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

Monomer Release from Dental Resins: The Current Status on Study Setup, Detection and Quantification for In Vitro Testing

Improvements in mechanical properties and a shift of focus towards esthetic dentistry led to the application of dental resins in various areas of dentistry. However, dental resins are not inert in the oral environment and may release monomers and other substances such as Bisphenol-A (BPA) due to incomplete polymerization and intraoral degradation. Current research shows that various monomers present cytotoxic, genotoxic, proinflammatory, and even mutagenic effects. Of these eluting substances, the elution of BPA in the oral environment is of particular interest due to its role as an endocrine disruptor. For this reason, the release of residual monomers and especially BPA from dental resins has been a cause for public concern. The assessment of patient exposure and potential health risks of dental monomers require a reliable experimental and analytical setup. However, the heterogeneous study design applied in current research hinders biocompatibility testing by impeding comparative analysis of different studies and transfer to the clinical situation. Therefore, this review aims to provide information on each step of a robust experimental and analytical in vitro setup that allows the collection of clinically relevant data and future meta-analytical evaluations.

Experimental design-based isotope-dilution SPME-GC/MS method development for the analysis of smoke flavouring products

For the implementation of Regulation (EC) No 2065/2003 related to smoke flavourings used or intended for use in or on foods a method based on solid-phase micro extraction (SPME) GC/MS was developed for the characterisation of liquid smoke products. A statistically based experimental design (DoE) was used for method optimisation. The best general conditions to quantitatively analyse the liquid smoke compounds were obtained with a polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibre, 60°C extraction temperature, 30 min extraction time, 250°C desorption temperature, 180 s desorption time, 15 s agitation time, and 250 rpm agitation speed. Under the optimised conditions, 119 wood pyrolysis products including furan/pyran derivatives, phenols, guaiacol, syringol, benzenediol, and their derivatives, cyclic ketones, and several other heterocyclic compounds were identified. The proposed method was repeatable (RSD% <5) and the calibration functions were linear for all compounds under study. Nine isotopically labelled internal standards were used for improving quantification of analytes by compensating matrix effects that might affect headspace equilibrium and extractability of compounds. The optimised isotope dilution SPME-GC/MS based analytical method proved to be fit for purpose, allowing the rapid identification and quantification of volatile compounds in liquid smoke flavourings.

New trends in sample preparation techniques for environmental analysis

Environmental samples include a wide variety of complex matrices, with low concentrations of analytes and presence of several interferences. Sample preparation is a critical step and the main source of uncertainties in the analysis of environmental samples, and it is usually laborious, high cost, time consuming, and polluting. In this context, there is increasing interest in developing faster, cost-effective, and environmentally friendly sample preparation techniques. Recently, new methods have been developed and optimized in order to miniaturize extraction steps, to reduce solvent consumption or become solventless, and to automate systems. This review attempts to present an overview of the fundamentals, procedure, and application of the most recently developed sample preparation techniques for the extraction, cleanup, and concentration of organic pollutants from environmental samples. These techniques include: solid phase microextraction, on-line solid phase extraction, microextraction by packed sorbent, dispersive liquid-liquid microextraction, and QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe).

Fuzzy logic based risk assessment of effluents from waste-water treatment plants

This paper presents a new methodology to assess the risk of water effluents from waste-water treatment plants (WWTPs) based on fuzzy logic, a well-known theory to deal with uncertainty, especially in the environmental field where data are often lacking. The method has been tested using the effluent's pollution data coming from 22 waste-water treatment plants (WWTPs) located in Catalonia (NE Spain). Thirty-eight pollutants were analyzed along three campaigns performed yearly from 2008 to 2010. Whereas 9 compounds have been detected in more than 70% of the samples analyzed, 7 compounds have been found at levels equal or higher than the river Environmental Quality Standards set by the Water Framework Directive. Upon combination of both criteria (presence and concentration), compounds of greatest environmental concern in the WWTP studied are nickel, the herbicide diuron, and the endocrine disruptors nonyl and octylphenol. It is remarkable the low variability of the pollutant concentration just differing for the case of nickel and zinc. These low values of exposure together with other pollutants' characteristics provide a medium or low risk assessment for all the WWTPs. The results of this new method have been compared with COMMPS procedure, a solid method developed in the context of the Water Framework Directive, and they show that the fuzzy model is more conservative than COMMPS. This is due to different reasons: the fuzzy model takes into account the persistence of chemical compounds whereas COMMPS does not; the fuzzy model includes the weights provided by an expert group inquired in previous works and also considers the uncertainty of the environmental data, avoiding the crisp values and offering a range of overlapping between the different fuzzy sets. However, the results even if being more conservative with fuzzy logic, are in good agreement with a solid methodology such as the COMMPS procedure.

