Imposex and organotin contamination in Nassarius reticulatus (L.) along the Portuguese coast

Nassarius reticulatus (whelk) imposex levels and organotin body burden (b.b.) were surveyed along the Portuguese coast, from Vila Praia de Âncora (northern limit) to Lagos (southern limit), between May and August 2003. The percentage of females affected with imposex (%I), the relative penis length index (RPLI), the vas deferens sequence index (VDSI) and the degree of female oviduct convolution index (AOS) were used to assess the level of imposex at each site. These imposex indices were determined for 23 sampling stations throughout the coast and were in the range 0.0–100%, 0.0–90%, 0.0–5.0 and 0.0–1.3 respectively. Sterile females (i.e. females carrying aborted egg capsules inside the capsule gland) were found inside the harbours of Viana do Castelo (8.5%) and Aveiro (3.7%). Organotin compounds were assessed at 10 sampling sites spread along the coast. Tributyltin (TBT) b.b. in females varied between 39 and 1679 ng g^?1 (as tin) dry weight, and dibutyltin (DBT) and monobutyltin (MBT) varied in the ranges 23–1084 ng g^?1 (as tin) d and 18–939 ng g^?1 dry wt respectively. Among the butyltins, the major fraction corresponded to TBT (47.4%), followed by DBT (27.6%) and MBT (25.0%), which indicates recent TBT inputs. Triphenyltin (TPT) levels ranged from <5 to 21 ng g^?1 (as tin), and, when quantifiable, represented on average 10% of that of TBT. TPT was the dominant phenyltin and was detected in 60% of the sampling stations. The imposex was significantly correlated to ln (TBT) (Spearman r = 0.918, p < 0.001 for RPLI; r = 0.864, p < 0.001 for VDSI; r = 0.828, p < 0.01 for AOS). The higher levels of imposex and TBT contamination occurred inside or close to harbours, which we identified as ‘hotspots’ of pollution along the coast. Comparing the results obtained in the current work with those reported in a similar survey in 2000, imposex and TBT b.b. varied locally but did not reveal any global trend in the variation of TBT pollution along the Portuguese coast over the 3 year period. Copyright © 2005 John Wiley & Sons, Ltd.     

Organotin contamination,imposex and androgen/oestrogen ratios in natural populations of Nassarius reticulatus along a ship density gradient

Levels of organotin body burden (expressed as tin), imposex and steroid hormones (testosterone, 17β‐oestradiol, testosterone glucuronide and sulfate conjugates) were investigated in natural populations of Nassarius reticulatus in the Ria de Aveiro (northwest Portugal) between 1997 and 1999. The tributyltin (TBT) whole body burden (b.b.) of females presented increasing gradients from the adjacent open coast (16–26 ng g^?1 dry weight (d.w.)) towards the ports inside the Ria de Aveiro (195–272 ng g^?1 d.w.). Triphenyltin b.b. was only detected at the most polluted port (22 ng g^?1 d.w.). Imposex also presented increasing values from the adjacent coast (vas deferens sequence index (VDSI): 0.0–0.5; relative penis length index (RPLI): 0.0–2.4; penis length index (PLI): 0.0–0.3 mm; percentage of affected females (%I): 0–30) towards the ports (VDSI: 3.8–4.8; RPLI: 51–80; PLI: 6.7–10.8 mm; %I: 100). The testosterone levels in females without imposex were always lower than in females with imposex, and the ratio of testosterone/17β‐oestradiol in females tended to increase with increasing imposex and organotin contamination. In spite of the large difference in the female testosterone and 17β‐oestradiol levels between summer and winter, related to the reproductive cycle, the spatial trend of the testosterone/17β‐oestradiol ratio was remarkably similar in shape and values in the two seasons. Imposex was significantly correlated with the TBT b.b. and the testosterone/17β‐oestradiol ratio in females. The testosterone conjugate levels did not show any clear pattern with the increasing values of imposex and TBT contamination. Copyright © 2005 John Wiley & Sons, Ltd.     

