Gas chromatography of 209 polychlorinated biphenyl congeners on an extremely efficient nonselective capillary column

The gas chromatographic–mass spectrometric (GC–MS) separation of all 209 polychlorinated biphenyl (PCB) congeners was studied on an extremely efficient 80 m × 0.1 mm i.d. capillary column coated with a 0.1 μm film of poly(5%-phenyl methyl)siloxane stationary phase. The quality of the separation and the number of resolved and coeluting peaks were compared to predictions according to the statistical overlap theory (SOT) and to literature data on PCB separations obtained by one-dimensional and comprehensive two-dimensional GC (GC × GC) and GC–MS. Mass spectral and chemometric deconvolution procedures were used to resolve overlapping peaks. On the highly efficient column, 195 PCB congeners were resolved in 96 min separation time using spectral and chemometric deconvolution. This number is comparable to the best separations described in GC × GC–MS mode. The novel method was developed for spectral deconvolution of overlapped PCB congeners which was verified determining the most toxic, dioxin-like PCBs both in the model mixture of 209 PCBs as well as in the Aroclor 1242 and Aroclor 1254 formulations.     

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.     

Enhanced comprehensive two-dimensional gas chromatographic resolution of polychlorinated biphenyls on a non-polar polysiloxane and an ionic liquid column series

A total of 196 out of 209 polychlorobiphenyl (PCB) congeners were resolved using GC×GC-TOFMS with a non-polar/ionic liquid column series consisting of poly(50%-n-octyl-50%-methyl)siloxane and (1,12-di(tripropylphosphonium)dodecane bis(trifluoromethansulfonyl)amide) in the first and second dimension, respectively. It has been found that 13 PCB congeners overlap in five doublets (CB12+CB13, CB62+CB75, CB70+CB76, CB97+CB125 and CB153+CB168) and one triplet (CB90+CB101+CB113). All toxic, "dioxin like" congeners were separated with no interferences from any PCB congener. The 109 PCBs present in Aroclor 1242 and the 82 PCBs present in Aroclor 1260 were resolved GC×GC-TOFMS analysis on this column set.     

Characterization of three Aroclor mixtures using a new cyanobiphenyl stationary phase

The retention characteristics of all 209 polychlorinated biphenyl (PCB) congeners were determined on a new p,p-cyanobiphenyl stationary phase using gas chromatography with electron capture detection (GC-ECD). Response factors were determined relative to decachlorobiphenyl, PCB 209. Several congeners that coelute on the phases routinely used for PCB analysis are separated on this phase, including the hexachlorobiphenyls 138, 163, and 164. The p,p-cyanobiphenyl stationary phase exhibits altered retention for planar congeners, such that the toxic coplanar PCBs 77, 126, and 169 are eluted free from interference. Of the 209 congeners, 61 were separated using the p,p-cyanobiphenyl phase in conjunction with GC-ECD. When analyzed by gas chromatography with mass selective detection (GC-MSD), the number of congeners determined increased to 133. Therefore GC-MSD was used with the p,p-cyanobiphenyl phase to characterize three PCB mixtures: Aroclor 1242, Aroclor 1254, and Aroclor 1260.     

非等间隔PCBs保留指数体系在光解行为研究中的应用

利用Ｃｈｕ等已建立的多氯联苯（ＰＣＢｓ）非等间隔保留指数体系,由文献中的相对保留时间计算出全部２０９种ＰＣＢｓ同类物（Ｃｏｎｇｅｎｅｒ）的保留指数（ＩＰＣＢ）。利用ＩＰＣＢ结合ＧＣ－ＭＳ对ＰＣＢ８７、ＰＣＢ１３８和ＰＣＢ１６９三种同类物的光解产物进行了定性分析,发现其光解产物主要为低氯代联苯。实验结果证明,非等间隔保留指数体系ＩＰＣＢ在ＰＣＢｓ同类物的定性分析中具有准确、实用、快捷、方便等优点。     

Ionic liquids monolithic columns for protein separation in capillary electrochromatography

