Gas chromatographic retention behaviour of polychlorinated naphthalenes on non-polar, polarizable, polar and smectic capillary columns

Health risk assessment to polychlorinated naphthalenes dioxin-like compounds in French sea food consumers

There has been a recent revival of interest in some historical contaminants such as polychlorinated naphthalenes (PCNs). However, occurrence data are still lacking in some countries although industrial production of PCNs has been reported. This observation led to the first ever assessment of their presence in fish and seafood products in France in the present work. Their analysis was integrated in an already validated method applied for polychlorinated dibenzodioxins/furans (PCDD/Fs) and polychlorinated biphenyls (PCBs), based on the structural similarity existing between these POPs. Performances of the method (LODs in the range 0.10-0.28 pg g^-1 wet weight (ww), LOQs in the range 0.33-0.93 pg g^-1 ww), enabled monitoring 69 di-to octachlorinated congeners in a large representative set of fish and seafood samples collected in 2005 in four coastal areas of the French mainland (n > 30). Their systematic presence was demonstrated in all the investigated seafood products, with levels (ΣPCNs in the range 2-440 pg g^-1 wet weight) close to those already reported in other European fish and seafood sampled at a similar period. In addition, the robust measurement of almost all possible PCNs (69/75) allowed a fine interpretation of the observed profiles, highlighting in particular the specificities between species and fishing areas. Compared to the PCDD/Fs, PCBs, and polybrominated diphenylethers levels also measured for this set of samples, PCNs were observed as minor contributors to total concentrations (0.05-3.2%). The specific PCN related dietary dioxin-like exposure could be evaluated at 0.028-0.051 pg of toxic equivalent (TEQ) per kg of body weight per week for an adult, based on fish and seafood consumption only. Overall, this study provides the first baseline data on the occurrence of a large number of PCNs in France, which will allow future evaluation of temporal trends and associated risks.

Characterization of 9 Gas Chromatography Columns by Linear and Lee Retention Indices for Polychlorinated Biphenyls and Polychlorinated Naphthalenes

Polychlorinated biphenyls (PCBs) and naphthalenes (PCNs) are ubiquitous environmental contaminants with varying degrees of toxicity. There are hundreds of possible congeners with similar chemical characteristics, which make these compounds difficult to isolate in environmental samples. Historically, PCBs and PCNs were identified by using an Aroclor or Halowax mixture instead of the individual compounds, which was impractical because of limited numbers of individual standards. A retention index database was developed with all 209 PCBs and 36 PCNs to help identify these chemicals in environmental and biological matrixes. This study uses linear and Lee retention indices to identify all 209 PCBs and 36 PCNs on nine gas chromatography columns. The most toxic congeners, the 12 dioxin-like PCBs, were compared across all columns to determine which stationary phases gave the best selectivity for those compounds. Column selectivity was also examined to determine columns for confirmatory analyses and GC×GC separations. The Rxi-17SilMS demonstrated the most drastic difference in PCB selectivity and, to a lesser extent, PCNs when compared with the other eight columns and could work as a confirmatory column or as a 2nd dimension column for GC×GC separations.

Is chlorination one of the major pathways in the formation of polychlorinated naphthalenes (PCNs) in municipal solid waste combustion?

The chlorination patterns of unsubstituted naphthalene were studied using a laminar flow reactor with a 1 cm particle bed of 0.5% (mass) copper(II) chloride (CuCl2) mixed with silicon dioxide (SiO2), operated over a temperature range of 100 to 400 °C and at gas velocities of 2.7 and 0.32 cm/s. The polychlorinated naphthalene (PCN) yield increased until a temperature reached at 250 °C, where a peak yield of 3.07% (percent of naphthalene input, carbon basis) was observed. All PCN homologue groups, mono- through octa-chlorinated naphthalenes, were observed. To test the hypothesis that PCNs in combustion processes are formed via chlorination pathways, the PCN homologue and isomer patterns from the experiments were compared with those observed in municipal solid waste combustion (MSW) incinerators. PCN congeners with 1,4-substituents dominated formation in the naphthalene chlorination experiments, whereas 2,3-substituents were major congeners in both MSW combustion flue gas and fly ash samples. These results suggest that contrary to the hypothesis, chlorination is not a primary PCN formation route in either the flue gas or fly ash from MSW combustion. Even so, naphthalene chlorination pathways presented in this paper provide an improved means for evaluating PCN formation mechanisms in combustion processes.

