Pyrolysis-GC/AED and pyrolysis-GC/MS analysis of chlorinated structures in aquatic fulvic acids and chlorolignins

A study was undertaken to evaluate whether pyrolysis-gas chromatography/atomic emission detection (PyGC/AED) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) can be used to systematically search for halogenated structures in natural organic matter. Two samples of aquatic fulvic acid (FA) and two samples of high molecular weight organic matter isolated from bleached-kraft mill effluents (BKME) were selected to respectively represent naturally and industrially chlorinated organic matter. Mono- and dichlorophenol were found in the pyrolysates of the naturally chlorinated samples, and methyl esters of 2,4-dichlorobenzoic acid, monochloro-4-methoxybenzoic acid and 3,5-dichloro-4-methoxybenzoic acid were the main compounds detected when a methylating agent, tetramethylammonium hydroxide (TMHA), was added to the samples prior to the pyrolysis. These results strongly indicate the presence of chlorinated 4-hydroxyphenyl structures in the original FA samples. For the BKME samples, on the other hand, the main chlorinated pyrolysis products were guaiacyl- and syringyl-derived compounds.