Chlorinated Paraffins Mixtures Research Articles

A Quasi Real-Time Evaluation of High-Resolution Mass Spectra of Complex Chlorinated Paraffin Mixtures and Their Transformation Products.

Chlorinated paraffins (CPs) are complex mixtures of polychlorinated n-alkanes with multiple carbon- (C-, nC = 9-30) and chlorine homologues (Cl-, nCl = 3-18). The mass spectrometric analysis of CPs is time-consuming and challenging, especially when interferences between CPs, their transformation products, or from the matrix are numerous. These analytical challenges and the lack of appropriate and accessible data evaluation tools are obstacles to their analysis. CP-Hunter is a web-based, open-access data processing platform for the automatic analysis of mass spectra of CPs and their transformation products. Extracts of two consumer plastic materials and sewage sludge were evaluated with CP-Hunter. C- and Cl-homologue distributions were obtained in quasi-real-time and the posterior calculated fingerprints were in agreement with the ones obtained by traditional methods. However, the data extraction and evaluation time were now reduced from several minutes to seconds. The implemented signal deconvolution method, i.e., to resolve mass spectrometric interferences, provides robust results, even when severe matrix effects are present. CP-Hunter facilitates the untargeted analysis of unknown products and the detection and elimination of false positive signals. Finally, data evaluation with CP-Hunter is performed locally without the transfer of data to external servers. The tool is safe, public, and accessible at https://cphunter.cheminfo.org/.

Are We Justified in Modeling Human Exposure to Chlorinated Paraffin Mixtures Using the Average Properties of Congeners and Homologues?

Concern over human exposure to chlorinated paraffin (CP) mixtures keeps increasing. The absence of a comprehensive understanding of how human exposure varies with the physicochemical properties of CP constituents has hindered the ability to determine at what level of aggregation exposure to CPs should be assessed. We answer this question by comparing exposure predicted with either a "complex" method that utilizes isomer-specific properties or "simplified" methods that rely on median properties of congener, homologue, or short-/medium-/long-chain CP groups. Our results demonstrate the wide range of physicochemical properties across CP mixtures and their dependence on molecular structures. Assuming unit emissions in the environment, these variances translate into an extensive disparity in whole-body concentrations predicted for different isomers, spanning ∼11 orders of magnitude. CPs with 13-19 carbons and 6-10 chlorines exhibit the highest human exposure potential, primarily owing to moderate to high hydrophobicity and slow environmental degradation and biotransformation. Far-field exposure is dominant for most CP constituents. Our study underscores that using average properties of congener, homologue, or S/M/LCCP groups yields results that are consistent with those derived from isomer-based modeling, thus offering an efficient and practical framework for future risk assessments and human exposure studies of CPs and other complex chemical mixtures.

Homologue Composition of Technical Chlorinated Paraffins Used in Several Countries over the Last 50 Years─SCCPs Are Still Out There.

Chlorinated paraffins (CPs) are widely produced chemicals, with certain CP subgroups facing global restrictions due to their environmental dispersion, persistence, bioaccumulation, and toxicity. To evaluate the effectiveness of these international restrictions, we assessed the homologue group contribution and the mass fraction of short-chain CPs (SCCPs: C10-C13), medium-chain CPs (MCCPs: C14-C17), and long-chain CPs (LCCPs: ≥C18) in 36 technical CP mixtures used worldwide over the last 50 years. Using low-resolution mass spectrometry (LC-ESI-MS/MS), we quantified 74 CP homologue groups (C10Cl4-C20Cl10). Additionally, high-resolution mass spectrometry (LC-ESI-QTOF-MS) screening was employed to identify unresolved CP contents, covering 375 CP homologue groups (C6Cl4-C30Cl30). Overall, 1 sample was mainly composed of <C10-CPs, 10 of SCCPs, 13 of MCCPs, and 12 of LCCPs. Specific homologue group contributions and mass fractions of CP subgroups varied considerably. However, the predominance of C11Cl6- and C14Cl6-CP homologue groups was in good agreement with that of the dominant homologue groups in environmental matrices and manufactured products. SCCP yields are still high in some technical CP mixtures, and three technical CP mixtures currently produced failed the Stockholm Convention restrictions on SCCPs. This study sheds light on significant challenges in implementing international CP restrictions effectively.

