Certified Reference Sediment Research Articles

Method development and validation for the determination of polybrominated diphenyl ether congeners in Brazilian aquatic sediments

An analytical method was developed and validated for the determination of nine PBDE congeners (BDE 28, 47, 66, 85, 99, 100, 138, 153 and 154) in aquatic sediment samples using ultrasonic solid-liquid extraction (acetone:n-pentane 1:1v/v) followed by gas chromatography coupled with electron capture detection. Values for LOD varied between 0.58 and 0.96ngg−1 while LOQ ranged from 1.92 to 3.21ngg−1. Fortified and certified reference sediments were investigated for method accuracy and precision. Recovery, varying from 87.7±6.6% (BDE-138) to 98.7±1.4% (BDE-28), was influenced by strong hydrophobic interactions between analytes and the sediment matrix. The validated method was successfully used to assess PBDE levels in a Brazilian sediment sample collected at the Paranoá Lake, in Brasília (Brazil). Results revealed environmental concentrations above the reported LOQ for two of the nine PBDE congeners being the BDE-66 the most prevalent (8.1±0.4ngg−1) followed by BDE-47 (2.51±0.02ngg−1). Further investigations are still needed to evaluate the contamination pattern of PBDE in Brazilian sediments, notably in urbanized regions.

Photochemical sample treatment for extracts clean up in PCB analysis from sediments

Sample purification can be considered the most polluting step of the whole analytical process for PCBs determination in sediment samples. The use of photochemical sample treatment represents an alternative methodology for extracts clean up allowing for a reduction of the used amount of organic solvents. The first application of a photochemical sample treatment for the selective removal or reduction of organic substances interfering with PCBs analyses in sediments is reported. The method's efficiency and robustness were compared with currently used chromatographic purification. Quality parameters such as recovery, linearity and reproducibility were studied. The entire procedure was validated by four replicate analysis of certified reference sediment. The quantification limits (LOQ) obtained by us ranged from 1 to 3.1ngg−1. The RSD for each congener was below 15% and recoveries were in the range 40–130%.Results based on the analysis of real and certified samples showed similar or improved detection thresholds and pointed out the advantages of the photochemical methodology in terms of costs and environmental friendly conditions.

Improvements of reliability for methylmercury determination in environmental samples

The determination of methylmercury (MeHg) in environmental samples by ethylation derivation–gas chromatography–atomic fluorescence spectrometry (ED–GC–AFS) is associated with an intimate problem of water moisture accumulation introduced in the ethylation step, which enters the detection system and cause a spectroscopic interference. With a simple modification on the GC–AFS system, this problem was eliminated and the analytical quality of the measurements was significantly improved. The presence of dissolved sulfide in samples can also cause serious chemical interference in the ethylation step resulting in lower or total loss of the MeHg signal. It was found that a masking system of CuSO 4–Na 2C 2O 4 was able to eliminate this interference. With this system, the accurate determination of trace amount of MeHg in high dissolved sulfide containing samples was achieved. Satisfactory analytical results were obtained with the certified reference sediment IAEA405, sulfate reducing bacteria culture and sulfide containing water samples. The limit of detection and quantitation of this masking system is 0.01 and 0.04 ng L −1 respectively. Other factors affecting ethylation are also discussed.

Coupling the extraction efficiency of imidazolium-based ionic liquid aggregates with solid-phase microextraction-gas chromatography–mass spectrometry: Application to polycyclic aromatic hydrocarbons in a certified reference sediment

Three ionic liquid (IL)-based aggregates, 1-hexadecyl-3-methylimidazolium bromide (HDMIm-Br), 1-hexadecyl-3-butylimidazolium bromide (HDBIm-Br), and 1,3-didodecylimidazolium bromide (DDDDIm-Br) have been applied to the development of a quantitative solid-phase microextraction (SPME)-gas chromatography (GC)–mass spectrometry (MS) method. A sensitivity factor (SF) is defined and introduced for the first time to quantitatively compare the efficiency of the IL-based aggregates by SPME-GC–MS and to evaluate the partitioning strength of several polycyclic aromatic hydrocarbons (PAHs) to the three IL-aggregates. The ILs HDBIm-Br and HDMIm-Br have been used successfully to extract seven PAHs from the certified reference sediment BCR-535 using focused microwave-assisted extraction followed by SPME-GC–MS. Average recoveries for six of the seven certified PAHs were 84.6% for HDMIm-Br and 101% for HDBIm-Br, with relative standard deviation values (RSDs) lower than 19%. The overall extraction method requires short extraction times (around 7 min for the microwave step) and avoids the use of organic solvents.

