Separation of titanium from silicates for isotopic ratio determination using multiple collector ICP-MS

Abstract

A new separation method of Ti from silicate materials is presented that is suitable for the determination of natural Ti isotope variations using multi-collector inductively coupled plasma source mass spectrometry (MC-ICP-MS). This method makes possible for the first time the separation of Ti from natural materials, with high purity, high recovery and no introduction of artificial mass fractionation. Following sample decomposition using HF, Ti is separated using a three-column procedure. In the first column using an anion-exchange resin, AG 1X8, major elements and the majority of trace elements are separated. In the second column, after eliminating F⁻ by evaporation with HClO₄ and re-dissolution with H₂O₂–HNO₃, Ti is separated from Zr and Hf using a liquid–liquid extraction resin, U/TEVA. In the third column, which is the same as the first column, trace amounts of Al and P are further removed. Recovery yields were almost unity, and no Ti isotope fractionation occurred from the overall chemical processing. The reproducibilities (2σ) of the Ti isotope ratio measurement for a meteorite (eucrite) and a lamproite were <0.5ε for ε⁴⁷Ti, ε⁴⁸Ti and ε⁴⁹Ti, and <1ε for ε⁵⁰Ti, which were comparable to those for the pure Ti standard solution.