Showing papers in "Trends in Analytical Chemistry in 2003"
TL;DR: In this paper, the state-of-the-art in the analysis of several groups of emerging contaminants (acidic pharmaceuticals, antibacterial agents, acidic pesticides and surfactant metabolites) in wastewaters is reviewed.
Abstract: The occurrence of trace organic contaminants in wastewaters, their behavior during wastewater treatment and production of drinking water are key issues in the re-use of water resources. Elimination of different classes of emerging contaminants, such as surfactant degradates, pharmaceuticals and polar pesticides in wastewater-treatment plants (WWTPs) was found to be rather low, so sewage effluents are one of the main sources of these compounds and their treatment-resistant metabolites. This article reviews the state-of-the-art in the analysis of several groups of emerging contaminants (acidic pharmaceuticals, antibacterial agents, acidic pesticides and surfactant metabolites) in wastewaters. It also discusses the elimination of emerging contaminants in WWTPs applying conventional activated sludge treatment (AST) and advanced treatment processes, such as membrane bioreactors (MBRs) and advanced oxidation processes (AOPs), as well as during production of drinking water.
728 citations
TL;DR: Although drinking-water disinfection byproducts (DBPs) have been studied for the last 30 years, significant, new concerns have arisen as discussed by the authors, including adverse reproductive and developmental effects recently observed in human populations, concerns that the types of cancer observed in laboratory animals (for regulated DBPs) do not correlate with the cancers observed in humans (indicating that other DBPs may be important), and concerns arising from human-exposure studies that show that other routes besides ingestion (i.e., inhalation and dermal adsorption) are also significant sources of DBP
Abstract: Although drinking-water disinfection by-products (DBPs) have been studied for the last 30 years, significant, new concerns have arisen. These concerns include adverse reproductive and developmental effects recently observed in human populations, concerns that the types of cancer observed in laboratory animals (for regulated DBPs) do not correlate with the cancers observed in human populations (indicating that other DBPs may be important), and concerns arising from human-exposure studies that show that other routes besides ingestion (i.e., inhalation and dermal adsorption) are also significant sources of DBP exposures. In addition, many drinking-water utilities are changing their primary disinfectant from chlorine to alternative disinfectants (e.g., ozone, chlorine dioxide, and chloramines), which generally reduce regulated trihalomethane and haloacetic acid levels, but can increase the levels of other potentially toxicologically important DBPs. For example, results of a new US Nationwide DBP Occurrence Study (discussed in this review) demonstrated that bromo-trihalonitromethanes, iodo-trihalomethanes, dihaloaldehydes, MX (3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone), and brominated forms of MX were formed at higher levels when alternative disinfectants were used to treat drinking water. Specific DBPs of emerging toxicological interest include brominated and iodinated compounds — including bromonitromethanes, iodo-trihalomethanes, iodo-acids, and brominated forms of MX — as well as nitrosodimethylamine (NDMA). In addition to concerns about DBPs, there are also new concerns about the presence of pharmaceuticals, organotins, methyl-tert-butyl ether (MTBE), perchlorate, and algal toxins in drinking water. This article will discuss these drinking-water contaminants of emerging concern and the analytical methods currently being used for their determination.
721 citations
TL;DR: Agarwal et al. as mentioned in this paper proposed a computer-aided method development approach to replace tedious trial-and-error procedures with fast simulations based on suitable kinetic and retention models.
Abstract: Solid-phase extraction using cartridge and disc devices is a widely used sample-preparation technique for isolation, concentration, clean-up and medium exchange. To meet the varied needs of contemporary applications, there is available an ever-increasing range of sorbent chemistries based on inorganic oxides, low-specificity (chemically bonded, porous polymer and carbon) and compound and group-selective (ion exchange, mixed mode, macrocyclic, restricted access, immunoaffinity and molecularly imprinted polymer) materials. Advanced device formats facilitate processing of problem samples combined with a high level of automation. Approaches to computer-aided method development promise to replace tedious trial-and-error procedures with fast simulations based on suitable kinetic and retention models.
