DRIFT DIFFERENTIAL MOBILITY ANALYZER

This work addresses the problem of narrowing the peak diffusive broade ning observed in the response of differential mobility analyzers (DMA) when dealing with nanoparticles and ions. Instead of achieving this t ask by solely increasing the sheath gas flowrate through the instrumen t (i.e. increasing the Peclet number, Pe), as done in recent studies, we show that the broadening can be further reduced by establishing an axial electric field upon the classical transverse one. This still non existing instrument would be what we call a drift-DMA (DDMA). The asym ptotic analysis (Pe >> 1) indicates that a well designed DDMA might tr iple the resolution of Resell's DMA (Rosell-Llompart et al., J. Aeroso l Sci. 27, 695-719) when both instruments run at the same Pe, placing this hypothetic instrument in an excellent position to even compete wi th standard ion drift tubes. On the other hand, the DDMA would yield t he same resolution of a Resell's DMA but running at a Reynolds number Re near one order of magnitude smaller, with the corresponding saving on pumping needs. (C) 1998 Elsevier Science Ltd. All rights reserved.