Simultaneous extraction of several persistent organic pollutants in sediment using focused ultrasonic solid-liquid extraction

Focused ultrasonic solid-liquid extraction (FUSLE) has been optimised for simultaneous analysis of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), phthalate esters (PEs), and nonylphenols (NPs) in sediment samples. Optimisation was performed using naturally polluted freeze-dried sediment samples. The variables studied during the optimisation process were: percentage of maximum power (10-60%), extraction time (10-300 s), number of cycles (1-9), composition of the extraction solvent (acetone-n-hexane, 10:90-90:10), and sample mass (0.1-1 g). The volume of the extractant was constant (10 mL) and the extraction was performed at 0 degrees C in an ice-bath during the optimisation process. All these variables were studied using an experimental design approach by means of The Unscrambler software. The extraction time and the operational variables (number of cycles and power) had no statistically significant effect in the extraction and they were held at 2 min, 20% power, and seven cycles, respectively. The mass and the addition of non-polar solvent (n-hexane) had a negative effect in the extraction yield and, thus, the mass was held at 0.5 g and pure acetone was used as extraction solvent. After those variables were optimised, the effect of the extraction temperature (0 degrees C or room temperature) was also studied. The validation of the extraction method was performed using NIST-1944 reference material in the case of PAHs and PCBs. Because no certified reference sediment is available for PEs and NPs, the results obtained for FUSLE were compared with those obtained for microwave-assisted extraction (MAE) under conditions optimised elsewhere. In all the cases the analysis were performed by gas chromatography-mass spectrometry (GC-MS). Good accuracy were achieved in all cases. The limits of detection (LODs) obtained were between 0.10 and 1.70 ng g(-1) for PAHs (except for naphthalene 5.33 ng g(-1)), 0.02 and 0.16 ng g(-1) for PCBs, 46 and 188 ng g(-1) for PEs, and 0.6 and 12.4 microg g(-1) for NPs. The precision was around 5-10% for most of the PAHs and PCBs and around 2-10% for most of the PEs and NPs.

Toxicity of Reference Sediment Samples

This study was done to determine toxicity of certified reference sediment to be used for quality assurance in sediment toxicity testing program. Certified Reference Harbor Sediment (HS-4B for PAHs) and Estuarine Sediment (LGC-6137 for Trace Metals) were procured commercially from LGC Company, UK, and repeatedly analyzed against solid phase Microtox toxicity assay to determine EC50 values. Both PAHs rich and trace metals rich sediments were very toxic to Microtox with EC50 405 mg L-1 and 554 mg L-1 respectively. Solvent extraction resulted in a drastic decrease in the toxicity of PAHs rich reference sediment sample but in trace metal rich sediment the decrease in the toxicity was marginal. The certified reference sediments with the availability of toxicity data can be incorporated for quality assurance as controls in Microtox toxicity determination of field samples of unknown toxicity.

The ionic liquid 1-hexadecyl-3-methylimidazolium bromide as novel extracting system for polycyclic aromatic hydrocarbons contained in sediments using focused microwave-assisted extraction

A method to extract PAHs from sediments is carried out using aqueous solutions containing aggregates of the ionic liquid (IL) 1-hexadecyl-3-methylimidazolium bromide (HDMIm-Br) as the extracting medium. Focused microwave-assisted extraction has been used to accelerate the extraction step, followed by HPLC with fluorescence detection without clean-up steps to remove the IL prior to injection. The method has been applied to certified reference sediment BCR-535 and marine sediments from Tenerife (Canary Islands) with successful results. The optimized method gave average absolute recoveries of 91.1% for six of the seven PAHs studied, with relative standard deviations lower than 10.4%. The overall method is characterized for presenting low extraction times (6 min), low amounts of the sediment (0.1 g), low amounts of IL (45 mM), and low volumes of aqueous extractant solution (9 mL). The use of small amounts of both IL and aqueous extractant solution allows the method to be considered environmental-friendly.

