Measurement of chlorine stable isotopic composition by negative thermal ionization mass spectrometry using total evaporation technique

A total evaporation negative thermal ionization mass spectrometry (TE-N-TIMS) technique for the isotopic analysis of chlorine was developed. This technique provides fast and reliable way to determine the isotopic signature of chlorine samples as small as 100 ng. Compared to the conventional N-TIMS method, the precision of the CI isotopic analysis is improved by a factor of up to 3 by minimizing the effect of mass fractionation. Using this method, reproducibility of 0.9‰ (R.S.D.: n = 25) can be achieved for ³⁷C1/ ³⁵C1 ratio of 200 ng CI. The analyzed results of the AgCl reagent expressed as a per-mil deviation (δ³⁷Cl) relative to the Standard Mean Ocean Chloride showed good concordance with the value obtained by conventional positive thermal ionization mass spectrometry (P-TIMS).