US EPA

4846794 

Journal Article 

Precise tellurium isotope analysis by negative thermal ionization mass spectrometry (N-TIMS) 

Fukami, Y; Yokoyama, T 

2014 

Yes 

Journal of Analytical Atomic Spectrometry
ISSN: 0267-9477
EISSN: 1364-5544 

29 

3 

520-528 

10.1039/c3ja50317h 

WOS:000332495200014 

We present a new method for precise isotope analysis of Te by thermal ionization mass spectrometry in negative ion mode (N-TIMS) along with an improved technique for chemical separation of Te from geochemical samples. In the chemical separation, Te was purified by a three-step column chemistry method employing an anion exchange resin and an extraction chromatographic resin, yielding 98% recovery. To achieve strong Te- beam intensity in N-TIMS, we evaluated the optimum analytical conditions with respect to the filament material, ionization activator, and filament heating protocol. The reproducibilities of Te isotope ratios obtained by static multicollection using Faraday cups were 0.9%, 0.04%, 0.06%, 0.01%, 0.005%, and 0.008% for Te-120/Te-128, Te-122/Te-128, Te-123/Te-128, Te-125/Te-128 Te-126/Te-128 and Te-130/Te-128, respectively. This result is comparable to those of previous MC-ICP-MS studies. The reproducibilities of Te isotopes obtained by SEM jumping measurements were approximately ten times worse than those obtained by Faraday cup runs, excluding the Te-120/Te-128 ratio for which the reproducibility was comparable to that obtained by Faraday cup runs due to the extremely low abundance of Te-120. To further improve the analytical precision, the Te-126/Te-128 ratio was determined by multidynamic collection for the study of Sn-126-Te-126 chronology. The 2s of the Te-126/Te-128 ratio of the multidynamic collection was 1.6 times better than that obtained by static measurements. Finally, the accuracy of our method was confirmed by the analysis of two carbonaceous chondrites and one terrestrial standard rock, which was consistent with previously reported values.