Methyltin Species Research Articles

Understanding Solid-Gas Reaction Mechanisms by Operando Soft X-ray Absorption Spectroscopy at Ambient Pressure: On the Importance of Surface Hydroxides in SnO <sub>2</sub> Heterogeneous Catalysts and Sensors

Ambient pressure operando soft X-ray absorption spectroscopy (soft-XAS) was applied to study the reactivity of hydroxylated SnO2 nanoparticles towards reducing gases. H2 was first used as a test case, showing that gas phase and surface states can be simultaneously probed: soft-XAS at the O K-edge gains sensitivity towards the gas phase, while at the Sn M4,-edges tin surface states are explicitly probed. Results obtained by flowing hydrocarbons (CH4 and CH3CHCH2) unequivocally show that these gases react with surface hydroxyl groups to produce water without producing carbon oxides, and release electrons that localize on Sn to eventually form SnO. The partially reduced SnO2-x layer at the surface of SnO2 is readily reoxidised to SnO2 by treating the sample with O2 at mild temperatures (> 200 °C), revealing the nature of “electron sponge” of tin oxide. The experiments, combined with DFT calculations, allowed hypothesizing a mechanism for dissociative hydrocarbon adsorption on SnO2, involving direct reduction of Sn sites at the surface via cleavage of C-H bonds, and the formation of methoxy- and/or methyl-tin species at the surface.

Behaviour of butyltin compounds in the sediment pore waters of a contaminated marina (Port Camargue, South of France)

Despite the ban on tributyltin (TBT) in marine paints, harbour sediments are still highly contaminated by this antifouling agent. Concentrations of TBT and its dealkylated products dibutyltin (DBT) and monobutyltin (MBT) were determined in the pore waters of Port Camargue, a large marina located on the French Mediterranean coast. Pore waters were sampled in the field using peepers deployed in summer 2012 and 2013 and in winter 2012–2013. The winter surveys were characterized by the presence of sulphides in pore waters from a depth of 5 cm, which was not the case in winter. In summer 2013, TBT was shown to be released into pore waters below the sediment–water interface (SWI) at concentrations of up to 70 ngSn L−1. This release was also observed in sediment anaerobic incubations and was attributed to the mineralization of the sedimentary organic matter, possible stabilization of TBT by complexation with sulphides, and lower debutylation rates in anoxic than in oxic conditions. In summer 2012, a comparatively lower concentration of TBT (around 20 ngSn L−1 below the SWI) was measured and the presence of methyltin species was detected. We hypothesize that the differences between the two surveys reflect different microbial activity. In winter 2012–2013, marked by Fe-reducing conditions in the sediments, TBT was released into solution at the SWI at concentrations of up to 40 ngSn L−1. Sediments are thus a continuing source of TBT for the overlying waters despite the ban on its use for boats in France.

The use of isotopically enriched tin tracers to follow the transformation of organotin compounds in landfill leachate

Landfill leachates are an important pool of organotin compounds (OTCs). Several studies have been performed on the occurrence of OTCs in landfill leachates, but only a few of them report degradation and biomethylation processes by bacteria. In the present study transformation of OTCs in landfill leachate was investigated under simulated landfill conditions over a time span of six months. The degradation and biomethylation processes of OTCs were followed by the use of isotopically enriched tin tracers, namely 117Sn-enriched tributyltin (TBT), 119Sn-enriched dibutyltin (DBT), 117Sn-enriched SnCl2, 117Sn-enriched SnCl4 and a 119Sn-enriched butyltin mix containing TBT, DBT and monobutyltin (MBT). Transformation of OTCs in spiked leachates was followed at m/z of the enriched spikes and at m/z 120, which allowed simultaneous observation of the transformation of OTCs in the leachate itself and of the added spike. In parallel, these processes were also monitored in a non-spiked leachate sample at m/z 120. Quantification of OTCs was performed by gas chromatography – inductively coupled plasma mass spectrometry (GC-ICP-MS). To discriminate the biotic and abiotic transformations of OTCs and inorganic tin species, sterilization of leachate was also performed and data compared to non-sterilized samples. During the course of the experiment the microbial degradation of TBT was clearly manifested in Sn-enriched spiked leachate samples, while abiotic pathway of degradation was observed for DBT. Biomethylation process was also observed in the leachate spiked with Sn-enriched Sn2+ or Sn4+, in concentrations close to those found for total tin in landfill leachates. Monomethyltin (MMeT) was formed first. Stepwise alkylation resulted in dimethyltin (DMeT) and trimethyltin (TMeT) species formation. Hydrolysis of Sn2+ and Sn4+ species was found to be a limiting factor which controlled the extent of methyltin formation. The results of the present investigation importantly contribute to a better understanding of the processes that OTCs undergo in leachates, and provide useful information to managers of landfills in taking measures necessary to prevent the release of toxic methyltin species to the nearby environment.

