title: Polydimethylsiloxane-air partition ratios for semi-volatile organic compounds by GC-based measurement and COSMO-RS estimation: Rapid measurements and accurate modelling.
abstract: Polydimethylsiloxane (PDMS) shows promise for use as a passive air sampler (PAS) for semi-volatile organic compounds (SVOCs). To use PDMS as a PAS, knowledge of its chemical-specific partitioning behaviour and time to equilibrium is needed. Here we report on the effectiveness of two approaches for estimating the partitioning properties of polydimethylsiloxane (PDMS), values of PDMS-to-air partition ratios or coefficients (KPDMS-Air), and time to equilibrium of a range of SVOCs. Measured values of KPDMS-Air, Exp' at 25 °C obtained using the gas chromatography retention method (GC-RT) were compared with estimates from a poly-parameter free energy relationship (pp-FLER) and a COSMO-RS oligomer-based model. Target SVOCs included novel flame retardants (NFRs), polybrominated diphenyl ethers (PBDEs), polycyclic aromatic hydrocarbons (PAHs), organophosphate flame retardants (OPFRs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs). Significant positive relationships were found between log KPDMS-Air, Exp' and estimates made using the pp-FLER model (log KPDMS-Air, pp-LFER) and the COSMOtherm program (log KPDMS-Air, COSMOtherm). The discrepancy and bias between measured and predicted values were much higher for COSMO-RS than the pp-LFER model, indicating the anticipated better performance of the pp-LFER model than COSMO-RS. Calculations made using measured KPDMS-Air, Exp' values show that a PDMS PAS of 0.1 cm thickness will reach 25% of its equilibrium capacity in ∼1 day for alpha-hexachlorocyclohexane (α-HCH) to ∼ 500 years for tris (4-tert-butylphenyl) phosphate (TTBPP), which brackets the volatility range of all compounds tested. The results presented show the utility of GC-RT method for rapid and precise measurements of KPDMS-Air.
authors.affiliation: Department of Physical and Environmental Science, University of Toronto Scarborough, 1265 Military Trail Toronto, ON, M1C 1A4, Canada.
authors.forename: Joseph O
authors.initials: JO
authors.lastname: Okeme
authors.affiliation: Chemical Properties Research Group, Department of Chemistry, Trent University, Peterborough, ON, K9J 0G2, Canada.
authors.forename: J Mark
authors.initials: JM
authors.lastname: Parnis
authors.affiliation: Air Quality Processes Research Section, Environment and Climate Change Canada, 6248 Eighth Line, Egbert, ON, L0L 1N0, Canada.
authors.forename: Justen
authors.initials: J
authors.lastname: Poole
authors.affiliation: Department of Physical and Environmental Science, University of Toronto Scarborough, 1265 Military Trail Toronto, ON, M1C 1A4, Canada; Department of Earth Sciences, 22 Russell Street, University of Toronto, Toronto, ON, M5S 3B1, Canada.
authors.forename: Miriam L
authors.initials: ML
authors.lastname: Diamond
authors.affiliation: Air Quality Processes Research Section, Environment and Climate Change Canada, 6248 Eighth Line, Egbert, ON, L0L 1N0, Canada. Electronic address: liisa.jantunen@canada.ca.
authors.forename: Liisa M
authors.initials: LM
authors.lastname: Jantunen
mesh_terms: D000388:Air; D002849:Chromatography, Gas / Q000379:methods*; D004129:Dimethylpolysiloxanes / Q000737:chemistry*; D005411:Flame Retardants / Q000032:analysis; D055768:Halogenated Diphenyl Ethers / Q000032:analysis; D001556:Hexachlorocyclohexane / Q000032:analysis; D006843:Hydrocarbons, Chlorinated / Q000032:analysis; D008962:Models, Theoretical; D010575:Pesticides / Q000032:analysis*; D011078:Polychlorinated Biphenyls / Q000032:analysis; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis; D011789:Quantum Theory; D055549:Volatile Organic Compounds / Q000032:analysis*
chemical_list: D004129:Dimethylpolysiloxanes; D005411:Flame Retardants; D055768:Halogenated Diphenyl Ethers; D006843:Hydrocarbons, Chlorinated; D010575:Pesticides; D011084:Polycyclic Aromatic Hydrocarbons; D055549:Volatile Organic Compounds; C040534:alpha-hexachlorocyclohexane; D001556:Hexachlorocyclohexane; D011078:Polychlorinated Biphenyls
keywords: COSMOtherm; K(PDMS-Air); PDMS; Passive air sampling; SVOCs; pp-LFER