Pulling and Gold-Coating Nanospray Capillaries

Nano-ESI capillaries were pulled using a Flaming/Brown P-97 micropipette puller (Sutter Instruments). In order to achieve a tip shape shown in Fig. 2.3, the parameters were carefully optimised by to obtain a satisfactory tip shape [7]. Although parameters can change when using different filaments, a typical set of values are detailed in Table 2.7. 

Once pulled, the capillaries were coated in gold using a home-built vacuum evaporator, depicted in (Fig. 2.4). Pre-pulled capillaries were placed into a supporting rack and placed in the evaporation chamber, directly underneath the evaporation boat. Gold wire ( 20 mg) was then placed into the evaporation boat, and a vacuum ( 1.2 x 10 mbar) was applied to the chamber. Once a suitable vacuum was achieved, 50 V was applied to the evaporation boat using an autotransformer and evaporation was allowed to proceed. Following evaporation (typically 2 min), the autotransformer was set to 0 V, and the chamber was vented using the vent valve. This procedure was performed twice to coat each side of the capillaries. 

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