Di‐ and tri‐phenyltin chlorides transfer across a model lipid bilayer

A compound's ability to penetrate the plasma membrane of a cell is the critical parameter that determines its potential to become a biologically potent factor. A well‐known group of organotin compounds that exhibit toxic properties in relation to biological systems are phenyltins. There are as yet no studies that in a direct manner have established whether organotin compounds such as diphenyltin dichloride (DPhT) and triphenyltin chloride (TPhT) diffuse, or not, through the lipid bilayer, although we know that at least some organotins absorb in both liposome and biological membranes. In this paper we present a series of experiments that show transfer of these compounds across the lipid membrane using the stopped‐flow technique. The results obtained demonstrate that DPhT and TPhT first adsorb onto the lipid bilayer surface, in a diffusion‐controlled manner and within a very short time (0.05 s), whereas the membrane crossing was observed to be on the order of a minute. The adsorption process was easily fitted with a single exponential for both the compounds studied, indicating a single process phenomenon. The longer time kinetics (characteristic of membrane crossing) showed a complex dependence on compound concentration and the presence of cholesterol in the membrane. On passing from the outer to the inner surface of the bilayer, organotins undergo desorption and enter the liposome interior, which has been shown in lipid monolayer desorption studies. In conclusion, it can be stated that amphiphilic DPhT and TPhT permeate the liposome membrane. Copyright © 2005 John Wiley & Sons, Ltd.     

Determination of organotin compounds by headspace solid-phase microextraction–gas chromatography–pulsed flame-photometric detection (HS-SPME–GC–PFPD)

A method based on Headspace solid-phase microextraction (HS-SPME, with a 100 μm PDMS-fiber) in combination with gas-chromatography and pulsed flame-photometric detection (GC-PFPD) has been investigated for simultaneous determination of eight organotin compounds. Monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT), monophenyltin (MPhT), and the semi-volatile diphenyltin (DPhT), triphenyltin (TPhT), monooctyltin (MOcT), and dioctyltin (DOcT) were determined after derivatization with sodium tetraethylborate. The conditions used for the extraction and preconcentration step were optimised by experimental design methodology. Tripropyltin (TPrT) and diheptyltin (DHepT) were used as internal standards for quantification of volatile and semi-volatile organotin compounds, respectively. The analytical precision (RSD) for ten successive injections of a standard mixture containing all the organic tin compounds ranged between 2 and 11%. The limits of detection for all the organotin compounds were sub ng (Sn) L⁻¹ in water and close to ng (Sn) kg⁻¹ in sediments. The accuracy of the method was evaluated by analysis of two certified reference material (CRM) sediment samples. The HS-SPME–GC–PFPD was then applied to the analysis of three harbour sediment samples. The results showed that headspace SPME is an attractive tool for analysis of organotin compounds in solid environmental matrices.     

Preparation, preservation and application of pure isotope-enriched phenyltin species

A method combining liquid/liquid extraction and chromatographic fractionation has been developed for the preparation of pure monophenyltin (MPhT), diphenyltin (DPhT), and triphenyltin (TPhT), synthesized from isotope-enriched Sn metal using phenylation of SnI₄ in diethylether (DEE) followed by quenching with HBr and water. After two successive extractions of the aqueous HBr phase with DEE, >99% of both DPhT and TPhT was recovered in the combined DEE phase and 94% of the MPhT remained in the aqueous phase. The MPhT in the aqueous phase was extracted into dichloromethane. The organic phases were vaporized and the PhTs were redissolved in MeOH/water/acetic acid/sodium acetate (59/30/6/8, v/v/v/w), which was also used as storing solution. Aliquots of the two solutions containing either DPhT and TPhT or MPhT were injected into a silica-based C₁₈ column for isolating and purifying single species. The yields of pure MPhT, DPhT, and TPhT, each synthesized from isotope-enriched ¹¹⁸Sn metal, ¹²²Sn metal, and ¹²⁴Sn metal, were better than 99%. After chromatographic separation, the single phenyltin compounds were mixed to prepare a spike for multiple-isotope species-specific isotope dilution (MI-SSID). MI-SSID was successfully used to determine phenyltin compounds in the certified reference material, mussel tissue BCR CRM-477. At −20 °C, all of the fractionated phenyltin species were stable in the storage solution for at least 197 days. When these standards were stored at 4 °C or 22 °C, 4–6% of the DPhT and TPhT degraded within 27 days. The degradation of DPhT and TPhT increased with the ionic strength and acidity of the storage solution.      