Development of cryogenic chromatography using thermoelectric modules for the separation of methyltin compounds

AbstractA nonliquid cryogenic gas chromatograph using thermoelectric modules for the cryogenic separation of low boiling‐point compounds was developed. The new system included four thermoelectric modules, a U shape heat exchanger, a cold block, a temperature controller, and three aluminum sheets. The minimum operating temperature of the assembly was –10°C. This thermoelectric system was used to directly cool the capillary column, without any need for a traditional cryogen and had a small volume. The system was cost‐effective and convenient to operate. It was successfully applied to the separation of methyltin species.

Determination of methyltin species in sediments using a pervaporation–gas chromatographic approach

AbstractA method for speciation of monomethyltin (MMT), dimethyltin (DMT) and trimethyltin (TMT) in sediments based on the coupling between a pervaporation module, a preconcentration system and a gas chromatograph coupled with a pulsed flame photometric detector is reported. All the species are derivatized using sodium tetraethylborate as an appropriate reagent in order to produce volatile compounds. The experimental approach consists of a high‐pressure injection valve. In one of the valve positions, the volatile tin species are driven to an appropriate minicolumn as a sorptive trap placed at the valve loop to preconcentrate the analytes. After a fixed time, the current valve position is changed for the injection mode and desorption of the preconcentrated analytes are obtained by heating in a furnace. Estimated detection limits (of tin) for MMT, DMT and TMT using 500 mg of sample are in all cases lower than 21 ng g−1. Excellent recoveries (between 90 and 98%) for tin species were obtained by this extremely simple and easily automated setup. Copyright © 2002 John Wiley & Sons, Ltd.

Speciation of Organotin Compounds, Total Tin, and Major Trace Metal Elements in Poisoned Human Organs by Gas Chromatography-Flame Photometric Detector and Inductively Coupled Plasma-Mass Spectrometry

The organ samples from a victim who died of organotin contaminated lard were studied by the technique which involved gas chromatography-flame photometric detector (GC-FPD) and inductively coupled plasma-mass spectrometry (ICP-MS). Organotin compounds were determined by the following steps: (1) digestion with 1 M CuSO4 and KBr−H2SO4 solutions; (2) extraction with 0.1% tropolone−cyclohexane; (3) derivatization with a n-pentyl Grignard reagent; (4) purification with florisil; and (5) analysis by GC-FPD. Experimental results showed that the victim's organs including the heart, the kidney, the liver, and the stomach contained extremely high levels of methyltin compounds and some amounts of inorganic tin, while the blank organs only contained nearly equal amounts of inorganic tin. The contents of all organotin compounds with methyltri(n-propyl)tin (MeSnPr3) acting as an internal standard were detected by GC-FPD and found between the levels of 0.10 and 1.93 μg/g (wet weight). The amounts of total tin ranged from 0.84 to 5.02 μg/g, and several major trace metal elements were measured by ICP-MS. To our knowledge, this is the first case of methyltin species found in human organs.

Extent and rate of solubilization of tin by iodomethane-water mixtures

The dissolution of tin metal by iodomethane–water mixtures has been studied and the influence of several parameters on both the extent and rate of reaction investigated. The rate-determining step shows a pseudo-first-order dependence on iodomethane (CH3I). The reaction is strongly dependent upon both water and oxygen. The activation energy of only 16 kJ mol−1 is interpreted in terms of a facile bond-breaking and making process at the metal surface, generating methyltin species. Analysis by hydride generation and GC–AA confirmed the formation of methylated species ranging from monomethyl- to tetramethyl-tin; inorganic tin (from hydrolysis) was the major form, however. These findings are similar to those made earlier by us on the solubilization of arsenic from GaAs by alkyl halide-water mixtures, and a similar multi-step scheme is proposed. © 1998 John Wiley & Sons, Ltd.

Tin sulfide clusters in zeolite Y, Sn4S6-Y

The synthesis of a tin sulfide cluster array, denoted Sn4S6-Y, using the quantitative sequential surface anchoring and reaction of tetramethyltin with hydrogen sulfide (metal organic chemical vapor deposition, MOCVD, reagents) within the supercages of acid zeolite-Y is detailed. The tethered methyltin species and their transformation to the encapsulated tin sulfide clusters are elucidated through gravimetry, coupled with mid-IR and 119Sn Mossbauer spectroscopy. Transmission electron microscopy (TEM) and Rietveld refinement of synchrotron powder X-ray diffraction (PXRD) data show that the clusters are internally confined and homogeneously dispersed in the supercages of the host zeolite, while optical spectroscopy show a cluster size dependent blue-shift of the absorption edge with respect to the bulk tin sulfide phase. A geometry is proposed for the encapusulated Sn4S6-Y cluster.