Selective and Fast Analysis of Chlorinated Paraffins in the Presence of Chlorinated Mono-, Di-, and Tri-Olefins with the R-Based Automated Spectra Evaluation Routine (RASER).

Chlorinated paraffins (CPs) are complex mixtures consisting of various C homologues (nC ≈ 10-30) and Cl homologues (nCl ≈ 2-20). Technical CP mixtures are produced on a large scale (>106 t/y) and are widely used such as plasticizers in plastic and coolants in metalwork. Since 2017, short-chain CPs (C10-C13) are classified as persistent organic pollutants (POPs) by the Stockholm Convention but longer-chain CPs are not regulated. Analysis of technical CP mixtures is challenging because they consist of hundreds of homologues and millions of constitutional isomers and stereoisomers. Furthermore, such mixtures can also contain byproducts and transformation products such as chlorinated olefins (COs). We applied a liquid-chromatography method coupled to an atmospheric pressure chemical ionization technique with a high-resolution mass detector (LC-APCI-Orbitrap-MS) to study CP and CO homologues in two plastic materials. Respective mass spectra can contain up to 23,000 signals from 1320 different C-Cl homologue classes. The R-based automated spectra evaluation routine (RASER) was developed to efficiently search for characteristic ions in these complex mass spectra. With it, the time needed to evaluate such spectra was reduced from weeks to hours, compared to manual data evaluation. Unique sets of homologue distributions could be obtained from the two plastic materials. CPs were found together with their transformation products, the chlorinated mono-olefins (COs), di-olefins (CdiOs), and tri-olefins (CtriOs) in both plastic materials. Based on these examples, it can be shown that RASER is an efficient and selective tool for evaluating high-resolution mass spectra of CP mixtures containing hundreds of homologues.

Nuclear magnetic resonance as a tool to determine chlorine percentage of chlorinated paraffin mixtures

A new simple method for chlorine percentage calculations (method C), from proton nuclear magnetic resonance (1H NMR) spectroscopy, has been established and applied to an industrial chlorinated paraffin (CP) mixture and 13 single-chain CPs of known carbon chain lengths. Two modified methods (method A and B), originating from the work of Sprengel et al., have been utilized on the same single-chain mixtures. All samples were analysed by 1H NMR and two-dimensional heteronuclear quantum coherence (HSQC) for this purpose. All three methods worked well for medium chlorinated (45–55% Cl) single-chain mixtures of known carbon chain lengths. Method A yielded the best result for mixtures of lower chlorine content (<45% Cl), method C gave better estimations for higher chlorine contents (>55% Cl). Compared to Mohr's titration, method A showed a deviation of 0.7–7.8% (3.6% average), method B 4.1–11.3% (7.0% average) and method C 0.6–11.6% (5.2% average), for all 13 single-chain mixtures. The new method C is the only method that could be applied for determining the chlorine percentage of industrial mixtures of multiple, unknown chain lengths.

Hormetic dose-response of halogenated organic pollutants on Microcystis aeruginosa: Joint toxic action and mechanism

