Sodium Tetraethylborate Research Articles

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 mum 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.

Determination of the acaricide fenbutatin oxide in water samples by automated headspace‐SPME‐GC/MS

The analysis of the acaricide fenbutatin oxide (FBTO) having a molecular weight of 1052.66 g mol(-1) in water samples by capillary GC/MS after in-situ derivatization with sodium tetraethylborate (NaBEt4) and headspace-SPME enrichment is described. Automated SPME is performed at 80 degrees C for 30 min. Detection is carried out in the ion monitoring mode with deuterated triphenyltin (TPhTd15) as internal standard. Good linearity (R2 = 0.9993) was obtained in the dynamic range 20 to 1000 ng L(-1) with a limit of detection of 16 ng L(1) (LOD at 3 S/N) and a limit of quantitation of 50 ng L(-1) (LOQ at 10 S/N). Intra-day RSD% for n=6 was 8.9 at the LOQ level.

Organotin speciation in Bizerte lagoon (Tunisia)

For the first time, organotins have been assessed in samples collected from Bizerte lagoon, in Tunisia, during two seasons (summer and winter). The organotin distribution was studied in marine sediments and mussels tissues of this lagoon. Butyl-, phenyl- and octyltins were determined using a rapid speciation analytical method based on one-step ethylation/extraction with sodium tetraethylborate in aqueous phase. Simultaneously to the ethylation, the extraction was performed by either liquid/liquid extraction (LLE) or head-space solid phase microextraction (HS-SPME). Gas chromatography with pulsed flame photometric detection (GC-PFPD) was used to perform quantitative determination. The technique has been validated using biological and sediment reference materials. The different samples from Bizerte lagoon were found to be moderately contaminated, especially by butyltins. This pollution was attributed to industrial activities, which are very important in this area. Organotins appeared accumulated in both sediments and mussels, while significant degradations of triorganotins to monosubstituted ones was observed in water.

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 Sn 118 and Sn 120 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 μg 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 μg kg −1 in the port of Antwerp up to 43 mg kg −1 near a ship repair unit.

Redistribution reactions of butyl- and phenyltin species during storage in methanol

The stability of organotin species, which are frequently used as standards, in methanol has been investigated by gas chromatography coupled to either quartz furnace atomic absorption spectrometry, inductively coupled plasma mass spectrometry or mass spectrometry. Ethylation with sodium tetraethylborate was used during sample preparation. The species composition of single or mixed standard solutions at a concentration of 10 μg g−1 was investigated after storing at −20 °C, +4 °C and +22 °C for various time periods. All butyltin species (monobutyltin—MBT, dibutyltin—DBT and tributyltin—TBT) were found to be stable for all storage conditions, even when mixed. The single triphenyltin (TPhT) standard was also stable, whereas mono-and diphenyltin (MPhT; DPhT) were unstable. MPhT redistributed to DPhT and inorganic tin (IOT), while DPhT redistributed to MPhT and to a minor extent to TPhT. In a mixture containing MBT, DBT, TBT, MPhT, DPhT and TPhT, besides the above mentioned reactions, DPhT was found to react strongly with MBT forming up to 73% monobutyl-monophenyltin (MBMPhT) and MPhT. The composition of MBMPhT was investigated by GC-MS. Suggestions for the type of reactions leading to the redistribution of OT species are outlined and suggestions on how to prepare stable OT standards are made.

Sample treatment selection for routine mercury speciation in seafood by gas chromatography-atomic fluorescence spectroscopy

A general analytical strategy for mercury speciation in seafood samples has been proposed to increase sample throughput. This consists of the initial determination of total mercury content, and then mercury speciation using gas chromatography coupled to atomic fluorescence spectroscopy. The appropriate sample treatment for mercury speciation is selected between a method based on aqueous ethylation with sodium tetraethylborate (Approach A: a rapid methodology for samples with methylmercury concentrations between 150 and 2000 ng g−1) and another one based on the determination of organomercury chlorides (Approach B: a much more time-consuming methodology, applicable to samples with methylmercury at 1.2–200 ng g−1). Both procedures have been used together for the analysis of bivalves and fish samples. Copyright © 2005 John Wiley & Sons, Ltd.

