Chromatography Forum

I just ran a flavor sample and encountered those same two sulfur compounds I've seen before last year only this time there are rather large quantites of them they are the largest peaks on the TIC other than triacetin. I though for sure one must be hexyl mercaptan based on the formula last year and the fact it is a known flavor compound

I ran the Kovats series today on a db-5 column. Both peaks have identical EI spectra. Peak one has a Ki of 904.11 and peak 2 945.97. As a control I calculated the Ki of trimethyl pyrazine as 1000.515 [published is 1000 even]. Neither matches 1-hexane thiol which has an index of 925.

Based on that I checked to see if it was 3-mercapto-2-pentanone and upon injection of the compound although the retention time was the same the EI spectra does not match. The defining characteristic of these two compounds is a base 74 m/z ion that is not present in any of the suspects I looked at. 1-hexane thiol's EI spectra is here
http://webbook.nist.gov/cgi/cbook.cgi?I ... 9&Mask=200.
none of the isomers of hexanethiol are known flavor compounds.

I am rerunning the kovats series on the wax column for more clues.

I ran it on an Innowax column and got 1284 and 1366 I's and Trimethyl pyrazine was 1383.6 (1395 published CM20). I am not finding any matches in Pherobase.

Going over the EI spectra the 74 ion indicates a loss of 44 (C2H4O) that would indicate an oxygen in the formular despite what TAMI indicated. 118 is likely the Molecular ion as all the sulfur compounds in that I range have 116-118 molecular weights and I can see their dimers with a 234 ion later in the chromatogram.

Very perplexing

I solved it. It is cis and trans 2-methyl-tetrahydrofuran-3-thiol. Kovats matches, aroma characters match. 57124-87-5. I guess TAMI was incorrect. the formular is C5H10OS.

BTW how do you have a cis and trans with no double bonds?

I would guess the cis and trans are (outmoded? E and Z maybe?) references to orientation across the cyclic (THF) part.