A series of ionic liquids (ILs) monolithic capillary columns based on 1-vinyl-3-octylimidazolium (ViOcIm⁺) were prepared by two approaches (“one-pot” approach and “anion-exchange” approach). The effects of different anions (bromide, Br⁻; tetrafluoroborate, BF₄⁻; hexafluorophosphate, PF₆⁻; and bis-trifluoromethanesulfonylimide, NTf₂⁻) on chromatography performance of all the resulting columns were investigated systematically under capillary electrochromatography (CEC) mode. The results indicated that all these columns could generate a stable reversed electroosmotic flow (EOF) over a wide pH range from 2.0 to 12.0. For the columns prepared by “one-pot” approach, the EOF decreased in the order of ViOcIm⁺Br⁻ > ViOcIm⁺BF₄⁻ > ViOcIm⁺PF₆⁻ > ViOcIm⁺NTf₂⁻ under the same CEC conditions; the ViOcIm⁺Br⁻ based column exhibited highest column efficiencies for the test small molecules; the ViOcIm⁺NTf₂⁻ based column possessed the strongest retention for aromatic hydrocarbons; and baseline separation of four standard proteins was achieved on ViOcIm⁺NTf₂⁻ based column corresponding to the highest column efficiency of 479 000 N m⁻¹ for cytochrome c (Cyt c). These results indicated that the property of ILs based columns could be tuned successfully by changing anions, which gave these columns potential to separate both small molecules and macro biomolecules.     

Relative performance of immunochemical (enzyme-linked immunosorbent assay) and gas chromatography-electron-capture detection techniques to quantify polychlorinated biphenyls in mussel tissues

Results from polychlorinated biphenyls (PCB) analyses of mussel tissue extracts by immunoassay (PCB RaPID Assay^®) and conventional gas chromatography-electron-capture detection (GC-ECD) are described and compared. Mussels from natural populations with diverse concentrations of PCBs, mussel tissue fortified with technical Aroclor^® 1254 and a certified reference material are included.A strong correlation is reported between “total” PCBs quantified by both techniques (r²=0.95, n=27). Immunoassay results, however, exhibited lower values compared to GC-ECD, particularly when GC results are corrected for procedural recovery. A reduced antibody response, due to differences in the congener composition between the mussel extracts and Aroclor^® 1254 (used to raise and calibrate the ELISA), provides the most likely explanation for this difference. Non-parametric statistical analyses confirmed that, although differing from Aroclor^® 1254, PCB congener compositions in the mussel extracts most closely resemble that of Aroclor^® 1254. At very high PCB concentrations (>30 μg g⁻¹ dry weight), however, ELISA results are statistically different (P<0.01) from GC-ECD results, which is likely to be related to the solvation capacity of ELISA diluent. Similarity analysis showed high correlations between the most prominent congeners in Aroclor^® 1254 and immunoassay results. This analysis did not, however, identify a specific chlorine substitution pattern to which the immunoassay preferentially responded.Whilst GC-ECD affords the capability to quantify individual congeners of different reactivity and toxicity, the data reported do indicate that immunoassay offers a rapid and inexpensive alternative method for estimation of “total” PCBs at environmentally significant levels. It is, however, necessary to remove extraneous lipids to reduce matrix effects in the immunoassay.     

Determination of dioxin-like polychlorinated biphenyls in 1 mL whole blood using programmable temperature vaporization large volume injection coupled to gas chromatogram and high-resolution mass spectrometry

A sensitive method based on programmable temperature vaporization large volume injection coupled to gas chromatogram and high-resolution mass spectrometry (PTV-GC–HRMS) has been developed for the determination of ultra trace levels of dioxin-like polychlorinated biphenyls (DL PCBs) in small amounts of human blood. Blood samples (1 mL) were first extracted by column extraction and then purified with column chromatorgraphies. Final extracts (20 μL) were introduced to the PTV injector under the solvent vent mode and detected by GC–HRMS (SIM mode). PTV parameters were observed by changing one factor at a time (practical conditions: vent flow: 50 mL min⁻¹, vent pressure: 0 kPa and vent time: 0.1 min), recoveries of most PCB congeners ranged from 55.1% to 108%, and method detection limits were in the range of 0.11–1.63 pg g⁻¹.     