Imposex in Sea Snails,Caused by Organotin (Tributyltin and Triphenyltin) Pollution in Japan: a Survey

A country-wide survey and laboratory experiments on imposex (a superimposition of male sex organs on female sea snails) in Japanese sea snails were carried out: 38 species were observed to be affected by imposex. For the rock shell, Thais clavigera , the percentage occurrence of imposex was 100% at almost all sites surveyed. The degree of imposex seemed to be positively correlated with the concentrations of tributyltin (TBT) and triphenyltin (TPT) in the species. The results of laboratory experiments showed that imposex in T. clavigera was initiated and promoted by both TBT and TPT. Many oviduct-blocked individuals, which were thought to be sterile, were observed in T. clavigera at sites near marinas and harbours. The effects of organotin pollution on the population of T. clavigera were observed at the sites near marinas. From the results of the additional country-wide survey on imposex in T. clavigera during 1993–1995, serious organotin pollution and imposex symptoms in the species are still continuing in Japan. © 1997 by John Wiley & Sons, Ltd.     

Search for triorganotins along the Mar del Plata (Argentina) marine coast: finding of tributyltin in egg capsules of a snail Adelomelon brasiliana (Lamarck, 1822) population showing imposex effects

Cases of imposex were clearly identified in Adelomelon brasiliana living in the Mar del Plata (Argentina) coastal area; percentages as high as 50.0% were determined among the samples studied. These were the first reported cases of ocurrence of imposex in this type of gastropod. Since this is one of the known tributyltin (TBTs) effects, and no previous reports of determination of TBTs in gastropods eggs were found, methods were developed for the speciation and quantitative determination of organotins in A. brasiliana egg capsules. Determination of organotins in samples collected in the Mar del Plata area showed contents of tributyltin chloride (TBT) as high as 400 ng l^?1 in water and 6.50 µg g^?1 in sediments of areas of intensive boat traffic. The results showed the presence of TBT in the egg capsules of A. brasiliana at three different instars (range 0.264–1.86 µg per egg). As far as we know, this is the first report of the finding of TBT in gastropod egg capsules. Copyright © 2004 John Wiley & Sons, Ltd.     

Tributyltin biomonitoring using prosobranchs as sentinel organisms

Tributyltin (TBT) compounds, some of the most toxic xenobiotics, produce a variety of pathological reactions in animals. A reliable biomonitoring method to assess the degree of environmental TBT pollution has been described based on investigations of virilization phenomena in prosobranch snails (Mollusca: Gastropoda). Examples are the imposex phenomenon in marine and freshwater species, the intersex reaction in littorinids and the reduction of female sexual glands and offspring numbers in further species resulting mainly in a sterilization of females. The degree of imposex or intersex in populations is determined by different biomonitoring indices which allow to assess the TBT pollution of the environment at low costs with high precision. The effectiveness of TBT legislations is analysed by extensive surveys in France and Ireland indicating that there is still a continuing threat to sensitive marine organisms. TBT disturbs the biosynthesis of steroid hormones on the level of estrogen biosynthesis. The observed virilization phenomena seem due to an inhibition of the cytochrome P-450 dependent aromatase by this organotin compound.     

Tributyltin biomonitoring using prosobranchs as sentinel organisms

Tributyltin (TBT) compounds, some of the most toxic xenobiotics, produce a variety of pathological reactions in animals. A reliable biomonitoring method to assess the degree of environmental TBT pollution has been described based on investigations of virilization phenomena in prosobranch snails (Mollusca: Gastropoda). Examples are the imposex phenomenon in marine and freshwater species, the intersex reaction in littorinids and the reduction of female sexual glands and offspring numbers in further species resulting mainly in a sterilization of females. The degree of imposex or intersex in populations is determined by different biomonitoring indices which allow to assess the TBT pollution of the environment at low costs with high precision. The effectiveness of TBT legislations is analysed by extensive surveys in France and Ireland indicating that there is still a continuing threat to sensitive marine organisms. TBT disturbs the biosynthesis of steroid hormones on the level of estrogen biosynthesis. The observed virilization phenomena seem due to an inhibition of the cytochrome P-450 dependent aromatase by this organotin compound.     

