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Chloroform GC-FID contaminating peaks?

gas chromatography GC-FID chloroform contaminating peaks spectrum

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#1 Jaff

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Posted 02 May 2014 - 07:05 AM

Hello all,

 

I was wondering if anybody has come across this anomaly when extracting lipids using the standard Folch protocol.  Having removed the chloroform phase, I evaporated it to dryness at 37oC in a vacuum evaporator and derivatised the resulting pellet to FAMEs for GC-FID analysis.  Amongst the expected FA peaks, I got these 3 contaminating peaks at 1.789, 2.896 and 3.027.

 

I repeated the process without the sample, so just chloroform:methanol, removed chloroform phase, evaporated to dryness and while no pellet was present, I used the tube to mix the reagents for FAME derivatisation.  I got the same 3 contaminating peaks at 1.789, 2.896 and 3.027 (see attached - peak at 9.815 is methyl behenate).

 

I have discounted contamination/issues with the column, GC system, FAME reagents, hexane etc.  The peaks were evident for 2 separate chloroform batches and were not present when chloroform was run directly on the GC.  The system is an Agilent 7890A with a DB-23 column.  

 

My best guess is that they are contaminating artefacts in the chloroform or from the plastic eppendorfs used during evaporation (I know plastic is generally considered a no-no with chloroform but it was only used during the evaporation stage and the peak at 1.789 is so intense that I find it hard to believe that there would be that much interference, given that detection is with FID and not MS - although maybe I am wrong?!)

 

Does anybody out there have any thoughts or suggestions or have had similar experiences?  I could just ignore the peaks but I would rather know what's going on!!

 

Thanks in advance

Jaff

Attached Thumbnails

  • GC FID Chloroform Contamination..PNG


#2 hobglobin

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Posted 02 May 2014 - 09:10 AM

Can this be by-products from the derivatisation? And you should use glassware to exclude issues with the plastics.


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#3 mdfenko

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Posted 05 May 2014 - 03:56 AM

the contaminants are most likely from the plastic but may also be extracted from the methanol (or both).

 

have you tried injecting methanol?


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