T03_P03

¹⁴C blank determination for compound-specific radiocarbon analysis of lignin phenols

Cao M¹, Hefter J¹, Grotheer H¹, Mollenhauer G^1,2

¹Alfred Wegener Institute For Polar And Marine Research, Bremerhaven, Germany, ²MARUM-Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany

Compound-specific radiocarbon analysis (CSRA) is one technique commonly used to constrain the cycling of biomarkers, such as lignin, between reservoirs. However, purification procedures of lignin for CSRA are prone to introduce extraneous (blank) carbon into the samples. These blanks will potentially lead to erroneous interpretation of lignin CRSA results, making the assessment of procedural blanks an important prerequisite. We describe a revised method for purification of lignin from sediment and evaluate F¹⁴C and the mass of the associated procedural blank following the method of Sun et al. (2020). We used two commercially available lignin phenol standards with known age and validated the procedure with lignin extracted from a standard sediment using the method of Goñi and Montgomery (2000). We isolated lignin phenols by HLB SPE cartridges (Waters Oasis, 200 mg, 6 ml) followed by single compound collection using high pressure liquid chromatography. Ten lignin-derived compounds were purified with a Phenomenex Synergi Polar-RP column and three compounds were isolated by a ZORBAX Eclipse XDB-C18 column. Radiocarbon analyses of several different sized aliquots of the standard compounds were performed on the miniaturized radiocarbon dating system at Alfred Wegener Institute, Germany (Mollenhauer et al., 2021). Samples were transferred into tin cups and combusted using an elementar analyser coupled with the gas interface system. We report the current status of carbon blanks associated with our preparation protocol for radiocarbon analysis of lignin phenols.