Time course of expression of the retinoid X receptor gene and induction of imposex in the rock shell, Thais clavigera, exposed to triphenyltin chloride

To examine the role of the retinoid X receptor (RXR) in the development of imposex in gastropods, we investigated the time course of expression of the RXR gene in various tissues (ctenidium, ovary or testis, digestive gland, penis-forming area or penis, and head ganglia) of female and male rock shells (Thais clavigera) exposed to triphenyltin (TPT) in a flow-through exposure system for 3 months. Accumulations of TPT in tissues were clearly observed in exposed individuals, whereas no accumulation of TPT was observed in the control groups. In females, 3-month exposure to TPT resulted in the development of imposex, and penis lengths in imposex-exhibiting females were significantly longer in small females (shell height <20 mm) than in large females (shell height ≥20 mm). RXR gene expression in the ovary, penis-forming area or penis, and head ganglia of females exposed for 3 months was significantly higher than expression in control females, and the highest RXR gene expression was found in the penis-forming area or penis. Moreover, RXR gene expression in the penis-forming area or penis of each female exposed to TPT seemed to be associated with an increase in penis length. In males, the ratio of penis length to shell height was significantly larger in the exposed groups than in the controls. Although RXR gene expression in males exposed for 3 months was not significantly higher than expression in control males in any tissues, the highest gene expression was observed in the penis of exposed males. These results suggest that RXR plays an important role in the development of male genitalia (i.e., penis and vas deferens) in gastropods, although RXR might also have other physiological functions.      

Distribution and fate of tributyltin in the united states marine environment

Tributyltin (TBT) has been measured in water in 12 of 15 harbors studied during US Navy baseline surveys. The highest concentrations of TBT (some exceeding laboratory toxicity limits) have been found in yacht harbors and near vessel repair facilities. Many sites (75%) in harbors and estuaries had no detectable (<5 ng dm^?3) TBT. TBT monitoring studies with increased detection limits (<1 ng dm^?3) have documented a high degree of TBT variability associated with tide, season and intermittent point source discharges. Although yacht harbors were shown to be the principal TBT source in most regions, dry-docks can be significant sources. Tributyltin degradation studies were conducted using unfiltered seawater from four geographic regions and incubated under natural conditions. Degradation half-lives were always in the range of 4–19 days, providing evidence that TBT is not highly persistent in the water column at environmental concentrations. Preliminary degradation experiments suggest that TBT has a longer residence time in sediment with a half-life of several months. Tributyltin is primarily in the dissolved form in unfiltered seawater, although the association with particulate fractions may increase in samples collected near yacht repair facilities, Partition coefficients for particulate TBT versus bulk water are frequently near 3000 and vary with the particulate concentration, salinity and presence of natural organics.     

Tributyltin levels in French Mediterranean coastal waters

Tributyltin (TBT) and its degradation products were measured in seawater samples in 1988 and 1989 at different locations of the French Mediterranean coast, including harbours, marinas and mariculture areas. Higher levels of TBT contamination were found in harbour (2–833 ng dm^?3) and marina waters (18–736 ng dm^?3) compared with mariculture areas (<2–111 ng dm^?3). Geographical distribution of TBT degradation products showed that a TBT hot spot finally results in a diffuse contamination of dibutyltin (DBT) and monobutyltin (MBT), even far distant from input areas.     