Three decades of TBT contamination in sediments around a large scale shipyard

Tributyltin (TBT) contamination in sediments was investigated in the vicinity of a large-scale shipyard in the years after the implementation of a total ban on the use of TBT based antifouling paints in Korea. Extremely high level of TBT (36,292ng Sn/g) in surface sediment was found at a station in front of a drydock and near surface runoff outfall of the shipyard. TBT concentration in surface sediments of Gohyeon Bay, where the shipyard is located, showed an apparent decreased TBT concentration gradient from the shipyard towards the outer bay. The vertical distribution of TBT contamination derived from a sediment core analysis demonstrated a significant positive correlation (r(2)=0.88; p<0.001) with the annual tonnage of ship-construction in the shipyard within the past three decades. TBT concentrations at six stations surveyed before (2003) and seven years after (2010) the total ban showed no significant differences (p>0.05). Despite the ban on the use of TBT, including ocean going vessels, surface sediments are still being heavily contaminated with TBT, and its levels well exceeded the sediment quality guideline or screening values.

Speciation of butyltin derivatives in surface sediments of three southern Brazilian harbors

For the first time, organotin compounds were determined in surface sediment samples collected from São Francisco do Sul, Itajaí-Navegantes and Imbituba Harbors, located in Santa Catarina State, Brazil. Butyltins (BTs) were determined by gas chromatography with a pulsed flame photometric detector (GC-PFPD) after being modified using the Grignard derivatization method. The concentrations of BTs derivatives ranged from n.d. to 1136.6 ng (Sn) g(-1) of dry weight (dw) sediment for tributyltin (TBT), n.d. to 394.4 ng (Sn)g(-1) dw for dibutyltin (DBT) and n.d. to 312.2 ng (Sn) g(-1) dw for monobutyltin (MBT). The highest concentration of total BTs was found at the Itajaí-Açu River dockyard, indicating intense inputs of antifouling paints to the environment. The relative difference in the BTs levels is a particular characteristic of sediments from harbors and may be related to the shipyards and the boat traffic which still use TBT-based antifouling paints.

Butyltin contamination in industrialized bays associated with intensive marine activities in Korea

Marine sediments and gastropod, Thais clavigera, were collected from industrialized areas and major harbors in Korea, to assess contamination sources and ecological risk to marine organisms by butyltin compounds such as tributyltin (TBT). TBT concentrations in sediments ranged from <LOD to 5372 ng Sn/g dry weight, and were comparable to or higher than concentrations in big harbors of other countries. The highest TBT concentrations were found in sediments close to shipyards in surveyed bays, suggesting that shipyard activities are a major contamination source of butyltins in Korean coastal waters. About half of the sediments showed potential risk of exceeding the guidelines and values proposed in in vivo studies. The occurrence of imposex in T. clavigera was 100% at all locations, indicating that the present levels of TBT contamination in industrialized bays in Korea are at concentrations reported to induce toxic effects on marine organisms, despite TBT's having been legally banned in Korea.

Multiresidue screening of endocrine-disrupting chemicals and pharmaceuticals in aqueous samples by multi-stir bar sorptive extraction-single desorption-capillary gas chromatography/mass spectrometry

A multiresidue method for screening endocrine-disrupting chemicals (EDCs) and pharmaceuticals in aqueous samples is presented. Four 10-mL aliquots of water were taken for stir bar sorptive extraction (SBSE) and they were treated in the following way. In sample one, in situ derivatization was performed with acetic acid anhydride to improve the extraction efficiencies and chromatographic analysis of phenolic compounds. For the same reasons, aliquot two was treated with ethyl chloroformate to improve amine and acid extraction and analysis, and aliquot three with tetraethylborate to enhance organotin compound extraction and analysis. Methanol was added to sample four to stop adsorption of apolar solutes on the wall. After SBSE, the four stir bars, together with a plug of glass wool impregnated with bis(trimethylylsilyl)trifluoroacetamide (BSTFA) to derivatize hydroxyl functionalities, were introduced into the same thermal desorption tube, heat-desorbed, and analyzed simultaneously by capillary GC/MS. The figures of merit of the method were evaluated with an EDC model mixture. In scan-mode MS, the limits of detection (LODs) were in the range 1-500 ng/L, while the LODs dropped by a factor of 50-100 when ion monitoring MS was applied to the targets. The performance of the method was illustrated by analysing some real-world water samples.

Current trends in solid-phase-based extraction techniques for the determination of pesticides in food and environment

Solid-phase extraction (SPE) procedures for pesticide residues in food and environment are reviewed and discussed. The use of these procedures, which include several approaches such as: matrix solid-phase dispersion (MSPD), solid-phase micro-extraction (SPME) and stir-bar sorptive extraction (SBSE), represents an opportunity to reduce analysis time, solvent consumption, and overall cost. SPE techniques differ from solvent extraction depending on the interactions between a sorbent and the pesticide. This interaction may be specific for a particular pesticide, as in the interaction with an immunosorbent, or non-specific, as in the way a number of different pesticides are adsorbed on apolar or polar materials. A variety of applications were classified according to the method applied: conventional SPE, SPME, hollow-fiber micro-extraction (HFME), MSPD and SBSE. Emphasis is placed on the multiresidue analysis of liquid and solid samples.

SPME in environmental analysis

Recent advances in the use of solid-phase microextraction (SPME) in environmental analysis, including fiber coatings, derivatization techniques, and in-tube SPME, are reviewed in this article. Several calibration methods for SPME, including traditional calibration methods, the equilibrium extraction method, the exhaustive extraction method, and several diffusion-based calibration methods, are presented. Recent developed SPME devices for on-site sampling and several applications of SPME in environmental analysis are also introduced.