FAME analysis via boiling point separation - any advice?

[mimeo]

Hi all,

I've just been given the task of quantifying FAMEs by boiling point separation on GC FID. The column I am using is ZB - 1 HT 15M x 0.18 ID x 0.1 um film thickness (the reason I am using an inferno column is because it will co-reside with another high temperature column in the oven and it needs to be able to withstand the high temperature). Can anyone give me any guidance? I am running the Supelco FAME mix but can only see a few of the peaks. Any advice will be gratefully received!

Thanks

Rebecca

[chromatographer1]

Your column will separate FAME according to chain length.

mono unsaturated fatty acid ME will elute just before the saturated, for example, oleic acid ME will elute immediately prior to stearic acid ME.

The poly unsaturates will elute at slightly later retention times but will generally overlap these two peaks of any chain length. Also any isostearic acid ME isomers will also elute just before stearic acid ME.

You should easily see the C12, C14, C16, C18, C18, and C20 FAMEs separated without a problem, each carbon number FAs will be bunched around their saturated normal carbon chain length homolog.

Is this clear?


best wishes,

Rodney George
consultant

[krickos]

Hi

Supelco has a number of mixes but here is a link to an application with a similar column that might help:

https://www.sigmaaldrich.com/analytical ... uity1.html

[Consumer Products Guy]

Your high-temperature column is overkill for the task of separating typical fatty acids. I suggest putting the high-temperature column you need for your other stuff in the rear position, and putting a polar column for the fatty acid methyl esters (such as SP-2330) in the front position, and merely taking out that front polar column when not expressly using it.

You're trying to make-do otherwise, which is usually not always the best scientific solution.

[mimeo]

Thank you all for your response!

The problem with Consumer Products Guy's suggestion is that the columns will be used on alternate days as we are a private analytical lab with paying customers and require a fast turnover time for the results. If I were to take out the polar column when it is not in use, I will need to shave the polar column and then re-determine the RT of each FAME everytime this is done?

In the meantime, I have managed to get all the peaks according to Sigma's Equity-1 column run on the Supelco 37 FAME mix. As with Sigma, I am unable to resolve the two most importand peaks in the run, the linoleic acid methyl ester and the apha-Linolenic acid methyl ester as they both have extremely similar boiling points. I have tried playing around with the temperature program but to no avail. Does this mean that separation of FAMEs via boiling point is futile?

Rebecca

[chromatographer1]

Yes.

COnsider that this is the reason that polar phase columns were developed.

You might hope that one of the new ionic liquids being developed by Supelco might have a higher limit of temperature and be adequate for the separations you require.

best wishes,

Rodney George
consultant

[Peter Apps]

Hi Rebecca

A boiling point separation is not going to work for two substances with extremely simialr boiling points, so you with the setup your are trying to use to give fast turnaround you can't give your customers what they want in terms of either turnraround or results.

You do not need to trim the column every time you change it. Leave the nuts and ferrules on it and seal the two ends by pushing them gently into a straight presstight connector. When you want to use it again take off the presstight, connect up, condition and away you go. That way you can use the specialist polar FAME column that you need without having to worry about its upper temp limit.

Peter

[CE Instruments]

FAMEs via boiling point is futile?

Yes the boiling points are too similar which is why you need a more polar phase and why you can buy special columns optimised for the separations. How hot does the non polar analysis have to go. Is it over the temperature limit for the polar column ?

[aldehyde]

Very useful responses guys thanks.

[mimeo]

Hi,

The non polar column needs to be ramped up to 380 C whereas the maximum temperature for the polar column is 250 C, so not a good idea to use the two together.

I will try using the polar column and then removing it when not in use. Thank you all so much for your comments and advice, they have been much appreciated.

Rebecca