Gas chromatography-high-resolution mass spectrometry based method for the simultaneous determination of nine organotin compounds in water,sediment and tissue

A GC-HRMS based method for the accurate and sensitive determination of nine organotin compounds, tetrabutyltin (TeBT), tributyltin (TBT), dibutyltin (DBT), monobutyltin (MBT), triphenyltin (TPhT), diphenyltin (DPhT), monophenyltin (MPhT), tricyclohexyltin (TCyT), and dicyclohexyltin (DCyT) in sediment, tissue and water samples is presented and discussed. Mass spectral features of these analytes via both low resolution quadrupole and high resolution magnetic sector, GC-HRMS conditions under selective ion monitoring mode and QA/QC criteria for the positive identification of analyte are all provided. Linearity of response and minimal detectable limits are illustrated for each of the nine compounds monitored and the estimates of method limits-of-detection were 7-29 ppt for water and 0.35-1.45 ppb for tissue or sediments. Sample preparation considerations and precision are discussed for spiked water and sediment samples, whereas method accuracy was established by analysing a certified reference material (CRM) mussel sample and comparing our results to the assigned values. Good agreement was found between our results and assigned or indicative values for MBT, DBT, TBT, DPhT and TPhT (cyclohexyl-tins were not present in the CRM).     

A quantitative extraction method for the determination of trace amounts of both butyl- and phenyltin compounds in sediments by gas chromatography-inductively coupled plasma mass spectrometry

A simple and reliable extraction method was developed for quantitative determination of both butyl- and phenyltin compounds in sediments by capillary gas chromatography combined with inductively coupled plasma mass spectrometry (GC-ICP-MS). Both types of organotin compounds were extracted quantitatively from sediment by mechanical shaking into tropolone-toluene and HCl-methanol. After phase separation and pH adjustment, these organotins were ethylated with sodium tetraethylborate. The method was evaluated by analyzing PACS-2 and NIES No. 12 sediment certified reference materials. The dibutyltin (DBT; 1.14 +/- 0.02 micrograms g-1) and tributyltin (TBT; 1.01 +/- 0.04 micrograms g-1) values observed in PACS-2 sediment closely matched the certified values (DBT, 1.09 +/- 0.15; TBT, 0.98 +/- 0.13 microgram g-1 as tin). The monobutyltin (MBT) value was higher (0.62 +/- 0.02 microgram g-1) by more than two fold over the reference value (0.3 microgram g-1 as tin). The concentrations of TBT (0.18 +/- 0.04 microgram g-1) and triphenyltin (TPhT; 0.0099 +/- 0.002 microgram g-1) in the NIES No. 12 sediment were also in good agreement with the certified and reference values of TBT (0.19 +/- 0.03 microgram g-1 as compound) and TPhT (0.008 microgram g-1 as compound), respectively. Recoveries of TBT, tripentyltin (TPeT) and TPhT from spiked sediments were satisfactory (TBT, 102 +/- 3.4%; TPrT, 96 +/- 3.4%; TPhT, 99 +/- 8.5%). The detection limits as tin were in the range 0.23-0.48 ng g-1 for a 0.5 g sample size. It is also noteworthy that clean-up of the extract is not necessary because of the superior selectivity of ICP-MS detection. The present method was successfully applied to marine sediment samples.     

The effect of some phenyltin compounds on the thermotropic phase behaviour and the structure of model membranes

The effects of diphenyltin dichloride (DPhT), triphenyltin chloride (TPhT) and tetraphenyltin (TTPhT) on the thermotropic phase behaviour of phosphatidylcholine bilayers were studied. All the phenyltin compounds investigated affected phase transitions differently. TTPhT broadened the main phase transition but it left the transition temperatures and enthalpy unchanged. TPhT reduced the transition temperatures and the enthalpies while DPhT showed a dual effect on the pretransition and the main transition. At low concentrations DPhT reduced the temperatures of the transitions slightly and at higher concentrations it increased them. Based on differential scanning calorimetry (DSC) and also ¹H NMR and ³¹P NMR measurements, it is suggested that DPhT induces interdigitated gel phase formation and TPhT induces hexagonal phase formation. TTPhT seems to affect the structure only a little. The toxic activity of DPhT and TPhT seems to be connected with their ability to induce changes in the membrane structure. Copyright © 2000 John Wiley & Sons, Ltd.     

