It is hard to say whether it has been volatiled some. If it is not very stable, such as volatile or reaction changing to other compounds. So, you had better take out very traces to test.

Thank you very much for your reply Hua Huang. Indeed, I did not consider these compounds can also react with other components present in the samples (including cage enrichment). I guess I will need to test this!

Go a head and do a test, even year and half is very long time but  I think at this temp. May be you will find them still in your samples. Because we preserve samples of fatty acid extraction at sane temp.

Let me know the results.

Regards.

Hi Mohamed,

Thank you very much for your suggestion. Based on all the answers here the wisest thing seems to be trying this out. I hope I can come back to you and share a positive result!

Thanks again,

José

dissolve a stool sample in water stirred for 5 min centrifuge and measure the pH. If the pH is very acid (5,5,) a good part of butyric acid is lost. Stool samples should be stored at -80 in tightly capped containers and processed very quickly within a maximum of 3 months.

Hi Antonio,

Thank you very much for your suggestion. Measuring the pH never occurred to me. This is definitely something I should also try before carrying out the rest of the protocol (saponification, etc.).

Thanks a lot!

José

We normally make our samples alkaline >ph9 with NaOH before storage.  This makes the  SCFA salts and not volatile.  we then make the samples acidic again before analysis. 

Thank you very much Christine. 

We are now trying to analyse the samples without adjusting the pH, so just by suspending faecal matter and caecum contents in distilled water. We haven't got the results back yet, but definitely your suggestion is something to implement next time. Thank you very much for your explanation!

José

Dear all,

Happy to report we were able to measure SCFA in mouse faeces and ceacum and colon contents after 6 months sotrage at -80°C. We used gas chromatography (GC) and we added acid to protonise the SCFA right before injecting the samples into the GC column.

Cheers,

José

Hello José Fernández-Calleja ,

could you provide me some references for the protocol you mentioned?

I am currently working on this and the protocols I have found are very complicated.

Thank you in advance!

Hi Ioanna Prapa,

Unfortunately the detailed protocol remained in the lab where I performed the experiments and I currently don't have access to it. However, you can look at the Methods of the associated paper where we describe the most important steps: https://www-nature-com.proxy.library.uu.nl/articles/s41598-018-33619-0

This should give you a good head start, I really hope it helps.

Best of luck,

José

José Fernández-Calleja thank you so much, I really appreciate it!!!

Hi José Fernández-Calleja, I am not able to access the link you provided

HI Mohita Gaur, you can try this other link: Article Non-invasive continuous real-time in vivo analysis of microb...

Cheers,

José