I can't find a compound that should be in a standard mix

I'm working with a  5977B MSD with an 8890 GC.  I've been trying to identify all of the compounds in the Sigma Terpene Mix B (https://www.sigmaaldrich.com/US/en/product/supelco/crm40937).  I'm able to identify all of them fine except for phytol.  I just can't seem to find it.  I'm also pretty sure that it's a mix of isomers, so there should be multiple peaks.

For a while I thought that I had found them, there are two significant peaks, one is coming up as palmitic acid and another as stearic acid.  They're both long hydrocarbon chains like phytol, but when I do a serial dilution of the mix they remain at more-or-less constant concentrations, so I think they are present as a result of some processing I'm doing.  They also come up later in the run (which from other reading I have done appears to be when phytol should come out.

I've searched in NIST for what the spectra should look like and have tried extracting ions in their chromatographs, but that doesn't seem to help (although it does pull up the palmitic acid and stearic acid).  There are other compounds that are highlighted, but they don't appear to be good matches either.

I didn't know if anyone had any suggestions for additional ways I could try to find this stubborn compound.  Thanks.

  • Hi  welcome to the Agilent Community!

    I moved your question to the GC/MS Forum for better visibility. 



  • FLMS-035_US(EN)_2 (agilent.com)  SDS for Phytol

    71 amu is an ion in so many hydrocarbons that it's difficult, nearly impossible, to search just that.  Phytol Molecular Weight 296.53 g/mo ... have you tried an extracted ion chromatogram of 296 +/-  1 amu or maybe a bit more?  I'm lazy so I'd use the default extracted ion chromatogram parameters and extract 294.5, 295.5, and 296.5  first - as I can do that faster than changing the advanced extraction parameters. 

  • So yes, I'm pretty sure I've tried this (as well as searching for 71, and other prominent peaks.  I'm ultimately trying to derivatize this, but haven't had much luck looking for either phytol or phytol-TMS.  I'm not near the machine today, but I will search a previous run tomorrow for 296, etc.  I'm pretty sure I did this already, but I'll do it again just in case.

  • Geraniol and Phytol would behave very similarly chemistry wise. Do you see good peak for Geraniol? Have you tried deconvolution in MH Qual? Standard that you have mentioned here is in MeOH. Maybe its MeOH that is not allowing you to get the other compounds derivatize properly as MeOH will eat away all the TMS. Which column are you using currently? 

    Palmitic is C16 and Stearic is C18 while the Phytol is C20. C16 and C18 are not coming from your C20. 

  • Thanks of the reply.  So I do see a good peak for Geraniol.  I haven't been able to figure out how to get deconvolution to work in Qual, but I have used it in Unknowns.  So I am very much aware of the MeOH in the standard mix (it's the bane of my existence).  But I have been able to derivatize the mix well with enough BSTFA and Pyridine.  As far as the column goes, I'm using two DB-35MS UI, 15 m x 250 µm, 0.25 µm capillary columns (Agilent: #122-3812UI) in sequence.  Thank you for clarifying the palmitic and stearic acids.  I did order a single phytol standard, I'm hoping that once that arrives I can use that to clearly identify it.

  • Hello, 

    Phytol should be straight forward to detect in this mixture. It elutes after the sesquiterpenes. What is your injection temperature? Make sure its high enough to vaporize the phytol. 230C or higher would be high enough. Same goes for the oven program. Make sure it goes high enough to elute the phytol. Going up to 250 C should be enough.

    What kind of column are you using?

    If you are seeing palmitic acid and stearic acid constantly your liner or column might be contaminated. Might want to clean that up. 

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