Analysis of Polychlorinated Dibenzofurans (PCDFs) Isomers in Soil Samples

Turk J Chem 25 (2001) , 151 – 156. c TÜBİTAK Analysis of Polychlorinated Dibenzofurans (PCDFs) Isomers in Soil Samples∗ Mustafa PEHLİVAN Dept. of Science E., Fac. of Edu., Selcuk University, 42090 Konya-TURKEY Erol PEHLİVAN Dept. of Chemistry, Selcuk University, 42031 Konya-TURKEY Received 09.10.2000 This study presents an analytical method for the separation of a series of polychlorinated dibenzofurans (PCDFs) emitted to the soil. PCDF contaminants were concentrated from soil samples and isolated from other materials by chromatographic methods and their quantitative determinations were performed by GC/MS (gas chromatography/mass spectroscopy). Key Words: Polychlorodibenzofurans, Toxic Materials, GC/MS, hyphenated technique Introduction Dioxin is one of the world’s most toxic chemicals. It is formed as an accidental and unavoidable by-product of some industrial uses of chlorine. The presence of PCDFs has been reported in the fly ash and flue gas of hazardous waste incinerators of municipalities and hospitals. The majority of these compounds are probably produced in the incinerator itself, by formation from precursors at high temperatures in the flame or by de novo synthesis at low temperatures in the post-combustion zone of the incinerator. The formation of PCDFs is explained by the extensive chlorine exchange reactions. A large number of mixed halogenated congeners are theoretically possible: 1550 brominated/chlorinated dibenzo-p-dioxins (PXDDs) and 3050 brominated/chlorinated dibenzofurans (PXDFs). Because of the complexity of the analytical procedures, it has been possible to characterize and determine only a small number of these compounds. The most toxic congeners are those substituted at positions 2, 3, 7 and 8, and they are considered to be among the most dangerous environmental pollutants the “super-poisons”1−6 . PCDFs are not known to occur naturally. They are not intentionally produced but are generated as undesired by-products in various processes. They can be formed by chemical, photochemical, or thermal reactions from precursors. Fires and incinerators cause the release of PVC’s toxic chemicals such as dioxin. Halogenated aromatic hydrocarbons (HAHs), such as polychlorinated dibenzo-p-dioxins, biphenyls and ∗ This paper has beed presented at MBCAC III (3rd Mediterranean Basin Conference on Analytical Chemistry) 4-9 June, 2000 Antalya-Turkey 151 Analysis of Polychlorinated Dibenzofurans (PCDFs)..., M. PEHLİVAN, E. PEHLİVAN dibenzofurans, are widespread environmental contaminants. During waste incineration, traces of dioxins have also been found. If dioxins or waste containing dioxins are introduced in high concentrations into the environment, entire tracts of land can be poisoned. 2,3,7,8- TCDF, the most biologically active and toxic member of this class of compounds, produces a wide variety of species- and tissue-specific effects7−10 . Dioxin is one of a family of compounds that has the ability to disrupt the body’s endocrine system. Because of the toxic nature of these compounds, care must be taken during sampling and analysis. Highly sensitive, selective and specific analytical methods (gas chromatography/mass spectrometry, or GC/MS) are required because of the large number of PCDF congeners. Sampling procedures are identical for all PCDFs, but the separation and determination of them differ slightly from those of their chlorinated analogues. Experimental Equipment A gas chromatograph (HP 5890) and a mass spectrometer (HP 5970B) from Hewlett-Packard (Böblingen, Germany) were used along with a Bio-Beads S-X3 gel chromatographic column (Bio-Rad, München, Germany), a CP-Sil 88 capillary column (Chrompack International, Middelsburg, The Netherlands), and a DB-5 column from J&W Scientific (Frankfurt, Germany). Chemicals 13 C12 -PCDF standards were purchased from Promochemie (Wesel, Germany). Nitrogen and helium gas were both purchased from Fa. Messer Griesheim (Germany). The organic solvents used were hexane, acetone, dichloromethane, benzene, toluene, cyclohexane, and ethyl acetates. All solvents were of nanograde purity and were obtained from Promochemie. Kieselgel-Silica Woelm 63 (active), Na2 SO4 , concentrated H2 SO4 , AgNO3 , Alumina B Super 1, and Woelm Pharma Eschwege were also from Promochemie. Procedure Soil samples were collected, freeze-dried and ground to a particle size of about 0.1 mm. The extraction and clean-up procedure for the PCDFs analysis were completed as shown in the Figure. Soil Sample ↓ 13 C12 -PCDF standards ↓ Soxhlet Extraction ↓ Column Chromatography ↓ GC/MS Analysis (Selected Ion Monitoring) Figure. Clean-up for PCDF analysis of soil sample 152 Analysis of Polychlorinated Dibenzofurans (PCDFs)..., M. PEHLİVAN, E. PEHLİVAN In the separation technique, known amounts of 13 C12 -PCDF standards were injected into the soil samples, and these samples were then extracted in a Soxhlet type extractor. The total PCDF isomers of the samples were first isolated and then concentrated by passing the extract through columns packed with Kieselgel/44 vol. % H2 SO4 , Macro Alumina B Super 1, Mix Column, Bio Beads S-X3 Gel Chromatography and Mini Alumina B Super 1 columns, all of which are basically chromatographic separation procedures. Isomer-specific PCDF analysis was carried out by GC/MS in multiple ion selection mode. Quantitative determinations were performed by recording the spectra of all PCDF extracts on a GC/MS instrument, and the results are given in the Table. Experimental Procedure The soil sample was vacuum dried at -3◦ C and ground to a fine powder. To 100-g aliquots of the dry sample; 5 ng each of 2,3,7,8-tetraCDF, 1,2,3,7,8-pentaCDF, and 1,2,3,6,7,8-hexaCDF and 10 ng each of 1,2,3,4,6,7,8heptaCDF and 1,2,3,4,6,7,8,9-octa CDF, were added from PCDF standards containing the 13 C12 -isotope. The samples were extracted in a Soxhlet apparatus with toluene for 18 hours. The extract was concentrated in vacuo to about 5 mL In the first chromatographic step, the concentrate was transferred to a chromatography column, which fully packed with a mixture of 40 g (kieselgel/44 vol. % of concentrated H2 SO4 ) and 15 g Na2 SO4 . The concentrate was eluted with a 250 mL (80 vol. % n-hexane/20 vol. % dichloromethane) mixture. The solution was evaporated to a volume of 5 mL in vacuo. This concentrate was transferred to a chromatographic column packed with a mixture of 30 g Alumina B Super 1 and 15 g Na2 SO4 , and then washed with 120 mL benzene and a 250 mL (98 vol. % n-hexane/2 vol. % dichloromethane) mixture respectively. The mixture was discarded, and the column was eluted with a 200 mL (50 vol. % n-hexane/50 vol. % dichloromethane) mixture. The obtained eluent was evaporated to 5 mL. This concentrate was transferred into a chromatographic column which was packed with a mixture of 1 g kieselgel + (2.5 g kieselgel/33 vol. % 1 N NaOH) + 1 g kieselgel + (10 g kieselgel/44 vol. % of concentrated H2 SO4 ) + 5 g Na2 SO4 . The (...truncated)