Multidimensional capillary gas chromatography of polychlorinated biphenyl marker compounds

Multidimensional chromatography was used to resolve the specific chlorobiphenyl (CB) congeners 28, 52, 101, 118, 138, 153, and 180 in technical aroclor standards. Single column analysis of polychlorinated biphenyls (PCBs) results in co-elution of key congeners with other components in the mixture; therefore using two columns of different selectivity was necessary to enhance the resolution achievable on just one column. The HT8 column (8% phenylpolycarborane-siloxane phase) has been reported to have specific selectivity characteristics for improved PCB separation. When coupled with a BPX5 column (5% phenylpolysiloxane-silphenylene phase), it has been shown here to provide unambiguous identification of 7 marker compounds which are used to monitor PCB occurrence and distribution. All seven marker CBs are present in aroclor 1254, and by adjusting the size of the heartcut window, it was possible to obtain resolution of the marker congeners from other congeners. Single column analysis is unable to achieve this result. This offers an alternative to GC-MS analysis.     

Application of C-labelled polychlorinated biphenyl congener 153 as internal standard in the gas chromatographic-mass spectrometric analysis of polychlorinated biphenyls

We developed a method of qualitative and quantitative GC-MS analysis of polychlorinated biphenyls (PCBs) in soil samples, to be able to determine the biodegradation efficiency for individual PCBs. ¹³C₁₂-Substituted PCB 153 was used as internal standard. The analyses were performed on a DB-5 capillary column. The identification procedure was based on the correlation analysis of the measured and published relative retention r₁₂ data using [¹³C₁₂]PCB 153 instead of octachloronaphthalene (OCN). [¹³C]PCB 153 was also used for quantification of individual PCBs in soil samples.     

Solid-phase microextraction of polychlorinated biphenyls

The extraction and analysis of 21 polychlorinated biphenyls (PCBs) ranging from di- to decachlorobiphenyls in ocean, wetland and leachate water samples were achieved using solid-phase microextraction (SPME) with a 100-μm poly(dimethylsiloxane) (PDMS) fiber and gas chromatography–electron-capture detection (GC–ECD). Severe carryover between samples (e.g., 20%) occurs on both stir bars and the SPME fibers demonstrating that it is important to use a new stir bar for each sample, as well as to perform SPME–GC blanks between samples to avoid quantitative errors. The equilibrium partitioning coefficients of individual PCB congeners between PDMS and water were found to be surprisingly different compared to their octanol–water partitioning coefficient (K_ow), demonstrating that K_ow cannot be used to estimate the partitioning behavior of PCBs in the SPME process. Using a 15-min SPME extraction, SPME analysis with GC–ECD was linear (r²≥0.97) from 5 pg/ml to the solubility limit of each congener. Concentrations in water samples obtained by 15-min SPME extractions compared favorably with those obtained by toluene extractions, demonstrating that SPME combined with GC is a useful technique for the rapid determination of PCBs in water samples.     

Measurements of coeluting unlabeled and C-labeled polychlorinated biphenyl congeners with partially overlapping fragment profiles using a tandem mass spectrometry

¹³C-labeled compounds are often employed as surrogate or internal standards to monitor the performance of extraction and instrumental analysis procedures for their unlabeled counterparts. However, labeled and unlabeled counterparts most often coelute chromatographically with overlapping mass ion fragments, posing a challenge to the accurate quantification of these compounds. In the present study, an analytical scheme, using coeluting unlabeled and ¹³C-labeled polychlorinated biphenyl (PCB) congeners as the model compounds, was developed with a low-resolution tandem mass spectrometer (MS/MS) to determine the appropriate ranges of PCB congener concentrations that satisfy the no-interference condition. Interferences from unlabeled PCBs to quantitation of labeled counterparts could be minimized when ¹³C-labeled PCB congeners were quantified in the MS/MS mode within a certain concentration range. In addition, good agreements between the measured and theoretically predicted quantitation errors were observed for all labeled PCB congeners except PCB 180. The exception with labeled PCB 180 was mainly attributed to the occurrence of instrumental analytical uncertainty, as analytical error was also observed with absence of unlabeled PCB 180. These results indicate that MS/MS techniques can serve as a useful tool to minimize interferences with quantitation of isotopically labeled compounds from their unlabeled counterparts, which possess partially overlapping ion fragment profiles.     

Determination of hydroxylated polychlorinated biphenyls by ion trap gas chromatography–tandem mass spectrometry

Hydroxylated polychlorinated biphenyls also known as biphenylols, are suspected estrogen mimics found in the environment. Various derivatization schemes were evaluated and a gas chromatography–ion trap mass spectrometry method was developed for the trifluoroacetyl derivative using MS–MS techniques for the analysis of eleven biphenylols. A time-segmented chromatographic method was developed using the respective MS–MS parameters to analyze all the eleven biphenylols in a single chromatographic run. Isomers were differentiated based on the MS–MS data of the trofluoroacetyl-biphenylol derivatives. The method was applied to detect 40 pg on-column of these compounds in a spiked egg sample which simulates a real world sample.     

