Aerosol fine particle fraction

Because of the nature of the enrichment process during combustion, potential tracer elements such as As, Se, and I are more enriched on fine than on coarse particles. Therefore, analyzing the fine particle fraction of source emissions and ambient aerosols increases the source-discriminating power of receptor models. 

Aqueous and ethanolic formulations have been employed with the Respimat and the in vitro aerosol performance determined. Zierenberg (1999) reported fine-particle fractions of 66% for an aqueous fenoterol formulation and 81% for an ethanolic flunisolide formulation. The respective MMADs were 2.0 0.4 pm for the aqueous formulation and 1.0 0.3 pm for the ethanolic formulation [284],... 

Another reason for using excipient carrier is to improve the availability of fine drug particles in the aerosol cloud. Surface texture of excipients appears to play a prominent role. The fine particle fraction of... 

Besides surface texture, excipient particle size also plays an important role in the fine particle generation as shown by budesonide, where the highest fine particle fraction was obtained with small-sized (<32pm) lactose as the carrier. Additionally, fine particle excipients such as fine lactose or polyethylene glycol were reported to improve the performance of carrier-based protein dry powder aerosols.However, there are some cases where carriers improved total powder emission but reduced the percent of active powders in the aerosol. To be useful carriers, the excipients must be physically stable. The important physicochemical characteristics for drug carrier selection are discussed in Ref.t f... 

Fig. 15 shows the drug mass recovered from the various stages of the impactor and device at a nominal drug dose of 75 pg per actuation. The amount of drug deposited on each stage was used to calculate the MMAD and GSD. The calculated MMAD was 2.85 pm with a GSD of 1.6. The fine particle fraction (FPF) of the aerosol was 90% (<5.8 pm) of the emitted dose, and 95% (<5.8 pm) of the dose distal to the USP throat. 

For pMDIs, in vitro studies do not take hygroscopic growth in the airways or the differences in plume geometry into account. The ability of the cascade im-pactor to predict the behavior of aerosolized drugs in vivo in a reliable way has been recently questioned. Indeed, it has been demonstrated that several generic pMDIs with fine particle fractions comparable to the original formulation (as measured in vitro) appeared to behave differently in vitro once attached to a large-volume spacer (3-5). 

Unintentional aerosols produced by industry are the visible and ubiquitous plumes of soot, fly ash and other products formed downwind from industrial stacks. The fine particle fraction (i.e. the ultrafine particles plus the accumulation mode particles, everything <2.5 pm diameter) is usually composed mostly of... 

For all fluids, Ghazanfari et al. [71] found that the Omron nebulizer generated aerosols with slightly larger droplet size and similar or smaller fine particle fraction (FPF) than those of the Aeroneb Pro device. The total aerosol output was generally independent of fluid properties. However, increased fluid viscosity resulted in a decrease in droplet size and a consequent increase in the FPF, but the nebulization time was prolonged and output rate decreased (Fig. 33.12). 

Monodisperse primary particles in pMDIs show a significantly narrower aerosol particle size distribution than pMDIs containing poly disperse primary particles. A narrow size distribution is crucial to achieve a very fine particle fraction (49.31 8.16%) for primary particles greater than 2jim. 

The MMAD is a parameter frequently used to characterise therapeutic aerosols. MMAD alone is not very useful however, as it provides no information about the size distribution in the aerosol and the mass fraction of the dose (label claim) processed into a suitable aerosol. Fine particle dose and fraction are more meaningful parameters, particularly for DPIs (see definitions). 

Improved control devices now frequently installed on conventional coal-utility boilers drastically affect the quantity, chemical composition, and physical characteristics of fine-particles emitted to the atmosphere from these sources. We recently sampled fly-ash aerosols upstream and downstream from a modern lime-slurry, spray-tower system installed on a 430-Mw(e) coal utility boiler. Particulate samples were collected in situ on membrane filters and in University of Washington MKIII and MKV cascade impactors. The MKV impactor, operated at reduced pressure and with a cyclone preseparator, provided 13 discrete particle-size fractions with median diameters ranging from 0,07 to 20 pm with up to 6 of the fractions in the highly respirable submicron particle range. The concentrations of up to 35 elements and estimates of the size distributions of particles in each of the fly-ash fractions were determined by instrumental neutron activation analysis and by electron microscopy, respectively. Mechanisms of fine-particle formation and chemical enrichment in the flue-gas desulfurization system are discussed. 

St. Louis Sample Collection. Ambient aerosols were collected in St. Louis in 6-h Intervals with a TWOMASS automated sequential tape sampler. This sampler fractionated the aerosol into two size classes, fine particles having aerodynamic diameters less than 3pm, and coarse particles with diameters greater than 3pm. It was equipped with a beta-attenuation mass monitor to determine fine-particle mass (11). Only the fine particle filter was examined in this study. Pallflex E70 glass-fiber filter tape with a detachable cellulose backing (Pallflex Inc. Putnam, CT) was used with this sampler. An aerosol sampler operating from the same inlet manifold as the... 

Indeed, based on the number, surface, and volume distributions shown in Fig. 9.6, Whitby and co-workers suggested that there were three distinct groups of particles contributing to this atmospheric aerosol. Particles with diameters >2.5 yu,m are identified as coarse particles and those with diameters 2.5 pm are called fine particles. The fine particle mode typically includes most of the total number of particles and a large fraction of the mass, for example, about one-third of the mass in nonurban areas and about one-half in urban areas. The fine particle mode can be further broken down into particles with diameters between 0.08 and 1-2 yxm, known as the accumulation range, and those with diam-... 

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