Determination of polychlorinated dibenzodioxins and dibenzofurans in fly ash

Summary Polychlorinated Dibenzo-p-dioxins (PCDD) and Dibenzofurans (PCDF) in fly ash samples from coalburning power plants in Greece have been determined by high resolution gas chromatography combined with mass spectrometric detection (HRGC-MS) applying the isotopic dilution technique. Concentrations of PCDFs were 20 to 600 fold higher than for PCDDs. The concentrations of PCDDs and PCDFs were in the range of 11–62 and 1254–7180 pg/g respectively. Fly ashes from coal-burning power plants were found to be potential sources of PCDFs.     

Use of supercritical fluid extraction in the analysis of polychlorinated dibenzodioxins and dibenzofurans

Summary Supercritical fluid extraction is a powerful technique with great promise in organic analytical chemistry. To date little has been published on the use of SFE in the analysis of polychlorinated dibenzodioxins and dibenzofurans (PCDD/F). The data point, however, to the feasibility of a selective and exhaustive extraction of these compounds. Solid phase trapping of the extracted PCDD/F allows for on-line class separation and clean-up and seems to be the most flexible choice of collection mode. Both CO₂ and N₂O can be used as supercritical fluids. Extraction recoveries can be improved with a small percentage of an organic solvent added to the supercritical fluid as modifier. Methanol and benzene have proven to be efficient. Relatively strong supercritical fluid conditions are needed for the extraction of PCDD/F from fly ash (350–400 atm at 330–370 K). Spiked internal standards are easily extracted even at mild conditions whereas native PCDD/F are not; thus caution should be taken when an isotopic dilution technique is used for a future evaluation of SFE in the analysis of PCDD/F.     

Formation of polychlorinated dibenzodioxins and dibenzofurans by heating chlorophenols and chlorophenates at various temperatures

Summary Polychlorinated dibenzodioxins (PCDD) and polychlorinated dibenzofurans (PCDF) are formed by pyrolysis of chlorophenols and chlorophenates. Under certain conditions the PCDD pattern is completely governed by the chlorine substitution of the starting molecules. Pyrolyses of chlorophenols at elevated temperatures, however, lead to complex PCDD/PCDF mixtures. Nearly all trito heptachlorodibenzodioxin and -dibenzofuran congeners can arise simultaneously from a mixture of only two trichlorophenols. In this case the substitution pattern of the products is no longer influenced by that of the chlorophenols used.

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Bildung von polychlorierten Dibenzodioxinen und Dibenzofuranen durch Erhitzen von Chlorphenolen und Chlorphenolaten bei verschiedenen Temperaturen

Zusammenfassung Polychlorierte Dibenzodioxine (PCDD) und polychlorierte Dibenzofurane (PCDF) werden durch Pyrolyse von Chlorphenolen und Chlorphenolaten gebildet, wobei unter bestimmten Bedingungen das PCDD-Muster vollständig von der Chlorsubstitution der Ausgangsmoleküle bestimmt wird. Die Pyrolyse von Chlorphenolen bei höheren Temperaturen führt jedoch zu komplexen PCDD/ PCDF-Gemischen. Fast alle Tribis Heptachlordibenzodioxine und -dibenzofurane können gleichzeitig aus einer Mischung von nur zwei Trichlorphenolen hervorgehen. In diesem Fall wird das Substitutionsmuster der Produkte nicht mehr von dem der eingesetzten Chlorphenole beeinflußt.

