A new procedure for titanium separation in geological samples for 49Ti/47Ti ratio measurement by MC-ICP-MS

Abstract

Here we present a convenient and efficient procedure for separating Ti from matrix elements in geological samples using a dual-column loaded with Ln-spec and AG50W-X12 resins. Boric acid was adopted to reduce the use of HF and to avoid precipitation of Ti. Ln-spec resin was used to remove most of the matrix elements. The residual matrix elements, such as Mo, V, Cr and trace Fe, were further removed using a column filled with AG50W-X12 resin. This procedure results in a Ti recovery near 100% with very low matrix element concentrations in the final Ti solution which has little influence on the measurement of Ti isotopes. Ti isotope measurement was carried out on a Neptune Plus multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS) with a standard-sample-standard bracketing technique. The intermediate precision of the NIST SRM 3162a solution for δ⁴⁹Ti was 0.047‰ (2SD, N = 130). The δ⁴⁹Ti_OL-Ti values (recalculated to the OL-Ti standard) of 14 geological reference materials and six kinds of minerals selected from a quartz monzonite were measured using this method, and the results of the reference materials were in good agreement with the published results within analytical error. The 14 geological reference materials display large δ⁴⁹Ti variations up to 1.7‰. Meanwhile, the variations of δ⁴⁹Ti_OL-Ti values of the six minerals are up to 1.5‰, indicating significant Ti isotope fractionation during the mineral crystallization process. Therefore, the analytical procedure established here provides a powerful tool to investigate Ti isotope variations. The results of the geological samples in this study show the potential application of Ti isotopes in tracing geological processes.