FMOC derivatization is somehow tricky. You do not need ADAM regent, in the aqueous phase and at room temperature, a reaction is being occurred already. Carefully inspect do you really need a catalyst?... For reproducible results, I suggest terminating the reaction by spiking a volatile acid (for the sake of MS analysis use FA or AA instead of inorganic ones). By decreasing the pH further byproduct formation induced by FMOC can be prevented and resulted target derivate can be kept stable. Do not forget to pay attention to using aggressive wash solutions (weak and strong combined) to prevent carry-over-like issues...

Good luck, İEA...

İsmail Emir Akyildiz Thank you very much for your reply. May I please ask what do you mean by "For reproducible results, I suggest terminating the reaction by spiking a volatile acid (for the sake of MS analysis use FA or AA instead of inorganic ones)."?

Currently, my buffer is at pH9. Do you suggest using lower pH system?

Definitely no. For versatile derivatization, you should perform the reaction under alkaline conditions. For this borate or carbonate buffers are needed and there is not any problem in your setup. I suggest you use FA at the end of the derivatization reaction as a stopping reagent. By lowering the pH after the experimentally defined incubation period, FMOC affinity is restricted, and formation of the further products or by-products is prevented. This will return as reproducible derivates. You may refer to my research which was conducted with a similar strategy but the target was aminoglycoside. It may be helpful for clarifying...Here is the link; Article Single Pot In situ Aqueous Derivatization and Subsequent Det...