     

Rapid determination of 2,3,7,8-tetrachlorodibenzo-p-dioxin in thermally treated soil

Summary Remedial action at an industrial site contaminated with chlorinated organic compounds including PCDD/PCDF involves thermal treatment of soil to reduce levels of 2,3,7,8-TCDD below a target value of 60 ng/kg. To guarantee the required quick turnaround for the analyses, a problem-oriented method was developed for the selective determination of 2,3,7,8-TCDD on a time scale of 2 – 4 h. Treated soil is extracted with an acidic solvent mixture (ethoxyethanol/toluene/6 mol/l sulphuric acid). The 2,3,7,8-TCDD in the extract is separated from matrix components and other PCDD/PCDF congeners by flash chromatography on alumina. The selectivity attained in this step allows final determination using isotope dilution GC/MS on a non-polar column. The method is in routine operation in an on-site laboratory. With a bench top quadrupole instrument, detection limits around 3 – 5 ng/kg are obtained. Previously: Institut biocontrol, now amalgamated with Institut Fresenius     

The determination of chlorinated biphenyls,chlorinated dibenzodioxins,and chlorinated dibenzofurans by GC-MS

High resolution gas chromatography, with mass selective detection, has been used for the analysis of PCB on methyl 50 % octyl polysiloxane (SB 50 Octyl), methyl octadecyl polysiloxane, and a smectic polysiloxane (SB Smectic); and for the analysis of polychlorodibenzodioxins and polychlorodibenzofurans with 1 to 8 chlorine substituents on 100 % cyanopropyl siloxane (SP 2331), smectic polysiloxane (SB Smectic), a new polar stationary phase (DB-Dioxin). The analysis has also been performed by column coupling.     

Separation of polychlorinated dibenzothiophenes from polychlorinated dibenzodioxins and -furans

Polychlorinated dibenzothiophenes (PCDT) have recently been identified in a series of environmental samples. Since their masses are very close to those of the polychlorinated dibenzodioxins (PCDD), low resolution mass selective detection cannot be used to distinguish between these two classes of compounds. A method is presented which may allow this, involving the oxidation of the PCDTs to the corresponding sulfones which have a higher mass than the PCDDs. If needed, the PCDTO₂s can easily be separated from the PCDDs and the polychlorinated dibenzofurans (PCDFs) by simple chromatographic techniques. The PCDDs/Fs are apparently stable under the oxidative conditions so that now a determination of PCDDs and PCDFs becomes possible without interference from PCDTs.     

Multiresidue procedures for the determination of chlorinated dibenzodioxins and dibenzofurans in a variety of foods using capillary gas chromatography-electron-capture detection

Multiresidue digestion-extraction procedures for the determination of chlorinated dioxins and furans in a wide variety of products are presented. Procedure selection is dependent upon the residue(s) of interest, and on the fat content of the product. Additional cleanup is accomplished using column chromatography and a Florisil trap. The separation of residues is achieved by fraction collection off of two high-performance liquid chromatographic systems. Capillary gas chromatography employing electron-capture detection is used for quantitation. The extracts are suitable for gas chromatography mass spectrometry or gas chromatography with Hall electrolytic conductivity detection. Results of analysis, recovery data, and interlaboratory comparisons are presented. Spike recoveries will typically average 90% +/- 10%.     

Gas chromatographic determination of isocitric and malic acid in the presence of a large excess of citric acid

Derivatization yields of different esters (methyl, ethyl, n-propyl, isopropyl, n-butyl and isobutyl) of citric, malic and isocitric acids with various acylating agents, such as acetic anhydride, propionic anhydride, trifluoroacetic anhydride and heptafluorobutyric anhydride, were investigated. The formation of acylated malic and isocitric acid esters is rapid and quantitative whereas the acylation of citric acid esters was slow and partial in most instances. It was found that selective analytical conditions can be achieved with the O-heptafluorobutyryl n-butyl esters. The analytical applicability of the separation and determination of the malic, isocitric and citric acid contents of model solutions and of pressed lemon juice is discussed. Concentrations of 1.2 × 10^?3 ?9.0 × 10^?3g per 100 g of isocitric acid and 4.2 × 10^?3 ?3.5 × 10^?2 g per 100 g of malic acid in the presence of 9.3 × 10^?1 g per 100 g of citric acid were measured with relative standard deviations of 7.5 and 4.2%, respectively.     

