Chromatographic properties of various polysiloxane stationary phases for separation of 2,3,7,8–chloro-substituted dibenzo-p-dioxin and dibenzofuran isomers–a systematic comparison

Glass capillaries coated with four crosslinked and surface-bonded OH-terminated polysiloxanes [PS 347.5, OV-17-OH, OV-225-OH, and OV-240-OH] were compared with commonly used methyl-terminated SP-2330-coated columns with respect to their selectivity for the separation of 2,3,7,8-chloro-substituted dibenzo-p-dioxins and dibenzofurans. The methyl- and phenyl-substituted phases [PS 347.5 and OV-17-OH] exhibit only moderate isomer selectivity which limits their applicability in this field. The examined 3-cyanopropyl-substituted phases [OV-225-OH, OV-240-OH, and SP-2330] allow complete separation of all 2,3,7,8-chlorosubstituted PCDDs and PCDFs. With SP-2330 longer columns are required (50 m) for baseline separation of critical groups of isomers. OV-225-OH was found to be the most suitable phase as to isomer selectivity. In comparison to SP-2330, the analysis times can be reduced by a factor of two.     

Fast matrix digestion with hot ethanolic alkali plus pyrogallol for polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and coplanar polychlorinated biphenyls analysis in biological samples

The efficiency of hot alkaline digestion of a sample matrix was investigated for determination of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and coplanar polychlorinated biphenyls (CoPCBs) in biological samples. Results of recovery tests of octachlorodibenzofuran (OCDF) after spiking into lean tuna showed degradation of OCDF and the production of a large quantity of lower-chlorinated dibenzofurans (LoCDFs) when the sample was digested with hot ethanolic KOH. However, it was also confirmed that pyrogallol (PG) prevented dechlorination of OCDF. The accuracy of the hot alkaline digestion method with PG was demonstrated by analyzing PCDD/Fs-spiked lean tuna. The proposed method is more suitable than conventional versions for the determination of dioxins in biological samples in terms of savings in time, adequate digestion of matrix and high degree of recovery of internal standards.     

Optimization of solid-phase extraction procedure for determination of polychlorinated dibenzo-<Emphasis Type="Italic">p</Emphasis>-dioxins,polychlorinated dibenzofurans,and coplanar polychlorinated biphenyls in humic acid containing water

A solid-phase extraction (SPE) method was optimized for accurate determination of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (CoPCBs) in humic acid containing surface water. Recovery experiments using humic materials revealed that humic acids permit dioxins to pass through an octadecylsilica (C₁₈) extraction disk by associating with them under weakly alkaline conditions. Acidification of the sample before percolation improved this otherwise insufficient recovery. The analysis of surface water acidified to pH 2 gave better recovery with surrogate standards and lower quantitative values for higher-chlorinated homologues than the sample at pH 9. In all samples, the native octachlorodibenzo-p-dioxin (OCDD) peak abundance showed no difference between at pH 2 and at pH 9, indicating overestimation of the quantitative value of the homologue at pH 9. Acidification of a humic acid containing water sample can avoid overestimation of higher-chlorinated congeners caused by insufficient recovery of their corresponding surrogates.     

A polymeric liquid crystal capillary column for GC-MS analysis of PCDD and PCDF

A newly developed side chain liquid crystal polysiloxane has been investigated as a stationary phase for the isomer-specific analysis of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans substituted at positions 2, 3, 7, and 8. The retention times from the chromatograms of a standard solution containing all PCDD and PCDF isomers were compared with those from solutions containing only those tetra- to octa-chlorinated compounds substituted at positions 2, 3, 7, and 8. In general, PCDDs substituted at positions 2, 3, 7, and 8 eluted later than most other isomers of the same congener group. The separations obtained on this stationary phase were compared with those obtained elsewhere using a commercially available product.     

