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The European Commission's Green Deal is a major policy initiative aiming to achieve a climate-neutral, zero-pollution, sustainable, circular and inclusive economy, driving both the New Industrial Strategy for Europe and the Chemicals Strategy for Sustainability. Innovative materials can help to reach these policy goals, but they need to be safe and sustainable themselves. Thus, one aim is to shift the development of chemicals to Safe- and Sustainable-by-Design, and define a new systems approach and criteria for sustainability to achieve this. An online workshop was organised in September 2020 by the Joint Research Centre and the Directorate-General Research and Innovation of the European Commission, with participants from academia, non-governmental organisations, industry and regulatory bodies. The aims were to introduce the concept of Safe- and Sustainable-by-Design, to identify industrial and regulatory challenges in achieving safer and more sustainable Smart Nanomaterials as an example of innovative materials, and to deliver recommendations for directions and actions necessary to meet these challenges. The following needs were identified: (i) an agreed terminology, (ii) a common understanding of the principles of Safe- and Sustainable-by-Design, iii) criteria, assessment tools and incentives to achieve a transition from Safe-by-Design to Safe- and Sustainable-by-Design, and (iv) preparedness of regulators and legislation for innovative chemicals/nanomaterials. This paper presents the authors' view on the state of the art as well as the needs for future activities, based on discussions at the workshop and further considerations. The case of Smart Nanomaterials is used to illustrate the Safe- and Sustainable-by-Design concept and challenges for its implementation. Most of the considerations can be extended to other advanced materials and to chemicals and products in general., Highlights • Safe- and Sustainable-by-Design chemicals contribute to the transformation of policy ambitions into a circular economy. • Smart nanomaterials are a case study of the challenges of Safe- and Sustainable-by-Design. • The development of criteria to guide the design of chemicals facilitates achieving sustainability. • Broad SSbD expert consultation is needed for consensus on principles and implementation. • Agreed terminology and assessment tools for Smart Nanomaterials help to achieve the EU green policy goals.

The European Green Deal, the European Commission's new Action Plan for a Circular Economy, the new European Industrial Strategy and the Chemicals Strategy for Sustainability launched in October 2020 are ambitious plans to achieve a sustainable, fair and inclusive European Union's economy. In line with the United Nations Sustainable Development Goals 2030, these policies require that any new material or product should be not only functional and cost-effective but also safe and sustainable to ensure compliance with regulation and acceptance by consumers. Nanotechnology is one of the technologies that could enable such a green growth. This paper focuses on advanced nanomaterials that actively respond to external stimuli, also known as ‘smart nanomaterials’, and which are already on the market or in the research and development phase for non-medical applications such as in agriculture, food, food packaging and cosmetics. A review shows that smart nanomaterials and enabled products may present new challenges for safety and sustainability assessment due to their complexity and dynamic behaviour. Moreover, existing regulatory frameworks, in particular in the European Union, are probably not fully prepared to address them. What is missing today is a systematic and comprehensive approach that allows for considering sustainability aspects hand in hand with safety considerations very early on at the material design stage. We call on innovators, scientists and authorities to further develop and promote the ‘Safe- and Sustainable-by-Design’ concept in nanotechnology and propose some initiatives to go into this direction., Highlights • Novel, stimuli-responsive (“smart”) nanomaterials are used in food, food packaging, cosmetics and agriculture. • Smart nanomaterials pose new challenges to safety and sustainability assessment due to their complexity and dynamic behaviour. • Existing regulatory frameworks are probably not fully prepared to address such challenges. • Smart nanomaterials should comply with the aims of the European Green Deal and the Chemicals Strategy for Sustainability. • ‘Safe- and Sustainable-by-Design’ integrates safety, circularity and functionality of materials throughout their life cycle.

This paper compares the extraction effectiveness of six different commonly applied extraction techniques for the determination of PCBs in soil. The techniques included are Soxhlet, Soxtec, ultrasonication extraction, supercritical fluid extraction, microwave-assisted extraction and accelerated solvent extraction. For none of the techniques were the extraction conditions optimized, but instead the extraction parameters were based on the experience from previous successful investigation published by a number of research groups worldwide. In general, all extraction techniques were capable of producing accurate data for one native PCB contaminated soil diluted with another soil sample to obtain two concentration levels. It could therefore be concluded that any of the investigated techniques can be used with success if the extraction conditions applied are chosen wisely.