Hepatic butyltin concentrations in beluga whales (Delphinapterus leucas) from the St Lawrence Estuary and northern Quebec,Canada

Butyltin (tributyltin TBT; dibutyltin DBT and monobutyltin MBT) speciation was measured in the liver of beluga whales from the St Lawrence Estuary and Hudson Strait (northern Quebec). Using GC–MS, liver samples were analysed from 21 beluga whales found dead, stranded along the shores of the St Lawrence during the period 1995–1998. In all cases, including a neonate specimen, the liver was contaminated with butyltin compounds with concentrations in the range 0.04–2.1 mg Sn kg⁻¹ on a dry weight basis. Liver samples of five beluga whales from Hudson Strait obtained in the summer of 1998 were also analysed. For these animals, hepatic butyltin concentrations were consistently below the detection limit (<0.5 ng Sn g⁻¹ for MBT and <0.2 ng Sn g⁻¹ for DBT and TBT). Compared with published data on the contamination by TBT of the marine mammals of the St Lawrence in 1988, these contemporary results clearly indicate that the level of contamination of the beluga whales in this coastal marine ecosystem has not decreased ten years after regulating the use of TBT‐based antifoulants on small craft. Copyright © 2000 John Wiley & Sons, Ltd.     

Emission to air of volatile organotins from tributyltin‐contaminated harbour sediments

An analytical method for determining the presence in air of volatile forms (e.g. chlorides) of tributyltin (TBT) and that of methylbutyltins Me _nBu_(4?n)Sn (n = 1–3) was developed and used to establish whether dredged harbour sediments contaminated with TBT served as sources of air pollution with respect to organotin compounds. The method was based on active sampling of the air being analysed and sorption of analytes onto Poropak‐N. Sorbed methylbutyltins were extracted with dichloromethane and analysed by gas chromatography using flame photometric detection. Other butyltins were converted into butyltin hydrides prior to analysis by gas chromatography. It was shown that TBT‐contaminated sediments from Marsamxett Harbour, Malta, placed in 0.5 l chambers through which air was displaced by continuous pumping for 11 days released mainly methylbutyltins, with concentrations (as tin) reaching maximum 48 h mean values of 8.7 (Me₃BuSn), 22.1 (Me₂Bu₂Sn) and 93.0 ng m^?3(MeBu₃Sn) being measured. Other volatile forms of TBT, dibutyltin and monobutyltin were detected in the headspace air, but very infrequently and at much lower tin concentrations (<2 ng m^?3). It was also shown that methylbutyltins dissolved in sea‐water ([Sn] = 0.2 to 400 ng l^?1) were very difficult to exsolve from this medium, even on prolonged evaporation of the solutions using mechanical agitation and active ventilation. The results suggest that emission of methylbutyltins from contaminated sediments probably occurs only from the surface of the material. The environmental implications of these findings in the management of TBT‐polluted harbour sediments are discussed. Copyright © 2002 John Wiley & Sons, Ltd.     

Organometallic complexes with biological molecules: XVI. Endocrine disruption effects of tributyltin(IV)chloride on metamorphosis of the ascidian larva

The effects of tributyltin(IV)chloride (TBT) on the metamorphosis of ascidian larvae of Ciona intestinalis, 2 h after hatching, were investigated. Ascidians are protochordates that lack thyroid follicles and possess thyroid hormones (THs) and their precursors, 3‐monoiodo‐tyrosine (MIT) and 3,5‐diiodo‐tyrosine (DIT), in their endostyle. According to recent findings, these hormones are also present at larval stages, localize in mesenchymal cells and their function seems to be mainly related to larval transformations. Here, we investigate the effects of TBT on thyroxine (T₄) content and localization by exposing larvae of C. intestinalis for different times to TBT concentrations known to block metamorphosis. The result is a blocking of the retraction of the tail, and larval immobility. As detected by immmunohistochemistry, in normal larvae, T₄ is found in all mesenchymal cells spread out in the body cavity, under the adhesive papillae and around the intestine. By contrast, in larvae exposed to 10^?5 M and 10^?7 M TBT, T₄ is detected only in 5% and 25% of total mesenchymal cells respectively. Radioimmunoassay shows a 70% decrease of T₄ content in TBT‐exposed larvae, with respect to unexposed larvae. In addition, neosynthesis of THs is inhibited. Even if parallelism does not exist between the endocrine systems of invertebrates and vertebrates, however, a close similarity exists for functions such as reproduction and metabolism. Our results indicate that TBT could behave as an endocrine disrupter (ED) in ascidians and could impair T₄ metabolism. These findings suggest that the ED activity of TBT could be conserved from invertebrates to vertebrates. Copyright © 2001 John Wiley & Sons, Ltd.     

