Hi to all,

I'm exeriencing some issues with my quantification standard I use to evaluate peaks eluted at hplc and analysed in ESI MS positive ion mode.

In particular, I observe a time-dependent decrease in the reserpine-peak area (my standard) and an increase in the areas of two peaks before and after the elution of the standard. The m/z of reserpine is 609.28. the m/z under that "satellite" peaks is 639.29. There is a delta of 30.01 Da corresponding, maybe, to a CH2O.

Furthermore, I observe this reserpine modification randomly, and i'd like to identify the root of this problem in order to avoid it in the next analysis.

Does anyone experienced similar issues? How did you get rid of it? Do you have any clues?

Thank you very much