Prediction of the environmental distribution of alkyl dinitrates – Chromatographic determination of vapor pressure p0, water solubility SH2O, gas-water partition coefficient KGW (Henry’s law constant) and octanol-water partition coefficient KOW
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Alkyl nitrates are complex mixtures of homologues and isomers and are part of the large NOy pool of important atmospheric trace compounds. The knowledge of their physico-chemical parameters allows to forecast their partitioning into the environment. Water solubility, octanol-water partition coefficient, vapor pressure, and gas-water partition coefficient have been determined for 26 alkyl dinitrates by RP-HPLC and HRGC, respectively. Octanol-water partition coefficient (KOW) and water solubility (SH2O) were determined by C18 reversed-phase liquid chromatography using phenylalkanes as reference standards. Retention data obtained with methanol-water mixtures as eluents were extrapolated to 100% water. The vapor pressures were determined by capillary gas chromatography on a non polar stationary phase (CP-Sil 2, Chrompack). The octanol-water partition coefficients ranges from log KOW = 1.4 for 1,2-ethyl dinitrate up to log KOW = 5.9 for 1,2-decyl dinitrate, respectively. The experimental results are within ± 0.15 log units in agreement with calculations of log KOW by the increment method according to Hansch and Leo. Water solubilities are in the range of 154 mol/m3 (23.1 g/L) for 1,2-ethyl dinitrate and 0.002 mol/m3 (0.5 mg/L) for 1,2-decyl dinitrate, respectively. The vapor pressures p0L ranges from 196 Pa for 1,2-ethyl dinitrate to 0.01 Pa for 1,10-decyl dinitrate (sub-cooled liquid value). The gas-water partition constants (dimensionless) or Henry’s law constants ranges from KGW = 0.0005 (H = 1.28 Pa m3/mol) for 1,2-ethyl dinitrate to KGW = 0.020 (H = 51.1 Pa m3/mol) for 1,2-decyl dinitrate.
KeywordsVapor Pressure Partition Coefficient Water Solubility Increment Method Environmental Distribution
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