Dabundo et al. reported significant contamination of commercial 15N2 gases available, especially the gases supplied by Sigma Aldrich:
The Contamination of Commercial 15N2 Gas Stocks with 15N–Labeled Nitrate and Ammonium and Consequences for Nitrogen Fixation Measurements (Dabundo et al. 2014, PLOS one)
I would be interested if anyone else of this community experienced similar problems and/or how suppliers reacted to inquirie.
Gases of Sigma Aldrich are for example not tested for such contamination, as the company stated upon request. Without testing of each batch, the use of gases of SA cannot be recommended then. As there was no reaction of SA upon release of the mentioned article, the support policy of SA also seems questionable and not what I would expect from a supplier of scientific products.
What is your experience and your recommendations of suppliers?
Hi Klaus-Holger,
we are using the 15N2 labelling in my lab, since the publication of the Dabundo paper we checked our gases for contamination and it turns out that Campro gases and Cambridge isotope gases were not contaminated since then. In addition to the contaminatio nissue, SA gases are very expensive- so I personally buy now from the other two suppliers..
Best,
Carolin
Thanks Carolin for your suggestions. So we will also change our suppliers to the ones you mention. I was also very unhappy with the bad answers by SA about this problem. They just replied that they do not check and that the gases still meet the specified properties of the material data sheet...
Do you set up any easy standard procedure for cleaning of gases in the lab? There are some more elaborate ways published, I know. We were testing to work with gas bags in which we fill the absorbent (either NaOH or KMnO4 solution) and add the gas. Then the gas can be easily handled in the lab without expensive and spacy equipment. The gas can be "pressed" from one bag into the other after each exposure. Thereafter the gas can be easily withdrawn using a syringe.
We did the cleaning via the method published by Klawonn et al. (http://journal.frontiersin.org/article/10.3389/fmicb.2015.00769/full). This works quite well, but your approach sounds interesting, too. What bags are you using? Something like Tedlar bags? You should publish some technical note on that- I would appreciate it!
Thanks for this easy-to-read paper. It is right, one shoudl really publish these standard procedured. We are not good at this yet I have to say.
We first used Tedlar bags for our gases but long term storage of test bags showed that they are not very gastight (oxygen is leaking in, gases are lost). Much more gas-tight are "tecotainer" bags
http://www.tesseraux.de/en/produkte/chemie/
They are usually used to protect food for long term storage. It is a three layer material, made of plastic-aluminum-plastic. You can buy them one side open, punch a hole to put in a Luer Valve, and then close them with a heated molding device for plastic pags. There is your gas bag :-)
Hi, We are also using 15N2 99% for Nitrogen fixation by free living in Soil. However, the difference in between samples of natural abundance (NA) and Enriched (EN) by 15N2 is very very close some times NA is higher than EN. Any suggestion....Thanks
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