Loss of Polychlorinated Dibenzo-p-dioxins, Polychlorinated Dibenzofurans and Coplanar Polychlorinated Biphenyls during Vacuum Concentration for Ultra-trace Analysis

Abstract

We investigated the effect of kinds of organic solvent on the losses of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/DFs), coplanar polychlorinated biphenyls (Co-PCBs), and their 13C12-labeled compounds during vacuum concentration. n-Hexane and toluene solutions containing the standards of those compounds were tested for the purpose. The kind of organic solvent has remarkable effect on the loss of 13C12-Co-PCBs from the standard solutions, while it has little or no effect on the losses of Co-PCBs, PCDD/DFs, and 13C12-PCDD/DFs from the standard solutions. The losses of lower chlorinated 13C12-Co- PCBs with n-hexane solution were greater than the loss of the compounds with toluene solution. The relative amounts of 13C12-Co-PCBs in the condensate solvent produced during the vacuum concentration show that those of the compounds with toluene solution were less than that of n-hexane solution. These results demonstrate that the minimization of loss of the compounds with n-hexane solution may be achieved by adding toluene before the vacuum concentration. We also examined the relationship between the relative amounts of Co-PCBs and 13C12-Co-PCBs in the condensate solvents and vapor pressures of those compounds. There was the difference in the regression line slopes of the relative amounts vs. in the vapor pressures between the n-hexane solution and toluene solution. This fact could be useful for the optimization of the vacuum concentration conditions in the convenient analytical methods.