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Looking for advice: how to keep samples for stable isotopes

Rocio Mariano-Jelicich, April 13, 2013

Hi everyone! I'm looking for some advice on stable isotope sample collection. I would like to separate plasma form blood cells for stable isotope analysis.

The problem is that it will take me more that a couple of hours to get back to the lab to centrifuge the samples.

My question is: how long can the blood samples be kept in ice before being centrifuge? and also: do I need to use heprin?

Thank you very much! Rocío

Comments ( 5 )

Katharine Goodenough

Katharine Goodenough

Hi Rocio,

You need some type of preservative or you will have serum instead of plasma from your samples. As soon as the blood begins to clot, the liquid portion of the blood sample becomes serum. You can use either EDTA or heparin but keep in mind that the preservatives will affect the carbon signatures. With preservatives, you can keep the samples on ice for 6-8 hours before centrifuging the samples.

Cheers, Kate

Robert Ronconi

Storage in tubes with EDTA is a good option which we have done and keep the blood cool on ice for several hours. There is one study that tested for effects of EDTA on isotope signatures and found none (Kakela et al. 2007). I also tested in the first year of using EDTA tubes and found no effects (though these data were not published).

Cheers, Rob

Käkelä A, Furness RW, Kelly A, Strandberg U, Waldron S, Käkelä R (2007) Fatty acid signatures and stable isotopes as dietary indicators in North Sea seabirds. MEPS 342:291–301.

Kyle Elliot

When we examined samples with and without heparin, we found no difference in carbon or nitrogen signature. In principle, heparin (or EDTA) is diluted ~1000-fold to make the solution and then you only use <0.01 mL for a 1-mL syringe, meaning that the heparin (or EDTA) concentration is probably lower than 10 ug/L. The noise from the carbon signature of the additive is therefore minuscule compared to many other confounding factors. Nonetheless, Lemons et al. (2011) did find a difference for several anticoagulants, albeit in sea turtle blood, and recommended heparin.

Lemons, G. E., Eguchi, T., LyonA, B. N., LeRoux, R., & Seminoff, J. A. (2011). Effects of blood anticoagulants on stable isotope values of sea turtle blood tissue. Aquatic Biology, 14(3), 201-206.

Katharine Goodenough

Katharine Goodenough

Thanks for the reference Rob! I was referencing Bugoni et al. (2008) when voicing concerns about the influences of preservatives on carbon signatures.

Bugoni, L.,McGill, R.A.R., and R.W. Furness. 2008. Effects of preservation methods on stable isotope signatures in bird tissues. Rapid Communications in Mass Spectrometry. 22:2457-2462.

Rocio Mariano-Jelicich

Thank you very much for all the suggestions!!!!