Congener-specific method for the determination of ortho and non-ortho polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in foods by carbon-column fractionation and gas chromatography-isotope dilution mass spectrometry

 The chromatographic behavior of ortho and non-ortho polychlorinated biphenyls (PCBs) on supported carbon columns has been investigated and the structure-affinity relationship of activated carbon towards PCB molecules established. Optimisation of the parameters controlling the elution of PCB congeners through the carbon column led to the development of a solvent scheme for the efficient separation of (i) ortho substituted PCBs, (ii) non-ortho substituted PCBs and (iii) polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in three separate fractions. A method for the extraction, clean-up, fractionation and determination of ortho and non-ortho substituted PCBs by GC-isotope dilution MS was developed and validated by analysis of a certified reference material. Possible losses of PCBs during freeze-drying and interferences of aliphatic hydrocarbons during mass spectrometric determination of ortho substituted PCBs are also discussed. Received: 23 June 1995/Revised: 9 May 1996/Accepted: 25 May 1996     

Validation of methods for measuring polychlorinated dibenzo- p -dioxins and furans,and dioxin-like polychlorinated biphenyls in flue gas

Method validation was performed on the collection and extraction procedures for an analysis of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (DLPCBs) in flue gas. The adoption of the rapid pressurized liquid extraction (PLE) technique was evaluated for extraction from polyurethane foam plugs (PUFPs) and fly ash. With respect to extraction from PUFPs, dichloromethane PLE showed an extraction efficiency equivalent to that of conventional acetone Soxhlet, while toluene PLE was found to have a lower extraction efficiency from fly ash than toluene Soxhlet. The collection ability of three sampling methods, employed in the Japanese standard analytical method JIS K0311 (revised in 2005) was evaluated by evaluating the distribution of gaseous PCDD/Fs and DLPCBs in each collection compartment in sampling trains. A DiOANA® fibrous alumina filter and a PUFP, newly employed trapping devices in the revised JIS method, were found to trap gaseous analytes effectively. The validation of the two newly employed sampling methods (DiOANA and PUFP) was tested by parallel measurements of the methods with a conventional five-impinger method, and good agreements on the PCDD/Fs and DLPCBs quantities were demonstrated.     

Polychlorinated biphenyls,dibenzo-p-dioxins and dibenzofurans in soil samples from airport areas of Croatia

Levels and patterns of polychlorinated biphenyls (PCBs) were studied in surface soil samples collected in the coastal part of Croatia within and surrounding four different airports and in the vicinity of two partially devastated electrical transformer stations. The compounds accumulated from air-dried soil samples by multiple ultrasonic extraction with an n-hexane?:?acetone 1?:?1 mixture were analysed by capillary gas chromatography with electron capture and ion-trap detection. PCBs were quantified against a standard Aroclor 1242/Aroclor 1260 mixture and a standard mixture of 17 individual PCB congeners (IUPAC No.: 28, 52, 60, 74, 101, 105, 114, 118, 123, 138, 153, 156, 157, 167, 170, 180, and 189). The mass fractions of total PCBs in 18 soil samples collected within the airport premises ranged from 3 to 41?327?µg/kg dry weight (dw) (median: 533?µg/kg?dw), and those in 21 samples collected at a distance ranging from several metres to 5?km away from the airport fence, from <1 to 39?µg/kg?dw (median: 5?µg/kg?dw). The highest PCB levels were determined in soils along the airport aprons where the aircrafts were serviced and refuelled. The PCB pattern was very similar to technical Aroclor 1260 in all airport soils. The PCB pattern in 22 soils collected in the vicinity of electrical transformer stations was dominated by congeners contained in Aroclor 1242. These soils contained 7 to >400?µg/kg?dw of total PCBs. One highly PCB-contaminated airport soil sample was analysed for polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). With an international toxic equivalent (I-TEQ) of 9.7?ng/kg?dw, the airport soil contamination was within values typical for urban and rural areas, and the congener patterns gave no clear indication for PCBs as the only source of PCDDs/PCDFs.     

Characteristics of major dioxin/furan congeners in melted slag of ash from municipal solid waste incinerators

