Performed GC/MS/MS without derivatization and found Epitestosterone, tert-butyldimethylsilyl ether, Pregnenolone,3-trifluoroacetate, Pregnenolone,3,2,1-bis(trimethylsilyl)oxyl-3(beta), Pregnenolone,3(acetyloxy)-cyclic 20-(1,2-ethanediylacetal) (3-beta) and phthalic acid, 2,6-dimethoxy phenyl methyl in my water samples? I am looking for what could be the possible reasons and did the compounds form bonds with esters to have the above resultant compounds?
Dear Mehak Puri,
to answer this question, it would be good to know how your sample preparation is done.
Many of the components you found are analytes that are usually detected by LC-MS. Especially the hormones should not be analyzable by GC-MS.
However, reactions with solvents such as methanol could be possible and esterification could occur as part of this sample preparation.
Silyl compounds and silanes are often components of cleaning and cosmetic products, especially the cyclic silanes D4, D5 and D6. These can open the ring without energy and then naturally enter into reactions with active functional groups.
Since our working group also works in the field of water analysis, the compounds detected by you do not seem unusual to me, as long as they are real samples. However, the concentration of hormones in our samples is very low and almost always at the edge of the detection limit.
I hope that my answer will lead you to a solution for your question.
Best regards and stay healthy
Joachim Horst
Dear Joachim Horst
I hope everything is good and safe at your end too!
Thank you for the response. For sample preparation, I went for SPE extraction followed by the acidic and basic compound extraction and further directly analyzed in GC/MS/MS without derivitization. As mentioned by you, the silyl compounds and silanes could be one reason. What possibly could be done to avoid such errors. Do you feel that I could detect Epitestosterone and Pregnenolone compounds as such if I had avoided the errors? Great to know and connect with you having similar working interests. Hope to hear more from you in the future regarding the water analysis on compounds with low detection limits.
Best Regards and Safe and Healthy well being
Mehak Puri
Dear Mehak Puri,
I did some work on GC-MS analysis of soil extracts. Therefore my thoughts on some of your components:
In soil extracts I sometimes observed colesterine-like structures like testosterones. I think they might be degradation products of biological material that show up with GC-MS.
Silyle components could originate from column or injector surfaces of your instrument.
Trifluoracetic acid seems to be a common metabolite of certain medicaments and pesticides. May be it forms esters as well?
Best regards
Ulrich
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