ALLEVIATION OF POLYATOMIC ION INTERFERENCES FOR DETERMINATION OF CHLORINE ISOTOPE RATIOS BY INDUCTIVELY COUPLED PLASMA MASS-SPECTROMETRY

A simple variation in sample preparation and introduction allows the measurement of chlorine isotope ratios by inductively coupled plasma mass spectrometry (ICP/MS). Dissolution of the sample in D2O rather than H2O attenuates the major polyatomic ion 36ArH+ and frees m/z 37 for determination of 37Cl+. The isotope ratio 35Cl/37Cl in a 50 mg/L solution of Cl as LiCl is determined with a relative standard deviation of 0.21%. Sample memory is low, as the 35Cl signal decays to less than 1% of its original value after ∼2 min of cleanout with D2O . The detection limit for Cl using this procedure is approximately 20 μg/L. © 1990 American Society for Mass Spectrometry.