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in slag of fly ash from three municipal solid waste (MSW) incinerators were analyzed to observe any changes in characteristics and distribution of their congeners by melting process. Actual concentration and Toxic Equivalent (TEQ) concentration profiles of 17 major congeners of PCDDs/PCDFs for gas, fly ash and melted slag were compared. The distributions of PCDDs/PCDFs in different streams macroscopically showed similarities with the generally known profiles for emission gas from a municipal waste incinerator. The total concentrations of PCDDs/PCDFs in off-gas and fly ash have been known to be a function of incineration conditions and of air pollution control device utilization; however, their normalized distributions were independent of such conditions. The concentrations of PCDDs/PCDFs in the melted slag of fly ash were not related to the concentrations of PCDDs/PCDFs congeners in fly ash but were rather a function of the melting furnace type and operation. The total amount of PCDDs/PCDFs in the melted slag of fly ash contained almost 150–27,000 times less dioxin than that in fly ash, however, the TEQ of dioxin in the slag was reduced by 435–43,500 times, which could enable them to be utilized as recycled construction materials. In normalized TEQ concentration profiles of 17 congeners of PCDDs/PCDFs, the ratio of PCDFs to PCDDs changed from 1.32 to 2.19 by melting, which showed relatively higher portion of furans left in melted slag than those in fly ash. By comparing reduction ratios of different congeners, PCDDs (dioxins) were relatively easier to destruct than PCDFs (furans) during melting process. The most difficult congener to destruct could be octa-chlorinated dibenzofuran (OCDF) among major congeners. For slag cooling methods, dioxin concentration in TEQ of slow cooled slag by air was four times higher than that of fast cooled slag by water. Thus cooling by water is more appropriate with the added beneficial effect of producing granules/particles, which can be utilized as roadbed materials.     

Comparison of series 5 gas chromatography column performances from a variety of manufacturers for separation of chlorinated dibenzo-p-dioxins and dibenzofurans using high-resolution mass spectrometry

An extended study of seven fused silica capillary gas chromatographic (GC) columns has been conducted with regard to separation of international toxic equivalent factor (I-TEF) isomers (tetra- through octa-chlorinated at 2,3,7,8 positions) of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/PCDFs) from closely co-eluted other isomers using high-resolution gas chromatography-high-resolution mass spectrometry (HRGC-HRMS). The data are explicated in mass chromatograms of Series 5 GC columns from a variety of manufacturers (Varian CP-Sil 8 CB LowBleed/MS, Phenomenex ZB-5UMS, Agilent HP-5MS, Restek Rtx-5MS, Supelco Equity-5, J&W Scientific DB-5 and DB-5MS), according to relative retention times, and 2,3,7,8-substituted isomer concentrations for each of the columns tested. Results showed differences between 5% phenyl methyl silicone and 5% silphenylene (Si-arylene) silicone polymer type GC stationary phases in separation of 2,3,7,8-substituted PCDDs/PCDFs from closely co-eluted isomers. The separation differences for Si-arylene type columns resulted in lower toxic equivalence (TEQ) values compared to the siloxane-based columns. Because of differences in product nomenclature and manufacturing practices by various manufacturers, incorrect assumptions and comparisons may be made regarding the interchangeability of these columns for PCCD/PCDF separations. The data presented are the most comprehensive to date and provide a valuable addition to operational criteria for the standard US Environmental Protection Agency methods 1613b and 8290.     

Molecular graph fingerprint: a new molecular structural characterization method for the modelling and prediction of chromatographic retention behaviour of several persistent organic pollutants

How to extract and characterize information on molecular microstructures is deemed to be the key task to accurately simulate and predict molecular properties. In terms of atomic attributes, atoms in a molecule are divided into three levels. Based upon that, inter-atomic correlations are mapped to certain reasonable spatial coordinates in virtue of radial distribution function, generating the novel molecular graph fingerprint (MoGF), which essentially provides insight into molecular inner structures. MoGF, committing itself to transformation of molecular structures into characteristic graph curves, shows valuable advantages such as easy calculation, experimental parameters-free, rich information content, and structural significance and intuitive expressions. QSRR studies were performed for 115 polychlorinated dibenzofurans (PCDFs), 41 polychlorinated dibenzo-p-dioxins (PCDDs), 62 polychlorinated naphthalenes (PCNs), and 210 polychlorinated biphenyls (PCBs including the biphenyl)) tested for their retention behaviours on gas chromatographic column DB-5. The resulting PLS models showed good performances with correlation coefficients for both training and test sets above 0.97.     