Combining NMR spectral and structural data to form models of polychlorinated dibenzodioxins,dibenzofurans, and biphenyls binding to the AhR

A three-dimensional quantitative spectrometric data-activity relationship (3D-QSDAR) modeling technique which uses NMR spectral and structural information that is combined in a 3D-connectivity matrix has been developed. A 3D-connectivity matrix was built by displaying all possible assigned carbon NMR chemical shifts, carbon-to-carbon connections, and distances between the carbons. Two-dimensional ¹³C-¹³C COSY and 2D slices from the distance dimension of the 3D-connectivity matrix were used to produce a relationship among the 2D spectral patterns for polychlorinated dibenzofurans, dibenzodioxins, and biphenyls (PCDFs, PCDDs, and PCBs respectively) binding to the aryl hydrocarbon receptor (AhR). We refer to this technique as comparative structural connectivity spectral analysis (CoSCoSA) modeling. All CoSCoSA models were developed using forward multiple linear regression analysis of the predicted ¹³C NMR structure-connectivity spectral bins. A CoSCoSA model for 26 PCDFs had an explained variance (r²) of 0.93 and an average leave-four-out cross-validated variance (q₄ ²) of 0.89. A CoSCoSA model for 14 PCDDs produced an r² of 0.90 and an average leave-two-out cross-validated variance (q₂ ²) of 0.79. One CoSCoSA model for 12 PCBs gave an r² of 0.91 and an average q₂ ² of 0.80. Another CoSCoSA model for all 52 compounds had an r² of 0.85 and an average q₄ ² of 0.52. Major benefits of CoSCoSA modeling include ease of development since the technique does not use molecular docking routines.     

Electrochemical masking of large amounts of copper in dpasv and the determination of thallium in the presence of a large excess of copper

The influence of the following surfactants on the peak of copper in 0.2M EDTA at pH 4.5 was investigated: polyoxyethylated alkylphenols having an average of 3 and 9.5 ethylene oxide units; polyoxyethylene alcohols having 4 and 7 ethylene oxide units; poly(ethylene glycols) having M.W. 4000, 9000 and 20000; hexadecyltributylphosphonium bromide (HDTBPB), tetraphenylphosphonium bromide (TPPB),N,N,N,N,N',N',N-examethylhexamethylenediammonium bromide (HMB), benzyl(di-isobutylphenoxyethoxy) dimethylammonium chloride (Hyamine 1622), hexadecyltrimethylammonium bromide (HDTMAB), hexadecyldimethylbenzylammonium chloride (HDDMBAC) and tetrabutylammonium chloride (TBAC). HDDMBAC, as well as all the substances examined which contained an ethylene oxide chain, completely suppressed the copper peak. HDTBPB and TPPB partially suppressed the peak, whereas HDTMAB, HMB and Hyamine 1622 enhanced it. TBAC was without effect. In 0.2M EDTA at pH 4.5 containing TBAC at 0.01M concentration and 10 ppm of Rokafenol N-3, Cu(II), Pb(II) and Bi(III) can be tolerated at concentrations of up to 0.05M, the height of the thallium peak being unaffected. The precision of the determination (3–10%) and the recovery are satisfactory. A 10³-fold ratio of Fe(III) to Tl(I) does not interfere with the determination.     

Selective pressurized liquid extraction of polychlorinated dibenzo-p-dioxins, dibenzofurans and dioxin-like polychlorinated biphenyls from food and feed samples