Static extraction, supercritical fluid extraction (SFE), pressurized liquid extraction (PLE) and Soxhlet extraction were compared for simultaneous extraction of di(2-ethylhexyl) phthalate (DEHP) and nonionic surfactants from house dust. Homogenized office floor dust from a vacuum cleaner dust bag (“standard dust”) was used for the evaluation. One portion of the extracts was used for analysis of nonionic surfactants with LC–MS and another portion was used for DEHP analysis with GC–MS. The extraction yield of DEHP was comparable for all the methods whereas SFE and PLE were the most efficient extraction techniques for the nonionic surfactants. The PLE extraction was found most suitable as a routine method for simultaneous extraction of both types of compounds and was used in a field study of floor dust from 15 Danish schools. The mean concentration of DEHP in the school dust samples was ∼4 times higher than observed in other studies of dust from homes in different countries. The concentrations of nonionic surfactants were one order of magnitude lower than soap and linear alkylbenzene sulfonates measured in other studies of floor dust from offices and other public buildings. However, for the first time nonionic surfactants have been identified in house dust.

A simple selective supercritical fluid extraction (SFE) method was developed for the determination of desorption behaviour of PCBs in sediments. This method was applied to determine the distribution of individual PCB congeners among sites of differing bonding strengths in two Swedish sediments (Lake Järnsjön and Baltic bay Orserumsviken). Four different PCB fractions were distinguished in each sediment by applying consecutively harsher supercritical fluid extraction conditions on the same sample. Even though the two sediments had completely different textures, they showed very similar extraction behaviour. It was shown that, in both sediments, a major part of the PCBs (58% and 65%, respectively) were located at "fast sites", from which they were extractable already with the mildest extraction conditions (60 min, 40 degrees C and 120 bar). Only a small fraction of the PCBs were so tightly bound to the sediments (located at "slow sites"), that they could be extracted only under the harshest conditions (60 min, 150 degrees C and 400 bar). Information of this kind should be of great value for the determination of bioavailability of pollutants in sediments and soils, and it is the author's belief that this technique has the potential to develop into a powerful tool in environmental risk assessment.

A wide range of alcohol and nonylphenol polyethoxylates was determined by separation on a reversed-phase liquid chromatographic column, followed by electrospray ionisation-mass spectral analysis. The compounds were separated chromatographically according to their aliphatic chain length. The mass spectral analysis functioned as a second separation step during which homologues of the ethoxylates were separated according to their polyethoxylate chain length. In this manner a truly orthogonal separation was obtained. The compounds were detected as ammonium complexes. The analysis presented is capable of qualitative and quantitative determination of a large number of ethoxylates as well as their metabolites in a single run. The method was applied to many different sample types, ranging from primary and treated wastewater to sludge. Batches of 50 real samples were routinely analysed without the need for cleaning the mass spectrometer or regeneration of the column. By utilising the extracted mass chromatograms, detection limits of 1 to 10 μg/l could be obtained for individual compounds in water samples, while the detection limits were around 100 μg/kg in sludge, depending on the degree of pollution.

This review updates our knowledge on pressurised liquid extraction, PLE (also known as accelerated solvent extraction and pressurised fluid extraction) of persistent organic pollutants such as polynuclear aromatic hydrocarbons and polychlorinated biphenyls from environmental matrices. The basic experimental set-up is presented, and parameters influencing the extraction process are discussed. PLE can be used for a broad range of applications, and clearly has the potential for replacing tedious classic extraction methods such as Soxhlet extraction.

This review article intends to introduce the possibility of utilizing selective supercritical fluid extraction (SFE) as a tool to study sorption/desorption processes and bioavailability of persistent organic pollutants (POP) in sediment. Sorption/desorption behavior and bioavailability studies of POPs is a large research area, but still many unsolved problems exists. Therefore novel approaches to investigate mechanistic behavior of POPs in sediments are needed. Present literature on SFE points to the fact that selective SFE measurements can improve our knowledge, and recent investigations have been performed that demonstrate this. Results obtained with selective SFE can be connected to desorption of POPs in sediments under natural conditions in aquatic ecosytems. The ultimate goal is to use selective SFE as a way to determine the bioavailable fraction present within a matrix. A few preliminary results are presented here which may serve as a starting point for future studies.

