Laser particle spectrometry is one of the leading measurement technologies engaged in environment... more Laser particle spectrometry is one of the leading measurement technologies engaged in environmental monitoring, measuring the aerosol contamination of the air inside and outside of urban regions. It has a number of benefits against other methods - e.g. the possibility of real time, in situ measurement with high time resolution. These features make the light scattering based measurement methods superior to others in a mobile environmental laboratory. Our previously developed instruments are based on laser light scattering collected from different angular regions (90°, forward and backward directions) and a special illumination system increase the sensitivity and the resolution of the sizing. A collection of the developed optical instruments and other devices based on different methods were installed into a mobile environmental laboratory for monitoring atmospheric aerosols, which allows the comparison of the results obtained from different measurement methods. This laboratory has been used in 3 measurement campaigns where measurements were performed in 6 different locations.
Publisher Summary Number concentration is one of the most frequently studied parameters for chara... more Publisher Summary Number concentration is one of the most frequently studied parameters for characterization of atmospheric aerosols and other particulate systems. Determination of aerosol number concentrations can be performed by means of various methods based on a number of different measuring principles. At comparatively low concentrations, single particle counting can be applied, however, at concentrations beyond several 10 3 cm -3 , integral methods are required, which are often based on empirical calibration. To contribute to a standardization of aerosol concentration measurements, intercomparisons of various instruments were recently performed during an international experimental workshop. For consistent standardization of concentration measuring instruments, properly defined calibration standards would be required, which allow a direct determination of the particle number concentration without empirical calibration with respect to external reference standards. This chapter describes an experimental system for determination of aerosol number concentration, which is based on the measuring principle of a condensation nuclei counter. The concentrations of the particles growing in an expansion chamber are determined from simultaneous observation of scattered and transmitted light fluxes. It is shown that this experimental method allows direct particle concentration measurements for concentrations up to more than 10 7 cm -3 , and can be considered as a primary calibration standard for particle number concentration measurement.
e used as a nucleus for the condensation of n-butanol vapor to generate large aerosol droplets wh... more e used as a nucleus for the condensation of n-butanol vapor to generate large aerosol droplets which could be easily detected by optical means condensation particle counter (CPC). The method, termed ESI gas-phase electrophoretic mobility molecular analysis (GEMMA), exhibited an excellent correlation between molecular mass of globular proteins up to 6.69 10 5 Da and the measured EM diameter in air. EM diameters were determined from aqueous solutions containing 20 mM ammonium acetate and the analytes (at g/mL concentrations) as parvalbumin, ovalbumin and monoclonal antibodies (IgG type). Flow rates in the low nL/min were used and detection limits in the low picomole range were determined. Proteins, which form structurally specific non-covalent complexes in solution (as quartenary protein structures or antibody-antigene complexes) are of fundamental biological importance. There is some evidence [7] that
Nanopartikel konnen naturlichen und industriellen Ursprungs sein. Befinden sie sich im luftgetrag... more Nanopartikel konnen naturlichen und industriellen Ursprungs sein. Befinden sie sich im luftgetragenen Zustand, handelt es sich um Nanoaerosole. Durch Ihren Beitrag zur Entwicklung der Nanotechnologie haben sie groses Interesse gewonnen. Nanopartikel konnen als Bausteine fur Nanostrukturen verwendet werden, dabei sind ihre Grose und Konzentration dominierende Parameter. Die Messung von Nanopartikeln und Nanoaerosolen, insbesondere organischen Ursprungs, wie auch etwa Viren, stellt stets eine grose Herausforderung fur Wissenschaft und Technologie dar.
Particle & Particle Systems Characterization, 1986
The performance of a narrow‐angle and a wide‐angle, forward scattering laser aerosol spectrometer... more The performance of a narrow‐angle and a wide‐angle, forward scattering laser aerosol spectrometer has been studied as a function of particle size and refractive index. The results have been compared with theoretical calculations based on light scattering theory. The results indicate that for the narrow‐angle instrument, the scattered‐light intensity is not a monotonic function of particle size for transparent particles (a monotonic relationship is required for unambiguous particle size measurement) above 0.7 μm. The instrument is therefore limited in its useful range to size distribution measurement between 0.2 μm – its lower particle size limit – and 0.7 μm for transparent particles. In the case of the wide‐angle instrument, the instrument output is a monotonic function of particle size for transparent particles, but the output is severely attenuated for light absorbing particles above 0.3 μm. The instrument, therefore, cannot be used for accurate size measurements above 0.3 μm for...
