Understanding and Predicting the Diffusivity of Organic Compounds in Polydimethylsiloxane Material for Passive Sampler Applications Using a Simple QSPR Model.

The diffusivity of 145 compounds in polydimethylsiloxane (PDMS) material was determined in the laboratory using a film stacking technique. The results were pooled with available literature data, providing a final data set of 198 compounds with diffusivity (D-PDMS) spanning over approximately 5 log units. The principal variables controlling the diffusivity of penetrants were investigated by comparing D-PDMS within and between different homologous series. The dipole moment, molecular size, and flexibility of penetrants appear to be the most prevalent factors controlling a compound's diffusivity. A nonlinear quantitative structure-property relationship is proposed using as predicting variables the molecular volume, the number of rotatable bonds, the topological polar surface area, and the number of O and N atoms. The final relationship has a correlation coefficient of R-2 = 0.81 and a mean absolute error of 0.26 m(2) s(-1) (log unit), approaching the average error for the experimentally determined values (0.12 m(2) s(-1)). The model, based on a heuristic approach, is ready for use by analytical chemists with no specific background in theoretical chemistry (notably for passive sampler development). (C) 2018 SETAC