Poly disperse aerosols

Martonen, T. B., and Katz, I. M. Deposition patterns of poly-disperse aerosols within human lungs. J. Aerosol Med., 6 251—274, 1993. 

There are few methods suitable for on-line chemical analysis of aerosol particles. Raman spectroscopy offers the possibility of identifying the chemical species in aerosol particles because the spectrum is specific to the molecular. structure of the material, especially to the vibrational and rotational modes of the molecules. Raman spectra have been obtained for individual micron-sized particles placed on surfaces, levitated optically or by an eiectrodynamic balance, or by monodisperse aerosols suspended in a flowing gas. A few measurements have also been made for chemically mixed and poly disperse aerosols. The Raman spectrum of a spherical particle differs from that of the bulk material because of morphology-dependent resonances that re.su It when the Raman scattered photons undergo Mie scattering in the particle. Methods have been developed for calculating the modified spectra (McNulty el al., 1980). 

Spray Chambers and Desolvation Systems. A nebulizer must produce droplets less than 10 /im in diameter in order to achieve a high aerosol transport efficiency (the percentage of the mass of nebulized solution that reaches the plasma), and rapid desolvation, volatilization, and atomization of the aerosol droplets. Pneumatic nebulizers, especially, produce highly poly dispersive aerosols with droplets up to 100 jwm in diameter and these large droplets must be removed by a spray chamber. 

Bandi, F., A. Khan, and C.R. Phillips, Effects of Aerosol Poly-dispersity on Theoretical Calculation of Unattached Fractions of Radon Progeny, this volume (1987). 

The geometric standard deviation (GSD) is defined as the size ratio at 84.2% on the cumulative frequency curve to the median diameter. This assumes that the distribution of particle sizes is lognormal. A monodisperse, i.e. ideal aerosol, has a GSD of 1, although in practice an aerosol with a GSD of <1.22 is described as monodisperse while those aerosols with a GSD >1.22 are referred to as poly dispersed or heterodispersed. 

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. 

Abbreviations A, acetone ASES, aerosol solvent extraction system DM, dichloromethane DMF, A/,A/-dimethyl-formamide E, ethanol GAS, gas antisolvent process H, hexane HYAFF-11, hyaluronic acid benzylic ester I, isopropanol PAN, polyacrylonitrile PCA, precipitation with compressed antisolvent PCL, polycaprolactone PHB, poly(p-hydroxybutyric acid) PLA, polylactic acid PLGA, poly(lactic-co-glycolic acid) SAS, supercritical antisolvent process SEDS, solution enhanced dispersion by supercritical fluids TFE, 2,2,2-trifluoroethanol Triblock polymer, p poly(L-lactide-CO-D,L-lactide-co-glycolide)(62.5 1 2.5 25). 

These same workers described an inverse emulsion-type polymerization process.109 They used a conventional process in which microemulsions of water in hydrocarbon readily form in the presence of Aerosol-OT(AOT). The droplets are essentially swollen cells, where radius is controlled by the water/AOT ratio. As droplets collide, hydrophilic reagents contained in them are exchanged. When pyrrole and (NH4)2S208 dispersions were mixed, eventually a sediment appeared. However, if poly(vinyl pyrrolidone) (PVP) was added at different intervals, stable dispersions of small particles could be prepared. 

Heath, D. and Tadros, Th.F. (1983) Influence of pH, electrolyte, and poly(vinyl alcohol) addition on the rheological characteristics of aqueous dispersions of sodium montmorillonite, /. Colloid Interf. Sci., 93, 307-19 (1983) Influence of pH, electrolyte, and poly(vinyl alcohol) addition on the rheological behaviour of aqueous silica (aerosol) dispersions, /. Colloid Interf. Sci., 93,320-28. 

---