AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
The Impact of Efficient Trapping Millions of Atmosphere-Sampled Singly-Charged Nanoparticles up to 200 nm
PETER T. A. REILLY, Xinyu Wang, Huijuan Chen, Katherine G. E. Donahoe, Washington State University
Abstract Number: 372 Working Group: Instrumentation and Methods
Abstract Recently our group has demonstrated trapping of atmosphere-sampled singly-charged nanoparticle by the millions at a point just before the exit end cap electrode of linear quadrupole ion trap. These ions were collected and held there until they were ejected on-demand in a well collimated plug into the entrance of an orthogonal acceleration time-of-flight mass analyzer. Normally, the ions are pulsed into the flight tube for high resolution mass analysis. The mass range for high resolution mass analysis of this instrument is defined by the detector and currently limited to approximately 10$^6 amu thereby permitting high resolution mass analysis below 10 nm. The expressed limit is set by the analyzer—not the inlet and trapping system. To define the mass/size limit of the inlet and trapping system, polydisperse aerosols of urea were generated by nebulization and dried. The dried aerosols were sampled through a commercial differential mobility analyzer (DMA) to size select the charged aerosol. The DMA effluent was split with approximately 100 ml/min sampled through the 100 micrometer diameter flow limiting inlet orifice. The rest of the effluent was sampled into a Faraday detector to define the number density of the monodisperse charged aerosol. The particles admitted into the mass spectrometer were sampled and trapped for varying periods to be subsequently ejected on demand to pass through the TOF acceleration region and into a Faraday plate detector. The gain of the detector was 10$^9 V/A. The baseline widths of the ions detected at the Faraday plate routinely measured between 125 and 150 microseconds across the entire range between 10 and 200 nm with amplitudes of 2-5 V. The results of these experiments will be presented and discussed to define the future of high resolution mass analysis to characterize aerosols