Degradation of dibutyltin in sea water by pyoverdins isolated from Pseudomonas chlororaphis

The yellow compounds pyoverdins were isolated from Pseudomonas chlororaphis, which was isolated from mud in Japan. Degradation of tributyltin (TBT), dibutyltin (DBT), and monobutyltin (MBT) by pyoverdin (20 mg) was carried in sea water (30 ml) containing a 6 µg l^?1 concentration of TBT, DBT, and MBT at 24 °C for 24 h in aerobic conditions. TBT, DBT, and MBT in sea water were analyzed by gas chromatography–mass spectrometry in selected ion monitoring mode. DBT in sea water was degraded to MBT by pyoverdins isolated from P. chlororaphis. However, TBT and MBT in sea water was not degraded by pyoverdins. The optimum degradation of DBT in sea water was at pH 4.8–8.2, at a temperature 25–30 °C. Copyright © 2002 John Wiley & Sons, Ltd.     

Chemical profiling and anti-psoriatic activity of methanolic extract of Andrographis nallamalayana J.L.Ellis

Andrographis nallamalayana is being widely used as tribal medicine in the treatment of leucoderma and mouth ulcers. Chemical profiling of methanolic extract of the whole plant (PE), using GC–MS and LC–MS, revealed the presence of compounds viz. α-tocopherol, β-sitosterol, tetradecanoic acid, monostearin, flavones/flavanones and their glycosides, chromones, etc. Topical application of imiquimod on the dorsal portion of male BALB/C mice resulted in the development of psoriatic symptoms (erythema, scaling, thickening and folding) with a mean disease activity index (DAI) of >7.0. Topical treatment with 100-μL PE (~6.4%/12.8%) formulations, for 12-days, resulted in the alleviation of disease symptoms. Compared to water-based formulations, emu oil-based formulation, PE400EO was found more effective in reducing the mean DAI (>84%), keratinocyte count (>65%) (p < 0.01) and interleukin-22 (~70%) (p < 0.05). We report, for the first time, anti-psoriatic activity of A. nallamalayana having great potential in developing a potent phytomedicine against psoriasis.     

Cardanol-based bisbenzoxazines

A new class of thermoset polymers was synthesized based on agrochemical renewable cardanol—a by-product of cashew nut industry. A solventless synthesis of bisbenzoxazine monomers based on bisphenol-A (b) and aniline (abbreviated as Bzb-A) and cardanol (c) with diamines namely bis-(4-(4-aminophenoxy)phenyl)ether (HP), bis-(3-(4-aminophenoxy)phenyl)ether (HM), 4,4′-diaminodiphenylsulphone (DDS) and 2,2-bis(4-(4-aminophenoxy)phenyl)propane (BA) was carried out. The benzoxazine monomers (Bzc-HP, Bzc-HM, Bzc-DDS and Bzc-BA) were characterized by ¹H-NMR and FTIR spectroscopy. The curing exotherm depended on the structure of the monomers. The onset curing temperature (T _o) was lowest for Bzb-A (460 K) and highest in Bzc-HM (518 K). The decomposition temperature for 5% mass loss (T _5%) of resins followed the order PBzb-A < PBzc-DDS < PBzc-BA < PBzc-HM ≈ PBzc-HP. The materials showed their potential as adhesives. Lap shear strength on steel plates followed the trend PBzc-DDS < PBzc-HM < PBzc-BA < PBzc-HP.     

