Loss of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and coplanar polychlorinated biphenyls during nitrogen gas blowdown process for ultra-trace analysis

This study examined standard solutions to assess the influence of the gas flow rate and organic solvent type on losses caused by gas blowdown of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/DFs) and coplanar polychlorinated biphenyls (Co-PCBs). Results obtained here will contribute to maintaining analytical method performance and system quality for PCDD/DFs and Co-PCBs analyses. An organic solvent (with 0.5 ml each of acetone, dichloromethane, n-hexane, and toluene), PCDD/DFs or Co-PCBs, and their 13C12-labeled compounds were put separately into 10 ml pear-shaped flasks. The samples were blown to dryness at room temperature until the last trace of solvent disappeared. They were subsequently reconstituted in those flasks. Analyte recoveries were calculated by comparing blown samples to those that had not been blown. Recoveries of Co-PCBs were more affected than those of PCDD/DFs when the gas flow rates were set at 203, 261, 332, and 456 ml/min. Losses of Co-PCBs were least at 203-332 ml/min. Regarding losses of PCDD/DFs and Co-PCBs, the toluene solution showed the least variation in recovery. An actual soil sample extract was also examined using optimized conditions for the gas flow rate and solvent types obtained by experiments in standard solutions. Thereby, the blowdown conditions gave quantitative recoveries of 13C12-labeled compounds in the sample extract.