Monitoring the equilibration of 228Th and decay products over time after extraction from ivory

  • Andreas SchmidbergerEmail author
  • Robert Schupfner


The worldwide population of elephants shows a rapid decline due to trafficking of ivory. Hence, a method is needed for the age determination to distinguish legal from illegal ivory. The analysis of 228Th and 232Th in ivory can be used for this purpose. This study provides a technique for the analysis of 228Th in ivory. The thorium was extracted from ivory and measured after various time periods applying α-spectrometry until a secular radioactive equilibrium between 228Th and its decay products was established. An equilibration period of 32 days was found. The uncertainty of the determination of the activity of 228Th could be reduced by integrating the counts of the equilibrated decay products into the determination process.


Ivory trafficking Age determination Secular radioactive equilibration Thorium series α-Spectrometry 



The authors thank the zoo of Wuppertal, which supported this work with an ivory sample.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© Akadémiai Kiadó, Budapest, Hungary 2019

Authors and Affiliations

  1. 1.Institute of Analytical Chemistry, Chemo- and BiosensorsUniversity of RegensburgRegensburgGermany

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