Determination of inorganic mercury and methylmercury in zooplankton and fish samples by speciated isotopic dilution GC-ICP-MS after alkaline digestion

Species-specific isotope dilution (ID) in combination with gas chromatography-inductively coupled plasma-mass spectrometry (GC-ICP-MS) for separation and determination of methylmercury (MeHg) and inorganic mercury (Hg) in fish tissue and zooplankton is described. Samples were digested with methanolic potassium hydroxide. Analytes were derivatized with sodium tetraethylborate and absorbed in an isooctane trap. ID analysis was performed using an enriched spike of 201Hg and a laboratory synthesized enriched spike of Me201Hg. The precision of repeated measurements was always less than 5%. The absolute detection limits obtained with GC-ICP-MS for MeHg and Hg were 2.8 ng and 4.6 ng, respectively. Analytical precision was typically better than 5% over ten repeated measurements. The accuracy of the method has been validated with certified reference materials (DORM-2 and BCR 414). The total mercury concentration results of the real samples as well as the CRM have been compared with those obtained by cold vapor-high resolution ICP-MS using ID approach.

Species specific isotope dilution with on line derivatisation for determination of gaseous mercury species

A species specific isotope dilution (SSID) method for determination of the volatile mercury (Hg) species Hg0, (CH3)2Hg, CH3HgX and HgX2 (where X is a counter ion) in gaseous samples was developed. The procedure involved on line derivatisation of ionic Hg species with sodium tetraethylborate during sampling, before collection of species on a Tenax TA tube in series with an Au–Pt tube. Collected species were thermally desorbed and determined by GC-ICP-MS. The procedure provided absolute detection limits of 0.5 pg for CH3HgX and (CH3)2Hg, 5 pg for HgX2 and 25 pg for Hg0. Recoveries and transformations of the investigated species were studied for the different procedural steps and the method was tested for microcosm experiments on brackish water sediment samples, as well as for laboratory air samples. As a result of methylation and reduction processes within the sediment, gaseous emission rates could be determined for all investigated species after addition of an isotope enriched aqueous inorganic 199Hg2+ standard to the sediment. Hg0 was the only specie detected in laboratory air samples (4.5 ng m−3). The procedure for derivatisation of ionic Hg species prior to collection on Tenax TA reduces memory effects and transformations of CH3HgX and HgX2, which is especially advantageous at low sample gas flow rates and for complex gaseous matrices, such as emissions from sediment samples. SSID provides simplified methodological development, as well as efficient correction for matrix induced losses and transformations of Hg species. The method could be useful for various biogeochemical studies of Hg, as well as for reliable risk assessments during, for example, waste management and soil remediation.

Determination of organotin compounds in water by headspace solid phase microextraction with gas chromatography–mass spectrometry

This investigation evaluates headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) to determine trace levels of organotins in water. The organotins were derivatized in situ with sodium tetraethylborate and adsorbed on a poly(dimethysiloxane) (PDMS)-coated fused silica fiber. The SPME experimental procedures to extract organotins in water were at pH 5, with extraction and derivatization simultaneously at 45 degrees C for 30 min in a 2% sodium tetraethylborate solution and a sample solution volume in the ratio of 1:1, and desorption in the splitless injection port of the GC at 260 degrees C for 2 min. Detection limits are determined to be in the low ng/L range. According to the analysis, the linearity range is from 10 to 10,000 ng/L with R.S.D. values below 12% except triphenyltin (24%). The proposed method was tested by analyzing surface seawater from the harbors on the Taiwanese coast for organotins residues. Some organotins studied were detected in the analyzed samples. Results of this study demonstrate the adequacy of the headspace SPME-GC-MS method for analyzing organotins in sea water samples.