Tunable separation of anions and cations by column switching in ion chromatography

A convenient ion chromatography method has been proposed for the routine and simple determination of anions (Cl⁻, SO₄²⁻ and NO₃⁻) and/or cations (Na⁺, NH₄⁺, K⁺, Mg²⁺ and Ca²⁺) using a single pump, a single eluent and a single detector. The present system used cation-exchange and anion-exchange columns connected in series via two 6-port switching valves or a single 10-port valve. The connection order of the ion-exchange columns could be varied by switching the valve(s). The present system therefore allowed the separation of either cations or anions in a single chromatographic run. While one ion-exchange column is being operated, the other ion-exchange column is being conditioned, i.e., the columns are always ready for analysis at any time. When 2.4 mM 5-sulfosalicylic acid was used as the eluent, the three anions and the five cations could be separated on the anion-exchange column and cation-exchange column, respectively. In order to obtain the separations of the target ions, the injection valve was placed between the two columns. Complete separations of the above anions or cations were demonstrated within 10 min each. The detection limits at S/N = 3 were 19-50 ppb (μg/l) for cations and 10-14 ppb for anions. The relative standard deviations of the analyte ions were less than 1.1, 2.9 and 2.8% for retention time, peak area and peak height, respectively. This proposed technique was applied to the determination of common anions and cations in river water samples.     

Resin‐supported palladium nanoparticles as recyclable catalyst for the hydrodechlorination of chloroarenes and polychlorinated biphenyls

This study focuses on the hydrodechlorination of chlorinated arenes as well as polychlorinated biphenyls (PCBs) utilizing a resin‐supported Pd(0) catalyst. Bearing in mind the dangers associated with toxic PCBs, treatment of the remnants of industrial wastes containing PCB congeners is indispensable. One such method is reductive hydrodechlorination. Instead of utilizing traditional sources of hydrogen, ammonium formate is used for in situ hydrogen generation. Moreover, palladium nanoparticles are supported on an anionic exchange resin which makes the process recyclable with a negligible change of yield after recycling experiments. The catalyst is demonstrated in the hydrodechlorination of a wide range of chlorinated compounds and PCB congeners including aroclors 1242, 1248 and 1254. Copyright © 2016 John Wiley & Sons, Ltd.     

Retention profile and subsequent chemical speciation of chromium (III) and (VI)) in industrial wastewater samples employing some onium cations loaded polyurethane foams

The retention of chromium (VI) from aqueous media onto tetraphenylarsonium chloride (TPAs⁺Cl⁻) or tetraphenylphosphonium bromide (TPP⁺Br⁻) immobilized polyurethane foams (PUFs) was fast and followed first order reaction. The kinetic data of the retention step were subjected to Weber-Morris, Lagergren, Bhattacharya and Venkobachar and Bt kinetic models. The results revealed that, film and intraparticle transport might be the two steps controlling the rate of chromium (VI) sorption from the aqueous acid solutions of pH ∼ zero. The positive values of the Δ H of chromium (VI) retention by the reagents loaded PUFs were interpreted as an endothermic process. Under the optimum pH (pH ∼ zero ) of the aqueous solution, the proposed TPAs⁺Cl⁻ or TPP⁺Br⁻ immobilized PUFs was successfully used in a series of medical syringe (30, 50 mL capacity) as pulse columns for complete collection of chromium (VI) species present in fresh and industrial wastewater samples at ultra trace low level of chromium (VI) (≤ 0.05 μg mL^− 1). The collected chromium (VI) species onto TPAs⁺Cl⁻ or TPP⁺Br⁻-PUFs was then stripped quantitatively (98-102 ± 2.6%) from the pulse columns with NaOH (2.0 mol L^− 1) and subsequently analyzed photometrically. The chromium (VI) ions could be pre concentrated up to 100-fold from large volume of water samples. The proposed pulse foam columns were applied successfully for complete collection, recovery (97.5 ± 2.6%, n = 5) and subsequent chemical speciation of chromium (III) and (VI) in wastewater samples. The results are in good agreement with the reported and standard methods at 95% confidence.     

