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Design and construction of a simple Knudsen Effusion Mass Spectrometer (KEMS) system for vapour pressure measurements of low volatility organics
1School of Earth, Environmental and Atmospheric Science, University of Manchester, UK
2Research Center Jülich, Germany
Abstract. A design of and initial results from a Knudsen Effusion Mass Spectrometer (KEMS) are presented. The design was adapted from high temperature alloy studies with a view to using it to measure vapour pressures for low volatility organics. The system uses a temperature controlled cell with an effusive orifice. This produces a molecular beam which is sampled by a quadropole mass spectrometer with electron impact ionization calibrated to a known vapour pressure. We have determined P298 and ΔHsub of the first 5 unsaturated straight chain dicarboxylic acids: 2.15±1.19×10−2 Pa and 75±19 kJ mol−1 respectively for Oxalic acid, 5.15±0.76×10−4 Pa and 91±4 kJ mol−1 for Malonic acid, 9.19±2.26×10−5 Pa and 93±6 kJ mol−1 for Succinic acid, 4.21±1.66×10−4 Pa and 123±22 kJ mol−1 for Glutaric acid and 5.21±3.84×10−6 Pa and 125±40 kJ mol−1 for Adipic acid.
Discussion Paper (PDF, 1408 KB) Interactive Discussion (Closed, 5 Comments) Final Revised Paper (AMT)
Citation: Booth, A. M., Markus, T., McFiggans, G., Percival, C. J., Mcgillen, M. R., and Topping, D. O.: Design and construction of a simple Knudsen Effusion Mass Spectrometer (KEMS) system for vapour pressure measurements of low volatility organics, Atmos. Meas. Tech. Discuss., 2, 893-914, 2009. Bibtex EndNote Reference Manager