Supercritical fluid extraction (SFE) with pure CO2 was used to quantitatively remove PCBs from historically contaminated sediments without substantially disturbing their bulk organic or inorganic matrix as evidenced by only small or undetectable changes in thermal gravimetric behavior, elemental (C, H, N, S) composition, ionic conductivity, and pH determined before and after SFE. The extracted PCBs were then spiked into water with the parent sediment, and sorption was allowed to occur for up to 18 days. The selective SFE conditions developed in part 1 were used to determine the proportion of PCBs which could be extracted under four conditions of increasing stringency. Comparing the selective SFE behavior of the PCBs from the water/sediment sorption samples to the original historically contaminated sediments demonstrated that 18 days was not sufficient for PCBs to migrate to the “slower” sediment-binding sites (those sites requiring more rigorous SFE conditions), which the PCBs had occupied in the historic...

A simple diffusion model is fitted to selective SFE profiles obtained in Part 1 for native (not spiked) PCBs in historically contaminated sediments and soils. The model takes two types of geometry into consideration, a spherical one (Hot Ball, HB) and a planar one (Finite Slab, FS) and is extended to describe the influence of increasing temperature during the extraction. In this work, soil/sediment organic matter (SOM) is treated as a polymer-like organic material (POM). Consequently, diffusion is considered to be an activated process where the diffusion coefficients depend on the temperature according to the Arrhenius equation. When using one type of POM in the model, the characteristic “temperature humps” obtained in the extraction profiles are simulated relatively well, but at least three types of POM are needed for excellent fits to experimental data. The final model, consisting of three different POMs with spherical geometry, was fitted to all matrixes to estimate diffusion coefficients and activatio...

Supercritical fluid extraction (SFE) conditions using pure CO2 from 40 to 150 °C were developed that allow sequential extraction of PCBs associated with “rapidly desorbing, moderately, slowly, and very slowly desorbing” sites on historically contaminated sediments and soil. Five samples with individual PCB concentrations ranging from a few to ∼100 000 ng/g all showed PCBs associated with each type of site, but the fraction of PCBs associated with rapidly desorbing or slowly desorbing sites varied greatly from sample to sample. Although some small differences in the desorption behavior of individual PCBs was observed from a particular sample, the differences among samples were much greater demonstrating that the sample matrix and not the PCB identity was most important in controlling desorption behavior. When all five samples were compared, simple considerations concerning sample particle size, water content, organic content, and PCB concentration could not predict desorption behavior, demonstrating that P...

The effectiveness of extracting native (not spiked) polychlorinated biphenyls (PCBs) from solid environmental samples by means of pressurized fluid extraction (PFE, Dionex trade name Accelerated Solvent Extraction) according to US Environmental Protection Agency (EPA) Method 3545, was determined. Three different certified reference materials, two sediments and one sewage sludge, were utilized. As opposed to most of the previous investigations, a thorough quantitative determination of the extracts obtained by PFE was performed and compared to certified values. Obtained data were in good agreement with certified values for all materials. However, materials with different particle sizes seemed to have influence on the extraction efficiency, with enhanced extraction for smaller particle size samples. PFE is concluded to be at least as effective as previously used methods in terms of quantitative extraction. When compared to data obtained with supercritical fluid extraction (SFE) using EPA Method 3562, the recoveries where slightly higher. This was explained by the less clean extracts obtained in PFE despite clean-up of the extracts. This is contrary to the clean extracts obtained by SFE which are ready for analysis. It can, however, not be excluded that PFE is really more efficient for extraction of very strongly bound analytes.

A single SFE method for field extraction of PCBs and PAHs in soils was developed for use in combination with capillary GC-ECD or FID without the need for cleanup steps after extraction. The method involves 20-min extractions using pure CO2 at 150°C and 400 bar. GC analysis was performed with 15-min (PCBs) or 22-min (PAHs) temperature programs. The final analytical method was demonstrated in field experiments (with the use of portable power sources) at different waste sites and was shown to give results in excellent agreement with conventional laboratory Soxhlet extraction. The practical determination limits of the method (as concentrations of the 5-g soil samples) without any concentration or cleanup of the SFE extracts was 2≈200 ppb of individual PAHs and 2≈10 ppb of individual PCBs (2≈100 ppb of total PCB as Aroclor 1260) Since the SFE collection solvent was acetone, the extracts were compatible with enzyme-linked immuno-sorbent assay (ELISA). ELISA and GC-ECD determinations of PCBs as total Aroclors agreed within 2≈50% when ELISA was performed in the laboratory. However, ELISA failed to yield useable results when performed outdoors under field conditions.

