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δ 13 C analyses of calcium carbonate: comparison between the GasBench and elemental analyzer techniques
Author(s) -
Skrzypek Grzegorz,
Paul Debajyoti
Publication year - 2006
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.2688
Subject(s) - carbonate , chemistry , calcite , calcium carbonate , analytical chemistry (journal) , mineralogy , isotope , paleosol , accuracy and precision , stable isotope ratio , geology , environmental chemistry , statistics , loess , physics , mathematics , organic chemistry , quantum mechanics , geomorphology
Measurements of stable carbon isotopic composition ( δ 13 C) of carbonates or carbonate‐rich soils are seldom performed in a continuous‐flow isotope ratio mass spectrometer (IRMS) using an elemental analyzer (EA) as an online sample preparation device. Such analyses are routinely carried out with an external precision better than 0.1‰ using a GasBench II (GB) sample preparation device coupled online with a continuous‐flow IRMS. In this paper, we report and compare δ 13 C analyses (86 total analyses) of calcium carbonates obtained by using both the GB and the EA. Using both techniques, the δ 13 C compositions of two in‐house carbonate standards (MERCK carbonate and NR calcite) and ten selected carbonate‐rich paleosol samples (of variable CaCO 3 content) were analyzed, and data are reported in the VPDB scale calibrated against international standards, NBS 18 and 19. For the in‐house standards analyzed by both techniques, a precision better than 0.08‰ is achieved. The analytical errors (1 σ ) computed from multiple analyses of the δ 13 C of both the MERCK and NR obtained by the above two techniques are nearly identical. In general, the 1 σ (internal error) of paleosol analyses obtained in the GB is better than 0.06‰, whereas that for the analyses in the EA (three repetitive analyses of the same sample) varies in the range 0.05–0.21‰. However, for paleosols having more than 85% CaCO 3 , 1 σ is better than 0.15‰ (similar to the instrument precision), and in this case the δ 13 C VPDB of samples obtained by the GB is similar to that obtained by the EA. Our results suggest that the δ 13 C of pure calcium carbonate samples can also be analyzed using the EA technique. Copyright © 2006 John Wiley & Sons, Ltd.