Promoting carboxylate salts in the ESI source to simplify positive mode MS/MS sequencing of acid-terminated encoded polyurethanes

Synthetic polymers prepared by solid-phase processes are often released from the solid support by hydrolysis, leading to an acidic α chain-end which can usefully be employed to perform mass spectrometry experiments in the negative ion mode. This is the case for sequence-defined polyurethanes, which exhibit very simple MS/MS pattern as deprotonated species in great contrast to data obtained in the positive ion mode. Indeed, after deprotonation of...