resolution distributions of porewater DOC concentrations in sediments at millimeter scales.