Dimethyl Tin Research Articles

MORPHOLOGY AND RESISTIVITY VALUE OF FLOURINE-DOPED TIN OXIDE (FTO) USING INDONESIAN LOCAL DIMETHYLTIN DICHLORIIDE (DTMC) PRECURSORS

Transparent Conductive Oxide (TCO) is the main component for solar cell fabrication. One of the promising types of TCO is fluorine-doped tin oxide (FTO). The method used in depositing the conductive layer of FTO is spray pyrolysis with an ultrasonic nebulizer. The precursor is a local Indonesian product, dimethyl tin dichloride (DMTC), with doping ammonium fluoride (NH4F). The variable that used in this study were variations in deposition time (5. 10. 15. 20, and 25 minutes) with a fixed substrate temperature at 300°C and doping variations (un-doped, 2 wt.% doped and 8 wt.% doped) to see the effect of adding F doping to the precursor solution. The resistivity value with deposition time of 5. 10. 15. 20 and 25 minute (2 wt.% doped) is 0.218x100; 0.449x10-1; 1,567x10-2; 0.676x10-2 0.377x10-2 Ω.cm. For doping variations (un-doped, 2 wt% doped and 8 wt% doped) the value is 0.883x10-2; 0.377x10-2; 0.506x10-3 Ω.cm. There is a decreasing trend in the resistivity values obtained along with the increase in deposition time and the addition of doping to obtain better conductive properties. The grain size will increase with increasing deposition time and the addition of doping. The optimum resistivity value obtained in this study was 0.377x10-2 Ω.cm, obtained at the deposition time of 25 minutes with 2 wt.% doping.

Occurrence and risk assessment of organotin compounds in the surface water of the upper Yangtze River Estuary

Organotin compounds (OTCs) are a category of persistent toxic substances with endocrine disrupting effects and may pose a risk to aquatic organisms and human health via water. This study collected 78 surface water samples from the drinking water source in the upper Yangtze River Estuary from July 2018 to November 2019. Out of the nine OTC targets, tributyltin (TBT), dimethyltin (DMT), trimethyltin (TMT), dibutyltin (DBT), and monobutyltin (MBT) were detected from more than 50% of the water samples, with cumulative concentrations of OTCs ranging from 42.5 ± 54.0 to 421 ± 176 ng Sn L−1. The composition and concentrations of OTCs in the stormy months were different from those in other months. The concentrations of OTCs with the ebbing tide exceeded those in the flooding tide and increased when the flooding tide transitioned to the ebbing tide. A pulsed trend in concentrations of OTCs in river water was evident due to the impact of rainfall runoff and tidal currents. Identified sources of OTCs included ship antifouling paints, agricultural pesticides, and plastic waste. TBT in water sources poses a low risk to human health and a risk to the ecosystem, particularly during the stormy months.

Antitumor pharmacological activity of hybrid organotin compounds on the Lewis epidermoid carcinoma model.

