Chapter 3.1.3 - Electrospray-differential mobility analysis (ES-DMA)

Abstract

Among the methods available for the characterization of nanostructured materials, electrospray-differential mobility analysis (ES-DMA), also known as electrospray scanning mobility particle sizer (ES-SMPS) or electrospray ionization-gas-phase electrophoretic mobility molecular analysis (ESI-GEMMA), has been identified as a powerful technique for the measurement of nanoparticle (NP) size distributions and has recently yielded promising results when measuring the absolute NP number concentrations in colloidal suspensions. ES-DMA typically consists of three units: (1) a charge reduced electrospray generator (ES), that is, an electrospray generator directly coupled to a neutralization source; (2) a differential mobility analyzer (DMA) that selects particles according to their electrical mobility equivalent diameter; and (3) a condensation nucleus counter (CNC) (also known as condensation particle counter, CPC) that counts selected particles. Electrical mobility equivalent diameter, or simply mobility diameter, is the diameter of a spherical particle with the same mobility (defined as the particle velocity produced by a unit external force) as the particle in question. In this chapter, we present an overview of the ES-DMA instrumentation and possible configurations as well as its applications to the measurement of number size distributions and particle number concentrations of nanostructured materials in colloidal suspensions.