An organically modified silicate molecularly imprinted solid-phase microextraction device for the determination of polybrominated diphenyl ethers

An organically modified silicate (ORMOSIL) SPME stationary phase molecularly imprinted with BDE-209 has been successfully fabricated by conventional sol-gel technique from phenyltrimethoxysilane and tetraethoxysilane. The thickness of the ORMOSIL-SPME stationary phase, on fused-silica optical fibres, was measured to be ca. 9.5 μm with a volume of ca. 0.12 μL. Rebinding assays and Scatchard analysis revealed that the imprinted ORMOSIL-SPME stationary phase possessed a binding affinity, K_B, of 7.3 ± 1.7 × 10¹⁰ M⁻¹ for BDE-209, with a receptor site density, B_max, of 1.2 × 10⁻³ pmol per SPME device. Besides its molecular template, the ORMOSIL-SPME stationary phase also showed good affinity (log K_B ≥ 9.5) for smaller BDE congeners commonly found in the natural environment. The density of receptor sites within the imprinted matrix for those smaller BDE congeners was even higher than that for BDE-209. This may be attributable to the binding site heterogeneity of the imprinting process that creates deformed binding sites that are suitable for the accommodation of the smaller BDE congeners. Compared to the commercially available polyacrylate and polydimethylsiloxane SPME stationary phases, the imprinted ORMOSIL-SPME devices showed much higher pre-concentration ability towards polybrominated diphenyl ethers (PBDEs), even in direct immersion sampling at room temperature. Coupled with GC-NCI-MS and GC-μECD, the imprinted ORMOSIL-SPME device was able to achieve detection sensitivity of 0.2-3.6 pg mL⁻¹ and 1-8.8 pg mL⁻¹, respectively, for commonly occurring BDE congeners, including medium to high molecular weight PBDEs. The imprinted ORMOSIL-SPME device has been successfully applied to monitor PBDE contents in municipal wastewaters.     

Long chain alkyl-polysiloxanes as non-polar stationary phases in capillary gas chromatography

Summary A new methyl-octadecyl polysiloxane phase with a distinct selectivity in PCB separation and a significantly improved temperature range has been developed. The basic structural element of the separation of PCBs on methyl-octadecyl-polysiloxane is the elution according to the number of the substituents in the ortho-positions 2,2 and 6,6. The 2,2,6,6-substituted congeners are eluted first, while the non-2,2,6,6-substituted coplanar PCB are eluted last. As compared to methyl-phenyl (5%) polysiloxane (SE 54) the standard stationary phase used for the separation of the PCBs, the methyl-octadecyl-polysiloxane has several unique features in an improved PCB separation. The Sil 5–50% C18 column resolves the pair PCB 31/28 and also the sets PCB 5/8, PCB 16/15/32, PCB 25/53, PCB 48/47, PCB 56/60, PCB 118/149, PCB 105, 132, 153, and PCB 170/190. All these separations are not achieved with a SE 54 column. No separation is observed for the pair PCB 138/163 on Sil 5–50% C18. The order of elution of the Cl_xB congeners reveals a rather stringent structure correlation. If the structure/retention correlation is extended to all 209 Cl_xB congeners, 20 groups with one ring fixed / one ring variable substitution can be distinguished.Dedicated to Prof. Dr. V. Krivan on the occasion of his 60th birthday.Presented at 14th International Symposium on Capillary Chromatography, May 25–29, Baltimore, USA.     

Separation of intact proteins on porous layer open tubular (PLOT) columns

Porous layer open tubular (PLOT) polystyrene divinylbenzene columns have been used for separating intact proteins with gradient elution. The 10 μm I.D. × 3 m columns were easily coupled to standard liquid chromatography–mass spectrometry (LC–MS) instrumentation with commercially available fittings. Standard proteins separated on PLOT columns appeared as narrow and symmetrical peaks with good resolution. Average peak width increased linearly with gradient time (t_G) from 0.14 to 0.33 min (t_G 20 and 120 min, respectively) using a 3 m column. With shorter columns, peak widths were larger and increased more steeply with gradient time. Theoretical peak capacity (n_c) increased with column length (tested up to 3 m). The n_c increased with t_G until a plateau was reached. The highest peak capacity achieved (n_c = 185) was obtained with a 3 m column, where a plateau was reached with t_G 90 min. The within- and between column retention time repeatabilities were below 0.6% and below 2.5% (relative standard deviation, RSD), respectively. The carry-over following injection of 0.5 ng per protein was less than 1.1%. The retention time dependence on column temperature was investigated in the range 20–50 °C. Proteins in a skimmed milk sample were separated using the method.     

