A method for the quantification of dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) in aqueous samples of less than 600 µL is described. Analysis of low volumes is achieved through modification of a Shimadzu HTC TOC analyzer, which in its conventional configuration requires at least 7 mL sample. The modification allows manual injection of sample directly into the high temperature combustion column, bypassing much of the instrument's dead volume. Instrument performance (blank, precision, and response factor) in the low volume configuration was equal to that of the instrument in its native larger volume, auto‐analyzer configuration. The low volume modification is simple, low cost (less than €25) and reversible, taking a matter of minutes to install or remove. It allows routine high precision and accuracy measurement of DOC and TDN in cases where sample volume is limiting. When sample volumes are not limiting, the standard configuration of the Shimadzu is recommended due to the ability to use the auto‐analyzer and reduce the labor required per sample run.