e15004 Background: New antitumor agents based on organic metal derivatives are intensively determined and created by now. Tin compounds are of great interest among them [Milaeva E.R.et al. Novel selective anticancer agents based on Sn and Au complexes. Pure & Applied Chemistry. 2020, 92, 1201-1216]. The results of studies on cell line models allowed us to conclude that cytotoxic effect of organotin compounds is pronounced, so it is advisable to hold their further studies on biological models in vivo [ Dodokhova M.A. et al. Pharmacotherapeutic potential’s evaluation of organotin compounds in vivo Biopharmaceutical journal, 13(3), 30 – 34 (2021); doi: 10.30906/2073-8099-2021-13-3-30-34]. For the specialists of experimental pharmacology and oncology is relevant to rate the antitumor activity of hybrid organotin compounds on experimental malignant tumors. Methods: The study was held on C57Bl/6 mice (females, n = 36, each cohort contained 12 mice) on a Lewis epidermoid carcinoma model (subcutaneous transplantation) [Kit O.I. et al. Influence of chronic neurogenic pain on the dynamics of the no-system functioning during melanoma B16/F10 growth in male mice. Siberian Journal of Oncology, 2021, 20(3), 67–75]. Bis-(3,5-di-tert-butyl-4-hydroxyphenyl)dimethyl tin(Me-3) and (3,5–di–tert–butyl–4–hydroxyphenylthiolate) triphenyl tin (Me-5) were used as chemotherapeutic agents. Groups of animals were formed as follows: I (experimental) - Me-3 at a dose of 75 mg / kg; II (experimental) - Me-5 at a dose of 50 mg / kg; III (control group) - without pharmacological substances. The doses were characterized as the most effective according to the results of a pharmacological activity screening study. The compounds were injected intraperitoneally daily for 5 days. All animals were euthanized since 21 days after the tumor cells transplantation. The antitumor effect was estimated by the percentage of tumor growth inhibition by weight (%). All manipulations were carried out in accordance with the European Convention for the Protection of Vertebrates Used for Experimental and Other Scientific Purposes (ETS 123). Results: After the intraperitoneal injection of chemical substances Me-3 and Me-5, there was revealed an inhibition of growth by weight of Lewis epidermoid carcinoma’s primary node for all experimental groups, 23.7% and 28% respectively. Conclusions: The injection of organotin compounds with different ligand groups allows us to suggest a biocidal activity of the organotin component on the primary tumor node cells.

DFT Analysis of Organotin Catalytic Mechanisms in Dehydration Esterification Reactions for Terephthalic Acid and 2,2,4,4-Tetramethyl-1,3-cyclobutanediol.

Polyesters synthesized from 2,2,4,4-tetramethyl-1,3-cyclobutanediol (TMCD) and terephthalic acid (TPA) are improved alternatives to toxic polycarbonates based on bisphenol A. In this work, we use ωB97X-D/LANL2DZdp calculations, in the presence of a benzaldehyde polarizable continuum model solvent, to show that esterification of TMCD and TPA will reduce and subsequently dehydrate a dimethyl tin oxide catalyst, becoming ligands on the now four-coordinate complex. This reaction then proceeds most plausibly by an intramolecular acyl-transfer mechanism from the tin complex, aided by a coordinated proton donor such as hydronium. These findings are a key first step in understanding polyester synthesis and avoiding undesirable side reactions during production.

Organotin Release from Polyvinyl Chloride Microplastics and Concurrent Photodegradation in Water: Impacts from Salinity, Dissolved Organic Matter, and Light Exposure

Photochemical weathering leads to degradation of microplastics and releases chemical additives, polymeric fragments, and/or byproducts. This study evaluated the release kinetics of organotin compounds (OTCs) from three different sized (10-300 μm) polyvinyl chloride (PVC) microplastics under UV- and visible light irradiation. Four OTCs, dimethyltin (DMT), monomethyltin (MMT), dibutyltin (DBT), and monobutyltin (MBT), were found to release from PVC particles after 24 h leaching in darkness ranging from 2 to 20 μg·g-PVC-1. Under UV/visible light irradiation, only DMT and DBT were detectable, whereas MMT and MBT were not detected due to rapid photodegradation. The total tin concentrations (including organic and inorganic tins) in the aqueous phase monotonically increased under light exposure. By contrast, they reached plateaus after 24 h in darkness, confirming the photodegradation of OTCs. A release kinetics model was established and correctly interpreted the microplastics size effect on the OTC release process. Finally, the impacts of salinity and dissolved organic matter (DOM) were investigated. The release and photodegradation of OTCs were both inhibited at high salinity conditions, probably due to the enhanced readsorption of OTCs on PVC microplastics and the formation of halogen radicals that were less reactive toward neutral OTCs. The presence of DOM, however, increased OTCs release probably because the excited state triplet DOM (3DOM*) formed and reacted with OTCs from PVC microplastics.

