SMALL-VOLUME AND LOW FLOW-RATE ELECTROSPRAY-IONIZATION MASS-SPECTROMETRY OF AQUEOUS SAMPLES

A new electrospray ionization source (emitter) has been developed whic h allows the effective utilization of very small sample volumes at muc h lower flow rates than previously demonstrated. A small diameter etch ed-tip capillary has been incorporated into a pressure-infusion electr ospray ionization source. The ability to electrospray aqueous solution s without the use of an ancillary sheath flow is demonstrated with sev eral biopolymers. High signal intensities and stable signals are obser ved for this source in a comparison with a standard methanol-sheath so urce.