[peptideismylife]

Hey people,

I am running a synthesis of a sequence. At the end I cleave the resin using TFA and TIS and I analyse by LC/MS. I can detect my product, but at the beginning of the chromatogram appears a big UV peak which a ion mass of 285, 484 and 683. I was checking the literature and I found a paper in which they are talking about TFA-non covalent complexes. In fact they described different clusters between TFA and piperidine which they have this exactly masses. I am using piperidine to deprotect Fmoc group and also TFA to cleave the resin. Even that I make sure to wash several times with DMF and DCM the resin before to do the cleavage with TFA. For that reason I am not sure that the formation of this clusters it must be the reason of this big UV peak at the begining of the chromatogram (even has these masses). But I can not find another reason....

Someone has any similar experience....

Could you expect a big UV peak at 220nm of TFA-piperidine cluster? (this is also something that make me feel confused...because I wouldnt expect that this cluster has a big absorbance in UV at 220nm....)

Thank u