Synthesis, characterization and biological activity of tin(IV) macrocyclic complexes derived from 1,2-diphenylethane-1,2-dione dihydrazone

AbstractThe reaction of dimethyl tin(IV) dichloride with 1,2-diphenylethane-1,2-dione dihydrazone in the presence of metal ions in a 2:2:1 molar ratio resulted in the isolation of macrocyclic complexes of the types [MLX

Speciation of organometallic compounds of Hg, Sn, and Pb in the market garden soil in Ngaoundéré (Cameroon)

The objective of this work is to study the contamination of market garden soils by organomercury compounds (OMC), organotin compounds (OTC), and organolead compounds (OLC) using combustion debris (CD) as fertilizers. Therefore, two parcels of land used for gardening are rented on two sites. Soils were plowed and amended with CD. Samples of non-amended and amended soils were treated and then organometallic compounds of Hg, Sn, and Pb were analyzed by GC–ICP–MS. The results obtained revealed the presence of methyl-mercury (MeHg) in the soil at concentrations varying from non-detected in non-amended soil to 171.6 µg/kg in amended soil. Among the OLC identified, tetra-ethyl-lead (TEtPb) is the most represented in the soil with concentrations ranging from 18.45 to 44,612 µg/kg. OTC has also been identified with a predominance of mono-butyl-tin (MBT) followed by tri-methyl-tin (TMT) and di-methyl-tin (DMT). Soil treatments to CD have a significant influence on soil contamination to OMC, OTC, and OLC. This means that a significant amount of organometallic compounds found in amended soils would come from either direct or indirect CD.

Structural and Biochemical Characterization of Organotin and Organolead Compounds Binding to the Organomercurial Lyase MerB Provide New Insights into Its Mechanism of Carbon-Metal Bond Cleavage.

The organomercurial lyase MerB has the unique ability to cleave carbon-Hg bonds, and structural studies indicate that three residues in the active site (C96, D99, and C159 in E. coli MerB) play important roles in the carbon-Hg bond cleavage. However, the role of each residue in carbon-metal bond cleavage has not been well-defined. To do so, we have structurally and biophysically characterized the interaction of MerB with a series of organotin and organolead compounds. Studies with two known inhibitors of MerB, dimethyltin (DMT) and triethyltin (TET), reveal that they inhibit by different mechanisms. In both cases the initial binding is to D99, but DMT subsequently binds to C96, which induces a conformation change in the active site. In contrast, diethyltin (DET) is a substrate for MerB and the SnIV product remains bound in the active site in a coordination similar to that of HgII following cleavage of organomercurial compounds. The results with analogous organolead compounds are similar in that trimethyllead (TML) is not cleaved and binds only to D99, whereas diethyllead (DEL) is a substrate and the PbIV product remains bound in the active site. Binding and cleavage is an exothermic reaction, while binding to D99 has negligible net heat flow. These results show that initial binding of organometallic compounds to MerB occurs at D99 followed, in some cases, by cleavage and loss of the organic moieties and binding of the metal ion product to C96, D99, and C159. The N-terminus of MerA is able to extract the bound PbVI but not the bound SnIV. These results suggest that MerB could be utilized for bioremediation applications, but certain organolead and organotin compounds may present an obstacle by inhibiting the enzyme.

Magnetic resonance imaging of leukoencephalopathy in amnestic workers exposed to organotin.

We report the clinical and neuroimaging findings of 4 men who worked in the production of inorganic metal tin ingot from organotin scrap who presented with similar episodes of reversible amnesia. T2-weighted-fluid-attenuated inversion recovery magnetic resonance imaging (FLAIR MRI) scans in 3 of the patients showed symmetric hyperintensity in the frontoparietal periventricular white matter and the corpus callosum, and reduced apparent diffusion coefficients (ADCs) based on diffusion weighted imaging (DWI). One patient had symmetric faint hyperintensity in the parietal periventricular white matter only in the FLAIR images. The patients had elevated urinary levels of dimethyltin (DMT) and trimethyltin (TMT), but these concentrations decreased following cessation of exposure. Triethyltin, however, was not detected in urine. We diagnosed the present cases with organotin intoxication based on 5 lines of evidence. First, all patients were workers in the same tin-processing industry, complained of similar clinical symptoms, and had similar neuroimaging results. Second, the clinical features are compatible with a diagnosis of organotin encephalopathy. Third, all 4 workers were exposed to organotin for several days, and had high urinary concentrations of DMT and TMT. Fourth, the clinical features and brain MRI results ruled out other cerebral diseases. Fifth, MRI findings support a diagnosis of organotin encephalopathy.

