Extraction procedure for organotin analysis in plant matrices: optimisation and application

Analysis of organotin compounds in vegetal samples is not well documented, and no specific extraction procedure of those species from vegetal matrix can be found in the literature. In order to develop such a procedure, we have compared in a first step the performances of six extracting solutions based on HCl, CH(3)COOH, NaOH, TMAH, enzymatic mixture and ethyl ethanoate. HCl-based extraction gives the highest recoveries. The whole extraction process was then optimised by investigating the influence of all the operating parameters. The resulting method, allowed a 100% recovery of tribultyltin and triphenyltin in spiked vegetal powders, without any noticeable degradation. The optimised extraction procedure was applied to the speciation of organotins in French beans and algae. Several mug (Sn) kg(-1) of butyltins were found in algae collected in an urban treatment plant and contents up to 800 mug (Sn) kg(-1) were detected in French beans cultivated with polluted nutritive solution. These results highlight the existence of a transfer of organotins from polluted waters to plants.     

Determination of organotin compounds in biological samples using accelerated solvent extraction,sodium tetraethylborate ethylation,and multicapillary gas chromatography–flame photometric detection

A method has been developed for species-selective analysis of organotin compounds in solid, biological samples. The procedure is based on accelerated solvent extraction (ASE) of analytes and includes extraction of the tin species with a methanol–water (90% methanol) solution of acetic acid/sodium acetate containing tropolone (0.03% w/v), their ethylation with NaBEt₄, and separation and detection by GC–FPD. The analytical procedure was optimized with an unspiked sample of harbor porpoise (Phocoena phocoena) liver. Effects of ASE operational variables (extraction temperature and pressure, solvent composition, number of static extraction steps) are discussed. Method detection limits (MDL) were in the range 6–10 ng(Sn) g^–1 dry weight and 7–17 ng(Sn) g^–1 dry weight for butyl- and phenyltin compounds, respectively. Recoveries were comparable with or better than those obtained by use of other procedures reported in the literature. The analytical procedure was validated by analysis of NIES No. 11 (fish tissue) certified reference material.     

Aqueous ethylation of organotin compounds in simple solution for speciation analysis by cryofocussing and detection by atomic absorption spectrometry — comparison with hydride generation

A 2³ factorial experimental design has been used to determine the optimum reaction conditions for organotin ethylation in simple aqueous solutions for speciation by Cryogenic Trapping/ Gas Chromatography/Atomic Absorption Spectrometry (CT/GC/AAS). The factors chosen and their levels of variation (? and +) were the pH of the solution (levels 3 and 5), the amount of NaBEt₄ added (levels 1 and 9 mg) to the organotins and the time of ethylation reaction (levels 10 and 20 min). Optimum conditions were investigated for monomethyltin (MMT), diethyltin (DET) and dibutyltin (DBT) in mixed solution at a concentration of 10 ng of each Sn compound in 50 ml of solution (200 ng·l^?1). The influence of the different factors on the yield of the ethylation reaction in the ranges investigated depends on the degree of substitution and the nature of the alkyl groups of the organotins. The ethylation reaction for DET and DBT is more efficient at high pH levels, MMT gives higher yields at lower pH. Both MMT and DET require a high amount of reagent, while reagent concentration has no real influence on the DBT signal. Comparison of hydride generation and ethylation as derivatisation procedures for organotin speciation has been performed in simple solutions. Under these analytical conditions, hydride generation is shown to be slightly more sensitive than ethylation by a factor of 1.4 for MMT and DET and 2 for DBT. However derivatisation using ethylation provides more reproducible results and is not affected by inorganic interferents.     

Certification of mono-, di-, and tributyltin compounds in marine sediment certified reference material by species-specific isotope dilution mass spectrometric analysis using synthesized <Superscript>118</Superscript>Sn-labeled butyltins

A new marine sediment reference material (NMIJ CRM 7301-a) for butyltins analysis was prepared and certified by the National Metrological Institute of Japan, National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). The original material of the sediment was collected at a bay near industrial activities in Japan. The sediment material was air-dried, sieved, homogenized, and packaged into 1,000 glass bottles (60 g each). Certification of NMIJ CRM 7301-a was carried out at NMIJ using two different types of species-specific isotope dilution mass spectrometry: isotope dilution–ethylation–gas chromatography/inductively coupled plasma mass spectrometry (GC/ICPMS) and isotope dilution–ethylation–gas chromatography/mass spectrometry (GC/MS). A mixture of ¹¹⁸Sn-enriched monobutyltin, dibutyltin, and tributyltin was synthesized in our laboratory and was used as a spike for both techniques. Certified values are given for tributyltin (0.044±0.004 mg kg^–1 as Sn), dibutyltin (0.056±0.006 mg kg^–1 as Sn, and monobutyltin (0.058±0.013 mg kg^–1 as Sn), being at lower levels than currently available sediment CRMs for the analysis of organotins.     

