The calcium isotope composition (δ44/40Ca) of NIST SRM 915b and NIST SRM 1486

The calcium isotopic composition of NIST SRM 915b and 1486 provided by the National Institute of Standards and Technology was analysed. The delta Ca-44/40 values of the two reference materials relative to NIST SRM 915a were: NIST SRM 915b = +0.72 +/- 0.04 parts per thousand and NIST SRM 1486 = -1.01 +/- 0.02 parts per thousand. NIST SRM 1486 did not require any chemical separation prior to measurement.