Accurate determination of Zn in geological and cosmochemical rock samples by isotope dilution inductively coupled plasma mass spectrometry

Inductively coupled plasma mass spectrometry (ICP-MS) procedures with isotope dilution were established for the accurate determination of trace Zn (in the level of 10(-4) to 10(-5) g g(-1)) in several tens of mg of geological and cosmochemical rock samples. Zinc was determined by Zn-66/Zn-67 and Zn-68/Zn-67 ratios with the use of an enriched isotope, i.e. Zn-67. Among possible interferences for Zn isotopes (Zn-66, Zn-67 and Zn-68), molecular ions from ambient gases and sample solutions were found to be negligibly small, whereas doubly charged Ba ions (Ba-132(2+), Ba-134(2+) and Ba-136(2+)) potentially interfered with the three Zn isotopes concerned. Either such interferences were eliminated by chemical separation in the matrix-separation ICP-MS procedure or they were mathematically corrected in the ICP-MS procedure without matrix separation. The three analytical procedure studies were evaluated in terms of analytical capability and data quality.