Sr/ Sr isotope ratios in rocks determined using inductively coupled plasma tandem mass spectrometry in O mode without prior Sr purification.

Rationale: An inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) instrument can be developed to determine Sr/ Sr ratios with an external precision better than 0.05% relative standard deviation (RSD) in "mass shift" mode without prior Sr purification. Previous studies suggested using CH F, N O, and SF as reaction gases for this method because a better reaction rate can be achieved with Sr than with O in the reaction cell.