News

09.07.2018

The CCiTUB participate in an international evaluation of isotopic analysis (δ18O and δ2H) in waters

The Stable Isotopes Laboratory of the Isotope Ratio Mass Spectrometry Technology at the CCiTUB has participated in an international interlaboratory exercise organized by the International Atomic Energy Agency (IAEA) in Vienna.

A total of 235 laboratories took part in the isotopic analysis of different types of water samples:

The isotopic ratios (δ18O and δ2H) of water are widely used as tracers in environmental studies, and obtaining precise and accurate data is essential to ensure rigorous interpretations.

The study includes a comparison among 3 analytical techniques for δ18O and δ2H analysis:
1 - Dual-inlet isotope ratio mass spectrometry (DI-IRMS)
2 - Continuous-flow isotope ratio mass spectrometry (CF-IRMS)
3 - Laser absorption spectrometry (LAS)

A comparison of the results obtained by the participating laboratories was also carried out, together with the corresponding statistical evaluation that determines acceptable and non-acceptable results due to lack of accuracy and precision, based on the concept of z-score.

According to these criteria, 73% of the results submitted by the 235 participating laboratories were accepted, including those from the CCiTUB Stable Isotopes Laboratory.

The analytical technique used at the CCiTUB Stable Isotopes Laboratory was CF-IRMS, with 2 different instruments and 2 different configurations:
1 - CF GasBench–IRMS equilibrium system, using a Thermo Fisher GasBench I coupled to a MAT253 isotope ratio mass spectrometer.
2 - CF pyrolysis–IRMS system, using a TC/EA pyrolysis unit coupled to a Thermo Fisher Delta Plus XP isotope ratio mass spectrometer.

The methods established by the laboratory were used regarding equipment verification, use of standards, sample and reference storage, calibration criteria, data normalization procedures, method uncertainties, etc.