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.

Comparative toxicity and apoptosis induced by diorganotins in rat pheochromocytoma (PC12) cells

As ubiquitous environmental toxicants, organotin (IV) compounds (OTC) accumulate in the food chain and potential effects on human health are disquieting. The present study compared the cytotoxicity of three diorganotins, namely, dimethyltin (DMT), dibutyltin (DBT) and diphenyltin (DPT), in rat pheochromocytoma (PC12) cells, and the molecular mechanisms responsible for their cytotoxic effects were also explored. Twenty-four hours exposure of PC12 cells to DBT and DPT resulted in a concentration-dependent decrease in cell viability with median lethal concentration (LC₅₀) of 2.97 μM and 7.24 μM, respectively. However, DMT at concentrations up to 128 μM had no obvious effect on cell viability. The mechanistic study revealed that the extent of apoptosis was greater for DBT than that for DPT, followed by DMT, as evidenced by acridine orange/ethidium bromide (AO/EB) fluorescent staining method and annexin V-FITC/PI staining flow cytometry analysis, as well as generation of intracellular reactive oxygen species (ROS), mitochondrial membrane potential (MMP) disruption, release of cytochrome c (Cyt c), and consequent activation of caspase-9, and -3. These investigations suggested that the cytotoxic potency of three diorganotins in PC12 cells was in the order of DBT>DPT≫DMT, and these compounds could induce PC12 cells apoptosis through ROS mediated mitochondrial pathway.

Degradation of poly(ethylene terephthalate) waste with dimethyl tin distanoxane as a catalyst

ABSTRACTIn this article, we report the degradation of poly(ethylene terephthalate) (PET), which occurs through glycolysis in the presence of dimethyl tin distanoxane [(CH3)2Sn(OCOCH3)2] as a catalyst, triethylene glycol (TEG) as a nucleophilic agent, and decaline like a solvent. A number of experiments were executed, which were derived from a factorial experimental design, in which the reaction time was between 40 and 60 min, the amount of TEG was between 3.4 and 5.6 g, and the amount of catalyst was between 0.04 and 0.06% in ratio to PET. The reaction temperature was constant at 175°C in all of the experiments. Once the glycolytic depolymerization occurred, oligomers with a molecular weight around 6000 g/mol were obtained. These oligomers were analyzed through gel permeation chromatography, differential scanning calorimetry, Fourier transform infrared spectroscopy, and 1H‐NMR. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3482–3488, 2013

Toxicity of Trimethyltin and Dimethyltin in Rats and Mice

Extensive uses of methyltin compounds in polyvinyl chloride (PVC) production have led to a dramatic increase of occupational-related methyltin poisoning accidents and the widespread contamination of methyltins in various environmental media. Here, we conducted studies to compare the acute toxicity induced by trimethyltin (TMT) and dimethyltin (DMT), and investigated the cumulative toxic effects of TMT in rats and mice. Neurobehavioral changes were observed in rats and mice treated with either DMT or TMT, but we also observed that both TMT and DMT exposure in rats significantly lowered the blood potassium level. Moreover, the cumulative toxic coefficient factor of TMT was 1.7 in rats versus 3.8 in mice, suggesting a high cumulative risk for rats and a moderate risk for mice. In summary, we demonstrated that acute and chronic exposure to methyltin compounds induced neurotoxicity and hypokalemia. Moreover, our study suggests that TMT can accumulate in the body and pose a risk for workers chronically exposed to a low dose of TMT.

