Surface roughening of a non‐tapered open tubular emitter for improved electrospray ionization mass spectrometry performance at low flow rates

Abstract

A non-tapered open tubular emitter with 75 microm internal diameter (i.d.) and 360 microm external diameter (o.d.) was developed by simply grinding the exit aperture of a fused-silica capillary. The roughened emitter, with a relatively large aperture, generates stable electrospray signals (generally <5% relative standard deviation (RSD) for most conditions studied) at less than 500 nL/min flow rates, and was characterized with atomic force microscopy. The surface treatment greatly extends the operational range of an open tubular emitter to lower flow rates, compared to that of a cleaved capillary with similar dimensions. The stabilized nanoelectrospray is attributed to the increased surface roughness and modified wetting characteristics of the emitter exit resulting from grinding. Electrospray performance was evaluated, and as a result of the enhanced sensitivity from a roughened emitter, five femtomoles of leucine enkephalin were detected at a 50 nL/min flow rate with a signal to noise (S/N) ratio of 48. Furthermore, trypsin-digested bovine serum albumin (BSA) was used to demonstrate the application of the emitter in protein identification, giving a sequence coverage of 60%. These emitters are robust, and may become a facile alternative to tapered emitters at moderate nano flow rates (e.g. 50 to 500 nL/min).

Sheathless capillary electrophoresis electrospray ionization‐mass spectrometry interface based on poly(dimethylsiloxane) membrane emitter and thin conducting liquid film

“…1 shows the extracted ion counts per ion compared to the flow rate. Similar to other results , the ion counts per analyte increased with the decreasing flow rate.…”

“…A similar trend was reported using a fused silica emitter with a 50 μm id and an etched od . In the flow rate sensitive region, ionization efficiency improved at very low flow rates . In other words, decreasing the flow rate may decrease the absolute ion counts, but increase the ion counts per analyte.…”

Piezoelectric inkjet assisted rapid electrospray ionization mass spectrometric analysis of metabolites in plant single cells via a direct sampling probe

“…Only a few studies have investigated the inuences of the emitter surface wetting characteristic to the ESI performance. 19,[24][25][26] For a solid surface, the wetting properties rely on the difference in surface energy between the liquid drop and the solid material. From a theoretical point of view, 27 high wettability indicates strong liquid-solid interactions at the solidliquid interface, which can lower the surface tension by forming a disjoining pressure and cause the liquid to spread along the surface.…”

Nanoelectrospray emitters: Trends and perspective

“…Using a different approach, Su, Marecak, and Oleschuk (2008) altered the wetting characteristics of the tip face by roughening it with sandpaper. The roughened end, analyzed by AFM and found to have surface features on the order of $5-15 mm, was proposed to be involved in a Wenzel contact state with the liquid in which the droplet penetrates the spaces between the surface features.…”