1-octanol-water partitioning as a classifier of water soluble organic matters: Implication for solubility distribution

Abstract

Water-soluble organic matters (WSOMs) play an important role in determining magnitudes of climatic and environmental impacts of organic aerosol particles because of their contributions to hygroscopic growth and cloud formation. These processes are dependent on water solubility as well as distribution of this property in a particle, yet no method has been available to quantify such characteristics. In this study, we developed a theoretical framework to classify WSOM by 1-octanolwater partitioning that has a strong correlation with water solubility. 1-octanol-water partitioning coefficient also has a strong correlation with a traditional solid phase extraction method, facilitating interpretation of data from the technique. The theoretical analysis demonstrated that the distributions of WSOM classified by 1-octanol-water partitioning depend on (1) the volume ratio of 1-octanol and aqueous phases, and (2) extraction steps. The method was tested by using organic aerosol particles generated by smoldering of a mosquito coil, which serves as a surrogate for biomass burning particles. The WSOM extracted from the mosquito coil burning particles was classified by 1-octanol-water partitioning at different volume ratios. These solutions, including both the 1-octanol and aqueous phases, were nebulized to generate particles for measurements using an online aerosol mass spectrometer. The mass spectra indicated that highly oxygenated species tend to be highly soluble, while high molecular weight compounds are less soluble. Linear combinations of these mass spectra allowed the estimation of the mass fractions of WSOM partitioned to 1octanol and aqueous phases, thereby facilitating the evaluation of the mass fractions of cloud condensation nuclei (CCN) active materials.

ORACLE 2-D (v2.0): an efficient module to compute the volatility and oxygen content of organic aerosol with a global chemistry–climate model

“…However, there are only a few atmospheric organic compounds with O : C higher than unity and the observed O : C of ambient OA rarely exceeds 1.1 (Ng et al, 2010;Kroll et al, 2011). The ability of ORACLE 2-D to simulate the degree of oxidation of OA allows for the simulation of its hygroscopicity by using proposed parameterizations that link the hygroscopicity parameter kappa with the O : C of OA Lambe et al, 2011;Kuwata and Lee, 2017). In the current application, the hygroscopicity of each OA compound is represented by a linear function of the form κ org = 0.18 (O : C) + 0.03 (Lambe et al, 2011).…”

Water uptake by fresh Indonesian peat burning particles is limited by water-soluble organic matter

“…Although it is the first hygroscopic measurement for WSOM classified with the 1-octanol-water liquid-liquid extraction technique, the value could be compared with those for hydrophilic fractions classified by the XAD-8 column. Kuwata and Lee (2017) demonstrated that classification of WSOM by the XAD-8 column, which is one of the most frequently used materials for solid-phase extraction of WSOM, has a strong relationship with the 1-octanol-water partitioning coefficient (K OW ). Namely, the XAD-8 column selectively traps hydrophobic chemical species in WSOM, which tend to partition to the 1-octanol phase (K OW > 1).…”

“…The aqueous phase following the 1-octanol-water extraction is denoted as A 1 (slightly less than 5 mL), corresponding to the highly water-soluble fraction. Details of the extraction method are provided in Kuwata and Lee (2017).…”

“…In addition, ratios of water-soluble organic carbon (WSOC) to organic carbon (OC) were quantified. The concurrent HTDMA and ToF-ACSM measurements were also performed for the bulk WSOM and its highly hydrophilic fraction classified with the 1-octanol-water partitioning method in terms of water solubility (Kuwata and Lee, 2017). This method provides a new angle (i.e., water solubility) to characterize chemical properties of WSOM, facilitating a more detailed investigation of particle water uptake properties with the first application of the method in HT-DMA measurements of a highly hydrophilic organic fraction.…”

“…The complexity in chemical composition inhibits understanding their water uptake properties at molecular levels (Asa-Awuku et al, 2008;Psichoudaki and Pandis, 2013;Riipinen et al, 2015). To overcome this difficulty, classification of organic compounds using multiple solvents Polidori et al, 2008;Chen et al, 2016), liquid-liquid extraction using 1-octanol and water (Kuwata and Lee, 2017), and solid-phase extraction (Asa-Awuku et al, 2008) has been conducted. Functional-group analysis of segregated organic matter has also been demonstrated as a strong tool to characterize complex mixture of organic compounds (Chen et al, 2016).…”