Production of artifact methylmercury during the analysis of certified reference sediments: Use of ionic exchange in the sample treatment step to minimise the problem

Production of artifact methylmercury (MeHg +) during the analysis of two certified reference sediments, CRM-580 and IAEA-405, was investigated. Leaching of the analyte from the solid sample was achieved by ultrasound assisted acidic extraction. The aqueous leachate was either ethylated (NaBEt 4) or phenylated (NaBPh 4) using acetic/acetate or citric/citrate to buffer the solution. Preconcentration of the volatile compounds was carried out by extraction with an organic solvent ( n-hexane) or solid phase microextraction (SPME). MeHg + was finally separated and detected by gas chromatography with atomic emission or mass spectrometry detection (GC–MIP-AED or GC–MS). In all the cases the concentrations obtained for MeHg + in the CRM-580 were significantly higher than the certified value. For the IAEA-405, however, the MeHg + concentration found was always statistically indistinguishable from the certified value. Experiments were also conducted with synthetic samples, such as aqueous mixtures of MeHg + and inorganic mercury (Hg 2+) or silica-gel spiked with both compounds. The methylation rates found (defined as the percentage of Hg 2+ present in the sample which methylates to give artifact MeHg +) ranged from not observable (in certain synthetic aqueous mixtures) to 0.57% (analysis of CRM-580 under certain conditions). As the amount of Hg 2+ available in the sample seems to be the main factor controlling the magnitude of the artifact, several experiments were conducted using an ionic exchange resin (Dowex M-41) in order to minimise the concentration of this chemical in the reaction medium. First, a hydrochloric leachate of the sample was passed through a microcolumn packed with the exchanger. Second, the resin was mixed with the sample prior to extraction with HCl. In both cases, the predominant Hg 2+ species, HgCl 4 2−, was adsorbed on the resin, whereas MeHg +, mainly as MeHgCl, remained in solution. Following the second option, a new method to analyse MeHg + in conflictive matrices like certain sediments was proposed. This approach produced better results for the CRM-580, but a MeHg + concentration slightly, but statistically significant, higher than the reference value was still obtained.

Validated analytical strategy for the determination of polycyclic aromatic compounds in marine sediments by liquid chromatography coupled with diode-array detection and mass spectrometry

The aim of this work was to optimise and validate the experimental conditions for the analysis of 20 polycyclic aromatic compounds (PACs) [19 polycyclic aromatic hydrocarbons (PAHs) and dibenzothiophene as polycyclic aromatic sulphur heterocycle (PASH)] in marine sediments by reversed-phase high-performance liquid chromatography (LC) coupled to photodiode array detection (DAD) and to mass spectrometry (MS). The LC–MS interface used was atmospheric pressure chemical ionization (APCI) in the positive ion mode. The operational parameters of the APCI interface and MS detection, such as organic modifier, fragmentation voltage, gain, vaporizer temperature, corona current, capillary voltage, drying gas (N 2) and nebulizer pressure, were studied. The sediments were subjected to microwave-assisted solvent extraction (MAE) and clean-up by solid-phase extraction (SPE). The relevance of the selected PACs lies in the fact that 16 PACs are classified by the US Environmental Protection Agency as priority pollutants; 17 PACs are detected in the Prestige oil spill; and 8 PACs are included in the priority substance list of the EU water policy. Recoveries from 47% to 102% were obtained for SRM 1944 certified reference sediment. The limits of quantitation were lower than 100 ng g −1 dry weight for most PACs, and good precision was achieved.

New cold-fiber headspace solid-phase microextraction device for quantitative extraction of polycyclic aromatic hydrocarbons in sediment

A new automated headspace solid-phase microextraction (HS-SPME) sampling device was developed, with the capability of heating the sample matrix and simultaneously cooling the fiber coating. The device was evaluated for the quantitative extraction of polycyclic aromatic hydrocarbons (PAHs) from solid matrices. The proposed device improves the efficiency of the release of analytes from the matrix, facilitates the mass transfer into the headspace and significantly increases the partition coefficients of the analytes, by creating a temperature gap between the cold-fiber (CF) coating and the hot headspace. The reliability and applicability of previously reported cold-fiber devices are significantly enhanced by this improvement. In addition, it can be easily adopted for full automation of extraction, enrichment and introduction of different samples using commercially available autosampling devices. Sand samples spiked with PAHs were used as solid matrices and the effect of different experimental parameters were studied, including the extraction temperature, extraction time, moisture content, and the effect of sonication and modifier under optimal experimental conditions, linear calibration curves were obtained in the range of 0.0009–1000 ng/g, with regression coefficients higher than 0.99 and detection limits that ranged from 0.3 to 3 pg/g. Reproducible, precise and high throughput extraction, monitoring and quantification of PAHs were achieved with the automated cold-fiber headspace solid-phase microextraction (CF-HS-SPME) device coupled to GC-flame ionization detection. Determination of PAHs in certified reference sediments using the proposed approach exhibited acceptable agreement with the standard values.

