Comparison of 36Cl measurements at three laboratories around the world

Abstract To verify groundwater dating using 36 Cl, we confirmed the precision of 36 Cl measurements by comparing three laboratories that have routinely measured 36 Cl. This comparison was conducted using the same 15 sample units consisting of a water sample and AgCl precipitation sample. The 36 Cl/Cl ratio of the sample ranged from −15 to 4 × 10 −13 . There was minor uncertainty in measurement of the 36 Cl/Cl ratio among the three laboratories when samples had relatively high ratios of more than 10 −14 . On the other hand, differences in the chemical separation processes are one of major factors in the high degree of uncertainty in measurement when the ratio of 36 Cl/Cl is lower than 10 −14 .