Radiocarbon (¹⁴C)-based source apportionment of aerosol carbon fractions requires the physical separation of OC from EC and minimizing of the incorporation of extraneous carbon. Using pure and mixed reference materials ranging in age from modern to fossil, we show that the ECT9 protocol effectively isolates OC and EC. This work expands existing opportunities for characterizing and monitoring sources of carbonaceous aerosols, including µg C-sized samples from the Arctic.