SIMPLIFIED GEL PERMEATION METHOD FOR THE ANALYSIS OF PCDD/FS IN STACK EMISSION AND WASTE SOLID SAMPLES FROM VARIOUS THERMAL INDUSTRIAL PROCESSES

as stated in the Community Strategy for dioxins, furans and polychlorinated biphenyls 1 and in method EPA 1613 2 . The analysis of dioxins can be carried out on different kind of samples. Sample preparation of dioxin extracts is one of the most challenging in analytical chemistry. Many coextractable and potentially interfering compounds present in the raw extract must be removed in order to achieve the enrichment of PCDD/Fs in the extracts, considering the small amount of analytes to be determined. Reference methods 2,3 for the quantitative analysis of PCDD/Fs involve successive clean-up steps on various chromatographic adsorbents (multi-layer silica, Florisil, alumina, activated carbon) which considerably increase the time needed for analysis. The cleanup step can be modified to overcome interferences or lower the cost of measurements, provided that all method equivalency and performance criteria are met. In order to simplify the clean-up step the use of two columns have been chosen: gel permeation and alumina. In this work, an assessment of a new automated clean-up system based on gel permeation chromatography (AccuPrep MPS TM , J2 Scientific) combined with an in-line concentration system (AccuVap TM , J2 Scientific) was performed. Gel-permeation chromatography (GPC) is a size exclusion clean-up procedure using organic solvents and hydrophobic gels in the separation of synthetic macromolecules. The removal of this high molecular weight, high boiling material may reduce contamination of GC injection ports and column heads, prolong column life, stabilize the instrument, and reduce column reactivity. The automated concentration system 4 combines heat and vacuum with precise level sensing technology to perform fast, accurate concentration of GPC collect fractions as they elute off the column. The objectives of this study were: i) to evaluate the chromatographic pattern of combined purification on size exclusion gel and alumina columns in samples with low organic content as ambient air, fly ashes and industrial emissions; ii) to verify the recovery of each 13 C 2,3,7,8-chlorine substituted congeners added before the extraction; iii) to apply the combined clean-up (GPC/alumina) to different matrices to evaluate the general applicability of this method and the possibility to extend it to more complex samples, such as biological samples and soils. Materials and methods Samples In order to evaluate the suitability of the method for real sample analysis a comparison between a well established manual clean-up procedure and the new automated system was made in several different environmental matrices for a total of about 200 samples, as summarized in table 1. Appropriate extraction techniques and standards were applied depending on the sample nature. Clean-up The manual clean-up process was based on the sequential use of open chromatographic multilayer silica and basic alumina columns. The multilayer silica column was composed of sequential layers (from bottom to top) silica, SiO2 ‐ AgNO3, silica, SiO2 - H2SO4, silica and Na2SO4. The extract applied to the top of the silica column was eluted with 150 ml of n-hexane and then concentrated prior to basic alumina column. PCBs were eluted