Stable Isotope Facility

Sample Preparation

Water Samples for Analysis by LC-DIC

Sample size should be 10-40mL, though lower sample volumes may be acceptable (please contact SIF to discuss these samples). Filtered water should fill vials completely with no headspace (i.e. have a positive meniscus) or bubbles.

To lower the risk of carbon dioxide diffusion, we recommend that samples be collected in glass vials with low-diffusion butyl rubber septa. Refrigerate samples (do not freeze) prior to shipping and ship in insulated containers as soon as possible after collection. Please contact us if you have questions.

Exetainer Gas Evolution Technique

You can prepare water samples in Exetainers with phosphoric acid as described here (see also Zhong-Ping et al. 2008). To prepare samples, first add 1 mL 85% phosphoric acid to each 12 mL Exetainer vial (Labco Ltd, High Wycombe, UK). Cap the vial and evacuate with a vacuum pump fitted with a needle to pierce the septum cap. Using a syringe and 24- gauge needle, add up to 4 mL water, depending on expected DIC concentration; helium flush-fill the vials if the added water ≤ 2 mL. Label each vial with a unique ID# as your data will reference your samples using this ID. Some estimate of the DIC concentration in your samples will help us prepare standards in the appropriate range and to decide whether cryofocussing of the CO₂ is needed.

Supplies

Manufacturer / Part#

Description

Unit

Labco UK + International or

Labco USA + Canada / 839W, 739W

12mL Soda Glass Vials, flat bottomed, labeled, white cap, evacuated (839W) or non-evacuated (739W)

Case of 1000

*Note: Labco has a new vial style that ends in ###W/W. We DO NOT accept these vials because the vials are too wide for our autosampler racks.

References
Atekwana, E.A., Krishnamurthy, R.V. 1998. Seasonal variations of dissolved inorganic carbon and δ¹³C of surface waters: application of a modified gas evolution technique. Journal of Hydrology 205: 265-278.

Zhong-Ping, L., Ming-Xin, T., Li-Wu, L., Zuo-Dong, W., Li, D., Ming-Feng, Z. 2007. Determination of isotope composition of dissolved organic carbon by gas chromatography- conventional isotope-ratio mass spectrometry. Chin. J. Anal. Chem. 35: 1455-1458.

Brandes, J.A. 2009. Rapid and precise δ¹³C measurement of dissolved inorganic carbon in natural waters using liquid chromatography coupled to an isotope-ratio mass spectrometer. Limnol. Oceanogr: Methods 7: 730-739.