Formation of naproxen-polylactic acid nanoparticles from supercritical solutions and their characterization in the aerosol phase.

Pure naproxen particles and mixed naproxen-polylactic acid particles were formed by pulsed rapid expansion of supercritical CO2 solutions (RESS). The characterization of the particles was carried out in the aerosol phase as a function of time after particle formation with rapid-scan infrared spectroscopy and with an aerosol particle sizer. After collection of the particles from the aerosol phase, the particles were characterized with scanning electron microscopy and powder diffraction.

Infrared spectroscopy of acetic acid and formic acid aerosols: pure and compound acid/ice particles.

Acetic acid aerosol particles, formic acid aerosol particles and mixed acid/ice particles were generated in a collisional cooling cell at a temperature of 78 K and investigated using in situ rapid scan Fourier transform infrared spectroscopy. The infrared spectra reveal that the internal structure of the particles critically depends on the particle formation conditions and, especially for the mixed particles, on the composition. The acetic acid particles are likely to have only a partially crystalline structure whereas the formic acid particles are likely to have an overall crystalline structure.