The distribution of methyltin species in different seas

The distribution of methyltin species in different seas

Influence of humic substances on sorption and methylation processes of inorganic- and organo-tin species

The influence of humic substances on sorption and methylation processes for inorganic- and organotin species is presented. Four sediment samples from different locations of the Rivers Elbe, Mulde and Spittelwasser, Germany, with different organotin and humic contents were selected to extract the humic and fulvic acids. The various fractions—the original sediment, the humic acid, the fulvic acid and the residual sediment—were analysed for their organotin content. The individual buyltin species show quite different distribution patterns. Monobutyltin is found mostly associated with humic acids. Dibutyltin shows a nonunique behaviour. At low total organotin content, dibutyltin is found bonded to humic and fulvic acids, whereas at high organotin content dibutyltin is distributed more with the residual sediment. Most of the tributyltin remains in the sediment unextracted; only small quantities of it are in the fulvic acid fraction. Tetrabutyltin is only in the humic acid fraction when it binds to humic matter; it mostly remains in the sediment. General observations indicate that ionic butyltin species bind to fulvic acids whereas the non-polar tetrabutyltin is not found in the fulvic acid fractions in any of the samples. The appearance of monomethyl- and dimethyl-tin species in the humic and fulvic acid fractions after the alkaline extraction was surprising. There is a correlation between the humic content of the sample and the formation of methyltin species. Evidence is provided by experiments that humic substances act as methylation agents.

Tin and organotin speciation during wastewater and sludge treatment processes

The speciation of inorganic tin and organotin compounds is studied in raw water samples and in filtered water samples collected along the main steps of the wastewater treatment plant of Bordeaux City (France). Analyses are performed by hydride generation, cryogenic trapping, chromatographic separation and detection by atomic absorption spectrometry. Results show that dissolved inorganic, methylated tin (mono-, di-, trialkylated forms) and butyltin compounds (mono- and dialkylated forms) occur at all stages of the water treatment process. Butyltins were found at low concentration levels which tends to show that the weathering of PVC is a minor phenomenon. High methyltin contents were however found which illustrate the high methylation rate in sewage water; a general removal trend from the water is observed for inorganic and methyl-tin species both in raw water and filtered water samples. Volatilization of tin compounds is observed in the anaerobic fermentation steps of the activated sludge. Possible pathways for transformation of tin (methylation, volatilization) during the wastewater treatment are discussed.

Tin compounds in sediments of Lake Maryut, Egypt.

Concentrations of inorganic, methyl- and butyltin compounds were quantified by a hydride derivatization/atomic absorption technique for eleven short sediment cores sampled from Lake Maryut, Alexandria, Egypt. All samples contained inorganic Sn concentrations ranging from 1875 to 8190 ng g(-1) dw, the highest levels occurring in the eastern portion of the lake. Methyltin concentrations were also highest in the eastern lake, decreasing considerably in the western lake. Mono- and dimethyltins were found at all sites, the former species being the highest in concentration. Trimethyltin was much lower than either, and was absent from four out of 11 sites. An opposite trend was observed for the butyltin species, their concentration being highest in the west lake, decreasing eastward. Mono- and dibutyltin were almost equal in concentration. Although tributyltin was absent from one site in the lake, it was much higher in concentration than the two other species, particularly in the western lake. In general, methyl- and butyltin concentrations decreased with depth in the cores. Methyltin compounds appear to form within the lake mainly by methylation of inorganic Sn, and butyltin compounds are derived from anthropogenic sources. No significant correlations were found between organic C and concentrations of methyltin species. A significant negative correlation was found between total butyltin concentrations and organic C in surficial sediments.

Environmental methylation of tin: An assessment

The chemical and biological methylation of tin under environmental conditions is reviewed. The question of whether methyltin species form in situ in the environment is also considered. Analytical approaches using hydridization techniques give quite sensitive results. Incubation studies of environmental microorganisms and sediment have demonstrated the formation of methyltin species, and similar conversions have been observed with chemical methylating agents such as methyl cobalamin and methyl iodide.

Biomethylation of tin (II) complexes in the presence of pure strains of Saccharomyces cerevisiae

AbstractThe methylation of several tin compounds by strains of Saccharomyces cerevisiae strains (yeast) is described. The production of the methyl tin species was established by gas chromatography and mass spectrometry. Monomethyl tin (IV) products dominated but some dimethyl tin products were observed. This appears to be the first report of a tin methylation by a pure strain of a methylating species rather than a complex mixture obtained from an environmental source.

