High precision measurement of titanium isotope ratios by plasma source mass spectrometry

A method using multiple-collector inductively coupled plasma source mass spectrometry for the precise measurement of Ti isotope composition in natural materials has been developed. Instrumental mass discrimination is corrected using a "standard-sample bracketing" approach by expressing the isotope ratios of samples relative to those of the bracketing standard. Variations in ⁴⁷Ti/⁴⁶Ti, ⁴⁸Ti/⁴⁶Ti, ⁴⁹Ti/⁴⁶Ti and ⁵⁰Ti/⁴⁶Ti ratios of samples are expressed in ε units which are deviations in parts per 10⁴ from the same isotope ratios of the reference material. The long-term repeatability at the 2 standard deviation level is 0.4, 0.6, 0.7 and 0.8 ε units in terms of ⁴⁷Ti/⁴⁶Ti, ⁴⁸Ti/⁴⁶Ti, ⁴⁹Ti/⁴⁶Ti and ⁵⁰Ti/⁴⁶Ti ratio measurements, respectively. The technique reported here makes it possible for the first time that both mass-dependent fractionation and isotope anomalies of Ti isotopes in natural materials can be measured to high precision.