Certification of SRM 1589a PCBs,pesticides, PBDEs,and dioxins/furans in human serum

The Certificate of Analysis for SRM 1589a PCBs, Pesticides, PBDEs, and Dioxins/Furans in Human Serum has been updated to include certified concentration values for 27 polychlorinated biphenyl (PCB) congeners, three chlorinated pesticides, and four polybrominated diphenyl ether (PBDE) congeners as well as reference concentration values for 27 additional PCB congeners, six additional chlorinated pesticides, three additional PBDE congeners, and selected polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). This represents an addition of concentration values for 29 PCB congeners and for PBDE congeners that were not quantified in the previous issue of SRM 1589a. With the increased number of certified and reference concentration values for PCBs and the inclusion of certified and reference concentration values for PBDEs, this serum material will be more useful as a reference material for contaminant monitoring in human tissues and fluids. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Supercritical fluid extraction of polychlorinated dibenzo-p-dioxins from municipal incinerator fly ash

The supercritical fluid extraction of polychlorinated dibenzo-p-dioxins from an incinerator fly ash sample has been investigated; supercritical nitrous oxide and its mixtures with methanol and toluene were employed as mobile phases. Recoveries of individual polychlorinated dibenzo-p-dioxins congeners were calculated from results of analysis of ¹³C-labeled dioxins by high resolution GC-MS employing selected ion monitoring. The extraction procedure was compared with extraction in a Soxhlet apparatus, which is currently used as a standard method for removing chlorinated dibenzo-p-dioxins from fly ash samples: the results indicated that the time required for the extraction and clean-up can be reduced from 24 to 2.5 hours/sample. Quantitative recovery of the chlorinated dibenzo-p-dioxins was achieved at μg/kg levels, the relative standard deviation was between 1.8 and 5.8%. The use of a virtually inert fluid such as pure nitrous oxide provides significant improvement over conventional extraction procedures because no solvent residue is left in the processed extract.     

Comparison of immunoaffinity column recovery patterns of polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans on columns generated with different monoclonal antibody clones and polyclonal antibodies

Evaluation of immunoaffinity columns (IACs) for dioxin serum sample clean-up requires a determination of the recovery of various dioxin congeners. We compared the IAC performance of different monoclonal and polyclonal anti-dioxin antibodies, measuring the recovery of congeners of polychlorinated dibenzo-p-dioxins (PCDDs). In addition, we measured the recovery of congeners of the structurally related polychlorinated dibenzofurans (PCDFs).The polyclonal antibody based IACs evaluated had lower recovery for highly chlorinated dioxin congeners, but were more specific toward 2,3,7,8-TCDD. The resemblance of the hapten to 2,3,7,8-TCDD appeared to play a clear role, but chlorines in the 2-, 3- and 7-positions of the hapten were essential. Recovery of 2,3,7,8-TCDD from the IAC showed some relation to the affinity for the antibody measured by either the K_a from accelerator mass spectrometry (AMS) or with 50% inhibition of color activity (IC₅₀) determined from an ELISA analysis.The IACs prepared from four monoclonal antibodies (Mabs) derived from a common hapten showed differences in their retention patterns of PCDDs/PCDFs. Comparison of IC₅₀ from ELISA with recovery from the IACs indicated that a minimum IC₅₀ of 100 ppb was required for satisfactory recovery from the IAC, but the correlation was poor, indicating other factors were involved. Mab DD3 showed the broadest spectrum of the Mabs and showed satisfactory recoveries of all of the dioxin congeners, except OCDD. In addition, DD3 showed good recovery toward 2,3,4,8-TCDF, 2,3,4,7,8-PeCDF and 2,3,4,6,7,8-HxCDF but has poor recovery when PCDFs have a chlorine substitution in the 1-position.     

Thermochemical properties of gaseous and liquid polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins, and dibenzofurans

The analysis and systematization of the known and calculation of the unknown thermochemical characteristics (the standard enthalpy of formation, the standard entropy, the heat capacity, etc.) of widespread hazardous isomers of gaseous and liquid compounds of polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins, and polychlorinated dibenzofurans are carried out.     

Cyclodextrin derivatives for the GC separation of racemic mixtures of volatile compounds. Part VI: The influence of the diluting phase on the enantioselectivity of 2,6-Di-O-methyl-3-O-pentyl-β-cyclodextrin

As a continuation of previous studies on the use of cyclodextrin derivatives (CD) for the separation of volatile compounds by capillary GC, the influence of diluting phases other than OV-1701 or OV-1701-OH has been investigated. 2,6-Di-O-methyl-3-O-pentyl-β-cyclodextrin (2,6-DiMe-3-Pe-β-CD) was taken as the reference CD derivative, because of the large number of volatile racemates it is able to separate; OV-1701 or OV-1701-OH was chosen as the reference diluting phase. The performance of a column coated with a 0.15 μm film of 10 % 2,6-DiMe-3-Pe-β-CD in OV-1701 was compared with that of analogous columns coated with films of the same thickness containing the same percentage of the CD derivative diluted with stationary phases of different polarity, i.e. PS-086, PS-347.5, and OV-225. Resolution values and separation factors of thirty racemates were used to evaluate the effect of different diluting phases on column performance.     