Flow injection chemical vapor generation of Au using a mixed reductant

Sodium tetraethylborate was used to enhance the chemical vapor generation (CVG) efficiency of gold. Volatile species of Au in a weakly acidified buffer medium were generated at room temperature by reaction with a mixed reductant containing 0.1% NaBH 4 and 0.01% NaBEt 4 in the presence of 0.03% sodium diethyldithiocarbamate (DDTC). A flow injection (FI) system was coupled to a heated quartz tube atomizer for atomic absorption spectrometry (AAS) detection. A precision of 2.5% RSD ( n=11, 0.4 mg/L level) was realized at sampling frequencies of 110/h. A detection limit of 2.8 ng/mL (3 σ) was obtained based on a 500-μL sample volume. Compared with FI-CVG-AAS using NaBH 4 as the sole reductant, sensitivity was increased 8- to 10-fold. In situ trapping of the analyte in a graphite furnace followed by electrothermal AAS detection, as well as signal monitoring using ICP-OES, was used to study the system. Generation efficiency is estimated to be in the range of 0.8–6%.

Determination of methylmercury and inorganic mercury in shark fillets

AbstractThree samples of deep‐frozen shark fillets were analysed according to the following procedure: dissolution in tetramethylammonium hydroxide, derivatization/ethylation with sodium tetraethylborate, extraction into iso‐octane and measurement with gas chromatography hyphenated to inductively coupled plasma mass spectrometry (GC–ICPMS) for the identification and quantification of methylmercury (MeHg+) and inorganic mercury (Hg2+). For the correction of procedural errors, two internal standards were used. The sample pretreatment was corrected by spiking with dibutyl‐dipentyltin (DBT‐pe), and the GC–ICPMS measurements were controlled by the signal stability of xenon which was added to the GC carrier gas.Furthermore, for comparisons, the total amount of mercury was determined by an independent technique, i.e. atomic fluorescence spectroscopy. Standard reference materials, which are only available in the form of lyophilisates and not as fresh fish materials, were also analysed to ensure the procedural quality control. The concentration range of total mercury measured in the shark fillets was between 0.9 and 3.6 µg mercury per gram thawed‐out shark fillet. Two samples contained higher concentrations than the European legislation. Speciation analysis leads to ≥94% mercury bound as MeHg+. Since MeHg+ is known as one of the most toxic compounds, this conclusion is of importance with respect to bioaccumulation of mercury species via fish into the human food chain. Copyright © 2004 John Wiley & Sons, Ltd.

Validation of a simplified field-adapted procedure for routine determinations of methyl mercury at trace levels in natural water samples using species-specific isotope dilution mass spectrometry

A field-adapted procedure based on species-specific isotope dilution (SSID) methodology for trace-level determinations of methyl mercury (CH(3)Hg(+)) in mire, fresh and sea water samples was developed, validated and applied in a field study. In the field study, mire water samples were filtered, standardised volumetrically with isotopically enriched CH(3) (200)Hg(+), and frozen on dry ice. The samples were derivatised in the laboratory without further pre-treatment using sodium tetraethyl borate (NaB(C(2)H(5))(4)) and the ethylated methyl mercury was purge-trapped on Tenax columns. The analyte was thermo-desorbed onto a GC-ICP-MS system for analysis. Investigations preceding field application of the method showed that when using SSID, for all tested matrices, identical results were obtained between samples that were freeze-preserved or analysed unpreserved. For DOC-rich samples (mire water) additional experiments showed no difference in CH(3)Hg(+) concentration between samples that were derivatised without pre-treatment or after liquid extraction. Extractions of samples for matrix-analyte separation prior to derivatisation are therefore not necessary. No formation of CH(3)Hg(+) was observed during sample storage and treatment when spiking samples with (198)Hg(2+). Total uncertainty budgets for the field application of the method showed that for analyte concentrations higher than 1.5 pg g(-1) (as Hg) the relative expanded uncertainty (REU) was approximately 5% and dominated by the uncertainty in the isotope standard concentration. Below 0.5 pg g(-1) (as Hg), the REU was >10% and dominated by variations in the field blank. The uncertainty of the method is sufficiently low to accurately determine CH(3)Hg(+) concentrations at trace levels. The detection limit was determined to be 4 fg g(-1) (as Hg) based on replicate analyses of laboratory blanks. The described procedure is reliable, considerably faster and simplified compared to non-SSID methods and thereby very suitable for routine applications of CH(3)Hg(+) speciation analysis in a wide range of water samples.