We present a modelled approach of scattering contribution to the radiation transmission through a... more We present a modelled approach of scattering contribution to the radiation transmission through a scattering medium, such as an aerosol, yielding a correction term to the Lambert-Beer law. The correction is essential because a certain amount of the forward scattered light flux is always overlaid on the transmitted radiation. Hence it enters together with the attenuated beam into the finite
Particle size measurement by means of optical spectrometry of single particles depends substantia... more Particle size measurement by means of optical spectrometry of single particles depends substantially on the angular range of light scattering and the refractive index of the particle. Knowledge of the latter determines implicitly the accuracy of measurement. In contrast to commonly used instrumental systems the configuration of the design concept presented here consists of two laser illumination sources with different wavelengths and four angular ranges for the collection of scattered light. As a result a set of four independent pulses from each measured particle can be obtained allowing simultaneous assessment of particle size and its complex refractive index. Based on the Mie theory of light scattering, light collection angles yielding a single-valued aerosol size measurement were identified and used to design a new optical system. Based on the modelling of the performance for an assumed instrumental arrangement the sizing errors were found to be about 2%. The accuracy of assessment of the complex index of refraction was found to be of the order of 10% over the range of particle diameters investigated (0.1-10 µm). The theoretical results show clearly the capability of this novel instrumental design for the measurement of aerosol particle sizes, their density and optical properties. Based on these model calculations an experimental set-up is under construction.
This study explores the potential of a novel electrospray‐based method, termed gas‐phase electrop... more This study explores the potential of a novel electrospray‐based method, termed gas‐phase electrophoretic mobility molecular analysis (GEMMA), allowing the molecular mass determination of peptides, proteins and noncovalent biocomplexes up to 2 MDa (dimer of immunglobulin M). The macromolecular ions were formed by nano electrospray ionization (ESI) in the ‘cone jet’ mode. The multiple charged state of the monodisperse droplets/ions generated was reduced by means of bipolar ionized air (generated by an α‐particle source) to yield exclusively singly charged positive and negative ions as well as neutrals. These ions are separated subsequently at atmospheric pressure using a nano differential mobility analyzer according to their electrophoretic mobility in air. Finally, the ions are detected using a standard condensation particle counter. Data were expressed as electrophoretic mobility diameters by applying the Millikan equation. The measured electrophoretic mobility diameters, or Millika...
Laser particle spectrometry is one of the leading measurement technologies engaged in environment... more Laser particle spectrometry is one of the leading measurement technologies engaged in environmental monitoring, measuring the aerosol contamination of the air inside and outside of urban regions. It has a number of benefits against other methods - e.g. the possibility of real time, in situ measurement with high time resolution. These features make the light scattering based measurement methods superior to others in a mobile environmental laboratory. Our previously developed instruments are based on laser light scattering collected from different angular regions (90°, forward and backward directions) and a special illumination system increase the sensitivity and the resolution of the sizing. A collection of the developed optical instruments and other devices based on different methods were installed into a mobile environmental laboratory for monitoring atmospheric aerosols, which allows the comparison of the results obtained from different measurement methods. This laboratory has been used in 3 measurement campaigns where measurements were performed in 6 different locations.
Publisher Summary Number concentration is one of the most frequently studied parameters for chara... more Publisher Summary Number concentration is one of the most frequently studied parameters for characterization of atmospheric aerosols and other particulate systems. Determination of aerosol number concentrations can be performed by means of various methods based on a number of different measuring principles. At comparatively low concentrations, single particle counting can be applied, however, at concentrations beyond several 10 3 cm -3 , integral methods are required, which are often based on empirical calibration. To contribute to a standardization of aerosol concentration measurements, intercomparisons of various instruments were recently performed during an international experimental workshop. For consistent standardization of concentration measuring instruments, properly defined calibration standards would be required, which allow a direct determination of the particle number concentration without empirical calibration with respect to external reference standards. This chapter describes an experimental system for determination of aerosol number concentration, which is based on the measuring principle of a condensation nuclei counter. The concentrations of the particles growing in an expansion chamber are determined from simultaneous observation of scattered and transmitted light fluxes. It is shown that this experimental method allows direct particle concentration measurements for concentrations up to more than 10 7 cm -3 , and can be considered as a primary calibration standard for particle number concentration measurement.
