DMSO as a Silylation solvent

[VSPKumar]

Greetings fellow chromatographers!

I am trying to silylate some AMP, ATP, and ADP samples for GC analysis. To dissolve the standards, I used DMSO as they didn't dissolve in pyridine, thf, or acetonitrile. Upon addition of silylation reagent (MTBSTFA+ ammonium iodide or TBDMSOTf) the solution started turning orange and quickly darkened to almost black along with the evolution of heat. When I tried to analyse these on the GC, the syringe of the autosampler got clogged with some sticky residue after a few samples.

Does anyone know what's going on here and how to prevent it from happening? I could use another solvent but most polar aprotic solvents are unable to dissolve ADP and ATP. I have sulfolane in mind, but haven't tried it yet.

[Consumer Products Guy]

Upon addition of silylation reagent (MTBSTFA+ ammonium iodide or TBDMSOTf) the solution started turning orange and quickly darkened to almost black along with the evolution of heat.

Did such reaction and heat result when you just added your reagent to the DMSO? If so - then something's reacting - so don't use !!

We derivatized a lot using BSTFA containing 1% TMCS but we used pyridine or N,N-dimethylformamide as solvents.

[VSPKumar]

Did such reaction and heat result when you just added your reagent to the DMSO? If so - then something's reacting - so don't use !!

The reaction happened only when the analytes were present. Adding just DMSO and the silylation reagents showed no reaction. This is why I feel that it was probably derivatisation happening, but the analysis seems to be a mess as it is just quite black and sticky after.

Could it be that DMSO itself is degrading because of the by-products of silylation i.e Hydrogen Iodide or trifluoromethane sulfonic acid and trifluoroacetamide? That would explain why it would happen only in the presence of the analyte and not just the reagents...