Organotin speciation in environmental matrices by automated on- line hydride generation-programmed temperature vaporization-capillary gas chromatography–mass spectrometry detection

In the present contribution, a new automated on- line hydride generation methodology was developed for dibutyltin and tributyltin speciation at the trace level, using a programmable temperature-vaporizing inlet followed by capillary gas chromatography coupled to mass spectrometry in the selected ion-monitoring mode acquisition (PTV-GC/MS(SIM)). The methodology involves a sequence defined by two running methods, the first one configured for hydride generation with sodium tetrahydroborate as derivatising agent and the second configured for speciation purposes, using a conventional autosampler and data acquisition controlled by the instrument's software. From the method-development experiments, it had been established that injector configuration has a great effect on the speciation of the actual methodology, particularly, the initial inlet temperature (−20 °C; He: 150 ml/min), injection volume (2 μl) and solvent characteristics using the solvent venting mode. Under optimized conditions, a remarkable instrumental performance including very good precision (RSD < 4%), excellent linear dynamic range (up to 50 μg/ml) and limits of detection of 0.12 μg/ml and 9 ng/ml, were obtained for dibutyltin and tributyltin, respectively. The feasibility of the present methodology was validated through assays upon in-house spiked water (2 ng/ml) and a certified reference sediment matrix (Community Bureau of Reference, CRM 462, Nr. 330 dibutyltin: 68 ± 12 ng/g; tributyltin: 54 ± 15 ng/g on dry mass basis), using liquid–liquid extraction (LLE) and solid-phase extraction (SPE) sample enrichment and multiple injections (2 × 5 μl) for sensitivity enhancement. The methodology evidenced high reproducibility, is easy to work-up, sensitive and showed to be a suitable alternative to replace the currently dedicated analytical systems for organotin speciation in environmental matrices at the trace level.

Method development for the determination of cadmium, copper, lead, selenium and thallium in sediments by slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry and isotopic dilution calibration

A procedure for the determination of Cd, Cu, Pb, Se and Tl by slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) with calibration by isotopic dilution is proposed. The slurry is prepared by mixing the sample with diluted nitric and hydrofluoric acids in an ultrasonic bath and then in a water bath at 60 °C for 120 min. The slurries were let to stand at least for 12 h, manually shaken before poured into the autosampler cups and homogenized by passing through an argon flow, just before pipetting it into the furnace. The analytes were determined in two groups, according to their thermal behaviors. The furnace temperature program was optimized and the selected compromised pyrolysis temperatures were: 400 °C for Cd, Se and Tl and 700 °C for Cu and Pb. The vaporization temperature was 2300 °C. The analyses were carried out without modifier as no significant effect was observed for different tested modifiers. Different sample particle sizes did not affect the sensitivity significantly, then a particle size ≤50 μm was adopted. The accuracy was checked by analyzing five certified reference sediments, with analytes concentrations from sub-μg g −1 to a few hundreds μg g −1. The great majority of the obtained concentrations were in agreement with the certified values. The detection limits, determined for the MESS-2 certified sediment, were, in μg g −1: 0.01 for Cd; 0.8 for Cu; 0.4 for Pb; 0.4 for Se and 0.06 for Tl. The precision was adequate with relative standard deviations lower than 12%. Isotopic dilution showed to be an efficient calibration technique for slurry, as the extraction of the analyte to the liquid phase of the slurry and the reactions in the vaporizer must help the equilibration between the added isotope and the isotope in the sample.

