Abstract
We present a detailed optimization and characterization of the analytical performance of SU‐8‐based emitters for electrospray ionization mass spectrometry (ESI/MS). The improved SU‐8 fabrication process presented here enhances patterning accuracy and reduces the time and cost of fabrication. All emitters are freestanding and enable sample delivery by both pressure‐driven and spontaneous flows. The optimized emitter design incorporates a sharp, double‐cantilevered tip implemented to the outlet of an SU‐8 microchannel and provides highly sensitive ESI/MS detection. Moreover, the optimized design allows the use of relatively large microchannel dimensions (up to 200 × 50 µm^2^, w × h) without sacrificing the detection sensitivity. This is advantageous with a view of preventing emitter clogging and enabling reproducible analysis. The measured limits of detection for the optimized emitter design were 1 nM for verapamil and 4 nM for Glu‐fibrinopeptide B with good quantitative linearities between 1 nM and 10 µM (R^2^ = 0.9998) for verapamil and between 4 nM and 3 µM (R^2^ = 0.9992) for Glu‐fibrinopeptide B. The measured tip‐to‐tip repeatability for signal intensity was 14% relative standard deviation (RSD) (n = 3; 5 µM verapamil) and run‐to‐run repeatability 4–11% RSD (n = 4; 5 µM verapamil) for all individual emitters tested. In addition, long‐term stability of < 2% RSD was maintained for timescales of 30 min even under free flow conditions. SU‐8 polymer was also shown to be chemically stable against most of the tested electrospray solvents. Copyright © 2008 John Wiley & Sons, Ltd.