Theoretical Studies of Solvent Effects on Binding of Sn (CH3)2(N-acetyl-L-cysteinate) with Single-walled Carbon Nanotube

The potential of nanotechnology to revolutionise medicine in particular seems endless, and one significant application of this technology is the use of carbon nanotubes for the targeted delivery of drug molecules. Sn(CH3)2(N-acetyl-L-cysteinate) is a drug that has been proposed as a therapeutic against the human hepatocarcinoma HCC Hep G2 cells. In our model, (N-acetyl-Lcysteinato-O,S) dimethyl tin(IV) (Sn(CH3)2(N-acetyl-L-cysteinate)) was binded to carbon nanotube. Quantum chemical ab initio calculations at HF/ (LanL2DZ+STO-3G), and HF/ (LanL2DZ+6-31G) levels in gas phase and solution have been carried out to calculate the optimized geometry, energies, dipole moments and thermochemical analysis of Sn(CH3)2(N-acetyl-L-cysteinate)-CNT complex. Results from frequency calculation (large negative values of the ΔG and high positive values of ΔS) confirmed the structural stability of the Sn(CH3)2(NAC) – CNT in both gas phase and in solution. NMR parameters such as isotropic magnetic shielding constants (σiso), anisotropic magnetic shielding tensors (σaniso), Chemical shifts (δ) and total atomic charges were also calculated using the GIAO and CSGT approaches in both gas phase and in solution to determine the structural characterization of the complex. The results in solution show that the δ, σiso, and σaniso are sensitive to hydrogen-bonding interactions. A different influence of various hydrogen bond types, N5-H·····O, C-O1·····H, and C=O24·····H was observed on the calculated NMR parameters. Finally the NMR parameters obtained from GIAO method are in good agreement with the CSGT results.

Di-μ-hydroxido-bis[dimethyl(thiocyanato-κN)tin(IV)

The SnIV atom in the centrosymmetric title complex, [Sn2(CH3)4(NCS)2(OH)2], adopts a distorted trigonal–bipyramidal coordination environment defined by two methyl C atoms and one bridging hydroxide group in the equatorial plane while the other bridging hydroxide group and the N atom of the thio­cyanate anion are in the apical >positions. The dinuclear species are linked through O—H⋯S and C—H⋯ S hydrogen-bonding inter­actions into a three-dimensional network.

Evaluation of the Thermal Stabilization Effect of the Bis (Mercaptoethanol Oleate) Dimethyl Tin on Polyvinyl Chloride

Bis (mercaptoethanol oleate) dimethyl tin was synthesized and added to polyvinyl chloride (PVC) with various ratios. Specimens were prepared by mixing and rolling through a double-roller mixer, and their static thermal stabilities were estimated by the oven static thermal aging experiments. The influence of the bis (mercaptoethanol oleate) dimethyl tin on the dynamic thermal stability of PVC was tested through a haack torque rheometer (HAAKE PolyLab QC). The tensile strength and rate of elongation at break of the PVC specimens were evaluated by a servo-controlled tensile testing machine. The results show that the bis (mercaptoethanol oleate) dimethyl tin has excellent static and dynamic thermal stabilization effect on PVC, and to some extent, can improve the breaking elongation rate the PVC sample.

Retraction Note: The sequential magnetic resonance images of tri-methyl tin leukoencephalopathy.

Organotin compounds are commonly used in industrial and agriculture. It causes toxic effects on skin, eyes, respiratory system, gastrointestinal system, and nervous system. After cleaning a di-methyl tin tank, 43-year-old man showed a dizziness, disorientation, visual hallucination, and agitation. Through a measurement by liquid chromatography and inductively coupled plasma-mass spectrometry, di-methyl tin and tri-methyl tin was detected. Although magnetic resonance (MR) image 3 days after exposure showed no abnormal signal intensity, follow-up MR images 15 days after exposure revealed abnormal extensive signal intensities in the white matter that was not ever coincident with previous reports. It was hardly explainable that previous abnormal signal intensities of MR image nearly disappeared 4 months later. We present a case of a patient who developed acute toxic leukoencephalopathy from an acute inhalational exposure to methyl tin with sequential MR images showing an involvement of white matter that was not ever reported.