Analysis of heavy metal distribution in superficial estuarine sediments (estuary of Bilbao, Basque Country) by open-focused microwave-assisted extraction and ICP-OES

Open-focused microwave-assisted extraction and ICP-OES determination of As, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn from surface sediments of the estuary of Bilbao (Basque Country, North of Spain) was carried out. All the samples were collected at three different tributaries of the estuary (Asua, Galindo and Nerbioi-Ibaizabal) every two months during 1999. The digestion procedure was proposed from the conclusions of a fractionated factorial design, and the precision and accuracy of the method was verified using a certified reference sediment (RTC008-050). The results of the analysis were statistically treated by means of principal component analysis and correlation analysis. The principal component analysis of sediment data (32 samples × 9 metals) indicated different patterns of contamination regarding the tributary and sampling station. The two main patterns observed were a steady increment of the metal concentration along all the campaigns in the samples collected in the Galindo River and a seasonal variation in the Nerbioi-Ibaizabal River, with higher metallic content during summertime and lower content during wintertime.

Determination of As, Hg, Se and Sn in sediment slurries by CVG–ETV–ICP–MS with trapping in an Ir treated graphite tube and calibration against aqueous standards

A method for the simultaneous determination of As, Hg, Se and Sn in sediment slurries using chemical vapor generation (CVG), in situ trapping electrothermal vaporization inductively coupled plasma mass spectrometry, is proposed. The vapors produced by the reaction of the sample slurry with the reducing agent are transported to the vaporizer and trapped at 150 °C in a graphite tube, treated with Ir as a permanent modifier, before vaporization at 2000 °C and transport to the plasma. The accuracy of the method was assured by the analysis of certified reference sediment samples, using external calibration with aqueous solutions, prepared in the same medium and subject to the same CVG and trapping procedure as the slurries. The obtained concentrations were in agreement with the certified values, using the t-Student test for a confidence level of 95%. The detection limits, in ng g−1, were: 0.8 for Hg, 0.04 for As, 0.01 for Se and 0.30 for Sn.

Development and validation of a method for analysis of “dioxin-like” PCBs in environmental samples from the steel industry

A method, previously used for determination of 2,3,7,8-substituted polychlorinated dibenzo- p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), has been modified for quantitative analysis of “dioxin-like” polychlorobiphenyls (PCBs) in environmental samples from the steel industry. The existing sample clean-up procedure, involving liquid chromatography on multi-layered silica and Florisil columns, has been extended to include a third chromatography stage on a basic alumina stationary phase. The additional clean-up stage is required for PCB analysis in order to eliminate interferences from relatively large concentrations of saturated cyclic and aliphatic hydrocarbons. Samples were analysed for WHO-12 congeners using high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS) and standard solutions of the method US EPA 1668A. Replicate analysis of method blanks revealed background contamination for PCBs 118, 105 and 77, which are generally abundant in ambient air. These contaminants were taken into account using a subtraction method. The entire procedure was validated by replicate analysis ( N=3) of a certified reference sediment. The RSD for each WHO-12 congener was below 15%, 13C 12-labelled PCB internal standard recoveries were in the range 70–95%. A waste dust sample collected in the electrostatic precipitator of a UK sinter plant was analysed for determination of PCDD/Fs and WHO-12 PCBs and exhibited a PCDD/F I-TEQ of 148.5 ± 21.2 ng kg −1 and a WHO-TEQ of 7.2 ± 1.5 ng kg −1. WHO-12 congeners contributed only 4.6% to the overall TEQ and PCB 126 was the major congener contributing to the WHO-TEQ (96%). The contribution to the overall TEQ of the waste dust sample was mainly attributed to PCDF followed by PCDD, which accounted for 86.6% and 8.7% to the overall TEQ, respectively.

Isotopically Labelled Compounds for Validating Organometallics Speciation Analysis

AbstractFor Abstract see ChemInform Abstract in Full Text.

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.

Using speciated isotope dilution with GC-inductively coupled plasma MS to determine and unravel the artificial formation of monomethylmercury in certified reference sediments.

