ABSTRACT. Extraneous carbon (C ex ) added during chemical processing and isolation of black carbon (BC) in environmental matrices was quantified to assess its impact on compound specific radiocarbon analysis (CSRA). Extraneous carbon is added during the multiple steps of BC extraction, such as incomplete removal of solvents, and carbon bleed from the gas chromatographic and cation columns. We use 2 methods to evaluate the size and 14 C values of C ex in BC in ocean sediments that require additional pretreatment using a cation column with the benzene polycarboxylic acid (BPCA) method. First, the direct method evaluates the size and 14 C value of C ex directly from the process blank, generated by processing initially empty vials through the entire method identically to the treatment of a sample. Second, the indirect method quantifies C ex as the difference between processed and unprocessed (bulk) 14 C values in a variety of modern and 14 C-free or "dead" BC standards. Considering a suite of hypothetical marine sedimentary samples of various sizes and 14 C values and BC Ring Trial standards, we compare both methods of corrections and find agreement between samples that are >50 µg C. Because C ex can profoundly influence the measured 14 C value of compound specific samples, we strongly advocate the use of multiple types of process standards that match the sample size to assess C ex and investigate corrections throughout extensive sample processing.