e used as a nucleus for the condensation of n-butanol vapor to generate large aerosol droplets wh... more e used as a nucleus for the condensation of n-butanol vapor to generate large aerosol droplets which could be easily detected by optical means condensation particle counter (CPC). The method, termed ESI gas-phase electrophoretic mobility molecular analysis (GEMMA), exhibited an excellent correlation between molecular mass of globular proteins up to 6.69 10 5 Da and the measured EM diameter in air. EM diameters were determined from aqueous solutions containing 20 mM ammonium acetate and the analytes (at g/mL concentrations) as parvalbumin, ovalbumin and monoclonal antibodies (IgG type). Flow rates in the low nL/min were used and detection limits in the low picomole range were determined. Proteins, which form structurally specific non-covalent complexes in solution (as quartenary protein structures or antibody-antigene complexes) are of fundamental biological importance. There is some evidence [7] that
Nanopartikel konnen naturlichen und industriellen Ursprungs sein. Befinden sie sich im luftgetrag... more Nanopartikel konnen naturlichen und industriellen Ursprungs sein. Befinden sie sich im luftgetragenen Zustand, handelt es sich um Nanoaerosole. Durch Ihren Beitrag zur Entwicklung der Nanotechnologie haben sie groses Interesse gewonnen. Nanopartikel konnen als Bausteine fur Nanostrukturen verwendet werden, dabei sind ihre Grose und Konzentration dominierende Parameter. Die Messung von Nanopartikeln und Nanoaerosolen, insbesondere organischen Ursprungs, wie auch etwa Viren, stellt stets eine grose Herausforderung fur Wissenschaft und Technologie dar.
Particle & Particle Systems Characterization, 1986
The performance of a narrow‐angle and a wide‐angle, forward scattering laser aerosol spectrometer... more The performance of a narrow‐angle and a wide‐angle, forward scattering laser aerosol spectrometer has been studied as a function of particle size and refractive index. The results have been compared with theoretical calculations based on light scattering theory. The results indicate that for the narrow‐angle instrument, the scattered‐light intensity is not a monotonic function of particle size for transparent particles (a monotonic relationship is required for unambiguous particle size measurement) above 0.7 μm. The instrument is therefore limited in its useful range to size distribution measurement between 0.2 μm – its lower particle size limit – and 0.7 μm for transparent particles. In the case of the wide‐angle instrument, the instrument output is a monotonic function of particle size for transparent particles, but the output is severely attenuated for light absorbing particles above 0.3 μm. The instrument, therefore, cannot be used for accurate size measurements above 0.3 μm for...
We present a modelled approach of scattering contribution to the radiation transmission through a... more We present a modelled approach of scattering contribution to the radiation transmission through a scattering medium, such as an aerosol, yielding a correction term to the Lambert-Beer law. The correction is essential because a certain amount of the forward scattered light flux is always overlaid on the transmitted radiation. Hence it enters together with the attenuated beam into the finite
Particle size measurement by means of optical spectrometry of single particles depends substantia... more Particle size measurement by means of optical spectrometry of single particles depends substantially on the angular range of light scattering and the refractive index of the particle. Knowledge of the latter determines implicitly the accuracy of measurement. In contrast to commonly used instrumental systems the configuration of the design concept presented here consists of two laser illumination sources with different wavelengths and four angular ranges for the collection of scattered light. As a result a set of four independent pulses from each measured particle can be obtained allowing simultaneous assessment of particle size and its complex refractive index. Based on the Mie theory of light scattering, light collection angles yielding a single-valued aerosol size measurement were identified and used to design a new optical system. Based on the modelling of the performance for an assumed instrumental arrangement the sizing errors were found to be about 2%. The accuracy of assessment of the complex index of refraction was found to be of the order of 10% over the range of particle diameters investigated (0.1-10 µm). The theoretical results show clearly the capability of this novel instrumental design for the measurement of aerosol particle sizes, their density and optical properties. Based on these model calculations an experimental set-up is under construction.
This study explores the potential of a novel electrospray‐based method, termed gas‐phase electrop... more This study explores the potential of a novel electrospray‐based method, termed gas‐phase electrophoretic mobility molecular analysis (GEMMA), allowing the molecular mass determination of peptides, proteins and noncovalent biocomplexes up to 2 MDa (dimer of immunglobulin M). The macromolecular ions were formed by nano electrospray ionization (ESI) in the ‘cone jet’ mode. The multiple charged state of the monodisperse droplets/ions generated was reduced by means of bipolar ionized air (generated by an α‐particle source) to yield exclusively singly charged positive and negative ions as well as neutrals. These ions are separated subsequently at atmospheric pressure using a nano differential mobility analyzer according to their electrophoretic mobility in air. Finally, the ions are detected using a standard condensation particle counter. Data were expressed as electrophoretic mobility diameters by applying the Millikan equation. The measured electrophoretic mobility diameters, or Millika...
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