Polychlorinated naphthalenes in polar environments--a review

Polychlorinated naphthalenes (PCNs) consist of naphthalene substituted with 1-8 chlorines, yielding 75 possible congeners. They were formerly used in industry, occur at trace levels in commercial PCB mixtures, and have current sources in combustion processes. PCNs are widespread in arctic air with higher levels in the European Arctic. Concentrations were higher during the cold months in arctic Canada and Russia, but no seasonality was noted in subarctic Canada and Greenland. "Marker" congeners indicative of combustion were evident at some sites. Total toxic equivalents (TEQ) in air due to PCNs+dioxin-like PCBs were dominated by PCNs in arctic Canada and Russia, but not in subarctic Canada. Deposition of PCNs in snow was measured in northern Norway and Svalbard. Surveys of PCNs in the lower food web are limited to the northern Baltic Sea and lakes/rivers of northern Scandinavia. PCNs showed little or no biomagnification in lower food webs of the northern Baltic and discrimination among congeners suggested preferential metabolism. There are no reports of PCNs in fish and invertebrates from the Arctic Ocean, and only one from Antarctica. Total PCNs in marine mammals followed the order: harbour seal~pilot whale>or=polarbear>beluga>ringed seal~Weddell seal. Total PCNs in seabirds varied over 100-fold, with higher concentrations in glaucous gull eggs and plasma from Bear Island, and livers of northern fulmar from the eastern Canadian Arctic. Lower concentrations occurred in eggs of glaucous gull from Svalbard and black-backed gull from the Faroe Islands. PCNs accounted for <1% of total TEQ in ringed seal, Weddell seal, seabirds and polar bear, but up to 6-15% in beluga and pilot whale. TEQ due to PCNs were generally low in harbour seal, but up to 9% of total TEQ in some animals.

Comprehensive two-dimensional GC (GCxGC) qMS analysis of tetrachloronaphthalenes in Halowax formulations

A combination of non-polar and shape selective columns in a comprehensive two-dimensional GC (GCxGC) system consisting of DB-5MS and LC-50 as the 1st and 2nd dimension columns was used to separate 22 tetrachloronaphthalene isomers. These columns enabled separation of all possible isomers of tetraCN found in the technical chloronaphthalene Halowax formulations into 18 peaks covering 15 single separated isomers and 7 co-eluting in triplicate (1,2,4,6-/1,2,4,7-/1,2,5,7-tetraCN; nos. 33/34/37) and in pairs (1,2,3,7-/1,2,4,5-tetraCN; nos. 30/32 as well as 1,3,5,8-/1,3,6,8-tetraCN; nos. 43/45). Twelve isomers of tetraCN resolved as single compounds by the GC x GC system used were found in Halowax 1001, 1013, 1014 and 1099 as well as in Equi-Halowax mixture. Three other tetraCNs that could be also resolved as single compounds were not detected in these materials, while the remaining 7 tetraCNs, which co-eluted, waits a further separation. The majority of constituents of the tetraCN homologue group of the Halowax formulations are isomers such as 1,4,5,8- (no. 46), 1,2,5,8- (no. 38), 1,2,4,8-tetraCN (no. 35), co-eluting 1,3,5,8-tetraCN (no. 43 in a pair nos. 43/45) and also co-eluting 1,2,4,6-/1,2,4,7-/1,2,5,7-tetraCN (nos. 33/34/37). The less abundant by amongst of tetraCNs in these mixtures are 1,4,6,7- (no. 47) and 1,3,5,7-tetraCN (no. 42). The remaining seven isomers, i.e., 1,2,3,4- (no. 27), 1,2,3,5- (no. 28), 1,2,3,6- (no. 29), 1,2,5,6- (no. 36), 1,2,6,7- (no. 39), 1,2,6,8- (no. 40) and 1,2,7,8-tetraCN (no. 41) are usually minor by quantity, while 1,2,3,7-/1,2,4,5-tetraCN (nos. 30/32) are also minor, or one of them is absent. Three tetraCNs not found in the Halowax formulations are isomers such as 1,2,3,8-tetraCN (no. 31), 1,3,6,7-tetraCN (no. 44) and 2,3,6,7-tetraCN (no. 48).

