Isotopic Analysis of Water δ2H, δ18O

Sample Material

Freshwater, seawater or porewater

Sample Size

2 ml (for a single analysis)

Sample

(filtration required)

Precision

±0.03 permil for δ¹⁸O, ±0.21 permil for δ²H

Method

Hydrogen and Oxygen isotope data (d²H and d¹⁸O vs VSMOW) are run at OSSIC by near infra-red, cavity ringdown spectroscopy using a Picarro L2130-i isotopic water analyzer.

OSSIC uses working standards for daily runs that are annually calibrated to international standard reference materials. Three working standards are used each run to calibrate d²H and d¹⁸O. An additional independent working standard with known isotopic composition and a matrix chosen to match the sample matrix (ie Saltwater, Freshwater, Brackish etc…) as close as possible is run for verification of calibration.

Water Collection Method (for δ¹⁸O analysis)

Start with a clean and dry glass container of at least 5 ml capacity that has a tight fitting lid preferably with a plastic seal of some sort (e.g., 20ml scintillation vials with polysealcap). Avoid using plastic vials. If samples are to be stored for a long period before analysis (> month) do not use caps with septa due to the potential for evaporation through the septa over time.
Carefully fill container with sample while preventing turbulence. If possible, use a tube to fill sample bottle from the bottom and flush bottle 1 or 2 times. Fill bottle completely and make sure there is no headspace or air bubbles on the sides of the bottle before capping. Once capped, no air should be in the sample bottle. Ideally, the sample should have limited exposure to air while sampling.
Wrap parafilm or tape around the cap to prevent the cap from loosening. When applying the parafilm (or tape) wrap it in the direction of tightening the cap otherwise it may inadvertently loosen the cap.
If possible store in a cool location. Do NOT freeze the sample.