Quinolones (QNs), dechloranes (DECs), and chlorinated paraffins (CPs) are three kinds of new halogenated organic pollutants (HOPs), which originate from the use of flame retardants, lubricants and pesticides. Since QNs, DECs, and CPs are frequently detected in waters and sediments, it is necessary to investigate the toxic effects of these HOPs with dwelling phytoplankton, especially for cyanobacteria, to explore their potential hormetic effects and contributions to algal blooms. In the present study, we investigate single and joint toxicity of QNs, DECs and CPs on Microcystis aeruginosa (M. aeruginosa), a cyanobacterium that is frequently implicated with algal blooms. The results indicate single QNs and DECs induce marked hormetic effects on the proliferation of M. aeruginosa but CPs do not. The stimulatory effect of hormesis is linked with accelerated replication of DNA, which is considered to stem from the moderate rise in intracellular reactive oxygen species (ROS). Joint toxicity tests reveal that both QNs & CPs mixtures and DECs & CPs mixtures show hormetic effects on M. aeruginosa, but QNs & DECs mixtures show no hormetic effect. QNs & DECs mixtures exhibit synergistic toxic actions, which may be caused by a sharp rise in intracellular ROS simultaneously produced by the agents. Joint toxic actions of both QNs & CPs, and DECs & CPs shift from addition to antagonism as concentration increases, and this shift may mainly depend on the influence of CPs on cell membrane hydrophobicity of M. aeruginosa. This study provides data and toxic mechanisms for the hormetic phenomenon of single and joint HOPs on M. aeruginosa. The hormetic effects of HOPs may benefit the proliferation of M. aeruginosa in the aquatic environment, aggravating the formation of algal blooms. This study also reflects the important role of hormesis in environmental risk assessment of pollutants.

A new synthesis approach for the generation of single chain CP mixtures composed of a few major compounds

Chlorinated paraffins (CPs) are complex mixtures, which consist of thousands of individual compounds with no dominant representative. Consequently, knowledge on structure and environmental relevance of individual CP congeners is poor. Similarly to the synthesis of individual CPs, the generation of less complex CP mixtures that can be thoroughly analyzed may be used to overcome some drawbacks of the highly complex technical CP mixtures. Here, we present a new synthesis approach to generate such simple CP mixtures by decarboxylation of polyunsaturated fatty acids followed by saturation of the double bonds by chlorination. Specifically, α-linolenic acid (18:3Δ9,12,15) was decarboxylated to heptadecatriene. The resulting raw product was chlorinated with SO2Cl2. Purification by column chromatography led to a main fraction consisting of four major peaks originating from hexachloroheptadecane (C17H30Cl6) isomers (∼80% of the total peak area) along with ∼20 low abundant by-products, according to gas chromatography with electron capture negative ion mass spectrometry. In the same way, decarboxylation and subsequent chlorination of other polyunsaturated fatty acids may lead to further simple CP mixtures with other chain lengths. Although these simple CP mixtures cannot fully reflect the various structural features present in technical mixtures they could be beneficial for transformation studies because changes in the CP pattern can easily be noted which is in contrast to technical CP mixtures. Such simple CP mixtures could also be used in toxicity tests which are difficult to perform with technical CP mixtures because of their high complexity.

Chlorinated paraffins – A historical consideration including remarks on their complexity

Chlorinated paraffins (CPs) are high production volume chemicals currently produced and used in higher quantities than any other medium-size polyhalogenated compound (class). In addition, the composition of industrial CP mixtures is highly complex and poorly understood. In this article, we searched in the literature for the beginning of the chlorination of alkanes and how this substance class developed from niche applications to unmatched quantities in various industrial applications. Also, an estimation was made on the theoretical variety of chloroparaffins and the possible complexity of industrial CP mixtures. These data may explain why little is known about CPs although the production volume throughout the industrial generation was virtually always higher than the one of PCBs and has continued to increase after the ban of the latter.

Determination of chlorinated paraffins (CPs): Analytical conundrums and the pressing need for reliable and relevant standards

The determination of chlorinated paraffins (CPs) has posed an intractable challenge in analytical chemistry for over three decades. The combination of an as yet unspecifiable number (tens - hundreds of thousands) of individual congeners in mass produced commercial CP mixtures and the steric interactions between them, contrive to defy efforts to characterise their residual occurrences in environmental compartments, food and human tissues. However, recent advances in instrumentation (mass spectrometric detectors and nuclear magnetic resonance), combined with interlaboratory studies, have allowed a better insight into the nature of the conundrums. These include the variability of results, even between experienced laboratories when there is insufficient matching between analytical standards and occurrence profiles, the poor (or no) response of some instrumentation to some CP congener configurations (multiple terminal chlorines or < four chlorines) and the occurrence of chlorinated olefins in commercial mixtures. The findings illustrate some limitations in the existing set of commercially available standards. These include cross-contamination of some standards (complex CP mixtures), an insufficient number of single chain standards (existing ones do not fully reflect food/biota occurrences), lack of homologue group standards and unsuitability of some configurationally defined CP congeners/labelled standards (poor instrument response and a smaller likelihood of occurrence in commercial mixtures). They also indicate an underestimation in reported occurrences arising from those CPs that are unresponsive during measurement. A more extensive set of standards is suggested and while this might not be a panacea for accurate CP determination, it would reduce the layers of complexity inherent in the analysis.