A study of the partitioning and sorptive behaviour of butyltins in the aquatic environment

This study was designed to investigate the partitioning and sorptive behaviour of tributyltin(TBT), and its degradation products dibutylitin (DBT) and monobutyltin (MBT), in the aquatic environment. Factorial experiments were undertaken to determine the importance of pH and particulate matter concentration in the sorption of butyltin compounds to solid phases. Results indicate that in freshwaters MBT, and to a lesser extent TBT, will be partitioned towards the particulate phase, whereas DBT exhibits a 50:50 partitioning between particulate and solution phases. In estuarine waters, whilst MBT will almost exclusively sorb on to particulates, TBT will be predominantly in the solid-phase fractions but 10–30% may remain in solution. DBT, in contrast, is solubilized in estuarine waters. A more detailed investigation of TBT sorption and particulate matter concentration was undertaken using adsorption isotherms on different sediment types. The results from batch isotherm tests plotted according to the Freundlich adsorption model revealed that TBT adsorption varied with sediment type, increasing in the order sandy-silt < silty-sand < silty-clay. TBT sorption was found to be reversible, indicating that contaminated sediments may release TBT to overlying waters following sediment distrubance. Interstitial water partitioning studies indicate that TBT predominates in the particulate phase with partition coefficients for TBT higher than for DBT and MBT. The TBT partition coefficient in interstitial waters appears to be related to total organic carbon loadings.     

Zur oxidativen Addition von 1-Halogenalk-1-inen – Synthese und Struktur von Phenylalkinylpalladium-Komplexen

On the Oxidative Addition of 1-Halogenalk-1-ynes – Synthesis and Structure of Phenylalkynylpalladium Complexes [Pd(PPh₃)₄] ( 2 ) reacts with IC≡CPh and ClC≡CPh in the sense of an oxidative addition to give trans-[Pd(C≡CPh)X(PPh₃)₂] (X = I: 3 a , X = Cl: 3 b ). As side products trans-[PdX₂(PPh₃)₂] (X = I: 4 a , X = Cl: 4 b ; < 10%) and PhC≡C–C≡CPh ( 5 ; X = I: ca 30%, X = Cl: < 4%) are formed. 3 a and 3 b were characterized by NMR (¹H, ¹³C, ³¹P) and IR spectroscopies as well as by X-ray single-crystal structure analyses. In the crystals of 3 a and 3 b isolated molecules were found. The Pd–C≡C–Ph unit is linear in 3 a and approximately linear in 3 b [Pd–C≡C 174.2(6)°, C≡C–C 179,0(7)°].     

Accumulation and toxic effect of organometallic compounds on algae

This paper reports toxic effects and bioaccumulation factors of organometallic compounds, mainly organotin species, on algae. We selected two species of microalgae as test algae: one was Scenedesmus obliquus as a representative of fresh-water algae, the other Dunaliella salina and Dunaliella viridis, to represent commonly mixed algae which exist abundantly in Tianjin Harbor, People's Republic of China. For comparison, Chlorella vulgaris was also used in this study. The toxic effect of ten organometallic compounds on the freshwater alga, S. obliquus, was investigated. The ten compounds were (as chlorides) tributyltin (TBT); triphenyltin (TPT); trimethyltin (TMT); dibutyltin (DBT); diphenyltin (DPT); dimethyltin (DMT); trimethyl-lead acetate (TML); dimethyl-arsine (DMA) and two new mixed-alkyltin pesticides, dicyclohexylmethylitin acetate (Cy₂MTA) and dicyclohexylmethyltin isobutyrate (Cy₂MTB). The order of toxicity of these compounds in fresh-water algae, S. obliquus, was TBT>TPT>DBT> Cy₂MTA=TML> Cy₂MTB>DPT>TMT>DMA>DMT, according to 96 h EC₅₀ values attained. The ten toxicants were divided into three groups according to the sequence of their toxicities; (a) TBT, TPT; (b) DBT, Cy₂MTA, TML, Cy₂MTB; (c) DPT, TMT, DMA, DMT. In each group the EC₅₀ values of each compound were quite similar. The difference of EC₅₀ values between two vicinal groups was approximately one order of magnitude. The bioconcentration factor (BCF) of TBT and TPT compared with water in the freshwater alga S. obliquus was >3.32 × 10⁵ and 1.14 × 10⁵, respectively. The BCF of the marine mixed algae was >3.48 × 10⁵. The marine microalga, Chlorella vulgaris, was adaptable to TBT at lower concentration. TBT at high concentration only inhibited the growth of S. obliquus, but it could cause chlorosis anddisintegration of D. salina and D. viridis. Resistance to toxicity of algae against TBT appears in order as follows: C. vulgaris>S. obliquus>D. salina and D. viridis. TBT was metabolized by algae to a less toxic product, DBT. The existence of algal cells accelerated the concentration reduction of TBT. The toxic mechanism of TBT was also studied.     

