Chromatography Forum

Dear Experts,

I would like to measure the amount of alcohol (or -OH Groups) present in a rather complex sample, mainly consisting of various isomers of C21 hydrocarbons (aliphatic and aromatic) amongst other impurities.

My idea is basically to derivatize present alkohols with BSTFA+TMCS to Si(CH3)3 (m/z = 73) and to analyse the sample in SIM-mode, while scanning for the 73 ion. By that, I hope to obtain an "alcohol chromatogram" of my rather complex sample.

Is this a possible solution for my analysis or are there any better ways to achieve the desired results?

Thanks in advance and best regards

Your derivatization idea should work fine; we often derivatized fatty alcohols with BSTFA to assay by GC and GCMS.

However, I'm not thrilled with using SIM, but don't want to argue against trying that. I think 73 ion will be contributed by other species in your matrix. How "trace" does your assay need to be?

That said: many trimethylsilyl derivatives will have a characteristic M - 15 ion using GCMS.

Would it be possible to use some sort of SPE phase to separate the oxygen containing analytes from the simple hydrocarbons?

Are the alcohol(s) short chains? In that case, could you perhaps extract them from the oil with acetonitrile (or methanol, but this might be an analyte for you).