Trapping efficiencies for selected polychlorinated benzenes, polybrominated biphenyls and polybrominated diphenyl ethers were studied to determine the trapping capability of these and similar compounds in real samples. A study was made of the effect on recovery of supercritical fluid extraction (SFE) temperature, pressure, flow-rate, addition of modifier, types of solid phase trapping material and elution parameters. Florisil and ODS, used as trapping materials, both produced satisfactory recoveries (>95%) for most compounds under optimised conditions, but the performance of Florisil was less dependent on SFE flow-rate. At higher flow-rates, ODS gave lower recoveries of the chlorinated benzenes and it generally could not trap the dichlorobenzenes, which Florisil recovered up to 95%. When pure CO2 was used at constant flow-rate, change in the SFE conditions did not significantly affect the trapping efficiency. Experiments with modifiers showed good recoveries with a trap temperature close to or above the boiling point of the modifier. Sequential SFE was applied to extract chlorinated and brominated organic pollutants from nine sediments. 80%–95% of the total SFE recovery was obtained with CO2 alone, and further recovery with addition of modifier. The recovery varied with the sediment, indicating that the usefulness of the modifier depends on the sample matrix. Altogether, 46 analytes were quantified in the sediment extracts in one run at levels down to 10 pg/g using two-channel GC with electron-capture detection. Polychlorinated biphenyls and common pesticides such as p,p′-DDE, p,p′-DDD and p,p′-DDT were found to be the most abundant pollutants in all sediment samples. Polybrominated aromatic compounds also were found in all samples, with the highest levels for dibromodiphenyl ether, polybrominated biphenyl 52, pentabromodiphenyl ether, 2,3,7,8-tetrabromodibenzo-p-dioxin and 2,3,4,7,8-pentabromodibenzofuran. Levels in Baltic Sea area sediments were in the low ppb (ng/g) range. The use of two capillary columns of different polarity greatly decreased the number of errors arising from coeluting compounds.

Three HRGC systems (1: 30m DB-XLB capillary with MS-SIM detection; 2: 60m DB-XLB capillary with full-scan, ion-trap MS detection; and 3: Parallel dual-column DB-17 and series-coupled HP5/HT5 with ECD detection) were used to completely characterize multiple lots of 8 different-numbered Aroclor mixtures by quantitative calibration against 9 solutions containing primary standards of all 209 PCB congeners. Despite lower absolute sensitivity and more Aroclor congener coelutions than the dual-column ECD system, the MS systems enabled measurement of more congeners per Aroclor since their greater linear response range did not require dilution of samples and standards. Pairs of different lots of Aroclors 1248 and 1254 displayed markedly different proportions of congeners, and the 1254 pair displayed strong differences in the extent of ortho-chlorine substitution. The tables of congener weight percent distributions among Aroclors are more comprehensive and quantitatively precise than those of prior publications. However, the limitations of single-level calibration precluded measurement of all congeners to the ±10% accuracy desirable for establishing these Aroclors as secondary standards for comprehensive, quantitative congener-specific PCB analysis.

Two certified reference materials, an industrial soil (CRM 481) and a river sediment (NIST 1939), were extracted by subcritical water at 50 atm and temperatures ranging from 50 to 300{degree}C. The extraction efficiency of PCBs is extremely dependent on water temperature, since the polarity (dielectric constant) of water can be dramatically lowered by raising the water temperature. While only traces of PCBs were extracted at 50 and 100{degree}C, quantitative PCB removal was reached at 250 and 300{degree}C. The extraction rate of subcritical water extraction is fast. For example, the largest quantities of all of the PCBs were extracted during the first 15 min at 250 or 300{degree}C (at liquid conditions). However, when the pressure was reduced to 50 atm at 300{degree}C (steam), the extraction was completed in less than 5 min. The recoveries reached by water extraction at 250-300{degree}C and 50 atm compare favorably to the certified values for both samples. The construction of an extraction/ collection system that allows quantitative extraction of PCBs with collection in a few milliliters of organic solvent is described. 41 refs., 4 figs., 4 tabs.