Analysis of organotin compounds by grignard derivatization and gas chromatography-ion trap tandem mass spectrometry

The determination of organotin compounds in water using gas chromatography-tandem mass spectrometry (GC-MS-MS) is described. Several organotin derivatives were synthesized by the reaction of organotin chlorides with Grignard reagents such as methyl-, propyl- and pentylmagnesium halides. After the optimization of the GC-MS-MS conditions, several derivatizations with the Grignard reagents were compared by evaluating the molar responses and volatilities of the derivatives and derivatization yields. As a result, the derivatizing reagent of choice is pentylmagnesium bromide. Calibration curves for the mono-, di- and tributyltins and mono-, di- and triphenyltins with pentylmagnesium bromide were linear in the range of 0.5-100 pg of Sn. The instrumental detection limits of six organotins ranged from 0.20 to 0.35 pg of Sn. The recovery tests from water samples (500 ml) were performed by using sodium diethyldithiocarbamate (DDTC) as a complexing reagent. Except for monophenyltin, the absolute recoveries of organotins from pure water at 200 ng of Sn/l were satisfactory. The recoveries calibrated by surrogate compounds (perdeuterated organotin chlorides) ranged from 71 to 109%. The method detection limits ranged from 0.26 to 0.84 pg of Sn (500-ml sample). This method was applied to the recovery of organotins from river water and seawater. The calibrated recoveries were between 90 and 122%.     

Organotin speciation in French brandies and wines by solid-phase microextraction and gas chromatography--pulsed flame photometric detection

An analytical method devoted to organotin compounds (OTC) determination in brandy and wine was developed. It is based on solid-phase microextraction (SPME) of ethylated organotins. The following operating factors were examined: SPME mode/nature of fibre coating, sample volume/dilution, and sampling time. The optimisation work led to dilute the sample in an aqueous buffer (1/11, v/v ratio) in order to satisfactorily decrease the matrix effects due to competitive sorption of non-OTC species onto/into fibre coating. The optimised operating conditions consist of polydimethylsiloxane (PDMS) coated fibre used in headspace mode for 30 min. In wines, the limits of detection (LOD) and quantification (LOQ) ranged from 1 to 40 and 3 to 80 ng(Sn)L(-1) respectively, according to the species. The analytical validation was made by evaluating the accuracy of OTC determination in spiked samples with various concentrations over the whole calibration range, i.e. from LOQ to 1000 ng(Sn)L(-1). Recovery was around 80-110% and precision (relative standard deviation, RSD) was between 12% and 25%. Despite the presence of two chromatographic peaks corresponding to sulphur compounds during brandy analysis, the selectivity of the method is adequate. The analysis confirmed the analytical performances and applicability of the method to wine and brandy samples. The obtained results emphasise the contamination of brandy and wine by organotins, the storage in plastic container seeming to be confirmed as the main OTC source.     

Organotin analysis by gas chromatography–pulsed flame-photometric detection (GC–PFPD)

Monobutyltin (MBuT), dibutyltin (DBuT), and tributyltin (TBuT) mixtures have been separated and quantified by gas chromatography with pulsed flame-photometric detection (GC–PFPD). The compounds were first derivatized with NaBEt₄, then extracted with hexane and injected into the GC in splitless mode. Optimum GC and detector conditions were established. For GC, various injector temperatures and oven temperature programs were tested. For the PFPD detector, gate settings (gate delay and gate width) and detector temperature were optimized. A very good linearity was obtained up to 100–150 ppb for all organotin compounds. The detection limits obtained were: MBuT (0.7 ppb), DBuT (0.8 ppb), and TBuT (0.6 ppb). RSD for repeatability and reproducibility were well below 20% when the instrument was in routine operation. A biological sample (CRM 477) was also analyzed for organotins. Extraction from the biological matrix was performed with TMAH. Besides the increased risk of contamination, the derivatization step seemed to be critical. pH and amount of derivatizing agent were tested. When using an internal standard (TPrT) between 90% and 110% of the certified amounts of organotin were recovered.     