Automated headspace-solid-phase micro extraction-retention time locked-isotope dilution gas chromatography-mass spectrometry for the analysis of organotin compounds in water and sediment samples

An automated method for the simultaneous determination of six important organotin compounds namely monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT), monophenyltin (MPhT), diphenyltin (DPhT) and triphenyltin (TPhT) in water and sediment samples is described. The method is based on derivatization with sodium tetraethylborate followed by automated headspace-solid-phase micro extraction (SPME) combined with GC-MS under retention time locked (RTL) conditions. Home-synthesized deuterated organotin analogues were used as internal standards. Two high abundant fragment ions corresponding to the main tin isotopes Sn118 and Sn120 were chosen; one for quantification and one as qualifier ion. The method was validated and excellent figures of merit were obtained. Limits of quantification (LOQs) are from 1.3 to 15 ng l(-1) (ppt) for water samples and from 1.0 to 6.3 microg kg(-1) (ppb) for sediment samples. Accuracy for sediment samples was tested on spiked real-life sediment samples and on a reference PACS-2 marine harbor sediment. The developed method was used in a case-study at the harbor of Antwerp where sediment samples in different areas were taken and subsequently screened for TBT contamination. Concentrations ranged from 15 microg kg(-1) in the port of Antwerp up to 43 mg kg(-1) near a ship repair unit.     

Determination of butyltin and phenyltin species by reversed-phase liquid chromatography and fluorimetric detection

Chromatographic separation of monobutyltin (MBT), monophenyltin (MPhT), dibutyltin (DBT), diphenyltin (DPhT), tributyltin (TBT) and triphenyltin (TPhT) was studied using end-capped reversed-phases (RP) and methanol-acetic acid-water or acetronitrile-acetic acid-water mixtures as mobile phases. Several RP columns were evaluated, and the effect of acetic acid, oxalic acid, triethylamine, and organic modifier on peak shape and retention was examined. A method based on gradient elution RPLC and fluorimetric detection is proposed for the determination of DBT, DPhT, TBT and TPhT. The sensitivity of the method makes it suitable for environmental analysis.     

The effect of phenyltin chlorides on the phase polymorphism of dipalmitoylphosphatidylcholine

The effects of diphenyltin dichloride (DPhT) and triphenyltin chloride (TPhT) on polymorphic phase behaviour of aqueous dispersions of a dipalmitoylphosphatidylcholine (DPPC) bilayer were investigated by means of ³¹P NMR. It is suggested that DPhT induces interdigitated gel phase formation and TPhT induces hexagonal phase formation. The toxic activities of DPhT and TPhT seem to be connected with their ability to induce changes in the membrane structure. Copyright © 2001 John Wiley & Sons, Ltd.     

Physico-chemical approach to study organotin sorption-desorption during solid-phase microextraction

Solid-phase microextraction (SPME) has become a real alternative to liquid-liquid extraction in the field of speciation of organometallic compounds. Despite the high performance of this preconcentration technique, matrix effects in natural samples can affect the analytical precision. In order to understand the origin of these disturbances and control the extraction step as best as possible, the sorption-desorption behaviour of organotins was studied. In the first part, this paper discusses the analytical problems encountered in the daily use of SPME due to the particular problems observed for phenyltins. The sorption profile of these compounds was modelled using experimental design methodology to confirm the first-order kinetics. Desorption of the compounds was also observed after a given time and could not be attributed to competition between organotin compounds. In the same way, butyl- and phenyltins were studied in the presence of humic substances, which acted as representatives of organic matter found in natural samples. These substances drastically decrease the extraction yields, but do not affect the sorption profile of butyl- and phenyltins.     

