Absolute isotopic composition and atomic weight of zinc

Gravimetric synthetic mixtures prepared from highly enriched isotopes of zinc in the form of oxides of well defined purity were used to calibrate a thermal ionization mass spectrometer. Measurements on natural zinc samples yielded an absolute isotopic composition of 48.27 (21) at. % Zn-64, 27.98 (5) at. % Zn-66, 4.10 (1) at. % Zn-67, 19.02 (8) at. % Zn-68, and 0.63 (1) at. % Zn-70, and the atomic weight of zinc as 65.409 (6) both with an uncertainty given on the basis of 95% confidence limit. (C) 2001 Elsevier Science B.V.