Stable Isotope Lab | ¹⁸O Water Analysis

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¹⁸O Water Analysis

• ¹⁸O in water is analyzed using the method described in the Thermo GAS Bench II operating manual, ThermoQuest, Oct 1999.

• In brief, 200 uL of water for both standards and samples are pipetted into 10 mL Exetainers and quickly sealed. The Exetainers are then purged with 0.2% CO₂ in Helium and allowed to equilibrate at room temperature for at least 48 hours. The ¹⁸O in the CO₂ is then analyzed on a Thermo Delta Plus XL mass spectrometer, using a Thermo Gas Bench II. Different sizes of water samples can be analyzed by preparing complete sets of standards and samples with the same water volume, down to 100 uL. For volumes less than 100 uL, the Exetainers are purged first with the 0.2% CO₂ in Helium, and then the water sample is added with a syringe through the Exetainer septa, and allowed to equilibrate for 5 days. This will work for volumes down to two drops (about 20 uL), after which the water all evaporates in the Exetainer.
   
• Although we can analyze as little as 25 uL water, this amount is hard to work with so we would recommend at least 200 uL and preferable 1 mL. Please contact us directly for shipping instructions and time needed for analysis.

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Email: stableisotopes@berkeley.edu. Phone: 510-643-1748/9.