*4.5. Production of NanoESI Capillaries*

NanoESI capillaries for offline measurements were prepared in-house from borosilicate glass tubes of 1 mm outer and 0.5 mm inner diameters (BF 100-50-10, Sutter Instruments, Novato, CA, USA), using a P-1000 Flaming/BrownTM micropipette puller system (Sutter Instruments, Novato, CA, USA). Capillaries were gold-coated using a sputter coater BalTec SCD 0045 (Bal-Tech, Balzers, Liechtenstein) with the following conditions: current was set to 20 mA for 150 s, table distance was 5 cm, while vacuum was ca. 10−<sup>3</sup> mbar and Argon gas pressure maintained at ca. 10−<sup>2</sup> mbar [16].
