Anion exchange resin and slow precipitation preclude the need for pretreatments in silver phosphate preparation for oxygen isotope analysis of bioapatites

Sarah Pederzani*, Christophe Snoeck, Ulrike Wacker, Kate Britton

*Corresponding author for this work

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Preventing the inclusion of oxygen bearing compounds from the organic fraction of skeletal tissues is often considered key to obtaining faithful δ 18O measurements of the mineral fraction, which are widely used across the archaeological, forensic and geochemical sciences. Here we re-explore the contentious issue of organic removal pretreatments by establishing how different silver phosphate preparation methods perform in producing pure silver phosphates with a faithful biogenic isotopic signal. We then compare this baseline performance to a pretreatment based approach. Our results show that anion exchange purification combined with slow precipitation of silver phosphate consistently produces silver phosphates of high purity without prior pretreatment. Rapid precipitation protocols without additional purification, while effective and time-efficient for low organic samples such as enamel, suffer from the inclusion of substantial amount of organic matter in silver phosphates from bone or dentine samples. However, despite substantial organic contamination in such samples, δ 18O values do not necessarily show substantial shifts. Further study is needed to clarify the reason for this, but for now the use of an anion exchange based protocol represents the most cautious approach to processing bone and dentine samples and we recommend its use for such samples. Confirming previous work we find H2O2 pretreatment to be only partially effective at removing higher amounts of organic matter. Both H2O2 and NaOCl pretreatments show unpredictable side effects on δ 18O values of both bones and inorganic samples. We additionally find no indication that the presence of organic material hinders the dissolution of bioapatite samples.
Original languageEnglish
Article number119455
Number of pages15
JournalChemical Geology
Early online date7 Jan 2020
Publication statusPublished - 20 Feb 2020

Bibliographical note

The authors would like to thank Wolfram Meier-Augenstein (Robert Gordon University) for advice on TC/EA677 IRMS and to Raquel Maria (Kimmel Center for Archaeological Science, Weizmann Institute of Science) for advice on FTIR-ATR. Thanks to Birke Brumme (MPI EVA) for practical support with sample preparation. Thanks are also due to Sahra Talamo (MPI EVA/University of Bologna) for providing aliquots of the S-EVA-2000 and S-EVA-2001 in-house bone standards and to Klervia Jaouen (MPI EVA/Géosciences Environnment Toulouse) for providing extracted collagen used in the preparation of synthetic bones. This research was funded by the Max-Planck-Society as part of SP’s doctoral research. The authors would also like to thank the Max-Planck-Society, the University of Aberdeen and the Vreije Universiteit Brussels for professional and financial support during the production of this manuscript. CS thanks the Research Foundation - Flanders for his post-doctoral fellowship. We also thank Christophe Lécuyer and an anonymous reviewer for their valuable comments and suggestions.


  • bioapatite phosphate
  • bone
  • enamel
  • palaeoclimate reconstruction
  • mobility
  • δ18O
  • delta O-18
  • Enamel
  • Bioapatite phosphate
  • Mobility
  • Palaeoclimate reconstruction
  • Bone
  • δ O


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