Sources wherein droplet formation is decoupled from electrophoretic charging (e.g., SAII, AMUSE or SAWN) can be softer than electrospray sources. However, no major differences in internal energies were found for ions produced from different variants of ESI, except for cold spray ionization (CSI). Among methods wherein the analytes are collected by ESI droplets, secondary electrospray ionization (SESI) is the softest, while desorption electrospray ionization (DESI) or electrospray of laser-desorbed analytes are energetically similar to electrospray.