Identification of photochemical methylation products of tin(ii) in aqueous solutions using headspace SPME coupled with GC-FPD or GC–MS

Methylation is an important transformation process for elements in the environment. Herein, headspace solid phase micro-extraction (HP-SPME) coupled with gas chromatography–flame photometric detection (GC-FPD) or gas chromatography–mass spectrometry (GC–MS) techniques were employed to study the photochemical methylation of inorganic tin(II) by eight organic compounds (including acetone, pyruvic acid, acetic acid, propionic acid, dimethyl sulfoxide, N,N-dimethylformamide, tert-butyl alcohol and isopropyl alcohol) in aqueous solutions. The major products were identified as monomethyltin (MMT) and dimethyltin (DMT), as well as trimethyltin (TMT) as the minor product. The yields of methyltin products were closely related to the chemical structures of methyl donors, and the pH and salinity of the reaction solution. The concentrations of methyltin products peaked at a pH of 5.0 and a salinity of 0.5 M. The dominating product also changed from MMT to DMT with an increase in pH value. Notably, pyruvic acid can readily methylate tin(II) under irradiation by sunlight in view of its absorption of sunlight, demonstrating that photochemical methylation is a possible transformation pathway for tin(II) in the environment.

Investigation of drug delivery on anticancer drug by SWCNT with theoretical studies

The interaction of anticancer drug Sn(CH3)2(N-acetyl-L-cysteinate), that is called (N-acetyl-L-cysteinato-O,S) dimethyl tin(IV), with single walled carbon nanotube (SWCNT) is investigated by Quantum chemical ab initio calculations at HF/(LanL2DZ+STO-3G) and HF/(LanL2DZ+6-31G) levels in gas phase and solution. The solvent effect is taken into account via the self-consistent reaction field (SCRF) method. Carbon nanotubes can act as a suitable drug delivery vehicle for internalization, transportation and translocation of Sn(CH3)2(N-acetyl-L-cysteinate) within biological systems. Thermodynamical analysis indicates that the relative energies (ΔE), enthalpies (ΔH) and free Gibbs energies (ΔG) are negative for Sn(CH3)2(N-acetyl-L-cysteinate)-CNT system, but the calculated entropies (ΔS) are positive, suggesting thermodynamic favorability for covalent attachment of Sn(CH3)2(N-acetyl-L-cysteinate) into carbon nanotube. Also, the results show that with increasing dielectric constant of solvent, the stability of Sn(CH3)2(N-acetyl-L-cysteinate)-CNT complex decreases. Furthermore, anisotropic chemical shift tensor (Δσ), total atomic charge and asymmetry parameter (η) have been calculated using the gauge-including atomic orbital (GIAO) method, results being compared with CGST data. From the nuclear magnetic resonance (NMR) calculations, it can be seen that the NMR (Δσ, η) parameters at the sites of nitrogen and oxygen, as well as C-2 and C-3 nuclei are significantly influenced by intermolecular hydrogen-bonding interactions, but the quantity at the site of S-27 is influenced by nonspecific solute-solvent interaction, such as polarisability/polarity. Key words: Sn(CH3)2(N-acetyl-L-cysteinate), nuclear magnetic resonance (NMR) parameters, single walled nanotube (SWNT), solvent.

Predicting the Migration Rate of Dialkyl Organotins from PVC Pipe into Water

Organotins (OTs) are additives widely used as thermal and light stabilizers in polyvinyl chloride (PVC) plastics. OTs can leach into water flowing through PVC pipes. This work examines the leaching rates of two potentially neurotoxic OTs, dimethyl tin (DMT) and dibutyl tin (DBT), from PVC pipe. Water was circulated in a closed loop laboratory PVC pipe system. Using a gas chromatograph-pulsed flame photometric detector (GC-PFPD), the change in concentrations of DMT and DBT in the water in the system was monitored over time and allowed to reach equilibrium. OT concentration as a function of time was analyzed using a mechanistic leaching rate model. The diffusion coefficient for OT in the PVC pipe material, the only unknown model parameter, was found to be 9 × 10(-18) m(2)/s. This value falls within with the range of values estimated from the literature (2 × 10(-18) to 2 × 10(-17) m(2)/s) thus increasing confidence in the leaching rate model.