Comparison of sodium tetraethylborate and sodium tetra(n-propyl)borate as derivatization reagent for the speciation of organotin and organolead compounds in water samples

The influence of pH on the propylation with sodium tetra(n-propyl)borate of butyl- and phenyltins as well as for trimethyl- and triethyllead was investigated. Ethylation and propylation with tetraalkylborates were compared with regard to derivatization yields and figures of merit for organotin compounds in real water samples. Similar results for limit of detection (3-12 ng/L as tin), derivatization yield (40-100%) and relative standard deviation of the method (3-10%) were achieved for derivatization with the two tetraalkylborates. Propylation is thus the preferred method for the simultaneous determination of environmentally relevant organotin and organolead compounds. The handling of the hygroscopic and air sensitive reagents NaBEt4 and NaBPr4 was simplified by dissolving them in tetrahydrofurane. The reagent solutions in tetrahydrofurane can be stored for at least one month at 4 degrees C in the dark without observing any decrease in the derivatization efficiency.     

Trace determination of organotin compounds in water,sediment and mussel samples by low-pressure gas chromatography coupled to tandem mass spectrometry

A fast method for the determination of eight organotin compounds (OTs), monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT), tetrabutyltin (TeBT), monophenyltin (MPhT), diphenyltin (DPhT), triphenyltin (TPhT) and tetraphenyltin (TePhT), in water, sediments and mussels, was developed using low-pressure gas chromatography/tandem mass spectrometry (LPGC/MS/MS). The method is based on sodium diethyldithiocarbamate (DDTC) complexation of the ionic organotins, followed by extraction of the target matrices and derivatization by a Grignard reagent, as described in a previously published method for water samples. Solid-phase extraction was selected as extraction method from water samples after comparison with liquid-liquid extraction, but extraction of the OTs from sediment and mussel samples was performed using toluene. Matrix-matched calibration standards were used to minimize matrix effects. The analytical process was validated by the analysis of spiked blank samples. Performance characteristics such as linearity, detection limit (LOD), quantitation limit (LOQ), precision, and recovery were determined. Recoveries of OTs in spiked matrices ranged from 86-108% in water and from 78-110% in sediments and mussels, with precision values lower than 18%. Detection limits ranged from 0.1-9.6 ng L(-1) in water, and 0.03-6.10 microg kg(-1) in the other matrices. The present implementation of LPGC rather than conventional capillary GC permitted use of large-volume injection and reduced analysis time by a factor of two. The proposed methodology was applied to the determination of OTs in real samples of water, marine sediments and mussels from the west coast of the Mediterranean Sea (Spain).     

Fast method for routine simultaneous analysis of methylmercury and butyltins in seafood

A simple, fast, and accurate method for the simultaneous determination of methylmercury (MeHg(+)), monobutyltin (MBT), dibutyltin (DBT) and tributyltin (TBT) in seafood is proposed. The method makes use of relatively cheap instrumentation and allows simultaneous analysis of those four species in a routine basis. The sample is treated with methanolic potassium hydroxide in an ultrasound bath, derivatised with sodium tetraethylborate (NaBEt(4)), preconcentrated into n-hexane and analysed by gas chromatography with atomic emission detection (GC-MIP/AES). The soft extraction conditions provided by ultrasound energy prevent chemical decomposition of the analytes and allow fast and efficient recovery of the species considered. Both the extraction and the derivatisation/preconcentration steps were optimised. Detection limits of 34, 3, 6 and 8 ng g(-1) (dry mass) were obtained for MeHg(+), MBT, DBT and TBT, respectively, using the best experimental conditions found. The uncertainty of the analysis ranged from 11% (MeHg(+)) to 15% (MBT). The accuracy of the method was checked by the analysis of several certified reference materials, e.g., BCR 477 (mussel tissue, MBT, DBT and TBT), DOLT-2 (dogfish liver, MeHg(+)), BCR 463 (tuna fish, MeHg(+)) and NIST 2976 (mussel tissue, MeHg(+)) with satisfactory results. Several oyster samples collected in the estuary of the Oka River (Urdaibai, Unesco Reserve of the Biosphere, Basque Country) during four sampling campaigns in 2003-2004 were processed following the proposed procedure. Concentrations ranging from 65 to 149 ng g(-1) (MeHg(+)), 相似文献   

