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Deuterium and oxygen‐18 determination of microliter quantities of a water sample using an automated equilibrator
Author(s) -
Uemura Ryu,
Matsui Yohei,
Motoyama Hideaki,
Yoshida Naohiro
Publication year - 2007
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.3022
Subject(s) - chemistry , deuterium , fractionation , isotope , stable isotope ratio , analytical chemistry (journal) , oxygen 18 , isotopic ratio , isotopes of oxygen , isotope ratio mass spectrometry , mass spectrometry , environmental chemistry , chromatography , nuclear chemistry , physics , quantum mechanics
We describe a modified version of the equilibration method and a correction algorithm for isotope ratio measurements of small quantities of water samples. The δ D and the δ 18 O of the same water sample can both be analyzed using an automated equilibrator with sample sizes as small as 50 µL. Conventional equilibration techniques generally require water samples of several µL. That limitation is attributable mainly to changes in the isotope ratio ( 18 O/ 16 O or D/H) of water samples during isotopic exchange between the equilibration gas (CO 2 or H 2 ) and water, and therefore the technique for µL quantities of water requires mass‐balance correction using the water/gas (CO 2 or H 2 ) mole ratio to correct this isotopic effect. We quantitatively evaluate factors controlling the variability of the isotopic effect due to sample size. Theoretical consideration shows that a simple linear equation corrects for the effects without determining parameters such as isotope fractionation factors and water/gas mole ratios. Precisions (1‐sigma) of 50‐µL meteoric water samples whose isotopic compositions of −1.4 to −396.2‰ for δ D are ±0.5 to ±0.6‰, and of −0.37 to −51.37‰ for δ 18 O are ±0.01 to ±0.11‰. Copyright © 2007 John Wiley & Sons, Ltd.