Hygroscopicity of Cholesterol in Various Organic Solvents

Abstract

Organic aerosols and partially soluble particles can uptake water, form droplets and act as Cloud Condensation Nuclei (CCN). Cholesterol is a well-known organic aerosol. Cholesterol is insoluble in water (<0.002 gram in 100 ml of H2O) but dissolves in organic solvents. In this study, we examine the ability of cholesterol generated in three dilutions of 3 alcohols (ethanol, isopropanol and acetone) to act as CCN. The apparent hygroscopicity, κ, varies over two orders of magnitude, from ~ 0.001 to 0.1. We use statistical analysis of variance (ANOVA) to define significant physical and chemical factors that modify κ. Results show that as volume of water increases, κ changes. However, the type of alcohol does not significantly modify the hygroscopicity. Increases in alcohol concentration decrease droplet surface tension and change aerosol shape. Thus, the apparent κ is corrected with surface tension and shape factor data and estimated to be ~0.028 ± 0.02.