Percutaneous penetration and dermal exposure risk assessment of chlorinated paraffins

The widespread occurrence of chlorinated paraffins (CPs) in environmental matrices has resulted in a high frequency exposure to CPs via dermal contact. To quantitatively estimate percutaneous penetration of CPs, Episkin® human skin equivalents (HSE) was applied as an in vitro model to evaluate the mechanism of percutaneous penetration of CPs. The co-exposure of CPs mixtures to HSE showed that about 11.7% and 10.2% of short-chain CPs (SCCPs) and medium-chain CPs (MCCPs) could penetrate the HSE and enter the receptor fluid, while no long-chain CPs (LCCPs) (C>17) were able to penetrate the HSE during the 36-h assay period. The experimentally obtained permeability coefficient (Kp) values for CPs were significantly (p < 0.01) negatively correlated with their log octanol–water partition coefficient (log Kow). Furthermore, 24 participants were recruited to assess direct human dermal exposure to CPs in China with the total CPs collected onto hand wipes and forehead wipes being 96,600 and 30,400 ng/person, respectively. The proportion of total SCCPs and MCCPs intake via dermal penetration (skin area investigated in this study) accounting for 2.0% of the total intake of CPs. Considering the total skin surface of human body is around 20 times of the area studied, the total intake of CPs through dermal penetration could be a significant exposure pathway.

Direct measurements and modeling of congener group specific vapor pressure for chlorinated paraffins

Chlorinated Paraffins (CPs) are a complex group of manmade chemicals detected widely in the environment. To predict their environmental fate and effects, it is important to understand their physical-chemical properties including vapor pressure. In this study, the first direct measurements of the vapor pressure for CP congener groups (C10–16Cl4–11) are presented. Vapor pressure was measured above three industrial CP mixtures with different congener distributions between 20 and 50 °C using a gas saturation method. The measured saturated vapor pressure (P∗) decreased with increasing carbon chain length and Cl content. ΔHvap ranged between 73 and 122 kJ mol−1, consistent with data from the literature and model prediction. The experimental log P∗ at 25 °C agreed well with predictions from an empirical regression model in the literature (R2 = 0.97; RSME = 0.25) and with those predicted from the COSMO-RS-trained fragment contribution model (R2 = 0.95; RSME = 0.35). A new empirical model was calibrated with the P∗ data for 35 congener groups measured in this study. Predicted log P∗ values correlate well with field-measured gas/particle partition coefficients and may therefore be used for estimating the environmental fate and pathways of a broad range of CPs in the environment.

Impurities in technical mixtures of chlorinated paraffins show AhR agonist properties as determined by the DR-CALUX bioassay

Chlorinated paraffins (CPs) are produced at more than one million tons per year. Technical CPs mixtures may contain impurities, which end up in consumer products. In the present study, 17 technical CPs mixtures were investigated for the potential occurrence of potential impurities. By applying the DR-CALUX bioassay, 3 out of 17 technical mixtures were shown to elicit responses at 4 h exposure time, but much lower at 48 h. Constitutional defined CPs materials did not show responses. Subsequently different groups of known AhR-agonists and compounds suspected to be present in technical CPs mixtures were investigated. Benzene, (poly)chlorobenzene, non-dioxin like polychlorinated naphthalenes (PCNs), and three-ringed polyaromatic hydrocarbons (PAHs) did not result in a significant response at 4 h or 48 h. TCDD, non-ortho PCBs, dioxin-like PCNs, four or five ringed PAHs and their chlorinated analogues resulted in a significant response. TCDD and the non-ortho PCBs showed the highest potency and stability, while dioxin-like PCNs, PAHs, and the chlorinated PAHs were clearly inactivated (metabolized) at longer incubation. Altogether, the present findings substantiate that AhR-mediated responses of CPs technical mixtures in the DR-CALUX bioassay are caused by impurities, most likely some intermediate stable AhR-agonists such as dioxin-like PCNs or (chlorinated) PAHs. The current study shows that impurities in CPs technical mixtures need to be investigated for assessing the safety of technical CPs mixtures.

