This article discusses aerosol generation technique using inkjet technology. Inkjet-based aerosol generation technique has been applied to a development of drug delivery systems and sample delivery to mass spectrometers. The inkjet aerosol generator (IAG) was first developed by Bottiger J. at US-Army, and the Bottiger-IAG generated bio-aerosols having particle diameter ranging from 1 to 10 µm at low concentrations (~ few particles per cm3 or below). Recently, a new type of IAG was developed at AIST, Japan, and it was applied to aerosol instrumentation. The most important characteristic of the AIST-IAG is that it can suppress the formation of doublets and satellite droplets; therefore, the AIST-IAG is able to generate highly monodisperse aerosol particles with precisely known generation rates. The particle diameter can be controlled between 0.4 and 10 µm. Some applications of AIST-IAG are (1) checking the particle-counting-capability of condensation particle counters (CPCs) on a daily basis, and (2) calibrating particle counting efficiency of optical particle counters (OPCs).
To establish the air-liquid interface cell-exposure and inhalation toxicology studies of secondary organic aerosol (SOA), we developed a small reaction chamber system for generating SOA through α-pinene/ozone reaction (p-SOA), and photo-oxidation of m-xylene (x-SOA) and 1,3,5-trimethylbenzene (t-SOA) under presence of nitric oxide (NO). Size-resolved particle number concentrations (0.01-20 µm) and gaseous materials were monitored in the chamber. It is important to control the particle size and the concentration of residual ozone for air-liquid interface cell-exposure and inhalation studies and we found that the particle size of SOA via coagulation and condensation depends on initial concentration of precursor and ratio of precursor/NO. SOA was collected on Teflon filters to determine their physical and chemical properties and toxicity. The cytotoxicity of p-SOA and x-SOA was similar and was higher than that of t-SOA. On the other hand, oxidative stress induced by x-SOA was much higher than that induced by p-SOA and larger amount of oxidant in p-SOA was measured compared to that in x-SOA. Cytotoxicity and oxidative stress were different depending on the species of SOA, indicating that the amount of oxidant in SOA as well as the redox activity of SOA determine the cytotoxicity and oxidative stress of SOA.
The electrodynamic balance (EDB), outgrowth of electrical device of Millikan’s oil drop experiment, uses superposed AC and DC electrical fields to trap a charged microparticle and fix it in space. The EDB has become a widely-employed experimental tool to study the physics and chemistry of particles and droplets ranging in size from less than 200 µm to more than 5 µm in diameter. This review has focused on the measurement principles and the experimental procedures of EDB and touched on the applications of EDB in the measurement of forces acting on the levitated particle.
Aerosol water droplets play important roles in the earth’s climate and in the atmospheric chemistry. Noncontact levitation of a single micrometer-sized water droplet in air can be achieved by a laser trapping technique and, therefore, the laser trapping technique is a powerful means to study the aerosol chemistry. In this paper, in situ characterization of the chemical composition and size of an aerosol water droplet is demonstrated by means of laser trapping and Raman spectroscopy. Furthermore, the laser trapping technique is applied to direct observation of freezing processes of single micrometer-sized water droplets in air. An artificial experimental model system corresponding to the initial steps of precipitation in clouds can be constructed by employing the laser trapping technique and an optical microscope.
Introduction of single particle mass spectrometry (SPMS) to the aerosol science community 20 years ago, enabled aerosol scientists to characterize size and composition of each individual particle in real time, having a large impact on aerosol research. Since then, SPMSs have been used for characterizing size-resolved aerosol compositions in various places and environments to facilitate our insight into complicated reality and nature of natural and anthropogenic aerosols. In recent years, unique ability of SPMS technique (e.g., diverse chemical detection capability, real-time and in-situ measurement capability, high sensitivity enough to analyze composition of 100 nm size of nanoparticles) let SPMS technique expand its way for new research applications. For instance, multidimensional aerosol characterization by coupling SPMS with other aerosol physicochemical measurement/separation instruments (e.g., hygroscopicity, optical property, particle shape), on-line and real-time detection of toxic particles and chemical substances is now realized with SPMS technique, emerging new SPMSs which can efficiently analyze nanoparticles with diameter less than 50 nm, and simultaneous single particle nm-scale X-ray imaging and mass spectrometry are examples of new applications. In this article, rather than ordinary single particle chemical analysis, recent unique SPMS applications, which take full advantage of the unique capability of SPMS technique, are reviewed.
A new 10-stage low-pressure impactor of MAIS-10 has been developed to sample size-segregated aerosol particles for subsequent chemical analysis by ion or X-ray beam method such as PIXE or XRF and thermo-optical analysis for carbonaceous components. The impactor has reversible impaction plates with the diameters of the aerosol deposition areas smaller than 10 mm for all stages and can employ the collection substrates of two different thicknesses. The collection efficiency curves were experimentally determined for all stages and the 50% cut-off diameters ranging from 30 nm to 8 µm agreed well with the theoretical calculations at each stage. The particle wall losses were experimentally obtained using oleic acid particles labeled with uranine. The performance of MAIS-10 has been tested to collect urban aerosols simultaneously with a commercially available impactor for 24 hrs. The samples were subjected to TXRF, PIXE and thermal optical analysis. MAIS-10 samples showed the reasonable size distributions of typical elements and carbonaceous components, while the levels of the samples collected by the usual impactor in the analytical areas were below the detection limit of each analytical method and the size distributions were not able to be determined.