PNNL

Abstract

An electrospray ionization mass spectrometry (ESI-MS) source and interface has been designed that enables efficient ion production and transmission in a 30 Torr pressure environment using solvents compatible with typical reverse-phase liquid chromatography (RPLC) separations. In this design, the electrospray emitter is located inside the mass spectrometer in the same region as an electrodynamic ion funnel. This avoids the use of a conductance limit ion inlet, as required by a conventional atmospheric pressure ESI source, and allows more efficient ion transmission to the mass analyzer. Performance of the low pressure ESI source and interface was evaluated by electrospraying standard solutions at 300 nL/min, and comparing results with those obtained from a standard atmospheric pressure ESI source that used a heated capillary inlet. The importance of desolvation was also investigated by electrospraying at different flow rates, which showed that the ion funnel provided an effective desolvation region to aid the creation of gas phase analyte ions. This initial study demonstrated a ~ 5-fold improvement in sensitivity when the low pressure ESI source was used compared to a standard atmospheric pressure ESI source.