This review focuses on recent attempts to understand the SFE process and on applications of that understanding to increase SFE recoveries of pollutants from environmental solids. Methods to decrease restrictor plugging and to increase the collection efficiencies of extracted analytes are evaluated. Approaches to obtain quantitative extractions include fluid choice, extraction flow-rate, modifiers, pressure and temperature are presented as is the potential for SFE to extract ionic and metals. Finally, the need for a better definition of “quantitative” extraction and the use of SFE in certification exercises for complex environmental samples is discussed.

A method for the interference-free analysis determination of polychlorinated biphenyl (PCB) congeners in sewage sludge in less than 2 h with quantification limits down to 10–20 ppb (w/w) is presented. Evaluations were made of four different trapping materials for the supercritical fluid extraction of PCBs from sewage sludge. The influence of modifiers at different concentrations and temperatures was studied for different trapping materials with respect to their trapping efficiency with spiked samples.

Although PCB in caulking materials has been forbidden for many years in most of Europe, including Denmark, there has been continued interest to measure PCB levels in the air of contaminated buildings and blood of the occupants (Mengon and Schlatter 1993, Fromme et al. 1996, Ewers et al. 1998, Currado and Harrad 1998, Gabrio et al. 2000). The relatively low priority for investigations of this contamination is probably due to the small quantities inhaled compared to exposure via food, and the rapid metabolism of the most volatile congeners demonstrated by low concentrations of all congeners in the blood of exposed persons (Ewers et al. 1998, Gabrio et al. 2000). There is, however, evidence that PCB containing caulking materials have been used even during the '90s (Fromme et al. 1996). In Denmark, it is estimated that 75 t PCB is still in buildings (Organization of Sealant Branch's Manufacturers and Distributors 2000). During an investigation of dust from buildings with excessive microbial growth (including 35 rooms from 9 buildings), the analysis of semivolatile compounds by thermal desorption-GC/MS of samples from a single building surprisingly revealed large amounts of PCBs containing 3, 4 and 5 chlorine atoms, 10-20 times the amounts found in samples from other buildings. Extraction of the dust by SFE followed by GC/ECD analysis for 12 PCB congeners showed that there was approximately 20 times the total PCB concentrations in dust from the polluted building compared to the levels in the other buildings. Subsequent headspace analysis of caulking material from the polluted building revealed this to be the source. Shelf dust functions as a passive sampling medium and, thus, can be used as a screening method to detect PCB and other semivolatile pollution indoors.

The congener-specific analysis of polychlorinated biphenyls (PCB) by high resolution gas chromatography on a 50 m × 0.25 mm fused silica column coated with a 0.26 μm film of 5% diphenyl polydimethylsiloxane (CPSil-8) has been significantly improved by series coupling with a 25 m × 0.22 mm column coated with a 0.10 μm film of 1,2-dicarba-closo-dodecarborane polydimethylsiloxane (HT-5). Using helium as carrier gas, a total of 64 congeners in technical PCB mixtures could be analyzed as resolved peaks by ECD (86 by MS) with the CPSil-8 column, and 84 by ECD (108 by MS) with the combination. The high upper temperature limit for these stationary phases (>300°C) enabled fast temperature programming and rapid analysis (60 min).

Static extraction, supercritical fluid extraction (SFE), pressurized liquid extraction (PLE) and Soxhlet extraction were compared for simultaneous extraction of di(2-ethylhexyl) phthalate (DEHP) and nonionic surfactants from house dust. Homogenized office floor dust from a vacuum cleaner dust bag ("standard dust") was used for the evaluation. One portion of the extracts was used for analysis of nonionic surfactants with LC-MS and another portion was used for DEHP analysis with GC-MS. The extraction yield of DEHP was comparable for all the methods whereas SFE and PLE were the most efficient extraction techniques for the nonionic surfactants. The PLE extraction was found most suitable as a routine method for simultaneous extraction of both types of compounds and was used in a field study of floor dust from 15 Danish schools. The mean concentration of DEHP in the school dust samples was approximately 4 times higher than observed in other studies of dust from homes in different countries. The concentrations of nonionic surfactants were one order of magnitude lower than soap and linear alkylbenzene sulfonates measured in other studies of floor dust from offices and other public buildings. However, for the first time nonionic surfactants have been identified in house dust.

