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Topic: Help_LC/MS analysis of tocopherol derivatives  (Read 600 times)

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Offline yhoon9408

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Help_LC/MS analysis of tocopherol derivatives
« on: April 11, 2022, 03:41:20 AM »
I synthesized tocopherol derivatives (e.g. alpha-TOS). However, I could not develop a LC/MS method to monitor the reaction. I am using Waters reverese phase HPLC/MS or UPLC-MS. Both are using ESI MS. Eluent system is either (Sol. B) MeOH/ (Sol A.) H2O or ACN/H2O containing 0.1% formic acid and it is hard to change eluent system. I started initially with 98% B then eluted to 100% B over 4 min and back to 10 % B. I tried both pos. and neg. mode with cone volate of 15 and 35, respectively. I was able to see the peaks in the uv spectra, but not in ms spectra. Can somebody please help me develop a method to monitor my reaction?

Offline Babcock_Hall

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Re: Help_LC/MS analysis of tocopherol derivatives
« Reply #1 on: April 11, 2022, 11:01:21 AM »
My first thought is that you might have a typo.  Did you start with 98% MPA or 98% MPB?  My second thought is to ask whether or not you have searched the literature for previous work.  It's a fairly common compound, although perhaps your derivatives are novel.

Offline yhoon9408

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Re: Help_LC/MS analysis of tocopherol derivatives
« Reply #2 on: April 11, 2022, 09:00:27 PM »
My first thought is that you might have a typo.  Did you start with 98% MPA or 98% MPB?  My second thought is to ask whether or not you have searched the literature for previous work.  It's a fairly common compound, although perhaps your derivatives are novel.
In the system, solvent A is DI (0.1% formic acid) and solvent B is MeOH or ACN with 0.1% formic acid. I started with 98% of my solvent B, which is MeOH or Acetonitrile containing 0.1% formic acid. Using this condition, I could see a peak in UV spectra but not in MS spectra. The compound is quite non-polar and, I guess, not easily ionizalbe. I could not see any peaks when I lowered the initial concentration of MeOH or ACN. Yes, it is a farily common compound and there are available literatures. Although there are reported MS values by ESI or CI in the literature, I could not find LC/MS method authors used for analysis. Here are some of the papers I referred to: 10.1002/cmdc.200900492, 10.1038/sj.bjc.6600981, 10.1194/jlr.D400044-JLR200.
I also think it is strange that I am not getting MS peaks when there are reported MS values. I must be missing something and I can not figure out what it is. I tried to manipulate MS scan range, capillary voltage, convoltage, detector gain, and neg/pos mode. I am so desperate to optimize LC/MS condition for this series of compounds. If you need more info, please let me know and if there are people with experience on tocopherols, I need your wisdom.

Offline Babcock_Hall

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Re: Help_LC/MS analysis of tocopherol derivatives
« Reply #3 on: April 12, 2022, 09:31:30 AM »
I am not an expert in mass spectrometry.  However I used "alpha-tocopherol mass spectrometry liquid chromatography" as my search term at PubMed and found over 300 articles (I realize that this is too many).  doi: 10.1016/j.jpba.2020.113104.  This paper used APCI as the ionization method.  I am not sure how many methods use this method of ionization.  This paper compares APCI with electrospray:   doi: 10.1016/j.chroma.2007.04.058.

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