New interface plate for microspray ionization mass spectrometry.

A new interface plate was employed in microspray ionization mass spectrometry (microESI-MS) to improve ion transmission from the sprayer into the sampling nozzle of the mass spectrometer at atmospheric pressure. Using a time-of-flight mass spectrometer (TOFMS), a fivefold increase in ion intensity and a sevenfold reduction in method detection limit were observed. The interface plate attenuated the dependence of the ion intensity on the sprayer position. Even when the distance between the sprayer tip and sampling nozzle was 15.0 mm, ion signals were still stronger than when the sprayer tip was positioned 3.0 mm in front of the sampling nozzle with the original interface plate. This enhancement in the performance of microESI-MS was due to the improved shapes of the equipotential lines near the sprayer tip and the long desolvation distance between the sprayer and the sampling nozzle of the MS.