Equilibrium and kinetic solid-phase microextraction determination of the partition coefficients between polychlorinated biphenyl congeners and dissolved humic acid

A conventional solid-phase microextraction (SPME) method combined with liquid–liquid extraction was applied under equilibrium and nonequilibrium conditions to determine the partition coefficients (K_doc) of 25 polychlorinated biphenyl congeners (PCBs) between Sigma–Aldrich humic acid (HA) and water. The values of log K_doc determined with equilibrium SPME were linearly correlated with the logarithm of the octanol–water partition coefficients (K_ow) for PCB congeners at log K_ow < ∼7.2, but the trends were disrupted for log K_ow from ∼7.2 to 8.18. In addition, short-term (5 min to 4 days) and long-term (5–44 days) uptake profiles of PCBs were established, from which a pseudo-equilibrium for sorption of PCBs was revealed at ∼4 days of extraction. To understand this phenomenon, the uptake profiles were fitted with two equations (one equation is often used for pure water samples and the other one is applicable for samples containing complex matrices) derived from a first-order kinetics model. Subsequently, K_doc values obtained through kinetic approaches were compared with those acquired from equilibrium SPME. The comparison of K_doc values indicated that the pseudo-equilibrium was caused by the slow desorption of PCBs from HA rather than the biphasic desorption mechanism.     

Determination of traces of polychlorinated biphenyls in pigments

PCB patterns in a new pigment brand are characterized using GC-MS in the single ion monitoring (SIM) mode. Specific PCBs are then used as external standards for GC-ECD quantification. The following PCB isomers or groups of isomers have to be determined (CB = chlorobiphenyl): total diCBs, 3,3′ diCB, 2,4,5-triCB, 2,2′,4,4′-tetraCB, 2,2′,5,5′-tetraCB, total pentaCB, total hexaCB. Capillary gas chromatography is performed on preseparated solutions (LC) of pigment. An electron caputure detector (ECD) is used for PCB detection and quantification. Calibration is based on the peak areas of external standards and the PCB isomers in the samples, all normalized for internal standard peak areas. Total concentrations of diCB, hexaCB, or pentaCB in a sample are calculated by summing the individual PCB isomer concentrations within the correcsponding elution ranges. Determination limits lie in the range of 1 mg/PCB-isomer/kg pigment.     

Supercritical fluid extraction and clean-up of organochlorine pesticides and polychlorinated biphenyls in mussels

The simultaneous extraction and clean-up of mussel samples followed by gas chromatography with electron-capture detection and mass spectrometric confirmation of 15 organochlorine pesticides (OCPs) and 11 polychlorinated biphenyls (PCBs) is developed using Florisil sorbent in the supercritical fluid extraction cell. The method detection limits vary from 1 to 10 ng/g for OCPs and from 2 to 15 ng/g for PCBs. Mean reproducibilities of 11% and 10% and mean recoveries of 80% and 53%, respectively, for OCPs and PCBs are obtained. The feasibility of the proposed supercritical fluid extraction method was confirmed by analyzing a certified reference material and mussels collected from Taiwan region. The method is simple, rapid and requires only small amounts of samples and solvents. It may serve as a screening protocol for the determination of OCPs and PCBs in mussels on a routine basis.     

Congener profile and toxicity assessment of polychlorinated biphenyls in human adipose tissue of Italians and Chileans

Human exposure to polychlorobiphenyls (PCBs) in humans was determined by analyzing adipose tissue samples collected in 1996–1997 from two different localities: Siena (Italy) and Concepción (Chile). ΣPCBs was higher in Italian samples than that from Chile (493 and 53 ng/g wet wt., respectively). Thirty-seven different PCB congeners were identified in all samples. The prevailing PCB congeners in both groups were 22′44′5 pentachlorobiphenyl (IUPAC no. PCB 118), 22′344′5′ (PCB-138) and 22′44′55′ (PCB-153) hexachlorobiphenyls and 22′33′44′5 (PCB-170), 22′344′55′ (PCB-180) and 22′34′55′6 (PCB-187) heptachlorobiphenyls. PCB-153 accounted for more than 20% of the total PCB residue in both groups, while the remaining six congeners accounted for approximately 70%. Hexachlorobiphenyls were the most abundant congeners in all samples, with 42% of total residue in those from Italy and 43% in the Chilean samples, followed by heptachlorobiphenyls with 41 and 36% in Italian and Chilean samples, respectively. Average concentrations of non-ortho substituted coplanar congeners were below 1 pg/g wet wt. In the samples from Siena no noticeable differences were observed between the three average coplanar concentrations, while in those from Concepción 33′44′tetrachlorobiphenyl (PCB-77) was much higher than 33′44′pentachlorobiphenyl (PCB-126) and 33′44′55′hexachlorobiphenyl (PCB-169). For each sample the contribution to the total toxic equivalent values (ΣTEQs) of each non-ortho, mono-ortho and di-ortho substituted PCB congeners was assessed. The overall TEQs calculated for the monitored PCBs, were 10.16 pg/g wet wt. in Italian samples and 1.09 pg/g wet wt. in Chileans ones. In both groups the main contribution to ΣTEQs were the di-ortho substituted PCB congeners (Siena: 6.17 pg/g wet wt.; Concepción: 0.56 pg/g wet wt.) and the mono-ortho substituted PCB congeners (Siena: 3.97 pg/g wet wt.; Concepción: 0.50 pg/g wet wt.).     