Gas‐phase interactions of organotin compounds with cysteine

The gas‐phase interactions of cysteine with di‐organotin and tri‐organotin compounds have been studied by mass spectrometry experiments and quantum calculations. Positive‐ion electrospray spectra show that the interaction of di‐ and tri‐organotins with cysteine results in the formation of [(R)₂Sn(Cys‐H)]⁺ and [(R)₃Sn(Cys)]⁺ ions, respectively. MS/MS spectra of [(R)₂Sn(Cys‐H)]⁺ complexes are characterized by numerous fragmentation processes, notably associated with elimination of NH₃ and (C,H₂,O₂). Several dissociation routes are characteristic of each given organic species. Upon collision, both the [(R)₃Sn(Gly)]⁺ and [(R)₃Sn(Cys)]⁺ complexes are associated with elimination of the intact amino acid, leading to the formation of [(R)₃Sn]⁺ cation. But for the latter complex, two additional fragmentation processes are observed, associated with the elimination of NH₃ and C₃H₄O₂S. Calculations indicate that the interaction between organotins and cysteine is predominantly electrostatic but also exhibits a considerable covalent character, which is slightly more pronounced in tri‐organotin complexes. A preferred bidentate interaction of the type ‐η²‐S‐NH₂, with sulfur and the amino group, is observed. As for the [(R)₃Sn(Cys)]⁺ complexes, their stability is due to the combination of the hydrogen bond taking place between the amino group and the sulfur lone pair and the interaction between the carboxylic oxygen atom and the metal. Copyright © 2016 John Wiley & Sons, Ltd.     

Trends in flow-based analytical methods applied to pesticide detection: a review

Landfilling is the most common disposal of municipal waste. During the decomposition of different waste materials, several toxic compounds are leached. Although organotin compounds (OTC) represent an important group of pollutants in landfill leachates, there are only few analytical procedures reported for their analysis. These procedures are complex or recommend the use of enriched stable isotopes that are available only for butyltins. In the present work analytical procedure for simultaneous routine speciation analysis of methyl-, butyl-, phenyl- and octyl-tins in landfill leachates by GC-ICP-MS was developed. For this purpose the applicability of methanol as co-extraction reagent and Tris-citrate buffer for adjustment of pH for derivatization of OTC in landfill leachates was carefully investigated. The use of NaBEt(4) and NaBPr(4) as derivatization reagents for liquid-liquid extraction into hexane was critically evaluated. 15m GC column was used for rapid separation of OTC. The developed analytical procedure was sensitive (LODs for OTC investigated in general better than 2 ng Sn L(-1)) with good repeatability of measurement (RSDs mostly better than 3%) and was successfully applied in the analysis of OTC in landfill leachates using standard addition calibration method. Due to its simplicity and reliability it is appropriate to be used in routine laboratories for monitoring of OTC in landfill leachates.     

Preconcentration and determination of Sn- and Pb-organic species in environmental samples by SPME and GC-AED

A new sample preparation and preconcentration technique – solid phase microextraction (SPME) – is reported for the application of several tinorganic compounds and tetrabutyllead in aqueous samples. The solvent-free procedure is rapid in comparison with liquid-liquid extraction or SFE but also sensitive. Analytical variables of the extraction such as adsorption and desorption time, stirring rate and temperature has been investigated. The determination has been performed by GC coupled with atomic emission detection (AED). After optimization of the conditions of SPME a calibration was realized on the basis of a multicomponent standard solution, prepared by ethylation of organotin salts directly in the sample using sodium tetraethylborate (NaBEt₄) without prior separation of the analytes from the matrix. The method permits preconcentration. Values of about 10 can be reached. A detection limit of 0.09 pg Sn and 0.08 pg Pb can be achieved under optimized conditions. The proposed procedure has been successfully applied to the analysis of organotin compounds in various slurry samples.     

Rapid determination of organotin compounds by headspace solid-phase microextraction

Headspace solid-phase microextraction (SPME) followed by gas chromatography (GC) coupled to pulsed flame photometric detection have been investigated for the simultaneous speciation analysis of 14 organotin compounds, including methyl-, butyl-, phenyl-, and octyltins compounds. The analytical process (sorption on SPME fibre and thermal desorption in GC injection port) has been optimised using experimental designs. Six operating factors were considered in order to evaluate their influence on the performances of a SPME-based procedure. The evaluation of accuracy, precision and limits of detection (LODs) according to ISO standards and IUPAC recommendations has allowed the method to be validated. The LODs obtained for the 14 studied organotins compounds are widely sub-ng(Sn) l(-1). The precision evaluated using relative standard deviation ranges between 9 and 25% from five determinations of the analytes at 0.25-125 ng(Sn) l(-1) concentrations. The accuracy was studied throughout the analysis of spiked environmental samples. These first results show that headspace SPME appears really as attractive for organotins determination in the environment and the monitoring of their biogeochemical cycle.     

