Has anyone had experience with detecting oxindole by GC? In the first instance I am going to dry derivatisation to form the trimethylsilylamine which hopefully will elute through a 100% polydimethylsiloxane column satisfactorily. However there may be better methods known.
We have tried HPLC but have not been able to obtain the desired sensitivity we require.
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By H.Schnorbus on Monday, July 3, 2000 - 04:24 am:
I have not found any data on oxindole but your approach (MSTFA) to the problem seems logical.(Let it react with the MSTFA for 30 Min at 80C.) I would also measure the unsilanized compound. The precalculated Kovat's indices are
oxindole Is(40) 1400 Is(170) 1800
oxindole-TMSi Is(40) 1520 Is(170) 1700
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By Tony Herlt on Thursday, July 6, 2000 - 09:50 pm:
Thank you for your reply, Harald. The unsilanized compound elutes as a rather broad peak on a 100% polydimethylsiloxane column. Silanizing with BSTFA/pyridine at 90C (I did not have any MSTFA in the lab) produces 1 sharp peak which from GC/MS has an M+ of 277 indicating the bistrimethylsilyl derivative. Thus the oxindole must have formed the enol and be silylated on both the nitrogen and oxygen. I think this method will give us the required sensitivity.
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