Physicochemical Parameters Affecting the Electrospray Ionization Efficiency of Amino Acids after Acylation.

Electrospray ionization (ESI) is widely used in liquid chromatography coupled to mass spectrometry (LC-MS) for the analysis of biomolecules. However, the ESI process is still not completely understood, and it is often a matter of trial and error to enhance ESI efficiency and, hence, the response of a given set of compounds. In this work we performed a systematic study of the ESI response of 14 amino acids that were acylated with organic acid anhydrides of increasing chain length and with poly(ethylene glycol) (PEG) changing certain physicochemical properties in a predictable manner.