Development of Remote Sampling ESI Mass Spectrometry for the Rapid and Automatic Analysis of Multiple Samples

Abstract

We report on combining a self-aspirated sampling probe and an ESI source using a single metal capillary which is electrically grounded and safe for use by the operator. To generate an electrospray, a negative H.V. is applied to the counter electrode of the ESI emitter to operate in positive ion mode. e sampling/ESI capillary is enclosed within another concentric capillary similar to the arrangement for a standard pneumatically assisted ESI source. e suction of the liquid sample is due to the Venturi eeect created by the high-velocity gas ow near the ESI tip. In addition to serving as the mechanism for suction, the high-velocity gas ow also assists in the nebulization of charged droplets, thus producing a stable ion signal. Even though the potential of the ion source counter electrode is more negative than the mass spectrometer in the positive ion mode, the electric eld eeect is not signiicant if the ion source and the mass spectrometer are separated by a suucient distance. Ion transmission is achieved by the viscous ow of the carrier gas. Using the present arrangement, the user can hold the ion source in a bare hand and the ion signal appears almost immediately when the sampling capillary is brought into contact with the liquid sample. e automated analysis of multiple samples can also be achieved by using motorized sample stage and an automated ion source holder.