Disappearance of some Tetra- and Penta-chlorinated Dibenzo-p-dioxins/dibenzofurans by Sulfuric Acid Treatment in the Analysis Process

Abstract

In the analysis of dioxins (PCDDs, PCDFs and dioxin-like PCBs), sulfuric acid treatment is an indispensable process of cleanup. In this study, we found that the disappearance of some TeCDDs, TeCDFs, PeCDDs and PeCDFs by longtime contact with sulfuric acid. No disappearance of these congeners occurs, provided that the sulfuric acid treatment is under gentle conditions of which the analytical manuals have proposed. The disappeared congeners had an unsubstituted benzene ring or a mono-chlorine-substituted one. Furthermore, it was found that sulfonated 1,2,3,4-TeCDD was produced by contacting 1,2,3,4-TeCDD with sulfuric acid. Therefore, it was suggested that the sulfonation reaction occurred in the lower-chlorinated benzene ring. Attention should be paid to sulfuric acid treatment when detailed congener information is required or when using 1,2,3,4-TeCDD and/or 1,2,3,4-TeCDF for sampling spikes. On the other hand, impurities were greatly removed by long-time contact with sulfuric acid. No disappearance was found for congeners with TEF values: Seventeen 2,3,7,8-PCDDs/PCDFs and twelve dioxin-like PCBs.