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.

Please also post any replies to my e-mail address (herlt@rsc.anu.edu.au)

TIA

Tony

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
(Your e-mail address does not respond)

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.

Regards,

Tony