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Gonser, Stefan ; Held, Andreas:
A chemical analyzer for charged ultrafine particles.
In: Atmospheric Measurement Techniques.
Bd. 6
(2013)
.
- S. 2339-2348.
ISSN 1867-8548
DOI: https://doi.org/10.5194/amt-6-2339-2013
Abstract
New particle formation is a frequent phenomenonin the atmosphere and of major significance for the Earth’sclimate and human health. To date the mechanisms leadingto the nucleation of particles as well as to aerosol growth arenot completely understood. A lack of appropriate measurementequipment for online analysis of the chemical compositionof freshly nucleated particles is one major limitation.We have developed a Chemical Analyzer for ChargedUltrafine Particles (CAChUP) capable of analyzing particleswith diameters below 30 nm. A bulk of size-separated particlesis collected electrostatically on a metal filament, resistivelydesorbed and subsequently analyzed for its molecularcomposition in a time of flight mass spectrometer. We reporton technical details as well as characterization experimentsperformed with the CAChUP. Our instrument was tested inthe laboratory for its detection performance as well as for itscollection and desorption capabilities. The manual applicationof defined masses of camphene (C10H16) to the desorptionfilament resulted in a detection limit between 0.5 and5 ng, and showed a linear response of the mass spectrometer.Flow tube experiments of 25 nm diameter secondary organicaerosol from ozonolysis of alpha-pinene also showed a linearrelation between collection time and the mass spectrometer’ssignal intensity. The resulting mass spectra from the collectionexperiments are in good agreement with published workon particles generated by the ozonolysis of alpha-pinene. Asensitivity study shows that the current setup of CAChUP isready for laboratory measurements and for the observation ofnew particle formation events in the field.