Selective non-chromatographic determination of tributyltin in sediments using EDTA and diphenylcarbazone as masking agent

Two analytical procedures based on the generation of volatile tributyltin derivatives, their separation by headspace solid-phase microextraction (HS SPME) and subsequent determination using plasma optical emission spectrometry (OES) have been developed for the selective determination of trace tributyltin (TBT) in the presence of other butyltins and inorganic tin in sediments without the use of chromatography. A microwave-assisted leaching of tin compounds from the sediment using 25%_v/v acetic acid is applied for sample pretreatment. The first method takes advantage of TBT chloride releasing from the lecheate after adding 3 M hydrochloric acid, and subsequent separation of the analyte by HS SPME using Carboxen-poly(dimethylsiloxane) (CAR/PDMS). The second method involves the use of masking agents, namely ethylenediaminetetraacetic acid (EDTA) and diphenylcarbazone (DFC), which form stable chelates with monobutyltin (MBT) and dibutyltin (DBT), respectively, followed by the ethylation of tributyltin at pH 5 using sodium tetraethylborate (NaBEt4) solution. The final concentration of NaBEt4 is 0.05%_w/v. The parameters affecting the TBT derivatisation and separation by HS SPME have been optimised including the selection of SPME fibre coating (PDMS, CAR/PDMS), the amount of masking agents and NaBEt4 added, sorption time (2–40 min) and sorption temperature (25–60°C). Higher sensitivity and robustness are attained with the method involving ethylation derivatisation, leading to the limit of detection (LOD) of 3 ng L^?1. The selective release of TBT is observed from aqueous solutions, where the concentrations of MBT and DBT were in 2–50-fold excess to TBT. The SPME-TD-MIP-OES methods have been validated against several certified reference materials (CRMs), including SOPH-1 marine sediment, PACS-2 marine sediment and BCR 646 freshwater sediment.     

Donor–acceptor‐structured naphtodithiophene‐based copolymers for organic thin‐film transistors

New donor–acceptor (D‐A) polymers, poly(4,5‐bis(2‐octyldodecyloxy)naphto[2,1‐b:3,4‐b']dithiophenebenzo[c][1,2,5]thiadiazole) (PNDT‐B) and poly(4,5‐bis(2‐octyldodecyloxy)naphto [2,1‐b:3,4‐b′]dithiophene‐4,7‐di(thiophen‐2‐yl)benzo[c][1,2,5]thiadiazole) (PNDT‐TBT), with the extended π‐electron delocalization of naphtho[2,1‐b:3,4‐b']dithiophene, were successfully synthesized by Suzuki and Stille coupling reactions. The structure and physical properties of polymers were characterized by DFT calculation, UV–vis absorption, cyclovoltammetry, TGA and DSC analyses. X‐ray diffraction studies indicated a relatively highly ordered intermolecular structure in PNDT‐TBT after annealing. This high degree of molecular order resulted from the crystallinity and increasing planarity, provided by the thiophene linker groups and the interdigitation of the long alkoxy side chains. The new D‐A polymer, PNDT‐TBT, exhibited a p‐type carrier mobility of 0.028 cm²/Vs and an on/off ratio of 5.9 × 10³. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 525–531