By Andreas on Saturday, June 22, 2002 - 02:07 am:
We are conducting fatty acid analysis using MTBSTFA derivatization. Usually for such derivatives the most abandoned ion is m/z=M-57 - fragment resulting from the elimination of tert.butyl group. In our case this is true for dicarboxylic acid,but not for monocarboxylic. For monocarboxylic fatty acid the main fragment ion is m/z=M-39 or in other words m/z=M-57+18.
If anybody can explain this anusual (at least for me) fragmentation pattern?
If this is water adduction, why not for dicarboxylic acid?
By Molever on Monday, June 24, 2002 - 04:19 pm:
I'm in the soap industry, and we have experience with fatty acid and derivatives. I tried pure myristic acid with MTBSTFA (we've used BSTFA before). With BSTFA I get trimethylsilyl derivative MW peak at 300 (228.4 + 73 -1 for hydrogen) and a larger (largest) peak at M/z 285, corresponding to a loss of a CH3 methyl group (MW-15). With MTBSTFA, I don't get a peak at M/z 300, just the large M/z at 285 (still) which corresponds to the MTBSTFA derivatized MW of 342.6 less 57 (loss of t-butyl group). I didn't see any MW-39 at all.
By Andreas on Wednesday, June 26, 2002 - 04:43 am:
Molever, can I ask what MS do you use - quadrupole or ion trap?
By Molever on Wednesday, June 26, 2002 - 08:25 am:
We have quadrupole (HP 5971A and 5972A). I just reprepared and reinjected Monday, for you.
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