Chromatography Forum

Hello, my colleagues!
My name is Dmitry, nice to meet you! This is my first post on this forum .
I work in the Russian laboratory, by safety crop production. In the department of mass spectrometry.

At the moment, I have one problem. I am doing research of the active substance in the soil isoxafutol and his metabolite. The study goes on the instrument Agilent TripleQuad LC/MS/MS 6410. (ESI-), MRM. My problem is as follows:
Isoxaflutol (M=359,35) has a similar mass to its metabolite (M=359,35). In the process of metabolism is being rebuilt structure, without loss of atoms. Consequently, in the MRM scan mode I have a similar product ions, as in isoxaflutol and metabolite. In the separation column, while output of both compounds is exactly the same.

Ask your help and tips to solve the problem of identification and separation of compounds.
Thank you very much!

Hi,
A long time ago, I remember a similar situation but for a steroid metabolite that had stereoisomer’s, we
reduced the compounds to the same (different) compound for GCMS.
It may be possible to add a reducing agent e.g. NaBH4, so that the parent compound that has a ketone
would be reduced to an alcohol, and the metabolite would be reduced to have two alcohols.

So the parent would now be M+2 (361.35) and the metabolite M+4(363.35),
But because now there are now alcohols these may form H20 during ionisation,
So you may see M+2 – (H20) (343.35) etc… or in switching mode get a better/different response in ESI+ you will have to experiment to find out of course.

It would be nice to have the instrument do all the work, but sometimes you just need to derivatise etc…

Alex

Thank you very much, chemstation!

You have a very interesting idea and it's an interesting proposal to transfer the chemical compound in alcohols. I'll keep idea in my head, for the future.

My solution was the separation of the two compounds using techniques common chromatography. Used different types of columns with different diameters of particle, different mobile phase, and varied pH aquatic environment. At this point, I have achieved a clear separation of compounds.

But following problem, I think, poor stability of isoxaflutole in the calibration solution and consequently the metabolism going. Is this possible?

Thank you!

If they are not stereo-isomers (in your case looks like unlikely), you have chances to find product ions that differentiate those two.

Do a product ion scan by infusion of pure compound if you haven't done so to find unique product ions. Hope this helps

Thank you very much for your help!
Fortunately, I solved the problem of changes in the chromatographic conditions and the selection of the analytical column.

But your suggestions are very valuable to me! Thank you, and are very pleased that there is a forum!