Speciated isotope-dilution mass spectrometry (SID-MS) is claimed to be an absolute method; however, it has been found to be affected by artifact monomethylmercury (MMHg) formation in sediments. The determination of MMHg in sediments was carried out by SID-MS after open-focused microwave extraction. The extracted mercury species were then ethylated and separated by capillary gas chromatography (CGC). Isotope ratios (peak area ratios at different masses) were measured by on-line ICP-MS detection of the CGC-separated compounds. Reproducibility of 202Hg/201Hg isotope ratio measurements were 0.60% for MeEtHg and 0.69% for Et2Hg; for 202Hg/199Hg, 0.43 and 0.46%, respectively, were determined. The absolute detection limits for CGC-ICPMS measurements were better than 26 fg for 202Hg, 20 fg for 201Hg, and 24 fg for 199Hg. For the direct determination of MMHg in sediment reference materials (CRM 580, IAEA 356, and IAEA 405), higher values than the certified were always found. Systematic experiments were carried out to localize the sources of the unintentional abiotic methylmercury formation during analysis. Different spiking and derivatization procedures (either ethylation, propylation, or derivatization by Grignard reagents) were tested. In addition, isotopically enriched inorganic mercury was spiked. The amount of inorganic mercury initially present in the sample was found to be the critical factor that should be known and carefully controlled. A simple solvent extraction technique involving no critical cleanup steps was applied in order to reduce high Hg2+ amounts. The method was applied to the determination of MMHg in sediment reference material IAEA-405 with satisfactory results after organic solvent extraction. The limitations of applicability of the proposed method are evaluated as related to inorganic mercury, organic carbon, and sulfur contents. The results obtained confirmed that available sediment reference materials are adequate to achieve traceable mercury speciation analysis and to detect potential sources of MMHg artifact formation.

Assessment of tin and butyltin species in estuarine superficial sediments from Gipuzkoa, Spain

Ten superficial sediments from river estuaries of Gipuzkoa (North Spain) were collected and analyzed for nine metals (including tin, Sn) and butyltin compounds (monobutyltin, MBT; dibutyltin, DBT; tributyltin, TBT). Total metal concentration in the fine fraction (<63 μm) of the sediment was determined in aqua regia––hydrofluoric acid extracts by atomic absorption spectrometry. The butyltin species (BTs) were firstly extracted from the sediments with hydrochloric acid–methanol mixture. After derivatization with sodium tetraethyl borate, the organotin compounds were extracted by solid phase microextraction (SPME) in headspace mode. A fiber coated with 100 μm poly(dimethylsiloxane) was used for SPME. The organotin species were analyzed by gas chromatography-flame ionization detection. Analysis of the certified reference sediment (PACS-2) shown the suitability of the procedures for determination of metal contents and DBT–TBT species in contaminated sediments. Factorial analysis was used to examine the main sources of metals. Three factors represented more than 89% of the total variance of the metal system, and the Sn was related with Cu–Zn–Pb suggesting the same pollution source. The BTs concentrations in the area were high (TBT ranged from 0.05 to 5.48 mg Sn kg −1). The percentage of total butyltin species (∑BTs) respect to the total Sn amount was higher than 4% in all the sediments, showing in the Bidasoa river estuary a remarkable value higher than 20%. Hence, the studied estuarine sediments reflect a pollution that is related with historical industrial and fishing activities of the area.

Isotopically-labelled compounds for validating organometallics speciation analysis

The possibilities of using isotopically-labelled species with GC-ICP-MS to validate speciation analysis of organometallic compounds in environmental samples are summarised. The analytical advantages of this unique way of quantification, based on isotope-ratio measurements in each separate species, are highlighted and compared with more conventional procedures. Particular emphasis is paid to validating published speciation procedures, which usually involve a large number of discrete steps, each a possible source of error. The preparation of isotopically-labelled butyltin species and its application to seawater and sediment organotin speciation quantitative analysis are reviewed. In addition, the impressive capability of the “multi-isotope-labelled multispecies” spikes to control every step in speciation, even the initial solid-liquid extraction of the species from a solid sample, is also addressed. Such an innovative strategy allows detection and correction for species degradation during this difficult step to follow the extraction process. Moreover, the use of such multi-isotope-labelled multispecies approaches opens the door to studies on reported extraction procedures in speciation work. This approach is shown to be extremely useful for both ensuring quantitative recoveries of the species being sought from the solid matrix and evaluating the extent of possible extraction-derived rearrangement reactions. The article reviews applications of this innovative tool to the study and validation of the reported solid-liquid extraction of butyltin species from a certified reference sediment (using different techniques, including mechanical shaking, microwave, ultrasonic and pressurized liquid extraction).