ε hexachlorocyclohexane

All the individual SCCP standards were purchased from Chiron, Norway and Dr. Ehrensforfer GmbH, Germany. The standards included 1,1,1,3,8,10,10,10-octachlorodecane (1,1,1,3,8,10,10,10-OctaCD), 1,1,1,3,10,11-hexachloroundecane (1,1,1,3,10,11-HexCU), 1,1,1,3,12,13-hexachlorotridecane (1,1,1,3,12,13-HexCT), 1,2,5,6,9-pentachlorodecane (1,2,5,6,9-PentaCD), 1,2,5,6,9,10-hexachlorodecane (1,2,5,6,9,10-HexCD), hexachlorodecane (1,2,4,5,9,10-HexCD), 1,2,4,5,6,9,10-heptachlorodecane (1,2,4,5,6,9,10-HepCD), 1,2,5,5,6,9,10-heptachlorodecane (1,2,5,5,6,9,10-HepCD), and 1,1,1,3,8,9-hexachlorononane (1,1,1,3,8,9-HexCN). Their concentrations and purities are listed in Table S1. The concentrations of chlorodecane standard solutions obtained from Ehrenstorfer GmbH have been adjusted according to the purity of the compounds as indicated. The injection internal standard, ε-hexachlorocyclohexane (ε-HCH, 10 mg∙L⁻¹ in cyclohexane, 99.9%), and CP reference standards of SCCP mixtures (C_10–13 with chlorine contents of 51.5, 55.5, and 63.0%) and MCCP mixtures (C_14–17 with 42.0%, 52.0%, and 57.0% chlorine content) were purchased from Ehrenstorfer GmbH (Augsburg, Germany). ¹³C₁₀-trans-Chlordane (100 mg∙L⁻¹ in n-nonane, 99.9%) was obtained from Cambridge Isotope Laboratories (Andover, USA) and used as the surrogate standard. Other details are described in Text S1.

1,2,5,6,9,10-Hexachlorodecane (1,2,5,6,9,10-hexCD, CP-4, 10 μg/mL in cyclohexane, 99.9%) and ¹³C-1,5,5,6,6,10-hexachlorodecane (¹³C-1,5,5,6,6,10-hexCD in cyclohexane, 100 ng/μL, >98%) were purchased from Cambridge Isotope Laboratories (Andover, USA). Standard stock solutions of MCCPs mixtures (C_14–17 with chlorine contents of 42%, 52%, and 57%, 100 μg/mL in cyclohexane) and the injection standard of ε-hexachlorocyclohexane (ε-HCH in cyclohexane, 10 ng/μL, 99.9%) were obtained from Dr. Ehrenstorfer GmbH (Augsburg, Germany). HPLC-grade methanol and acetone were purchased from Fisher chemical (Waltham, MA). Ultra resi-analyzed ethyl acetate, pesticide-grade dichloromethane, n-hexane, and cyclohexane were obtained from J.T. Baker (Phillipsburg, NJ). Supelclean LC-Florisil SPE Tubes (1 g, volume 6 mL) were bought from Supelco (Sigma-Aldrich, St. Louis, MO). HLB 6 cm³ (200 mg) columns were purchased from Waters (Milford, MA). Ultrapure water (18.2 MΩ·cm) was prepared with a milli-Q purification system (Millipore, Billerica, MA).