The Zenobi group ) determined the internal energy distributions of ions produced by nano-ESI, standard ESI, and sonic spray ionization (SSI). The latter does not use any voltage, and thus droplets are charged only to a low level (just statistically) and ions are supposedly produced only through a charge residue scenario. The internal energy distributions obtained with all three ionization methods were found overlap (the one with ESI is only slightly higher in energy). The authors concluded that benzylpyridinium ions in ESI and nano-ESI are also produced via a charged residue scenario.