Does anyone have any idea as to why dansyl derivatives of hydroxyl groups appear to result in a 171 M/Z fragment while dansyl derivatives of amines tend to result in 170 M/Z fragments?
In our research we have consistently found that there is a 1 Da difference between the fragments detected for compounds that result from Dansyl derivation of hydroxyl groups compared to amine groups when performing SRM and MRM on both QqQ and qTOF mass spectrometer systems. However there are times that this difference was not seen. It should not be due to the initial ionization as the fragmentation takes place after precursor selection in Q1 or q.
Also the sensitivity appears to be less by an order of magnitude when performing SRM relative to the precursor ions.
Another observation is that multiply Dansyl derived precursor have preference for single charged ions despite applying the highest usable ionization voltages.
Many thanks for the feedback John.
I will send you some spectra if you provide an email address. I have seen the article you suggested which again shows 171 as the fragment for hydroxyl derivatives. I fully agree that the nitrogen or oxygen atom plus the sulphonyl group remain part of the precursor molecule fragment.
We are almost of the opinion that a radical is the preferred fragment for amine derivatives while a proton a adduct is the preferred fragment for hydroxyl derivatives, but it does not make sense to me as both are being fragmented in the gas phase in the collision cell under essentially the same conditions.
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