MESURE RAPIDE DE LA DISTRIBUTION EN TAILLE AVEC UN SMPS EN UTILISANT UN NOUVEAU CLASSIFICATEUR T. Tritscher* (1), J. Farnsworth (2), E. Filimundi (3), S. Elzey (2), H.-G. Horn (1), and O.F. Bischof (1) (1) TSI GmbH, 52068 Aachen, Germany
*
[email protected]
(2) TSI Incorporated, 55126 Shoreview, MN, USA (3) TSI France, 13382 Marseille Cedex 13, France
TITLE
Fast Particle Size Distribution Measurements with SMPS utilizing a Novel Classifier
ABSTRACT Measurements of particle number and size distributions based on the Scanning Mobility Particle Sizer (SMPS) technique are widely used in the size range from about 1 nm to 1 µm. Particles are selected in a Differential Mobility Analyzer (DMA) after which the size-selected particles are individually counted by a Condensation Particle Counter (CPC). All SMPS have a relatively long response time as their common drawback (typically 1 min or longer, depending on particle distribution and concentration). In order to meet the need for faster spectrometers with the same reliability, a next generation classifier (TSI Model 3082) has been developed. We show validation data with PSL reference particles and lab aerosols that demonstrate the good agreement of both classifiers at traditional scanning rates and the advantages of the new classifier at short scan times. Data from case studies will provide practical examples of the extended possibilities with the novel SMPS in particle research and monitoring applications.
RESUME La technique utilisée pour la mesure du nombre de particules et de leur distribution en taille avec le granulomètre de mobilité électrique séquentielle (SMPS) est très largement répandue et est devenue le choix principal dans la gamme de tailles de 1nm à 1µm. Après une étape de conditionnement, les particules sont triées par taille grâce à l’analyseur de mobilité différentielle (DMA) et les particules de la taille sélectionnée sont comptées individuellement par un compteur à noyaux de condensation (CPC). L’inconvénient de tous les systèmes SMPS est leur temps de réponse relativement long. Le temps nécessaire pour réaliser un scan est en général de 1min ou plus. Dans le but de répondre au besoin de mesures plus rapides avec la technique de tri par mobilité électrique séquentielle tout en conservant la même fiabilité, un nouveau classificateur (TSI modèle 3082) a été développé pour permettre des temps de scan plus court jusqu’à 5 secondes. Des données de validation avec des particules de référence, PSL et aérosol de laboratoire, démontreront un très bon accord entre les deux classificateurs pour des mesures à des temps de scan traditionnels, ainsi que les avantages du nouveau modèle à des temps de scan réduits. Les données issues des études fourniront des exemples pratiques illustrant les capacités supplémentaires de ce nouveau SMPS dans le domaine de la recherche et de la mesure en continu.
Measurements of particle number and size distributions based on the Scanning Mobility Particle Sizer (SMPS) technique (Knutson and Whitby 1975; Wang and Flagan 1990) are widely used and have become the method of choice in the size range from about 1 nm to 1 µm. In the SMPS technique, particles are conditioned (impactor removes large particles), bipolar charged and subsequently selected in a Differential Mobility Analyzer (DMA). After the DMA the size-selected particles are individually counted by a Condensation Particle Counter (CPC). The technique has a considerable reputation for its reliability and the fact that it is based on basic physical principles. Recently, a compact and portable version, the NanoScan SMPS, was introduced to open up new fields of application (Tritscher et al. 2013). All SMPS spectrometers, including component systems such as those based on Electrostatic Classifiers (TSI Model 3080), have a relatively long response time as their common drawback. Typical scans will last about 1 min or longer, depending on particle distribution and concentration. For a reliable measurement the aerosol concentration should be more or less stable during one scan. In order to meet the need for faster measurements of differential mobility spectrometers with the same reliability, a next generation classifier (TSI Model 3082) has been developed. Faster scanning improves the time resolution of the size distribution measurements and thus can show dynamic processes and developments of the aerosol population. TSI’s SMPS Model 3938 is using the new classifier 3082 and is the rd 3 generation of SMPS, trusted by researchers for many years. Fig. 1 shows on the left side the flow schematic and main components of the novel classifier and on the right side a photo of the classifier with a long DMA installed. It retains the functions and flexibility of the previous TSI classifier generation, but features essential improvements and additional characteristics such as dual polarity high voltage (HV) control, increased sheath flow up to 30 L/min for improved size resolution, and integrated, removable accessories (soft x-ray neutralizer and lower-pressure drop pre-impactor). The calibration of the new classifier fully complies with ISO standard 15900, which provides the methodology for adequate quality control of differential mobility analyzers.
Fig. 1: Flow schematic of the new classifier with main components (left) and photo of TSI Model 3082 from outside with long DMA.
The faster response time of the HV control (
