Direct Measurements of Vapor Pressures of Chlorinated Paraffin Congeners from Technical Mixtures

Abstract

<p>Chlorinated Paraffins (CPs) are a complex group of manmade chemicals detected widely in the environment. To predict their environmental fate and effects, it is important to understand their physical-chemical properties including vapor pressure. In this study, the first direct measurements of the vapor pressure for CP congener groups (C<sub>10–16</sub>Cl<sub>4–11</sub>) are presented. Vapor pressure was measured above three industrial CP mixtures with different congener distributions between 20 and 50°C using a gas saturation method. The measured saturated vapor pressure (<i>P</i><sup>*</sup>) decreased with increasing carbon chain length and Cl content. Δ<i>H</i><sub>vap</sub> ranged between 73 and 122 kJ mol<sup>-1</sup>, consistent with data from the literature and model prediction. The experimental log <i>P</i><sup>*</sup> at 25°C agreed well with predictions from an empirical regression model in the literature (<i>R</i><sup>2</sup> = 0.97; RSME = 0.25) and with those predicted from the COSMO-RS-trained fragment contribution model (<i>R</i><sup>2</sup> = 0.95; RSME = 0.35). A new empirical model was calibrated with the <i>P</i><sup>*</sup> data for 35 congener groups measured in this study. Predicted log <i>P</i><sup>*</sup> values correlate well with field-measured gas/particle partition coefficients and may therefore be used for estimating the environmental fate and pathways of a broad range of CPs in the environment.</p> <p><b> </b></p>