Chlorinated naphthalene formation from the oxidation of dichlorophenols

Polychlorinated naphthalenes (PCNs) formed along with dibenzo-p-dioxin and dibenzofuran products in the slow combustion of dichlorophenols (DCPs) at 600 degrees C were identified. Each DCP reactant produced a unique set of PCN products. Major PCN congeners observed in the experiments were consistent with products predicted from a mechanism involving an intermediate formed by ortho-ortho carbon coupling of phenoxy radicals; polychlorinated dibenzofurans (PCDFs) are formed from the same intermediate. Tautomerization of the intermediate and H2O elimination produces PCDFs; alternatively, CO elimination to form dihydrofulvalene and fusion produces naphthalenes. Only trace amounts of tetrachloronaphthalene congeners were formed, suggesting that the preferred PCN formation pathways from chlorinated phenols involve loss of chlorine. 3,4-DCP produced the largest yields of PCDF and PCN products with two or more chlorine substituents. 2,6-DCP did not produce tri- or tetra-chlorinated PCDF or PCN congeners. It did produce 1,8-DCN, however, which could not be explained.

Advances in the environmental analysis of polychlorinated naphthalenes and toxaphene

Recent advances in the analysis of the chlorinated environmental pollutants polychlorinated naphthalenes (PCNs) and toxaphene are highlighted in this review. Method improvements have been realized for PCNs over the past decade in isomer-specific quantification, peak resolution, and the availability of mass-labeled standards. Toxaphene method advancements include the application of new capillary gas chromatographic (GC) stationary phases, mass spectrometry (MS), especially ion trap MS, and the availability of Standard Reference Materials that are value-assigned for total toxaphene and selected congener concentrations. An area of promise for the separation of complex mixtures such as PCNs and toxaphene is the development of multidimensional GC techniques. The need for continued advancements and efficiencies in the analysis of contaminants such as PCNs and toxaphene remains as monitoring requirements for these compound classes are established under international agreements.

Chloronaphthalenes composition of several batches of Halowax 1051

Halowax 1051 is the highest chlorinated technical chloronaphthalene mixture among seven known formulations of the Halowax series. Octa- and heptaCN homologue groups are the main CN constituents of Halowax 1051 with declared 90% and 10% contents, respectively. In this study, using an isotope dilution technique and HRGC/HRMS, octaCN and heptaCNs contents of six batches of Halowax 1051 were between 82-93% and 6.2-17%, respectively. Also mono- to hexaCNs were found in Halowax 1051, and their content more or less varied according to the batch; also, the abundance of a particular CN congeners varied. Tetra-, penta- and hexaCNs have been found in all six batches of Halowax 1051 examined, and their contents varied between 0.0024-0.77%, 0.031-0.22%, and 0.21-0.82%, respectively. TriCNs have been found in three of six batches, and mono- and diCNs in two of six batches with 0.0020-0.40, 0.0017-0.25 and 0.0012-0.34% for positive findings, respectively. 2,3-DiCN (no. 10), 1,8-diCN (no. 9) at < 0.0002 mg/g, 1,6,7-/2,3,6-triCNs (nos. 25/26), 1,3,8-triCN (no. 22) at < 0.0002 mg/g, 1,3,6,7-tetra (no. 44), 1,2,3,6-tetra- (no. 29), 1,2,7,8-tetraCN (no. 41) and 1,2,3,6,7,9-hexaCN (no. 70) at < 0.0005 mg/g have not been found in Halowax 1051.