Simultaneous analysis of polychlorinated biphenyls and polychlorinated naphthalenes by isotope dilution comprehensive two-dimensional gas chromatography high-resolution time-of-flight mass spectrometry

Polychlorinated biphenyls (PCBs) and polychlorinated naphthalenes (PCNs) are listed as persistent organic pollutants (POPs) under the Stockholm Convention. Because they have similar physical and chemical properties, they are coeluted and are usually analyzed separately by different gas chromatography high-resolution mass spectrometry (GC-HRMS) methods. In this study, a novel method was developed for simultaneous analysis of six indicator PCBs, 12 dioxin-like PCBs, and 16 PCNs using isotope dilution comprehensive two-dimensional gas chromatography with high-resolution time-of-flight mass spectrometry (GC × GC-HRTOF-MS). The method parameters, including the type of GC column, oven temperature program, and modulation period, were systematically optimized. Complete separation of all target analytes and the matrix was achieved with a DB-XLB column in the first dimension and a BPX-70 column in the second dimension. The isotope dilution method was used for quantification of the PCBs and PCNs by GC × GC-HRTOF-MS. The method showed good linearity from 5 to 500 pg μL⁻¹ for all the target compounds. The instrumental limit of detection ranged from 0.03 to 0.3 pg μL⁻¹ for the 18 PCB congeners and from 0.09 to 0.6 pg μL⁻¹ for the 16 PCN congeners. Repeatability for triplicate injections was always lower than 20%. The method was successfully applied to the determination of 18 PCBs present at 0.9–2054 pg g⁻¹ and 16 PCNs present at 0.2–15.7 pg g⁻¹ in three species of fish. The GC × GC-HRTOF-MS results agreed with those obtained by GC-HRMS. The GC × GC-HRTOF-MS method proved to be a sensitive and accurate technique for simultaneous analysis of the selected PCBs and PCNs. With the excellent chromatographic separation offered by GC × GC and accurate mass measurements offered by HRTOF-MS, this method allowed identification of non-target contaminants in the fish samples, including organochlorine pesticides and polycyclic aromatic hydrocarbons.     

Neuro-genetic multioptimization of the determination of polychlorinated biphenyl congeners in human milk by headspace solid phase microextraction coupled to gas chromatography with electron capture detection

Polychlorinated biphenyls (PCB) can eventually contaminate breast milk, which is a serious issue to the newborn due to their high vulnerability. Solid phase microextraction (SPME) can be a very convenient technique for their isolation and pre-concentration prior chromatographic analysis. Here, a simultaneous multioptimization strategy based on a neuro-genetic approach was applied to a headspace SPME method for determination of 12 PCB in human milk. Gas chromatography with electron capture detection (ECD) was adopted for the separation and detection of the analytes. Experiments according to a Doehlert design were carried out with varied extraction time and temperature, media ionic strength and concentration of the methanol (co-solvent). To find the best model that simultaneously correlate all PCB peak areas and SPME extraction conditions, a multivariate calibration method based on a Bayesian Neural Network (BNN) was applied. The net output from the neural network was used as input in a genetic algorithm (GA) optimization operation (neuro-genetic approach). The GA pointed out that the best values of the overall SPME operational conditions were the saturation of the media with NaCl, extraction temperature of 95 °C, extraction time of 60 min and addition of 5% (v/v) methanol to the media. These optimized parameters resulted in the decrease of the detection limits and increase on the sensitivity for all tested analytes, showing that the use of neuro-genetic approach can be a promising way for optimization of SPME methods.     

Radiation degradation of polychlorinated biphenyls

Gradual dechlorination of the polychlorinated biphenyls (PCBs) in alkaline solutions in 2-propanol under the effect of high energy electrons (4.5 MeV) produced by electron accelerator has been studied using a flow-through apparatus of the volume of about 50 L. The dependence of both relative radiation chemical yield and the dechlorination degree on the initial concentration of OH⁻ ions or PCBs, absorbed dose as well as on dose rate has been investigated.     