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.     

Optimized determination of polybrominated diphenyl ethers and polychlorinated biphenyls in sheep serum by solid-phase extraction-gas chromatography-mass spectrometry

We describe a solid-phase extraction (SPE) method, followed by gas chromatography-mass spectrometry (GC-MS), for the simultaneous determination of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in sheep serum samples. The denaturation of serum proteins by formic acid, water-1-propanol and water-2-propanol were compared and optimized. Seven different solid-phase sorbents were tested and it was found that Strata-X cartridge (200 mg, 6 mL) gave the best recoveries (92-106%, SD < 6%, n = 3) for all the target analytes. The different extraction solvents (iso-hexane and dichloromethane), either alone or in combination, were used to extract these persistent organic compounds from spiked serum samples by SPE. Removal of co-extracted biogenic materials was achieved using adsorption chromatography with acid modified silica and activated silica. Iso-hexane was found to be the most appropriate solvent for clean-up providing good recoveries and clear chromatographic separation; its use is preferable to that of DCM because it is less environmentally toxic. The limits of detection (LOD) of the proposed method were 47-105 pg g⁻¹ and 16-24 pg g⁻¹ for the different PBDEs and PCBs studied, respectively. The developed method was linear over the range from 0.05 to 30 ng g⁻¹, for all PBDEs except PBDE 183 (0.10-30 ng g⁻¹), and from 0.02 to 30 ng g⁻¹ for all tested PCB congeners. The established method was successfully applied to sheep serum samples from Scotland, UK, for the determination of the target PBDEs and 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.     

Preconcentration and speciation of inorganic and methyl mercury in waters using polyaniline and gold trap-CVAAS

Applicability of polyaniline (PANI) has been investigated for the preconcentration and speciation of inorganic mercury (Hg²⁺) and methyl mercury (CH₃Hg⁺) in various waters (ground, lake and sea waters). Preliminary experiments (batch) with powdered PANI for the quantitative removal of both Hg²⁺ and CH₃Hg⁺ showed that the retention of Hg²⁺ was almost independent of pH while a pH dependent trend from pH 1 to 12 was seen for CH₃Hg⁺ with maximum retention at pH > 5. Time dependence batch studies showed that a contact time of 10 min was sufficient to reach equilibrium. The K_d values were found to be ∼8 × 10⁴ and ∼7 × 10³ for Hg²⁺ and CH₃Hg⁺, respectively.Subsequently column experiments were carried out with PANI and the separation of the species was carried out by selective and sequential elution with 0.3% HCl for CH₃Hg⁺ and 0.3% HCl-0.02% thiourea for Hg²⁺. This was then followed by further pre-concentration of mercury on a gold trap and its determination by CVAAS. The uptake efficiency studies showed that the PANI column was able to accumulate up to 100 mg Hg²⁺/g and 2.5 mg CH₃Hg⁺/g. This method allows both preconcentration and speciation of mercury with preconcentration factors around 120 and 60 for Hg²⁺ and CH₃Hg⁺, respectively. The interfering effects of various foreign substances on the retention of mercury were investigated.     

Microwave assisted extraction and sonication of polychlorobiphenils from river sediments and risk assesment by toxic equivalency factors

Summary Microwave extraction and ultrasonication of dioxin-like polychlorobiphenyls (PCBs) from sediment samples were investigated. After separation of dioxin-like PCBs from a sample matrix on an acidic-alkaline silica gel column, dioxin-like PCBs were determined by GC-ECD, using dual capillary columns. Recoveries of dioxin-like PCBs in river sediment samples exceeded 80% by both extraction techniques. Toxic equivalency factors and their use for the PCB congeners investigated were applied. Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997