MultiSimplex optimisation of the solid-phase microextraction-gas chromatographic-mass spectrometric determination of polycyclic aromatic hydrocarbons,polychlorinated biphenyls and phthalates from water samples

Solid-phase microextraction coupled to GC-MS was optimised for the determination of polycyclic aromatic hydrocarbons (PAHs), phthalate esters and polychlorinated biphenyls (PCBs) in water samples. A 30-microm polydimethylsiloxane fiber was immersed in a 30-ml water sample that contained the analytes of interest (PAHs, PCBs and phthalate esters) and the variables studied were extraction time (15-60 min), extraction temperature (30-90 degrees C), desorption time (1-5 min), desorption temperature (220-270 degrees C) and the addition of sodium chloride (0-9 g). The MultiSimplex programme based on the simplex algorithm was used to establish the optimal conditions. MultiSimplex allowed the simultaneous study of the variables mentioned above and considered the answers of all types of compounds studied in this work. Thus, the optimal conditions obtained allowed the simultaneous determination of PAHs, phthalate esters and PCBs. Furthermore, the accuracy and repeatability of the developed method were calculated from water samples spiked at known concentrations of the analytes. Finally, the optimised method was used to analyse water samples from different sampling points of the Urdaibai and Nerbioi-Ibaizabal estuaries (Biscay, Spain).     

Speciation analysis of mercury by solid-phase microextraction and multicapillary gas chromatography hyphenated to inductively coupled plasma-time-of-flight-mass spectrometry

This paper reports the development of an analytical approach for speciation analysis of mercury at ultra-trace levels on the basis of solid-phase microextraction and multicapillary gas chromatography hyphenated to inductively coupled plasma-time-of-flight mass spectrometry. Headspace solid-phase microextraction with a carboxen/polydimethylsyloxane fiber is used for extraction/preconcentration of mercury species after derivatization with sodium tetraethylborate and subsequent volatilization. Isothermal separation of methylmercury (MeHg), inorganic mercury (Hg2+) and propylmercury (PrHg) used as internal standard is achieved within a chromatographic run below 45 s without the introduction of spectral skew. Method detection limits (3 x standard deviation criteria) calculated for 10 successive injections of the analytical reagent blank are 0.027 pg g(-1) (as metal) for MeHg and 0.27 pg g(-1) for Hg2+. The repeatability (R.S.D., %) is 3.3% for MeHg and 3.8% for Hg2+ for 10 successive injections of a standard mixture of 10pg. The method accuracy for MeHg and total mercury is validated through the analysis of marine and estuarine sediment reference materials. A comparison of the sediment data with those obtained by a purge-and-trap injection (PTI) method is also addressed. The analytical procedure is illustrated with some results for the ultra-trace level analysis of ice from Antarctica for which the accuracy is assessed by spike recovery experiments.     

The transformation of phenyltin species during sample preparation of biological tissues using multi-isotope spike SSID-GC-ICPMS

A multi-isotope spike species-specific isotope dilution (MI-SSID) calibration strategy in connection with gas chromatography-inductively coupled plasma mass spectrometry was applied to evaluate different extraction procedures for the speciation analysis of phenyltin (PhT) compounds in biological materials: mussel tissue BCR CRM-477 and fish tissue NIES-11. Three different isotope-enriched PhT compounds, ¹¹⁸Sn-enriched monophenyltin (MPhT), ¹²²Sn-enriched diphenyltin (DPhT), and ¹²⁴Sn-enriched triphenyltin (TPhT), were used for the preparation of spikes to follow and correct for six possible interconversion reactions between PhT species that can take place in a sample. The acidity of the extractant, the presence of complexing reagents, and the use of ultrasonic or microwave agitation were found to affect the degradation of PhT compounds. No formation of PhTs through phenylation and negligible degradation of MPhT to inorganic tin were observed under the conditions investigated. The degree of degradation increased with increased acidity of extractant and when ultrasonication or microwave agitation was used. Under relatively mild extraction conditions, the degradation factors for DPhT and TPhT in the two reference materials studied were found, using MI-SSID, to be between 10 and 55% and 2 and 10%, respectively. Using the degradation factors, we calculated corrected concentration values for the organotin species. When microwave extraction at high power output was used, hydrogen radicals were formed that can enhance the degradation of DPhT and TPhT. The hydrogen radicals were trapped using N-tert-butyl-α-phenylnitrone and detected by electron spin resonance spectrometry. The effect of different extraction parameters on the degradation of PhT compounds in biological samples is discussed.     

