Saturation vapor pressure characterization of selected low-volatility organic compounds using a residence time chamber

Abstract

Saturation vapor pressure (psat) is an important thermodynamic property regulating the gas-to-particle partitioning of organic compounds in the atmosphere. Low-volatility organic compounds (LVOCs), with sufficiently low psat values, primarily stay in the particle phase and contribute to aerosol formation. Obtaining accurate information on the psat of LVOCs requires volatility measurements performed at temperatures relevant to atmospheric aerosol formation. Here, we present an isothermal evaporation method using a residence time chamber to measure psat for dry single-compound nanoparticles at 295 K. Our method is able to characterize organic compounds with psat spanning from 10−8 to 10−4 Pa at 295 K. The compounds included four polyethylene glycols (PEGs: PEG6, PEG7, PEG8, and PEG9), two monocarboxylic acids (palmitic acid and stearic acid), two dicarboxylic acids (azelaic acid and sebacic acid), two alcohols (meso-erythritol and xylitol), and one ester (di-2-ethylhexyl sebacate). There was a good agreement between our measured psat values and those reported by previous volatility studies using different measurement techniques, mostly within 1 order of magnitude. Additionally, quantum-chemistry-based COSMOtherm calculations were performed to estimate the psat values of the studied compounds. COSMOtherm predicted the psat values for most of the studied compounds within 1 order of magnitude difference between the experimental and computational estimates.