Advances in analytical techniques for polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and dioxin-like PCBs

Analytical techniques for the determination of polychorinated dibenzo-p-dioxins (PCDD), polychlorinated dibenzofurans (PCDF) and dioxin-like PCBs (DLPCB) are reviewed. The focus of the review is on recent advances in methodology and analytical procedures. The paper also reviews toxicology, the development of toxic equivalent factors (TEF) and the determination of toxic equivalent quantity (TEQ) values. Sources, occurrence and temporal trends of PCDD/PCDF are summarized to provide examples of levels and concentration ranges for the methods and techniques reviewed.     

Extractability of dioxins from soil: II. Effects of acid or alkaline pretreatment on the extractability of dioxin homologues from soil samples

The effects of sample pretreatment on the extractability of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (CoPCBs) from three suburban soil samples were evaluated. The samples were treated with 0.1?M HCl or 0.1?M NaOH and extracted by pressurized liquid extraction (PLE) with toluene. In addition, untreated soil samples were subjected to PLE with acetone. The extractability values were compared to values obtained by toluene extraction without pretreatment. Alkaline pretreatment increased the extractability of higher-chlorinated CDDs (HiCDDs), whereas acid pretreatment slightly decreased their extractability. No change in extractability was observed for higher-chlorinated CDFs under any conditions. The extractability of lower-chlorinated CDD/Fs (LoCDD/Fs) and CoPCBs was increased only by acetone extraction. PCDD/F homologue profiles in soil humic acid fractions and those in dead leaves, a major raw material of soil humus, were also determined. These results suggest that the variations in the extractability of dioxin homologues are due mainly to variations in their physical state in the soil, especially their interactions with soil humus.     

Development of new cleanup method of polychlorinated dibenzo-p-dioxins/dibenzofurans in fish by freezing-lipid filtration

Freezing-lipid filtration as a new method has been developed for the rapid determination of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/Fs) in biological samples. This method can effectively reduce the time of sample pretreatment, labor and amount of solvents compared with conventional methods. By freezing-lipid filtration procedure, about 90% of lipids in extract could be removed without any significant loss of PCDD/Fs. For further cleanup of extracts after freezing-lipid filtration, automatic parallel LC columns including silica gel, alumina and carbon columns were applied. During automatic parallel LC columns cleanup, most of co-extracted interferences such as residue lipids and fatty acids could be eliminated and dioxins could be separated from many other dioxin-like congeners such as polychlorinated biphenyls by this procedure. The extracts after cleanup were analyzed by high-resolution gas chromatography (HRGC)/high-resolution mass spectrometry (HRMS) using an isotope dilution method. The average recoveries and relative standard deviation (R.S.D.) of 17 native congeners in the spiked fish samples at 8-80 pg/g (n = 3) were ranged between 85.3 and 117.2% and 5.7-20.3%, respectively.     

Atmospheric pressure ionization mass spectrometry of the polychlorinated dibenzo-p-dioxins

The branching ratios for the reaction pathways of 39 polychlorinate dibenzo-p-dioxins (PCDDs) under oxygen negative chemical ionization/atmospheric pressure ionization mass spectrometric conditions were measured. These results demonstrated that the PCDDs could be separated into 14 groups by this technique. These results were compared with those reported previously for 14 PCDDs using oxygen negative chemical ionization mass spectrometry.     

Near-ultraviolet femtosecond laser ionization of dioxins in gas chromatography/time-of-flight mass spectrometry

Gas chromatography/multiphoton ionization/time-of-flight mass spectrometry (GC/MPI/TOF-MS) was applied to the trace analysis of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs). To determine the optimum wavelength for analysis of PCDD/Fs, the wavelength of the femtosecond laser utilized for multiphoton ionization was converted to near-ultraviolet status using stimulated Raman scattering. A femtosecond laser emitting at 300 nm completely eliminated the background signal arising from the bleeding compounds generated from a stationary phase of the capillary column in GC.