Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 8 5 2008 10.5194/acpd-8-17631-2008 http://www.atmos-chem-phys-discuss.net/8/17631/2008/ http://www.atmos-chem-phys-discuss.net/8/17631/2008/acpd-8-17631-2008.html http://www.atmos-chem-phys-discuss.net/8/17631/2008/acpd-8-17631-2008.pdf 17631 17660 2008-09-29 Performance evaluation of a high-resolution parallel-plate differential mobility analyzer J. P. Santos E. Hontañón E. Ramiro M. Alonso RAMEM S.A., Sambara 33, 28027 Madrid, Spain National Center for Metallurgical Research (CENIM-CSIC), Avda. Gregorio del Amo 8, 28040 Madrid, Spain A high-resolution differential mobility analyzer (DMA), specially designed for (i) the measurement of ion mobility spectra, and (ii) the generation of a continuous stream of monomobile ions, has been developed and tested. The apparatus consists of two parallel-plate electrodes between which an electric field is applied. The test ion stream flows into the instrument through a narrow rectangular slit made in one of the electrodes, and migrates toward the other electrode driven by the applied field, while being transported by a stream of clean air which flows parallel to the plates at Reynolds number between 2×104 and 9×104 in laminar flow conditions. The collector electrode contains also a narrow slit through which ions of the desired mobility are withdrawn out of DMA. The classified ion current is measured with a high-sensitivity electrometer having a noise level around 0.1 fA. The theory behind the DMA operation is first discussed, focusing on the special case of parallel-plate geometry. Some generic results showing the stability and repeatability of the measurements and the resolving power of the instrument are presented next. The last part of the paper deals with the application of the apparatus to the study of the effect of humidity and aging time on the mobility spectra of air ions generated by a low-activity 241Am source. Alonso, M.: Reducing the diffusional spreading rate of a Brownian particle by an appropriate non-uniform external force field, J. Aerosol Sci., 33, 439–450, 2002. Buryakov, I. A.: Express analysis of explosives, chemical warfare agents and drugs with multicapillary column gas chromatography and ion mobility spectrometry, J. Chromatogr. B, 800, 75–82, 2004. Chen, D. R., Pui, D. Y. H., Humes, D., Fissan, H., Quant, F. R., and Sem, G. J.: Design and evaluation of a nanometer aerosol differential mobility analyzer (Nano-DMA), J. Aerosol Sci., 29, 497–509, 1998. Chen, D. R., Pui, D. Y. H., Mulholland, G. W., and Fernandez, M.: Design and testing of an aerosol/sheath inlet for high resolution measurements with a DMA, J. Aerosol Sci., 30, 983–999, 1999. Chen, Y. H., Hill, H. H., and Wittmer, D. P.: Thermal effects on electrospray ionization ion mobility spectrometry, Int. J. Mass Spectrom., 154, 1–13, 1996. Clemmer, D. E. and Jarrold, M. F.: Ion mobility measurements and their applications to clusters and biomolecules, J. Mass Spectrom., 32, 577–592, 1997. de Juan, L. and Fernández de la Mora, J.: High resolution size analysis of nanoparticles and ions: running a Vienna DMA of near optimal length at Reynolds numbers up to 5000, J. Aerosol Sci., 29, 617–626, 1998. Flagan, R.C.: History of electrical aerosol measurements, Aerosol Sci. Technol., 28, 301–380, 1998. Hagwood, C., Sivathanu, Y., and Mulholland, G.: The DMA transfer function with Brownian motion: a trajectory/Monte-Carlo approach, Aerosol Sci. Tech., 30, 40–61, 1999. Hill Jr., H. H. and Martin, S. J.: Conventional analytical methods for chemical warfare agents, Pure Appl. Chem., 74, 2281–2291, 2002. Karpas, Z., Cohen, M. J.,Stimac, R. M., and Wernlund, R. F.: On the effects of structure and charge distribution on the mobility of ions, Int. J. Mass Spectrom., 74, 153–159, 1986. Karpas, Z., Stimac, R. M., and Rappoport, Z.: Differentiating between large isomers and derivation of structure information by ion mobility spectrometry/mass spectrometry techniques, Int. J. Mass Spectrom., 83, 163–175, 1988. Knutson, E. O. and Whitby, K. T.: Aerosol classification by electric mobility: apparatus, theory, and applications, J. Aerosol Sci., 6, 443–451, 1975. Kousaka, Y., Okuyama, K., and Mimura, T.: Effect of Brownian diffusion on electrical classificatrion of ultrafine particles in differential mobility analyzers, J. Chem. Eng. Jpn., 19, 401–407, 1986. Loscertales, I. G.: Drift differential mobility analyzer, J. Aerosol Sci., 29, 1117–1139, 1998. Martínez-Lozano, P. and Fernández de la Mora, J.: Resolution improvements of a nano-DMA operating transonically, J. Aerosol Sci., 37, 500–512, 2005. Martínez-Lozano, P., Labowsky, M., and Fernández de la Mora, J.: Experimental tests of a nano-DMA with no voltage change between aerosol inlet and outlet slits, J. Aerosol Sci., 37, 1629–1642, 2006. Ramiro, E. and Rivero, A.: Wide range differential mobility analyzer (DMA) with very high resolution, International Patent WO 2007/020303 A1, 2007. Reischl, G. P., Mäkelä, J. M., Karch, R., and Necid, J.; Bipolar charging of ultrafine particles in the size range below 10 nm, J. Aerosol Sci., 27, 931–949, 1996. Rosell-Llompart, J., Loscertales, I. G., Bingham, D., and Fernández de la Mora, J.: Sizing nanoparticles and ions with a short differential mobility analyzer, J. Aerosol Sci., 27, 695–719, 1996. Rosser, S. and Fernández de la Mora, J.: Vienna-type DMA of high resolution and high flow rate, Aerosol Sci. Tech., 39, 1191–1200, 2005. Salm, J.: Diffusion distortions in a differential mobility analyzer: the shape of apparent mobility spectrum, Aerosol Sci. Tech., 32, 602–612, 2000. Song, D. K. and Dhaniyala, S.: Change in distributions of particle positions by Brownian diffusion in a non-uniform external field, J. Aerosol Sci., 38, 444–454, 2007. Stolzenburg, M.: An ultrafine aerosol size distribution measuring system, Ph.D. thesis, University of Minnesota, USA, 1988. Swing, R. G., Atkinson, D. A., Eiceman, G. A., and Ewin, G. J.: A critical review of ion mobility spectrometry for the detection of explosives and explosive related compounds, Talanta, 54, 515–529, 2001. Tammet, H. F.: The aspiration method for the determination of atmospheric-ion spectra, Keter Press, Jerusalem, Israel, 1970. Tammet, H., Mirne, A., and Tamm, E.: Electrical aerosol spectrometer of Tartu University, Atmos. Res., 62, 315–324, 2002. Vautz, W., Zimmerman, D., Hartmann, M., Baumbach, J. I., Nolte, J., and Jung, J.: Ion mobility spectrometry for food quality and safety, Food Addit. Contam., 23, 1064–1073, 2006. Whitby, K. T. and Clark, W. E.: Electrical aerosol particle counting and size distribution measuring system for the 0.015 to 1 μ size range, Tellus, 18, 573–586, 1966. Winklmayr, W., Reischl, G. P., Lidner, A. O., and Berner, A.: A new electromobility spectrometer for the measurement of aerosols size distributions in the size range from 1 to 1000 nm, J. Aerosol Sci., 22, 289–296, 1991.