Preliminary test for I measurement of CaCO samples in JAEA-AMS-TONO

Mitsuguchi, Takehiro ; Okabe, Nobuaki*; Miyake, Masayasu*; Matsubara, Akihiro; Fujita, Natsuko   ; Watanabe, Takahiro   ; Kokubu, Yoko   

A preliminary test for AMS I measurement of CaCO samples was performed using a tandem Pelletron AMS system at Tono Geoscience Center, Japan Atomic Energy Agency (JAEA-AMS-TONO). An annually-banded coral collected from Vietnam was used for this test. The procedure of the test was as follows: (1) an annual-band sample of AD 1946-47 from the coral was treated with 1% HCl for removal of its surface portion; (2) the treated sample was dissolved in HPO solution; (3) an aliquot from the sample solution was used for I measurement by ICP-MS; (4) the Woodward iodine standard was added as a carrier to the sample solution; (5) iodine was extracted from the solution by solvent extraction and back-extraction, resulting in an aqueous phase with extracted iodine; (6) AgNO(aq) was added to the aqueous phase to obtain AgI precipitate; (7) the AgI precipitate was mixed with Nb and pressed into a copper cathode for I measurement by JAEA-AMS-TONO. A blank test of this procedure was also made to evaluate the background I effect in the sample preparation. Results we obtained were as follows: (1) the background I/I ratio was [4.3 0.1] 10 and (2) the background-corrected coral I/I ratio was [1.53 0.76] 10. The coral I/I ratio is generally in agreement with previously-reported values of Chang et al. (2016), suggesting that AMS I measurement of CaCO samples has been generally established in JAEA-AMS-TONO.