O Brinkkemper1, F Braadbaart2, B van Os1, A van Hoesel1, A A N van Brussel3, R Fernandes4,5. 1. Cultural Heritage Agency, PO Box 1600, 3800, BP, Amersfoort, The Netherlands. 2. Department of Earth Sciences-Geochemistry, Utrecht University, PO Box 80021, 3058, TA, Utrecht, The Netherlands. 3. Department of Plant Molecular Biology (Sylvius Laboratories), Leiden University, PO Box 9502, 2300, RA, Leiden, The Netherlands. 4. Department of Archaeology, Max Planck Institute for the Science of Human History, Kahlaische Strasse 10, D-07745, Jena, Germany. 5. McDonald Institute for Archaeological Research (University of Cambridge), Downing Street, Cambridge, CB2 3ER, UK.
Abstract
RATIONALE: Isotopic analysis of archaeological charred plant remains offers useful archaeological information. However, adequate sample pre-treatment protocols may be necessary to provide a contamination-free isotopic signal while limiting sample loss and achieving a high throughput. Under these constraints, research was undertaken to compare the performance of different pre-treatment protocols. METHODS: Charred archaeological plant material was selected for isotopic analysis (δ13 C and δ15 N values) by isotope ratio mass spectrometry from a variety of plant species, time periods and soil conditions. Preservation conditions and the effectiveness of cleaning protocols were assessed through Fourier transform infrared spectroscopy and X-ray fluorescence (XRF) spectrometry. An acid-base-acid protocol, successfully employed in radiocarbon dating, was used to define a contamination-free isotopic reference. Acid-base-acid isotopic measurements were compared with those obtained from untreated material and an acid-only protocol. RESULTS: The isotopic signals of untreated material and the acid-only protocol typically did not differ more than 1‰ from those of the acid-base-acid reference. There were no significant isotopic offsets between acid-base-acid and acid-only or untreated samples. Sample losses in the acid-base-acid protocol were on average 50 ± 17% (maximum = 98.4%). Elemental XRF measurements showed promising results in the detection of more contaminated samples albeit with a high rate of false positives. CONCLUSIONS: For the large range of preservation conditions described in the study, untreated charred plant samples, water cleaned of sediments, provide reliable stable isotope ratios of carbon and nitrogen. The use of pre-treatments may be necessary under different preservation conditions or more conservative measurement uncertainties should be reported.
RATIONALE: Isotopic analysis of archaeological charred plant remains offers useful archaeological information. However, adequate sample pre-treatment protocols may be necessary to provide a contamination-free isotopic signal while limiting sample loss and achieving a high throughput. Under these constraints, research was undertaken to compare the performance of different pre-treatment protocols. METHODS: Charred archaeological plant material was selected for isotopic analysis (δ13 C and δ15 N values) by isotope ratio mass spectrometry from a variety of plant species, time periods and soil conditions. Preservation conditions and the effectiveness of cleaning protocols were assessed through Fourier transform infrared spectroscopy and X-ray fluorescence (XRF) spectrometry. An acid-base-acid protocol, successfully employed in radiocarbon dating, was used to define a contamination-free isotopic reference. Acid-base-acid isotopic measurements were compared with those obtained from untreated material and an acid-only protocol. RESULTS: The isotopic signals of untreated material and the acid-only protocol typically did not differ more than 1‰ from those of the acid-base-acid reference. There were no significant isotopic offsets between acid-base-acid and acid-only or untreated samples. Sample losses in the acid-base-acid protocol were on average 50 ± 17% (maximum = 98.4%). Elemental XRF measurements showed promising results in the detection of more contaminated samples albeit with a high rate of false positives. CONCLUSIONS: For the large range of preservation conditions described in the study, untreated charred plant samples, water cleaned of sediments, provide reliable stable isotope ratios of carbon and nitrogen. The use of pre-treatments may be necessary under different preservation conditions or more conservative measurement uncertainties should be reported.
Authors: Patrick Roberts; Ricardo Fernandes; Oliver E Craig; Thomas Larsen; Alexandre Lucquin; Jillian Swift; Jana Zech Journal: Rapid Commun Mass Spectrom Date: 2018-03-15 Impact factor: 2.419
Authors: Darren R Gröcke; Edward R Treasure; Jonathan J Lester; Kurt J Gron; Mike J Church Journal: Rapid Commun Mass Spectrom Date: 2021-03-15 Impact factor: 2.586