For the analysis, a multi-step gradient was applied using acetonitrile (Solvent A) and 0.1% TFA (Solvent B): 5% A to 15% A in 1 min, then to 35% A in a further 9 min, then to 95% A in a further 2.5 min and finally back to 5% A in a further 2.5 min (A + B = 100%...