HRGC/HRMS analysis of chloronaphthalenes in several batches of Halowax 1000, 1001, 1013, 1014 and 1099

Chloronaphthalene (CN) congeners and homologue groups have been quantified in up to three batches of several types of technical CN formulations of the Halowax series (Halowax 1031, 1000, 1001, 1013, 1014 and 1099), to elucidate possible batch-to-batch compositional variations. Using isotope dilution and HRGC/HRMS a relatively large variation in CN congeners and homologues composition among the batches of particular types of the Halowax formulations could be noted, and also when compared to the composition declared by the manufacturer. Depending on the type of the Halowax formulation and its batch in total up to 54 peaks from chloronaphthalenes (Agilent Ultra 2 liquid phase), which represented 70 of 75 CN congeners theoretically possible, could be found in these mixtures. These congeners represented all CN homologue groups from mono- to octaCN but some co-eluted. A co-eluting congeners were such as: 1,4-/1,6- (nos. 5/7), 1,5-/2,7- (nos. 6/12), 2,6-1,7- (nos. 11/8) of diCNs; 1,3,6-/1,3,5- (nos. 20/19), 1,3,7-/1,4,6- (nos. 23/24), 1,6,7-/2,3,6- (nos. 25/26) of triCNs; 1,2,5,7-/1,2,4,6-/1,2,4,7- (nos. 37/33/34), 1,3,6,8-/1,2,5,6- (nos. 45/36), 1,2,3,5-/1,3,5,8- (nos. 28/43), 1,2,3,4-/1,2,3,7- (nos. 27/30), 1,2,5,8-/1,2,6,8- (nos. 38/40) of tetraCNs; 1,2,3,5,7-/1,2,4,6,7- (nos. 52/60), 1,2,3,5,8-/1,2,3,6,8- (nos. 53/55) of pentaCNs; 1,2,3,4,6,7-/1,2,3,5,6,7- (nos. 66/67), 1,2,3,4,5,7-/1,2,3,5,6,8- (64/68) and 1,2,4,5,6,8-/1,2,4,5,7,8- (nos. 71/72) of hexaCNs. Absent in the Halowaxes were CN congeners such as 1,3,8-triCN (no. 22) (<0.0002 mg/g), 1,3,6,7-tetraCN (no. 44), 1,2,3,6-TetraCN (no. 29), 1,2,3,6,7-pentaCN (no. 54) and 1,2,3,6,7,8-hexaCN (no. 70) (<0.0005 mg/g).

Temperature-dependent formation of polychlorinated naphthalenes and dibenzofurans from chlorophenols

To investigate the gas-phase formation of polychlorinated naphthalenes (PCNs) and dibenzofurans (PCDFs) from chlorinated phenols in combustion exhaust gas, experiments were performed with each of the three chlorophenols in a laminar flow reactor over the range of 550-750 degrees C under oxidative conditions. Maximum PCN and PCDF yields were observed between 625 and 725 degrees C. The degree of chlorination of naphthalene and dibenzofuran products decreased as temperature increased, and on average, the naphthalene congeners were less chlorinated than the dibenzofuran congeners. Congener distributions are consistent with proposed PCN and PCDF formation pathways, both involving phenoxy radical coupling at unchlorinated ortho-carbon sites to form a dihydroxybiphenyl keto tautomer intermediate. Tautomerization of this intermediate and subsequent fusion via H2O loss results in PCDF formation, whereas CO elimination and subsequent fusion with hydrogen and/or chlorine loss leads to PCN formation. PCDF isomer distributions were found to be weakly dependent on temperature. PCN isomer distributions were found to be more temperature sensitive, however, with selectivity to particular isomers decreasing with increasing temperature. These results contribute to the understanding of PCN and PCDF formation in combustion and provide information on how to predict and minimize these emissions.

Liquid-crystalline stationary phases for gas chromatography

Physico-chemical properties of new liquid-crystalline stationary phases (LCSPs) for gas chromatography are reviewed. The mechanism of chromatographic separation on liquid-crystalline stationary phases is discussed and examples of analyses of complex mixtures of organic compounds using capillary and packed columns are given.

