LONG-LIVED METALLIZED TIPS FOR NANOLITER ELECTROSPRAY MASS-SPECTROMETRY

Sheathless electrospray at nL/min flow rates combined with Fourier-tra nsform mass spectrometry has made possible high resolving power (> 50, 000) mass spectra of subattomole samples of > 8 kDa proteins separated by capillary electrophoresis (Valaskovic, G. A.; Kelleher, N. L; McLa fferty, F. W. Science, 1996, 273, 1199-1202). However, for this new me thod the mechanical stability of the thin (35 to 100 nm) gold film ele ctrodes has limited tip lifetime to 15 to 30 min. A technique for SiOx coating of the gold is described that provides a steady ion current ( +/-10 pA) for 1 to 2 h, even with arcs or interruptions of the electro spray voltage. (C) 1996 American Society for Mass Spectrometry.