汞的形态分析研究 Ⅱ.固相萃取预富集-液相色谱分离测定不同形态的有机汞

本文报道了固相萃取预富集处理样品继以液相色谱分离测定不同形态痕量有机汞的方法.二乙基二硫代氨基甲酸钠(DDTC)作络合剂及甲醇作洗脱液的预富集系统能在线富集甲基汞(MeHg)、乙基汞(EtHg)和苯基汞(PhHg).用于测定加标海水中MeHg、EtHg和PhHg,回收率分别为96.9％、102.4％和98.0％;相对标准偏差分别为3.5％、5.0％和5.0％;检测下限分别为 1.0μg/L、1.2 μg/L和 1.2 μg/L.     

Spindle-inhibiting effects of organotin compounds. II. Induction of chromosomal supercontraction by di- and tri-alkyl and -aryl compounds

Spindle-inhibiting effects of chemical compounds may be studied indirectly by quantitation of chromosomal contraction. The effects of the trimethyltin (TMT), dimethyltin (DMT), tributyltin (TBT), dibutyltin (DBT), triphenyltin (TPhT) and diphenyltin (DPht) moieties as the chloride on chromosomal contraction was studied by measurement of the average length of chromosome No. 1 from asynchronous cultures of human peripheral lymphocytes. TMT, TBT, TPhT and DPhT appear to be very strong inducers of chromosomal supercontraction, indicating that these compounds conceivably are spindle inhibitors, whilst DMT and DBT seem to be ineffective. The different effects of aryl versus alkyl and trivalent versus divalent organic substituents of tin on chromosome length may relate to different modes of action.     

Species specific isotope dilution for the accurate and SI traceable determination of arsenobetaine and methylmercury in cuttlefish and prawn

Methods based on species specific isotope dilution were developed for the accurate and SI traceable determination of arsenobetaine (AsBet) and methylmercury (MeHg) in prawn and cuttlefish tissues by LC-MS/MS and SPME GC-ICPMS. Quantitation of AsBet and MeHg were achieved by using a ¹³C-enriched AsBet spike (NRC CRM CBET-1) and an enriched spike of Me¹⁹⁸Hg (NRC CRM EMMS-1), respectively, wherein analyte mass fractions in enriched spikes were determined by reverse isotope dilution using natural abundance AsBet and MeHg primary standards. Purity of these primary standards were characterized by quantitative ¹H-NMR with the use of NIST SRM 350b benzoic acid as a primary calibrator, ensuring the final measurement results traceable to SI. Validation of employed methods of ID LC-MS/MS and ID SPME GC-ICPMS was demonstrated by analysis of several biological CRMs (DORM-4, TORT-3, DOLT-5, BCR-627 and BCR-463) with satisfying results.     

Optimization of the solid phase extraction method for determination of Cu(II) in natural waters by using response surface methodology

A solid-phase extraction method was proposed for the preconcentration of Cu(II) in different samples in a mini-column packed with functionalized multi-walled carbon nanotubes (MWCNTs-COOH) as an effective sorbent, without using any complexing reagent, prior to its determination by flame atomic absorption spectrometry using response surface methodology. The experimental optimization step was performed by both a two-level full factorial design, with a center point, and a Box-Behnken design combined with response surface methodology. Three variables (pH, amount of Cu(II), and sample volume) were regarded as factors in the optimization. It was found that pH is the most significant factor affecting the preconcentration of Cu(II). The preconcentration factor was obtained as 100. The linear range was 1-5 mg L(-1) (R(2) = 0.999). Under the optimized experimental conditions, the detection limit (3s) of the proposed method followed by FAAS was found to be 0.27 μg L(-1). The relative standard deviation for 10 replicate measurements of 50 and 100 μg L(-1) Cu(II) was 2.39% and 0.98%, respectively. The response surface methodology was successfully applied to the determination of Cu(II) in water samples and mussel samples, and in a certified standard reference material (BCR-320R, Channel sediment).