Vapor Pressures of the Polybrominated Diphenyl Ethers

The supercooled liquid vapor pressures P L of 23 polybrominated diphenyl ether congeners were determined as a function of temperature with a gas chromatographic retention time technique. P L at 298.15 K ranged from 0.1 Pa for monobrominated diphenyl ethers to 10 - 6 Pa for heptabrominated diphenyl ethers. The halogen substitution pattern was found to influence PBDE vapor pressure, indicating that congeners with bromine substitutions in the ortho positions to the ether-link have higher vapor pressures. The enthalpy of vaporization Δ vap H for the 23 PBDE congeners ranged from (−67 to −116) kJ/mol, decreasing with each additional bromine substitution by about (7 to 8) kJ·mol - 1 . Δ vap H was also found to be influenced by the number of ortho bromines. Using a Junge−Pankow approach, the fraction of chemical adsorbed to aerosols as a function of temperature was estimated for three congeners and used to speculate on the likely environmental behavior of these chemicals.