Comparison of GC-ICP-MS and HPLC-ICP-MS for species-specific isotope dilution analysis of tributyltin in sediment after accelerated solvent extraction

This study describes a direct comparison of GC and HPLC hyphenated to ICP–MS determination of tributyltin (TBT) in sediment by species-specific isotope dilution analysis (SS-IDMS). The certified reference sediment PACS-2 (NRC, Canada) and a candidate reference sediment (P-18/HIPA-1) were extracted using an accelerated solvent extraction (ASE) procedure. For comparison of GC and LC methods an older bottle of PACS-2 was used, whilst a fresh bottle was taken for demonstration of the accuracy of the methods. The data obtained show good agreement between both methods for both the PACS-2 sediment (LC–ICP–IDMS 828±87 ng g^–1 TBT as Sn, GC–ICP–IDMS 848±39 ng g^–1 TBT as Sn) and the P-18/ HIPA-1 sediment (LC–ICP–IDMS 78.0±9.7 ng g^–1 TBT as Sn, GC–ICP–IDMS 79.2±3.8 ng g^–1 TBT as Sn). The analysis by GC–ICP–IDMS offers a greater signal-to-noise ratio and hence a superior detection limit of 0.03 pg TBT as Sn, in the sediment extracts compared to HPLC–ICP–IDMS (3 pg TBT as Sn). A comparison of the uncertainties associated with both methods indicates superior precision of the GC approach. This is related to the better reproducibility of the peak integration, which affects the isotope ratio measurements used for IDMS. The accuracy of the ASE method combined with HPLC–ICP–IDMS was demonstrated during the international interlaboratory comparison P-18 organised by the Comité Consultatif pour la Quantité de Matière (CCQM). The results obtained by GC–ICP–IDMS for a newly opened bottle of PACS-2 were 1087±77 ng g^–1 Sn for DBT and 876±51 ng g^–1 Sn for TBT (expanded uncertainties with a coverage factor of 2), which are in good agreement with the certified values of 1090±150 ng g^–1 Sn and 980±130 ng g^–1 Sn, respectively.     

Evaluation of a combined fractionation and speciation approach for study of size-based distribution of organotin species on environmental colloids

Results relating to the first original application of an analytical approach combining asymmetric flow field-flow fractionation (As-Fl-FFF) with multi-detection and chemical speciation for determination of organotins in a landfill leachate sample are presented. The speciation analysis involved off-line head-space solid-phase microextraction (HS-SPME)–gas chromatography with pulsed-flame photometric detection (GC–PFPD) performed after three consecutive collections of five different fractions of interest from the As-Fl-FFF system and cross-flow part (assumed to be representative of the <10 kDa phase). After 0.45 μm filtration and without preconcentration before fractionation and speciation analysis, limits of detection (LOD) were 4–45 ng (Sn) L⁻¹ in the sample, with relative standard deviations (RSD) of 3–23%. The As-Fl-FFF fractionation of this sample enables characterization of two distinct populations—organic-rich and inorganic colloids with gyration radius up to 120 nm. Total Sn and mono and dibutyltins (MBT and DBT) appear to be distributed over the whole colloidal phase. Tributyl, monomethyl, monooctyl, and diphenyltins (TBT, MMT, MOcT, and DPhT) were also detected. Quantitative speciation analysis performed on the two colloidal populations and in the <10 kDa phase revealed concentrations from 130 ± 10 (MMT) to 560 ± 50 ng (Sn) L⁻¹ (DPhT).     

超临界流体萃取法对有机锡化合物的选择性萃取

 研究了用超临界流体萃取法直接从脂肪基质的固体样品（大豆粉）中选择性地萃取有机锡化合物的方法。模拟试样萃取结果表明：用较低压力和较高温度的超临界态ＣＯ２作流动相时，有机锡达到最大萃取率，而脂肪类物质仅被少量萃取，从而消除了脂肪类物质对超临界流体色谱法测定有机锡的干扰。     

Speciation of organotin in environmental sediment samples

An optimized sample preparation procedure for organotin speciation in sediment samples has been applied to the analysis of sediments collected in the environment. The method is based on tropolone complexation of the ionic organotins, followed by extraction into a hexane-ethylacetate mixture and derivatization by NaBEt(4). The method was applied to the determination of organotin in various harbour, shipyard and dry-dock sediments in Belgium. Butyltin compounds were detected in all samples analyzed, often at high mg kg(-1) levels. A limited number of samples showed the presence of phenyltin compounds. Further, the method was adapted to the analysis of river sediments sampled from the vicinity of shipyards. Butyltin concentrations were detected at the microg kg(-1) level in the majority of samples.     