Refinement and extension of COSMO-RS-trained fragment contribution models for predicting the partition properties of C10-20 chlorinated paraffin congeners.

COSMO-RS-trained fragment contribution models (FCMs) to predict the partition properties of chlorinated paraffin (CP) congeners were refined and extended. The improvement includes (i) the use of an improved conformer generation method for COSMO-RS, (ii) extension of training and validation sets for FCMs up to C20 congeners covering short-chain (SCCPs), medium-chain (MCCPs) and long-chain CPs (LCCPs), and (iii) more realistic simulation of industrial CP mixture compositions by using a stochastic algorithm. Extension of the training set markedly improved the accuracy of model predictions for MCCPs and LCCPs, as compared to the previous study. The predicted values of the log octanol/water partition coefficients (Kow) for CP mixtures agreed well with experimentally determined values from the literature. Using the established FCMs, this study provided a set of quantum chemically based predictions for 193 congener groups (C10-20 and Cl0-21) regarding Kow, air/water (Kaw), and octanol/air (Koa) partition coefficients, subcooled liquid vapor pressure (VP) and aqueous solubility (Sw) in a temperature range of 5-45 °C as well as the respective enthalpy and internal energy changes.

Protein-affinity guided identification of chlorinated paraffin components as ubiquitous chemicals

Chlorinated paraffins (CPs) have been extensively examined to identify their components. Short-chain CPs with a carbon number of 10–13 have been strictly restricted or banned due to their addition to the list of Persistent Organic Pollutants in the world. However, more constituents with potential toxicities in these complicated mixtures are still unclear. In the present study, a purification method based on the protein affinity of thyroid hormone-related proteins (transthyretin and thyroid receptor) was established. The protein-based affinity extraction coupled with high-throughput scanning successfully discover a new group of chlorinated compounds (CP(O2)) in commercial CP mixtures. The CP(O2)s were purified from the commercial mixtures and identified to be chlorinated fatty acid methyl esters (CFAMEs) with a carbon chain length of 17–19 and 3–11 chlorines by a combination of liquid-liquid extraction, hydrolysis, Fourier transform infrared spectrometry and Orbitrap mass spectrometry. The newly identified CFAMEs were found to be ubiquitous in the environmental matrices, and concentration ratios of ∑CFAMEs/∑CPs ranged from 0.01 to 35 in air, soil and food samples. CFAMEs were also detected in blood samples of general populations, and accumulated in humans through dietary uptake. CFAMEs can compete with T4 for binding TTR with higher potencies than CPs, possibly leading to disruptions of thyroid hormone homeostasis.

NMR and GC/MS analysis of industrial chloroparaffin mixtures

Chlorinated paraffins (CPs) are high-volume chemicals used worldwide in various industries as plasticizers, lubricants, and flame retardants. CPs are produced by chlorination of alkane mixtures which leads to complex products of thousands of homologs and congeners. Classic mass spectrometric analyses of CPs allow determining carbon chain lengths and degrees of chlorination while information on the substitution patterns cannot be derived. Therefore, we performed different one- and two-dimensional nuclear magnetic resonance spectroscopy (NMR) experiments, elemental analysis (EA), and gas chromatography coupled with electron capture negative ion mass spectrometry (GC/ECNI-MS) for the analysis of ten technical CP products with 42%, 52%, and 70% chlorine content from four producers. Slight differences in chlorine content but varying chain length compositions were observed for similarly labeled products from different manufacturers. Two-dimensional heteronuclear spectral quantum coherence (HSQC) measurements helped to evaluate ten structural elements in the products and confirmed the presence of geminal chlorine atoms in primary and secondary carbons in products with 70% chlorine. The variation of signal groups increased with increasing chlorine content of the products. Two-dimensional heteronuclear multiple bond coherence (HMBC) analysis of one sample and GC/ECNI-MS measurements indicated the presence of impurities (e.g., C9-CPs, iso-alkanes) in different technical CP products. These methods could in future allow for better distinction of CP mixtures, and an improved trace-back of environmental CPs to the source, based on specific structural features. Additionally, further structural characterization could help in the development of more accurate analysis processes.Graphical