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 (Hg 2+) 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 × 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 Hg 2+. The repeatability (R.S.D., %) is 3.3% for MeHg and 3.8% for Hg 2+ for 10 successive injections of a standard mixture of 10 pg. 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.

Application of a Gas Chromatography/Mass Spectrometric Method for the Determination of Butyltin Compounds in Sediment

A gas chromatography/mass spectrometric (GC/MS) method has been developed for the determination of trace mono-n-butyltin (MBT), di-n-butyltin (DBT), and tri-n-butyltin (TBT) compounds in sediments. Samples were extracted by 10% acetic acid in methanol containing 0.03% tropolone and were then derivatized for GC/MS analysis. Ethylation by sodium tetraethylborate and phenylation by sodium tetraphenylborate were evaluated as a derivatization reaction of the organotins in sample extract. n-Hexane was added into reaction media in the beginning of the reaction for the continuous extraction of derivatized organotins. Ethylation requires less than 2 hours to get proper derivatization yields for MBT, DBT, and TBT altogether and produces relatively low amounts of side reaction products. Compared to ethylation, phenylation requires much longer time but provides relatively lower yield and produces considerable amounts of side reaction products. Therefore, the ethylation reaction was applied for the analysis of organotin compounds in sediment. An isotope dilution mass spectrometric (IDMS) method based on GC/MS has been applied to the accurate determination of DBT compounds in the sediments. The IDMS results from the analyses of sediment samples showed a reasonable repeatability and a good agreement with the values obtained by IDMS based on liquid chromatography/induced coupled plasma/mass spectrometry.

Speciation of organotin compounds in waters and marine sediments using purge-and-trap capillary gas chromatography with atomic emission detection

A procedure for the simultaneous determination of six organotin compounds, including methyl-, butyl- and phenyltins, in waters and marine sediments is developed. The analytes were leached from the solid samples into an acetic acid:methanol mixture by using an ultrasonic probe. The organotins were derivatized with sodium tetraethylborate (NaBEt 4) in the aqueous phase, stripped by a flow of helium, pre-concentrated in a trap and thermally desorbed. This was followed by capillary gas chromatography with microwave-induced plasma atomic emission spectrometry as the detection system (GC–AED). Each chromatographic run took 22 min, including the purge time. Calibration curves were obtained by plotting peak area versus concentration and the correlation coefficients for linear calibration were at least 0.9991. Detection limits ranged from 11 to 50 ng Sn l −1 for tributyltin and tetramethyltin, respectively. The seawater samples analyzed contained variable concentrations of mono-, di- and tributyl- and monophenyltin, ranging from 0.05 to 0.48 μg Sn l −1, depending on the compound. Some of the sediments analyzed contained concentrations of dibutyl- and tributyltin of between 6.0 and 13.0 ng Sn g −1. Analysis of the certified reference material PACS-2, as well as of spiked water and sediment samples showed the accuracy of the method. The proposed method is selective and reproducible, and is considered suitable for monitoring organotin compounds in water and sediment samples.

