I think, you can use these samples. Fatty acids can be identified methylation. But studies of the composition of fatty acids are best used fresh samples. During storage, the fatty acid composition may change.

Sorry for my English.

Thank you!

Dear Carolina,

You can carry out lipid profiling work on those samples. Ideally should be fresh but if they have been stored in -80C and with few freeze/thaw cycles to minimize sample degradation then it should be ok.

Please beware to minimize the use of plastic ware during lipid extract preparation (do the extraction step in glass tubes and use glass pipettes to collect the organic extract ). Finally store the dried lipid extract in amber vials in -80C until further analysis.

Hope this helps, Ana

Thank you Ana!

Dear Carolina,

For detection of fatty acids, you must take the fat or lipid portion of your samples. And as you know, lipid is extractable only in organic solvents. Do you want only to extract the lipid for fatty acid composition, or any other objective you have? What kind of sample is this? Is it any animal tissue, or any plant part? You may go for cold extraction if possible. And do this quantitatively. Take small portion of your sample and extract the lipid either by chloroform-methanol or by cold extraction (by petroleum ether B.P. 4-60 deg C, acetone, methanol whatever gives best yield). Then methylated it and run in GC. You can try it. Thank you.

You should be able to take an aliqote of your homogenate and extract using the Folch method or Bligh and Dyer method, but you would need to take into consideration the total water in the sample to get the correct organic solvent to water ratio. You would also have to take into consideration how dilute your sample is in your PBS to make sure there are enough fatty acids in the end to analyse, and at what stage and concentration to add internal standard to help with quantification.