Application of thermodesorption and pyrolysis-GC-AED to the analysis of river sediments and sewage sludges for environmental purpose

Flash Pyrolysis coupled with Gas Chromatography and Atomic Emission Detection (PyGC-AED) is applied to river sediments and sewage sludges. The chromatograms obtained on such samples are complex and special care must be taken in the tuning of the pyrolyzer, the chromatographic program and the atomic emission detector. Thus, thermodesorption and pyrolysis conditions are defined in order to obtain a good reproducibility of the pyrograms. The atomic emission detector parameters (make-up flow, reactant gases purity and pressures) are studied in order to obtain a good compromise between selectivity and sensitivity. Tuning and analyses are focused on C, N, S, O, Cl. Multi-elemental detection is shown to be a useful tool for specifying the organic heteroatomic compounds distribution in the pyrograms of river sediments and sewage sludges. Comparison with PyGC-MS analyses performed in similar conditions is made. The variability in composition of the samples is clearly revealed. Furthermore, the presence of chlorinated organic compounds is evidenced in some samples. Step by step thermodesorption combined with flash pyrolysis is used in order to gain information on how the chlorine is associated to the matrix; i.e. adsorbed and/or tightly bound chlorine. The total chlorine content and the adsorbed/bound chlorine ratio of the samples are measured using compound independent calibration. (C) 2002 Elsevier Science B.V. All rights reserved.