The data acquired with µF/mnESI also featured markedly less species with multiple adducts compared to the conventional AF/ESI configuration, observed both in the lipid standard injections and cell extracts. As the injected cell samples were desalted with the selected sample preparation procedure, the difference in the amounts of injected matrix cannot be considered. The high number of sodiated lipids in the AF/ESI data could originate from the high amount of solvent delivered to the ion source, as it contains metal cations leeched from glass bottles 30 . This suggestion is again supported by the reduction of sodiation upon transition from the 5-to the 8-nozzle configuration, to a smaller flow rate per nozzle. In addition, faster evaporation of the smaller droplets generated by the µF/mnESI setup could create an excess of ammonium ion in the gas phase at much faster rates. Consequently, the already reduced quantity of sodium ions is further outcompeted by their ammonium counterparts during the ionization process.