Application of a retention database to the identification of individual polychlorinated biphenyl congeners in Aroclors mixture using selected polychlorinated biphenyls as a reference series

The database of the relative retention times (RRTs) of polychlorinated biphenyls (PCBs) reported in literature was used to calculate the retention indices (RIs) of all 209 PCB congeners on temperature programmed capillary column Rtx-5. Calculation of retention indices was based on reference series of seven congeners (PCB IUPAC Nos. 18, 52, 101, 143, 185, 203 and 206) that exhibit linear relative retention time behaviour as a function of chlorine number. The calculated indices were compared to those determined in our laboratory as well as to those obtained by other authors. The proposed indices system was applied for identification individual congeners in mixture of Aroclors 1242:1254:1260, using only reference series of PCBs.     

Novel pressurized solvent extraction vessels for the analysis of polychlorinated biphenyl congeners in avian whole blood

Persistent organic pollutants remain a serious threat to many food-chain systems. New pollutants continue to emerge. The present study has created novel extraction vessels which are compatible with readily available commercial instrumentation to validate the analysis of one class of persistent organic pollutants, polychlorinated biphenyls (PCBs), in avian blood. The volumes used can be reasonably sampled without sacrificing individuals, or comprising breeding or migratorial success. The procedure consists of the pressurized solvent extraction (PSE) of analytes in a novel PSE extraction vessel. The new extraction cell contains a 38-cm long, coiled, re-packable, in situ clean-up column. Lipid elimination, using Florisil, occurs within the coiled region of the extraction vessel, eliminating the requirement for post extraction clean-up. For development, 0.2 g samples of chicken whole blood have been used. Extract volumes are reduced from (30 to 10) cm³, compared to unmodified systems. The new PSE vessel with its integrated clean-up method showed satisfactory performance for the analysis of ten environmentally relevant PCB congeners in chicken whole blood samples with recoveries in the range of (70-130)%. Detection limits using gas chromatography coupled with large volume injection ion-trap mass spectrometry (GC-LVI-ITMS-MS) were in the range of (0.05-0.5) ng g⁻¹. The relative standard deviations for all congeners investigated were better than 5%. This is the first PSE validation to have been conducted on unaltered whole blood samples.     

Use of topological indices of polychlorinated biphenyls in structure-retention relationships

Topological parameters (Balaban index and electrotopological index) were used as structural parameters in the structure-retention relationships (SRRs). These relationships were found to be statistically valid and useful in the prediction of retention data of polychlorinated biphenyls (PCBs) despite of the temperature program used in the gas chromatographic experiment.     

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.     

Gas chromatographic separation of atropisomeric alkylated and polychlorinated biphenyls using modified cyclodextrins

Selectively alkylated cyclodextrins have been used to resolve the enantiomers of 2,2′ alkylated biphenyls. The configurational stability of 2,2′-dimethyl and 2,2′-diethyl biphenyls is insufficient for gas chromatographic separation even at ambient temperature. 2-Isopropyl-2′-t-butyl- and 2,2′-di-t-butylbiphenyl are configurationally stable under the conditions applied, whereas 2,2′-diisopropyl- and 2,2′-bis(trifluoromethyl)biphenyl show temperature-dependent interconversion of the enantiomers during chromatography. The gas chromatographic separation of the enantiomers of some ortho trichlorinated biphenyls carrying 4, 5, and 6 chlorine substituents has been demonstrated for the first time.     

Development and characterization of new polyclonal antibodies specific for three polychlorinated biphenyls

Three polychlorinated biphenyls(PCBs)congeners and their corresponding haptens bearing four carbon length carboxylic groups that can be linked to a protein for raising antibodies were synthesized.The three resultant immunogens were fabricated and used to stimulate immune responses in rabbits to survey the characteristics of the haptens.Three of the resultant polyclonal antibodies(Pabs)were obtained.The antiserum exhibited relatively high antibody titres(1:32-64)in double agar diffusion.◎2008 Hui Sheng Zhuang.Published by Elsevier B.V.on behalf of Chinese Chemical Society.All rights reserved.     

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.     

微波萃取/气相色谱-质谱测定土壤中的多氯联苯

分别对多氯联苯的微波萃取条件进行了优化。优化后的分析条件为微波功率1200 W,萃取温度115℃,萃取时间20 min,萃取溶剂为V(正己烷)∶V(丙酮)=1∶1。方法的检出限为20~30 ng/g,线性范围40~4000 ng/mL(多氯联苯总量),相关系数均大于0.9990,样品基体加标回收率为92.2%~115%,相对标准偏差为9.4%(n=6)。