Two developed supercritical fluid extraction (SFE) methods [one for the determination of total petroleum hydrocarbon (TPH) and polychlorinated biphenyls (PCBs), and one for polycyclic aromatic hydrocarbons (PAHs) and creosote components in soil] were evaluated in a Nordic laboratory intercomparison study with 11 participating laboratories. The interlaboratory comparison showed that excellent recoveries can be obtained with SFE for PAHs and PCBs compared to the solvent extraction. For the TPH, the recoveries were significantly higher than those achieved with solvent extraction. The accuracy, expressed as the relative standard deviation, was higher than expected (generally 8-25% for PAHs, 6-20% for PCBs and less than 18% for TPH with a few very high values, especially for PCBs), but not different from the other intercomparison studies. Difference between liquid- and solid-phase collection in SFE was found to be significant only for more volatile PAH components such as naphthalene and fluorene. For PCBs and TPH, there were some variation in the results obtained with the two trapping methods.

Two extraction methods that independently have been developed on conceptually different automated supercritical fluid extraction systems, ISCO SFX 3560 (syringe pump and liquid trapping) and Hewlett-Packard 7680T SFE (reciprocating pump and solid-phase trapping), were compared for the extraction of polychlorinated biphenyls from two Swedish sediments. The results demonstrated that the high-temperature ISCO method in some cases yields a more exhaustive extraction, but also less clean extracts due to co-extraction of unwanted matrix components which are all present in the trapping solvent. The medium-temperature Hewlett-Packard method may sometimes cause problems with quantitative recoveries, but on the other hand it yields very clean extracts due to the extra selectivity resulting from collection on a solid-phase trap.

Supercritical fluid extraction (SFE) was compared to traditional Soxhlet extraction for the determination of polychlorinated biphenyl congeners in three standard reference materials: SRM 1941a (Organics in Marine Sediment), SRM 1944 (New York/New Jersey Waterway Sediment) and SRM 2974 [Organics in Mussel Tissue (Mytilus edulis) (Freeze-Dried)]. The concentrations determined using SFE compared well with the certified concentrations for the majority of the polychlorinated biphenyl congeners.

The mono-ortho chlorobiphenyls (CBs) 60, 74, 114, 123, 157, 167 and 189 were determined in Aroclor mixtures and aquatic organisms by multidimensional gas chromatography with electron capture detection (MDGC/ECD), using a combination of an Ultra 2 and an FFAP column. MDGC/ECD is recommended as the most suitable technique for direct determination of these CBs, without a liquid chromatographic (LC) pre-separation of mono-ortho CBs from the other CBs. Dependent, to some extent, on the stationary phase used, single-column determinations of these CBs easily yield too high results due to the presence of interferences. The contribution of the mono-ortho CBs studied to the total 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) equivalents (TEQs) from CBs in fish is highly dependent on the toxic equivalency factors (TEFs) used and varies between 0.02 and 22%. This contribution is mainly due to CBs 74, 114, 157 and 167 which may easily be determined by taking three heart-cuts and combining them into one MDGC/ECD run. The analytical error is negligible compared with the huge uncertainty of the TEFs. A need for more precise TEFs is emphasized. © 1995.

A method for the rapid interference free analysis of polychlorinated biphenyl congeners (chlorinated biphenyls, CBs) in lyophilized fish tissue is presented. The method was developed on a lyophilized tuna muscle tissue that contained 2.8% lipid (dry mass based), and native CB concentrations in the range of 3–84 ng/g. Sample preparation was made by supercritical fluid extraction using pure CO 2 as extraction fluid. Analysis by high-resolution gas chromatography-electron-capture detection analysis was carried out with on-column injection on two parallel coupled columns, a 60 m DB-17 column and a series combination of a 25 m SIL-8 column and a 25 m HT-5 column. Supercritical fluid extraction was compared with Soxhlet extraction and found to give quantitative recoveries, detection limits of 0.5–2 ng/g and standard deviations of less than 5% on average. The developed method was confirmed on nine different lyophilized fish samples which contained 6.1–26.5% lipid (dry mass based), and native CB concentrations in the range 0.8–134 ng/g.

Reaction of the geminal α,α-dichloroketones (3) and (5) with the 4,5-dimercapto-1,3-dithiole-2-thionedianion (2) yields the spiro 1,3,4,6-tetrathiapentalene-2-thiones (4) and (6). The structure of 1,3,4,6-tetrathiapentalene-2-thione-5-spiro-3'-benzo[c]furan-1'-(3H-one (4) was determined by X-ray crystallography