An Alternate Method of Diluting Dissolved Organic Carbon Seawater Samples for 14C Analysis

Abstract

We present a time-saving modification to the ultraviolet (UV) oxidation method for analyzing dissolved organic carbon (DOC) concentration, ∆14C, and δ13C measurements in seawater and standard materials. A low background (~0.2 ± 0.2 μM) was reported for pre-irradiated Milli-Q (MQ) water that was used to dilute samples for DOC 14C analysis (Beaupré et al. 2007). We use MQ water without pre-irradiation (background ~0.9 ± 0.2 μM) to dilute the sample. This method is suitable for small-volume, high-concentration samples (mass of sample DOC overwhelms mass of MQ water DOC). An acceptable precision of ∆14C measurements (5-9‰) is maintained. This revised method reduces the preparation time for diluted DOC ∆14C samples from 2 days to 1 day.