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A simple cryogenic method for efficient analysis of triple oxygen isotopes in silicates
Author(s) -
Ghoshmaulik Sangbaran,
Bhattacharya Sourendra Kumar,
Roy Pallab,
Sarkar Anindya
Publication year - 2020
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.8833
Subject(s) - chemistry , analytical chemistry (journal) , oxygen , isotopes of oxygen , mass spectrometry , quartz , silicate , isotope , mineralogy , environmental chemistry , chromatography , nuclear chemistry , geology , paleontology , physics , organic chemistry , quantum mechanics
Rationale Oxygen isotopic ratios of silicates are excellent tools to reconstruct paleotemperature and isotopic composition of the precipitating fluid. However, the measurement of 17 O/ 16 O is difficult due to the low abundance of 17 O. The present study reports a simplified high‐precision analytical technique for measuring the two oxygen isotope ratios, 17 O/ 16 O and 18 O/ 16 O, in silicates. Methods Silicate samples were ablated by a CO 2 laser in a BrF 5 environment. The released oxygen (O 2 ) was then cryogenically trapped in a molecular sieve zeolite (MSZ). Associated contaminants such as BrF 5 , F 2 , NF 3 etc. were cleaned by passing the gas through a NaCl trap followed by a cooled (−25°C) MSZ‐packed U‐tube trap. The purified O 2 was analysed in a MAT 253 isotope ratio mass spectrometer for oxygen isotope ratios. Results The δδ 17 O and δ 18 O values of the working gas were calibrated by NBS‐28 and crosschecked by inter‐laboratory references UWG‐2, SCO and IMAU‐O 2 . The average analytical precisions (using aliquots of NBS‐28, UWG‐2, SCO, and laboratory internal standards IIT‐KGP‐SQ quartz and IIT‐KGP‐NQ quartz) of the δ 17 O, δ 18 O and ∆′ 17 O values were 0.04‰, 0.08‰ and 4 per meg, respectively. Conclusions A new cryogenic cleaning technique was developed that does not require GC but efficiently removes NF 3 ‐contaminants from oxygen gas produced by laser fluorination of silicates. The technique is simple, quick and cost‐effective and provides highly precise and accurate δ 17 O, δ 18 O and ∆′ 17 O values.