Selective pressurized liquid extraction (PLE) of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) from various food and feed samples was performed with a selective PLE method previously developed for bulk PCBs. The method utilizes sulfuric acid impregnated silica inside the extraction cell to oxidize coextracted fat. Extractions were performed at 100 degrees C with n-heptane for 5 min in two cycles. Data obtained by selective PLE combined with gas chromatography/high-resolution mass spectrometry (GC-HRMS) were compared to concentrations derived from reference laboratories applying conventional sample preparation and GC-HRMS. Experiments performed on spiked vegetable oil, naturally contaminated crude fish oil and oil containing compound feed samples showed good results for these relatively simple matrices. The accuracy was generally +/-20% as compared to spiked levels or to values obtained by the reference laboratories. The precision, measured as the relative standard deviation (RSD) for 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalency values (TEQs), was below 10% in all cases. The method was also tested on naturally contaminated herring tissue, chicken tissue, pork tissue and sepiolitic clay, which all caused some trouble. It was observed that sufficient amounts of sodium sulfate should be used for dehydration of tissue samples and additionally, the cells should not be packed too dense in order to avoid suppressed extraction efficiency. Once this was attended to, satisfactory data could be obtained, except for sepiolithic clay. This study demonstrates that selective PLE can be applied with success to a number of food and feed matrices in analysis of PCDD/Fs and dl-PCBs. Since the fat removal step is on-line, the selective PLE method will reduce time and solvent consumption for sample preparation as compared to traditional clean-up.     

Photocatalytic UV-degradation of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the presence of silver doped zeolite

Silver incorporated into the Y zeolite framework was prepared and characterized. Low temperature luminescence analysis indicates the formation of silver-silver excimers (excited state dimers) and exciplexes (excited state trimers) that were found to be activated at 250 nm and 300 nm, respectively. The catalytic activity of the modified material was tested toward the photodecomposition of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The site selective activity was evaluated using two sources of UV irradiation at 254 and 302 nm. The catalyst was found to effectively decompose TCDD in a methanol/tetrahydrofuran solution to reach 86% after 5 h. In the presence of the catalyst, a hydroxyl derivative was identified as an intermediate for the 302 nm catalytic pathway. This was not observed for the 254 nm process. Furthermore, irradiating of TCDD under 254 nm UV source for 6 h resulted in the formation of three products with molecular ion peaks of 113, 128, and 158 amu. On the other hand, the 302 nm gives two major products with molecular ion peaks of 220 and 252 amu. The study also indicates that the hydroxyl derivative could be potentially more toxic than the parent TCDD while all other isolated products were found to be less toxic than TCDD.     

Polychlorinated dibenzodioxins and dibenzofurans in suspended particulate matter of the River Elbe 1994

In April/May 1994 during a period of high discharge in the German part of the River Elbe (9 stations) and its main tributaries (3 stations) samples of suspended particulate matter (SPM) have been collected by means of sedimentation chambers with sampling periods of three or four weeks. Subsequent analyses for polychlorinated dibenzodioxins and dibenzofurans (PCDD/F) have shown that the river enters Germany with a rather low PCDD/F-load which almost steadily increases to below Hamburg. Major sources of contaimination has been the input by the tributary Mulde and resuspension of contaminated sediments along the riversides. Downstream of Hamburg marine influence have caused a sharp decrease of PCDD/F-contents. Changes in the result of 1989, 1992/93 have been discussed.     

Separation of seventeen 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins and dibenzofurans and 12 dioxin-like polychlorinated biphenyls by comprehensive two-dimensional gas chromatography with electron-capture detection

Comprehensive two-dimensional gas chromatography (GC x GC) with electron-capture detection (ECD) has been optimized for the separation of seventeen 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins and dibenzofurans and 12 dioxin-like polychlorinated biphenyls, with emphasis on the selection of the first- and second-dimension, commercially available, columns. When eight second-dimension columns were subsequently combined with a 100% methylpolysiloxane stationary phase (DB-1) in the first dimension to create orthogonal conditions, a complete separation of all congeners with different TEF values was obtained with two column combinations, DB-1 x VF-23 and DB-1 x LC-50. When other types of first-dimension columns were used (and orthogonality was partly sacrificed), a DB-XLB column combined with 007-65HT, VF-23 and LC-50 was found to provide a complete separation of all 29 priority congeners. Next, the potential of these three column combinations for real-life analysis was preliminarily studied. With a spiked and fractionated milk extract, DB-XLB x LC-50 was found to be the most powerful column combination, because of the good separation of the 29 priority congeners from each other as well as from the matrix constituents. Quantitative performance (close to three-order linearity; LODs, 30-150 fg injected; R.S.D.s, 1.5-6.5% (n = 10)) was satisfactory.     

