PNNL

Abstract

Subambient Pressure Ionization with Nanoelectrospray (SPIN), an electrospray ionization source that operates at 30 Torr inside the first vacuum chamber of a mass spectrometer, has been demonstrated for reversed-phase liquid chromatography-mass spectrometry analysis of a protein tryptic digest solution. A 5–12-fold improvement in sensitivity relative to a standard atmospheric pressure ESI source was observed for a variety of detected peptides. The low liquid chromatographic flow rate (300 nL/min) allowed stable electrospray to be established before the onset of electrical discharge, and the higher operating pressure of the SPIN source relative to previous low-pressure ESI source designs prevented the solvents from freezing. The range of accessible flow rates for the SPIN source was also extended to 2.5 µL/min by using an array of electrospray emitters that divided the flow to 6 discrete electrosprays.