Identification of sulfur interferences during organotin determination in harbour sediment samples by sodium tetraethyl borate ethylation and gas chromatography-pulsed flame photometric detection

Identification of sulfur interferences during organotin determination in harbour sediment samples by sodium tetraethyl borate ethylation and gas chromatography-pulsed flame photometric detection

Identification of sulfur interferences during organotin determination in harbour sediment samples by sodium tetraethyl borate ethylation and gas chromatography-pulsed flame photometric detection

Because of the high toxicity of organotin compounds and the current regulation about their applications, analytical method usable in routine analysis is required. A speciation procedure based on NaBEt 4 ethylation and GC-PFPD analysis has shown to be suitable for the organotin determination. Unfortunately, some matrix effects were observed during the analysis of harbour sediments from Chile. These effects were identified as the alkylation of elemental sulfur and the coelution between the organotin compounds and some dialkylsulfides. The re-optimization of GC parameters and application of solid phase microextraction (SPME) were proposed to solve these analytical problems. Certified reference materials and different harbour sediment samples were analysed in order to evaluate the suitability of the methods for organotin control in complex environment samples.

Reducing blank values for trace analysis of ionic organotin compounds and their adsorption to different materials

Organotin compounds (OTC) are highly toxic pollutants strongly affecting many ecosystems. As analytical techniques for OTC have improved in the past, problems with blank values and adsorption to container walls have been revealed. In this study, OTC adsorption to different materials was studied, and different methods such as derivatization, complexation, extraction, UV-light treatment, nitric acid baths, glowing at high temperatures, and rinsing with detergents and distilled water were tested to reduce OTC blank values from chemicals, solutions, and containers of different materials. Rinsing with detergents and distilled water was effective for decontaminating containers of different materials. Glowing at high temperatures was specifically suitable for glassware and chemicals with high melting points. UV-light treatment was suitable only for solutions. However, OTC underwent disproportionation, and tin became methylated under high temperatures and UV-light treatment. Methods combining sodium tetraethylborate and organic solvent extraction had the best decontamination effects among all methods but were not economical. Sodium borohydride provided another alternative but was less effective. However, use of sodium tetraethylborate and sodium borohydride was restricted to aqueous solution and in certain pH ranges. No material was found without adsorption of all OTC in this study. Tributyltin and dibutyltin adsorbed strongly in the Teflons, polyethylene, and silanized glass. Monomethyltin and monobutyltin had strong adsorption in most materials. Different materials should be used for different OTC in adsorption studies. The use of extraction reagents to recover OTC from container walls is suggested to avoid underestimation of OTC concentrations in waters.

Determination of butyltins in environmental samples using sodium tetraethylborate derivatisation: characterisation and minimisation of interferences

Interferences affecting the determination of butyltin species by sodium tetraethylborate (STEB) derivatisation followed by purge–trap preconcentration were systematically studied using synthetic solutions, natural water samples and sediment extracts. Substances that did not cause interferences included most common cations (apart from those metal ions listed below), anions, metalloids and polar organic compounds. Natural organic matter (NOM) specifically interfered with tributyltin (TBT) due to a mechanism involving partitioning of the butyltin to the hydrophobic portions of the NOM. The metal ions Ag(I) (≥2 μM), Cd(II) (≥2 μM), Cu(II) (≥0.5 μM) interfered predominantly with the determination of monobutyltin (MBT) due to catalytic degradation of the STEB reagent. Pb(II) (≥14 μM) interfered with butyltin determination by an unknown mechanism. Other interferences to the purge–trap method were shown to occur in the presence of chelating agents (e.g. EDTA) or hydrophobic liquids such as diesel fuel. A mixture comprising methanol (MeOH), EDTA and Mn(II) was used to partially mask the effect of interfering NOM and metals. Spike recoveries (mean±S.D. of n=7 different samples) of MBT, dibutyltin (DBT) and TBT in contaminated natural water samples were improved from 70±36,90±11 and 91±24 to 102±10,98±3 and 98±4%, respectively. Spike recoveries (mean±S.D. of n=5 different samples) of MBT, DBT and TBT in aliquots of sediment extracts were improved from 86±17,79±18 and 59±32 to 97±6.2,103±3.6 and 103±5.0%, respectively. The ability to analyse larger aliquots of sediment extracts in the presence of the masking mixture improved the detection limit four-fold if MBT and DBT determination was required and 10-fold if only TBT determination was required.

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 NaBEt(4), 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.