Distribution of tin in the northeastern Mediterranean

Concentrations of tin, one of the naturally methylated elements, was determined in sea water, sediments and organisms, collected from the Northeastern Mediterranean. A hydride generation technique was employed, in which the tin and methyltin, were converted to their hydrides. The hydrides produced were detected by atomic absorption spectrophotometer. On the average, the inorganic tin content of sea water samples ranged between 1.1–236 ng/1. Although the dominant methyltin species was dimethyltin, all forms of methyltins (mono, di and tri-methyltins) were detected. The sediment samples were analyzed for the acid extractable tin content and the concentrations were found to range between 0.17–2.30 ug/g (dry weight). Methyltin concentration ranged between 0.1–9.7 ng/g (dry weight). The organism (Limpet) samples were analyzed for their total tin and methyltin contents. Total tin ranged between 7.2–564 ng/g (dry weight), and the methyltins ranged between 0.5–13.9 ng/g (dry weight).

Determination of picogram quantities of methyltins in sediment

An extremely sensitive purge and trap method is described for the determination of methyltins in complex matrices. Organotins were determined directly from sediments and culture medium as the volatile methylstannanes. Hydride derivatives were prepared with NaBH/sub 4/ in a closed, flow-through system consisting of a purge vessel, gas chromatograph, and mass spectrometer. Borate buffer added to samples generated H/sub 2/ from NaBH/sub 4/, resulting in high purge efficiencies for mono-, di-, and trimethyltin. Selected ion mode monitoring with the mass spectrometer gave detection limits for methyltins of 3-5 pg as Sn. The concentration detection limits for a 5-g sediment sample were < pg/g with a standard deviation of 6-18%, depending upon the methyltin species and sample type. Sensitivity achieved was 2 orders of magnitude lower than previously reported for methyltins in sediment. The method reported is both selective and specific, eliminating most interferences while permitting positive identification of individual methyltin species.

Occurrence of organotin compounds in water and sediment in Canada

Water and sediment samples from 265 locations across Canada were analyzed for butyltin and methyltin species, and inorganic tin. In 10% of the water samples the highly toxic tributyltin species was found at concentrations which could cause growth retardation upon chronic exposure to a sensitive organism, rainbow trout yolk sac fry. High concentrations of tributyltin were found in some sediments (up to 10 mg Sn/kg dry weight), but the biological availability of sediment-associated tributyltin is unknown. Tributyltin was mainly found in areas of heavy boating and shipping traffic, which is consistent with its use as an antifouling agent in some paints for boats, ships and docks. The methyltin species were found much less frequently in water and sediment than tributyltin and its degradation products.

Methylgermanium in natural waters

Biological methylation of metallic elements1 and the occurrence and cycling of organometals in the environment have been investigated in Japan during the 1950s and 1960s, where the ingestion of fish and shellfish contaminated with methylmercury compounds caused mercury poisoning2,3. Biomethylation ability has been demonstrated in bacteria, fungi and algae for As, Cd, Hg, Pb, Se, Sn, Te and Tl4–7. Naturally-occurring methylated species have been reported in estuaries and seawater for Sb8, As9, Ge10–13 and Sn14, although recent evidence suggests that some reports of methyltin species result from interferences by Ge and volatile sulphur compounds15. With the exception of Sb8, As9,12,16 and Ge11,12, there are no consistent estuarine or oceanic profiles for methylmetal compounds in the literature from which to judge their biogeochemical behaviour. Early investigations17–19 reported that methylgermanium species do not exist in the aquatic environment. Subsequently, we identified monomethylgermanium (MMGe) and dimethylgermanium (DMGe) in estuaries10,12, the Baltic Sea11 and the Bering and Sargasso seas13. We report here recent measurements of methylgermanium compounds in river water, estuaries, seawater and anoxic basins.

Determination of tin and methyltin species by hydride generation and detection with graphite-furnace atomic absorption or flame emission spectrometry

A method for the determination of tin and organotin species by hydride generation is described. Tin hydrides are detected by graphite-furnace atomic absorption, quartz-cuvette atomic absorption, or flame emission spectrometry with detection limits of 50, 50, and 20 pg as tin, respectively. Germanium interferences are eliminated with a dual-detector flame photometer with an electronic cancellation circuit.

Tin and Methyltin Species in Seawater: Concentrations and Fluxes

The concentrations of tin and methyltin species in rivers, an estuary, and the surface and deep ocean generally are less than 50 picomoles of tin per liter. Estuarine profiles and river concentrations suggest that the dissolved riverine input of tin is only a minor source of this element to the oceans. Oceanic concentrations of inorganic tin decrease both with distance from land and with increasing depth from the surface, an indication of atmospheric transport to the surface ocean. Most of the contemporaneous eolian influx of tin to the oceans is anthropogenic. The vertical structure oftin concentrations in the northwestern Atlantic can be explained in terms of a model based on eolian input, advective processes, and removal of tin by particulate scavenging.