On the isolation of elemental carbon for micro-molar ¹⁴C accelerator mass spectrometry; evaluation of alternative isolation procedures, and accuracy assurance using a hybrid isotopic particulate carbon reference material

L. A. Currie (1) , J. D. Kessler (1)

1 NIST - National Institute of Standards and Technology [Gaithersburg]

The primary objective of the research reported here has been the development of an hybrid reference material (RM) to serve as a test of accuracy for elemental carbon (EC) isotopic (¹⁴C) speciation measurements. Such measurements are critically important for the quantitative apportionment of fossil and biomass sources of ''soot'' (EC), the tracer of fire that has profound effects on health, atmospheric visibility, and climate. Previous studies of ¹⁴C-EC measurement quality, carried out with NIST SRM 1649a (Urban Dust), showed a range of results, but since the ''truth'' was not known for this natural matrix RM, one had to rely on isotopic-chemical consistency evidence (¹⁴C in PAH, EC) of measurement validity (Currie et al., 2002). Components of the new Hybrid RM (DiesApple), however, have known ¹⁴C and EC composition, and they are nearly orthogonal (isotopically and chemically). NIST SRM 2975 (Forklift Diesel Soot) has little or no ¹⁴C, and its major compositional component is EC. SRM 1515 (Apple Leaves) has the ¹⁴C content of biomass-C, and it has little or no EC. Thus, the hybrid RM can serve as an absolute isotopic test for the absence of EC-mimicking pyrolysis-C from SRM 1515 in the EC isolate of the hybrid RM, together with testing for conservation of its dominant soot fraction through the isolation procedure.

Domaines: Océan, Atmosphère

L. A. Currie, J. D. Kessler. On the isolation of elemental carbon for micro-molar ¹⁴C accelerator mass spectrometry; evaluation of alternative isolation procedures, and accuracy assurance using a hybrid isotopic particulate carbon reference material. Atmospheric Chemistry and Physics Discussions, 2005, 5 (3), pp.3341-3366. ⟨hal-00301463⟩