Chlorines Are Not Evenly Substituted in Chlorinated Paraffins: A Predicted NMR Pattern Matching Framework for Isomeric Discrimination in Complex Contaminant Mixtures.

Chlorinated paraffins (CPs) can be mixtures of nearly a half-million possible isomers. Despite the extensive use of CPs, their isomer composition and effects on the environment remain poorly understood. Here, we reveal the isomeric distributions of nine CP mixtures with single-chain lengths (C14/15) and varying degrees of chlorination. The molar distribution of CnH2n+2–mClm in each mixture was determined using high-resolution mass spectrometry (MS). Next, the mixtures were analyzed by applying both one-dimensional 1H, 13C and two-dimensional nuclear magnetic resonance (NMR) spectroscopy. Due to substantially overlapping signals in the experimental NMR spectra, direct assignment of individual isomers was not possible. As such, a new NMR spectral matching approach that used massive NMR databases predicted by a neural network algorithm to provide the top 100 most likely structural matches was developed. The top 100 isomers appear to be an adequate representation of the overall mixture. Their modeled physicochemical and toxicity parameters agree with previous experimental results. Chlorines are not evenly distributed in any of the CP mixtures and show a general preference at the third carbon. The approach described here can play a key role in understanding of complex isomeric mixtures such as CPs that cannot be resolved by MS alone.

Chlorinated paraffins in the technosphere: A review of available information and data gaps demonstrating the need to support the Stockholm Convention implementation

Abstract Chlorinated paraffins (CPs) have been produced for a wide range of applications, mostly in open uses, such as metalworking fluids, lubricants, coolants or additives in consumer goods. The production volume is more than one million tonnes requiring control of the lifecycle of these persistent and bioaccumulative chemicals. In May 2017, the Stockholm Convention amended its Annex A to list short chain chlorinated paraffins (SCCPs) as a Persistent Organic Pollutant (POP). Additionally, a limit for the presence of SCCPs in other CP mixtures was set at 1% by weight. CPs can be released to the environment throughout their lifecycle. Therefore, the major objective of this review was to assess and compile information on SCCPs and other CPs regarding their lifecycle in the technosphere to support the Stockholm Convention implementation. A few studies have assessed CP production plants and contamination in the surrounding environments. However, there was no systematic investigation of release routes from production and no assessment of associated landfills, even though these are known major pollution sources at other organochlorine production sites. Some studies have reported that industrial areas, where CPs have likely been used, have elevated levels of CPs in sediments and soil. However, although CPs are largely released when used as metalworking fluids or lubricants, no systematic assessment of releases has been conducted at the thousands of sites where CPs are used in high volumes. Many CPs, mainly medium chain chlorinated paraffins (MCCPs) and SCCPs, are used as additives in the production of consumer goods, resulting in exposure risks. Levels above the European Union regulation for SCCPs of 1500 mg kg−1 and up to approx. 20% are frequently found. The end-of-life management of CP-containing products is difficult since no labelling requirement exists even for products containing SCCPs. The Stockholm Convention prohibits the recycling of SCCP-containing products, which will result in challenges recycling the impacted waste categories. The activities under the Stockholm Convention related to SCCPs, such as the inventory, phase-out, and management of impacted products, provide opportunities to address existing data gaps and challenges. Special attention needs to be given to developing countries with lacking analytical capacity as well as waste management and destruction capacity.

