The Preparation of Water (DIC, DOC) and Gas (CO₂, CH₄) Samples for Radiocarbon Analysis at AEL-AMS, Ottawa, Canada

Abstract

ABSTRACT Sample preparation techniques for radiocarbon analysis of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) in freshwater, as well as CO 2 and CH 4 in gas mixtures are presented. Focused efforts have been on developing a robust and low-background wet oxidation extraction method for DOC in freshwater, following routine methods developed for stable carbon isotope analysis and adapted for radiocarbon ( 14 C) analysis. DIC (by acidification) and DOC (by wet oxidation) are converted to CO 2 in pre-baked septum-fitted borosilicate bottles, where the resulting CO 2 is extracted from the dissolved and headspace portions on a low-flow He-carrier flow-through system interfaced to a vacuum extraction line. A peripheral CH 4 extraction line interfaces to the flow line to separate CH 4 from environmental samples following the methods of Pack et al. 2015. High sample throughput and low blanks are achievable with this method. DIC and DOC blanks are consistently <0.7 pMC, while CO 2 and CH 4 blanks are typically <0.1 pMC.