Simultaneous extraction of organotin, organolead and organomercury species from soils and litter

Extracting organotin compounds (OTC) from soils is difficult due to the high cation exchange and complexation capacity of soils, and little information about OTC in soils is available. In this study, a new extraction method, combining 1 M CaCl₂, 0.1% tropolone, and glacial acetic acid was developed. Recoveries of mono-substituted OTC from spiked plant litter, and soil samples were improved substantially to 40% compared to classical glacial acetic acid extraction commonly used in sedimentology, yielding <10% recovery in C-rich soil samples. Simultaneously, the recovery of other OTC, trimethyllead and monomethylmercury was satisfactory. The recoveries of most species from the spiked litter, upland and wetland soils exceeded 70%. The new method extracted much more organometallics from unspiked organic soils and litter than microwave- and ultrasound-assisted extraction and accelerated solvent extraction, most likely due to exchange of organometallics from the solid phase by Ca²⁺. The method is simple, highly efficient and with low contamination. Together with GC-ICP-mass spectrometry, the method allows the detection of these organometallics in the pg g⁻¹ range and it is particularly suitable for soil and plant materials with low organometallics contents.     

Gas‐phase interactions of organotin compounds with glycine

Gas‐phase interactions of organotins with glycine have been studied by combining mass spectrometry experiments and quantum calculations. Positive‐ion electrospray spectra show that the interaction of di‐ and tri‐organotins with glycine results in the formation of [(R)₂Sn(Gly)‐H]⁺and [(R)₃Sn(Gly)]⁺ ions, respectively. Di‐organotin complexes appear much more reactive than those involving tri‐organotins. (MS/MS) spectra of the [(R)₃Sn(Gly)]⁺ ions are indeed simple and only show elimination of intact glycine, generating the [(R)₃Sn]⁺ carbocation. On the other hand, MS/MS spectra of [(R)₂Sn(Gly)‐H]⁺complexes are characterized by numerous fragmentation processes. Six of them, associated with elimination of H₂O, CO, H₂O + CO and formation of [(R)₂SnOH]⁺ (?57 u),[(R)₂SnNH₂]⁺( ?58 u) and [(R)₂SnH]⁺ (?73 u), are systematically observed. Use of labeled glycines notably concludes that the hydrogen atoms eliminated in water and H₂O + CO are labile hydrogens. A similar conclusion can be made for hydrogens of [(R₂)SnOH]⁺and [(R₂)SnNH₂]⁺ions. Interestingly, formation [(R)₂SnH]⁺ ions is characterized by a migration of one the α hydrogen of glycine onto the metallic center. Finally, several dissociation routes are observed and are characteristic of a given organic substituent. Calculations indicated that the interaction between organotins and glycine is mostly electrostatic. For [(R)₂Sn(Gly)‐H]⁺complexes, a preferable bidentate interaction of the type η²‐O,NH2 is observed, similar to that encountered for other metal ions. [(R)₃Sn]⁺ ions strongly stabilize the zwitterionic form of glycine, which is practically degenerate with respect to neutral glycine. In addition, the interconversion between both forms is almost barrierless. Suitable mechanisms are proposed in order to account for the most relevant fragmentation processes. Copyright © 2013 John Wiley & Sons, Ltd.     

Voltammetric speciation of butyltin compounds

A sensitive and selective procedure for the determination of tributyltin chloride (TBT), dibutyltin dichloride (DBT) and monobutyltin trichloride (MBT) based on solid phase extraction (SPE) with ENVI-Carb non-porous carbon as column material followed by adsorptive cathodic stripping voltammetry (AdSV) in the presence of tropolone is reported. The determination limits achieved using a 500 mL water sample were 210 ng L^–1 (as Sn) for TBT, 30 ng L^–1 (as Sn) for DBT and 40 ng L^–1 (as Sn) for MBT. The method was used to determine the levels of butyltin species in surface water from the yacht harbour at Zewen on the Mosel River and in the tap water supply in Trier.Dedicated to Professor Dr. K. Doerffel and Professor Dr. H. Kriegsmann on the occasion of their 70th birthdays