Dynamic method to measure partition coefficient and mass accommodation coefficient for gas-particle interaction of phthalates

The particle-gas partition coefficient (K-p) and mass accommodation coefficient (alpha) are two parameters characterizing the gas-particle interaction of semi-volatile organic compounds (SVOCs). Most of the available methods for measuring K-p require equilibrium at the chamber outlet, implying substantial preliminary testing. The need to separate gas-phase and particle-phase SVOCs also reduces the method accuracy. Few studies measuring alpha for indoor-related SVOCs are available, and they usually ignore the wall loss of SVOCs, resulting in reduced measurement accuracy. To overcome these deficiencies, we developed a dynamic method coupling a laminar flow tube chamber and an SVOC mass transfer model. Using the interaction between gas-phase di-2-ethylhexyl phthalate (DEHP) and (NH4)(2)SO4 particles (with diameters in the range of 10-600 nm) as an example, experiments were performed to evaluate the effectiveness and accuracy of the dynamic method. For the experimental conditions investigated (temperature = 25 degrees C and relative humidity <10%), gas-particle interaction between DEHP and (NH4)(2)SO4 particles is governed by surface adsorption because (NH4)(2)SO4 particles are in solid state. In this case, gas-particle partitioning should be characterized by the surface-area-normalized partition coefficient (K-pA). K-pA and alpha were measured to be 260 +/- 80 m and 0.20 +/- 0.05, respectively. Both are consistent with results reported in the literature. The method applicability for other SVOC-particle combinations and the improvement of method accuracy require further study. Copyright (c) 2019 American Association for Aerosol Research