Inorganic salts

Solvents used during the extraction and analysis were all of analytical grade; n-hexane, acetone, methanol and dichloromethane were purchased from Merck (Darmstadt, Germany). Indoor dust SRM 2585 was purchased from NIST (Gaithersburg, MD, USA). Empty polypropylene filtration SPE cartridges (3 mL) were obtained from Sigma-Aldrich (Gillingham, UK). Silica gel (40 µm pore size) was purchased from J.T.Baker (London, UK). Anhydrous sodium sulfate (Na2SO4) and concentrated sulfuric acid (H2SO4, 98%) were purchased from Merck (Darmstadt, Germany). Standards of individual HBCDs (α-HBCD, β-HBCD, γ-HBCD), labelled 13 C HBCDs (α-, β-, γ-) and d18 γ-HBCD were purchased from Wellington Laboratories (Guelph, ON, Canada).
Glass fibre filters (GFFs, 12.5cm diameter, 1 µm pore size) were purchased from Whatman (Maidstone, UK). Florisil (60-100 mesh) and Silica gel (60Å, 60-100 mesh)
were purchased from Sigma-Aldrich (Dorset, UK). Oxygen-free nitrogen gas was purchased from BOC Gases (Manchester, UK).
For the CE-PBET model, analytical grade inorganic salts were obtained from Fisher Scientific (Loughborough, U.K) and organic components were purchased from Sigma-Aldrich (Dorset, UK). All glassware was cleaned by soaking for at least 12 h in a phosphate-free alkali solution, rinsed with water followed by distilled water and dried at 100°C for at least 12 h.