Triple-isotope calibration of in-house water standards supplemented by determination of ¹⁷O content of USGS49-50 reference materials using cavity ring-down laser spectrometry

ABSTRACT

The procedure of calibrating in-house water standards suitable for routine analyses of triple-isotope composition of water samples using Picarro L2140-i CRDS analyser is presented and discussed. Such standards are indispensable for achieving and maintaining high quality of isotope analyses of water in terms of their precision and accuracy. A set of seven different water standards consisting of three in-house standards and four secondary standards commercially available was calibrated against VSMOW2/SLAP2 primary reference materials. The calibrated standards cover a wide range of isotopic composition, with δ values ranging from close to zero to the values comparable with SLAP2. The apparent consistency of the calibrated values of δ²H, δ¹⁸O and d-excess with corresponding certified values for commercially available USGS47-50 standards and the consistency of the calibrated values of δ¹⁷O and Δ¹⁷O with its literature values for USGS47-48 standards confirm the high quality of the performed calibration. Moreover, the calibration exercise allowed to obtain δ¹⁷O and Δ¹⁷O values for USGS49 and USGS50 standards, not reported so far.

KEYWORDS:

• Calibration
• hydrogen-2
• oxygen-18
• oxygen-17
• oxygen-17 excess
• reference standards

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported through funding from the National Science Centre [grant Number UMO-2016/23/B/ST10/00909] and the subsidy from the Ministry of Science and Higher Education [grant number 16.16.220.842 B02].