Polychlorinated naphthalenes in animal aquatic species and human exposure through the diet: a review

Polychlorinated naphthalenes (PCNs) are a group of environmental pollutants, which contain one to eight chlorine atoms per naphthalene molecule, forming a total of 75 possible congeners. Several of the PCN congeners display toxicity similar to that of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) through AhR-mediated mechanisms. There are toxicological similarities between PCNs and other well known environmental contaminants such as polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and biphenyls (PCBs). However, in contrast to these compounds, information on exposure to PCNs for non-occupationally exposed populations is rather scarce. In this article, information on human exposure to PCNs through dietary intake is reviewed. Because this information is very limited and taking into account that most data on PCN levels in potential foods concern to aquatic species, these data are also reviewed. It is concluded that further investigations on dietary intake and potential human health effects of PCNs are clearly necessary.

Dependence of GC-RRTs on the solvent-accessible surface area of dioxins and related compounds

The correlation between gas chromatograph relative retention times (GC-RRTs) of dioxins and related compounds, polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated naphthalenes (PCNs), and their solvent-accessible surface area (SAS) was analyzed for congeners and isomers. GC-RRTs were linearly dependent on SAS for congeners while there was little dependence for isomers. However, by using classification parameters, Nad-Cl, Nad-H, N1,9Cl, and NalphaCl, based on the substitution positions and patterns of chlorine and/or hydrogen atoms bound to the molecular skeleton, a linear relationship was found among isomers. Furthermore, the GC-RRTs of CDD, CDF, and CN isomers, which are planar, decreased despite increasing SAS, and this tendency was enhanced with the above classification. The retention behavior was explained in terms of the effective enhancement of molecular hydrophobicity caused by an increase in the number of adjacent chlorine pairs.

Tissue distribution of polychlorinated naphthalenes (PCNs) and non-ortho chlorinated biphenyls (non-ortho CBs) in harbour porpoises (Phocoena phocoena) from Swedish waters

Polychlorinated naphthalenes (PCNs) and non-ortho chlorinated biphenyls (non-ortho CBs) were analysed in blubber, nuchal fat, liver, muscle, kidney and brain of three male harbour porpoises (Phocoena phocoena) from the west coast of Sweden. To estimate spatial variation, PCNs and non-ortho CBs were analysed in six blubber samples collected at different anatomical sites of each animal. Highest wet weight concentrations of sigma PCNs were detected in the lipid rich tissues (blubber and nuchal fat) and liver (520-730 and 520 pg/g, respectively) and lowest in brain (22 pg/g). TetraCNs were most abundant in muscle, kidney and brain, while the hexaCNs were most abundant in the lipid rich tissues and liver. The highest lipid weight concentration recorded (11 ng/g) was for the hexaCN congeners no. 66/67 in liver. These coeluting hexaCN congeners accounted for 80-100% of total hexaCNs in all tissues examined. Concentrations of sigma non-ortho CBs were highest in lipid rich tissues (220-280 pg/g wet weight). Non-ortho CB no. 77 and 169 constituted between 62-86% and 4.9-9.3%, respectively, of total sigma non-ortho CBs. No major variation of sigma non-ortho CB concentrations was found between the six different blubber sites but higher sigma PCN concentrations (wet weight) were found dorsally at the peduncle. Toxic equivalent concentrations (TEQs) showed that non-ortho CB no. 126 was the main contributor to total TEQs in all tissues, except liver in which hexaCN congener nos. 66/67 contributed to about 50% of total TEQs.

Polychlorinated naphthalenes: an environmental update

Polychlorinated naphthalenes (PCNs; CNs) form a complex mixture of up to 75 congeners containing from one to eight chlorine atoms per naphthalene molecule. Chloronaphthalenes are widespread global environmental pollutants which accumulate in biota. All chloronaphthalenes are planar compounds and can contribute to the aryl hydrocarbon (Ah) receptor-mediated mechanism of toxicity with a combination of various 2,3,7,8-tetrachlorodibenzo-p-dioxin like toxic responses. There are three known main sources of environmental pollution with PCNs: technical PCN formulations, technical polychlorinated biphenyl formulations, and thermal and other processes in the presence of chlorine. The purpose of this paper is to briefly review the most recent data on environmental pollution, chemistry, analysis, sources, formation, persistence, toxicity and behavior of PCNs.