Models of polychlorinated dibenzodioxins, dibenzofurans, and biphenyls binding affinity to the aryl hydrocarbon receptor developed using (13)c NMR data

Quantitative spectroscopic data-activity relationship (QSDAR) models for polychlorinated dibenzofurans (PCDFs), dibenzodioxins (PCDDs), and biphenyls (PCBs) binding to the aryl hydrocarbon receptor (AhR) have been developed based on simulated (13)C nuclear magnetic resonance (NMR) data. All the models were based on multiple linear regression of comparative spectral analysis (CoSA) between compounds. A 1.0 ppm resolution CoSA model for 26 PCDF compounds based on chemical shifts in five bins had an explained variance (r(2)) of 0.93 and a leave-one-out (LOO) cross-validated variance (q(2)) of 0.90. A 2.0 ppm resolution CoSA model for 14 PCDD compounds based on chemical shifts in five bins had an r(2) of 0.91 and a q(2) of 0.81. The 1.0 ppm resolution CoSA model for 12 PCB compounds based on chemical shifts in five bins had an r(2) of 0.87 and a q(2) of 0.45. The models with more compounds had a better q(2) because there are more multiple chemical shift populated bins available on which to base the linear regression. A 1.0 ppm resolution CoSA model for all 52 compounds that was based on chemical shifts in 12 bins had an r(2) of 0.85 and q(2) of 0.71. A canonical variance analysis of the 1.0 ppm CoSA model for all 52 compounds when they were separated into 27 strong binding and 25 weak binding compounds was 98% correct. Conventional quantitative structure-activity relationship (QSAR) modeling suffer from errors introduced by the assumptions and approximations involved in calculated electrostatic potentials and the molecular alignment process. QSDAR modeling is not limited by such errors since electrostatic potential calculations and molecular alignment are not done. The QSDAR models provide a rapid, simple and valid way to model the PCDF, PCDD, and PCB binding activity in relation to the aryl hydrocarbon receptor (AhR).     

Comparison of gas chromatography-ion-trap tandem mass spectrometry systems for the determination of polychlorinated dibenzo-p-dioxins, dibenzofurans and dioxin-like polychlorinated biphenyls

Two gas chromatography-mass spectrometry systems equipped with an ion-trap mass analyzer working in tandem mode (GC-MS-MS) were evaluated for the determination of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (PCBs) in food samples. The performance of the two ion-trap instruments, which dispose of an external ion source (ThermoFinnigan GCQ/Polaris) and internal ionization (Varian Saturn 2,200), have been compared in terms of linearity, repeatability, limit of detection and long-term precision. Both instruments provided similar run-to-run and day-to-day precisions, ranging from 2% to 8% and between 2% and 13%, and instrumental limits of detection between 0.09 and 0.36 pg injected for PCDD/Fs and from 0.03 to 0.09 pg injected for dioxin-like PCBs. Although both instruments seem to be suitable for food analysis, only the use of external ionization allowed to achieve reliable results for PCDD/F determination at concentrations close to the maximum residue levels established by the EU for foods. Internal ionization provides high limits of detection (from 10- to 30-fold higher) and worse precision (RSD, 14-43%). In contrast, for dioxin-like PCBs both instruments allowed to obtain excellent results with precisions lower than 15%.     

Dual-column high-performance liquid chromatographic cleanup procedure for the determination of polychlorinated dibenzo-p-dioxins and dibenzofurans in fish tissue

A high-performance liquid chromatographic cleanup procedure employing normal-phase alumina and carbon--silica separations was developed for isolating polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) from other polychlorinated pollutants present in fish tissue. The method utilizes a column-switching step where the dioxins and furans are trace enriched onto a carbon-silica column as they are eluted from the alumina column. Interfering components such as polychlorinated biphenyls and chlorinated diphenyl ethers elute through the carbon--silica column. The PCDDs and PCDFs are subsequently recovered by backflushing the carbon--silica column using toluene.