Characterization of single chain length chlorinated paraffin mixtures with nuclear magnetic resonance spectroscopy (NMR)

Chlorinated paraffins (CPs) are complex mixtures of polychlorinated n-alkanes of different chain length. Despite their environmental relevance, quantification is still a challenge. Moreover, the individual structures of the molecules in technical CP mixtures are largely unknown. Here, we synthesized 21 and studied 29 single chain length CP mixtures ranging from C10- to C17-CPs with different chlorine contents between 41.8% and 62.6% Cl and analyzed them by means of nuclear magnetic resonance spectroscopy (NMR). Discrete ranges of chemical shifts were observed in one-dimensional 1H and 13C NMR spectra. Two dimensional heteronuclear single quantum coherence spectroscopy (HSQC) enabled to assign nine substructures. These measurements also verified the presence of [-CCl2-] groups and chlorine atoms on terminal carbons in highly chlorinated (>59% Cl) mixtures. 1H NMR spectra of different chain length and the same degree of chlorination looked virtually the same. However, with increasing degree of chlorination the observed patterns in the spectra were slightly shifted downfield. Based on these findings, a calculation mode was developed to estimate the chlorine content (%) of the single chain length CP mixtures. The results agreed well (<0.9% mean deviation) with parallel measurements by elemental analysis.

Short-chain chlorinated paraffins in soil, sediment, and seawater in the intertidal zone of Shandong Peninsula, China: Distribution and composition

Short-chain chlorinated paraffins (SCCPs) are components of chlorinated paraffins (CPs) with high persistence, bioaccumulation potential, and toxicity, and SCCPs have been listed on Stockholm Convention as persistent organic pollutants. In this work, we investigated the distribution and homologue group patterns of SCCPs in the intertidal zone of the Shandong Peninsula, which is surrounded by the Bohai Sea (BS) and Yellow Sea (YS). Total SCCP concentrations (ΣSCCPs) in the samples from the sites along the coast of BS were 64.14–452.9 ng/g (mean = 181.0 ng/g), which were higher than those of the YS (17.59–155.5 ng/g, mean = 108.5 ng/g). ΣSCCPs were generally higher in intertidal sediments than in coastal soils along the BS, which could be ascribed to local industrial emissions through river runoff and mid-estuarine maximum phenomenon that resulted from seawater intrusion. In contrast, the opposite trend was observed along the YS. The contribution of shorter chain (C10) and lower chlorinated (Cl5-7) SCCP congeners was higher when the sampling sites were more proximal to the sea than heavier ones because of their greater potential for long-range transportation. Similar homologue group patterns were observed in the intertidal zone of Shandong, thus indicating a uniform use of commercial CP mixtures. High SCCP concentrations and similar homologue group patterns as those of the STP effluent were observed in seawater samples, thus suggesting that massive insufficiently purified or nonpurified industrial effluents were discharged into the BS.

Synthesis and characterization of eight single chain length chlorinated paraffin standards and their use for quantification.

Quantification of chlorinated paraffins (CPs) via gas chromatography coupled with electron capture negative ionization low-resolution mass spectrometry (GC/ECNI-MS) is a very common practice, although the quality of the results has been disputed due to insufficient mass resolution and the strong impact of the degree of chlorination on the GC/ECNI-MS response. For further tests we synthesized eight single chain length CP standards (C10 -C17 ) with chlorine contents between 51.1% and 61.3%. The individual single chain length standards, 1 + 1 mixtures of two chain length standards and self-prepared mixtures of short-chain and medium-chain CPs were quantified by linear regression according to a previously reported method (method 1) as well as by exponential regression (method 2). Concentrations obtained from single chain length CP standards deviated between -74% and 152% from the target value. However, the error became smaller when self-prepared CP mixes with two and four chain lengths were analysed. For short-chain CP (SCCP) mixture analysis, both methods produced good results (<25% deviation from the target value). In the case of medium-chain CP (MCCP) mixtures, however, method 2 (17-34% deviation) was more accurate than method 1 (43-52% deviation). Both methods 1 and 2 are fit for GC/ECNI-MS analysis of SCCP mixtures, while the improved method 2 is recommended for quantification of MCCP mixtures.