Hello, I need to determine tocopheroels and phytosterols by GC-MS but I do not have the reagents to derivatize (TMS, TMCS, BSTFA, etc.) that most of the consulted literature generally uses. I wanted to know if I can determine these analytes without derivatization or with a simple derivatization methodology. Thank you so much
Dear Carolina,
In general, silylation derivatization is a quite simple procedure. But if there are any specific reasons do not use it, I would start from looking to the MS library provided with your instrument, or NIST on their website to see if any of these compounds are reported there as being detected without derivatization (I think some of them - yes, but can be wrong too).
You can analyze the tocopherols directly. On-column injection will help, but you can do this with a conventional split/splitless detector. I'm not certain about the phytosterols but you are dealing with compounds that are similar to the tocopherols. The derivatization in this case is typically used to make the compounds more volatile rather than less polar, and newer column technology has extended out the range for GC-MS. See Article Simultaneous determination of eight vitamin E isomers and α-...
O-methylation of Hydroxyl-containing Organic Substrates such as sterols and tocopherol may be an alternative...I still prefer TMS derivatization but to suggest an alternative way to perform GC analysis, I can pinpoint the A number of methylating agents have been employed to affix methyl group to molecule matrix via an oxygen atom.
Look for permetylation of the glycans, for example, using oxidizing conditions with NaOH and CH3I as methyl donors...Never tried it personally but it may work for your case as well. Underivatized analysis would be troublesome and not suggested.
Gang Chen
Thank you very much for your reply. I am in Argentina and any reagent that has a price in dollars is a problem for research in our country.
I'm going to work on the answers, if I'm successful I'll let you know.
When you have underivatized phenols peak shape could be a major issue---wider peaks, tailing peaks, sensitive to surface conditions (i.e., unreliable numbers), to just name a few. You would end up spending tons of times and money, and you may not have the sensitivity for what you need. TMS-Cl is not an expensive reagent or embargoed goods. If cost is an issue, then don't buy "MS-grade" reagent, but fractionally distill your own TMS-Cl.
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