624 citations
TL;DR: The liquid-phase microextraction (LPME) as mentioned in this paper is a sample-preparation technique that uses a hollow fiber impregnated with an organic solvent to accommodate or protect microvolumes of acceptor solution.
Abstract: The development of faster, simpler, inexpensive and more environmentally friendly sample-preparation techniques is an important issue in chemical analysis. Recent research trends involve miniaturisation of the traditional liquid-liquid extraction (LLE) principle by greatly reducing the acceptor-to-donor phase ratio. One of the emerging techniques in this area is liquid-phase microextraction (LPME), where a hollow fibre impregnated with an organic solvent is used to accommodate or protect microvolumes of acceptor solution. This novel methodology proved to be an extremely simple, low-cost and virtually solvent-free sample-preparation technique, which provided a high degree of selectivity and enrichment by additionally eliminating the possibility of carry-over between runs. This article presents the different modes and hollow-fibre configurations of LPME, followed by an up-to-date summary of its applications. The most important parameters and practical considerations for method optimisation are also discussed. The article concludes with a comparison of this novel method with solid-phase microextraction (SPME) and single-drop microextraction (SDME).
565 citations
TL;DR: In this article, the applications of ultrasound as auxiliary energy for accelerating leaching processes are reviewed to alert analysts to its advantages, and the widely used batch systems are compared with dynamic systems, the use of which is still very rare.
Abstract: The applications of ultrasound as auxiliary energy for accelerating leaching processes are reviewed to alert analysts to its advantages. The widely used batch systems are compared with dynamic systems, the use of which is still very rare. Comparison of ultrasound-assisted leaching with other sorts of leaching, such as Soxhlet, microwave-assisted and supercritical fluid extraction, shows the potential of ultrasound for leaching in a number of areas.
469 citations
TL;DR: In this paper, an overview of recent developments in the determination of veterinary and human drugs in solid environmental matrices, including soil, sediment and sludge, is presented, as well as sources, fate, persistence, and effects of pharmaceuticals in the environment.
Abstract: Human and veterinary drugs are continually being released in the environment mainly as a result of manufacturing processes, disposal of unused or expired products, and excreta. Because of their physical and chemical properties, many of these substances or their bioactive metabolites end up in soils and sediments, where they can accumulate and induce adverse effects in terrestrial or aquatic organisms. Among these effects, bacterial resistance is increasingly observed and is caused by the extensive use of antibiotics in animal and fish farming and the growing practice of adding manure and sewage sludge to agricultural fields, which is of particular concern. Literature on the environmental analysis and occurrence of drugs has addressed a very small percentage of these compounds, so very little information is available about the fate and the potential effects of drugs in the environment. This article presents an overview of recent developments in the determination of veterinary and human drugs in solid environmental matrices, including soil, sediment and sludge. The analysis of pharmaceuticals in the such samples has always been carried out by high-performance liquid chromatography coupled to ultraviolet detection, and, to a lesser extent, to mass spectrometry and fluorescence detection. In most cases, sample pretreatment includes extraction of the solid sample and further purification of the extract by solid phase extraction with C18 sorbents. In addition to analytical articles, this overview includes papers concerning usage of drugs, as well as sources, fate, persistence, and effects of pharmaceuticals in solid environmental matrices.
454 citations
TL;DR: In this article, the information obtained for Cd, Cr, Cu, Ni, Pb and Zn, when applying various single extraction and sequential extraction procedures, is critically assessed for contaminated samples with distinct origins and characteristics.
Abstract: Comparison of the information obtained from the application of leaching/extraction procedures to contaminated soils and sediments is required to make the most appropriate choice for studying a given metal. In this article, the information obtained for Cd, Cr, Cu, Ni, Pb and Zn, when applying various single extraction and sequential extraction procedures, is critically assessed for contaminated samples with distinct origins and characteristics. The single-extraction procedures comprised the application of mild (CaCl 2 and NaNO 3 ) and acidic (CH 3 COOH) extractants and complexing agents (EDTA and DTPA). The original and modified BCR three-step sequential extraction procedures are also compared. Finally, useful criteria are proposed for the selection of leaching/extraction tests in certain scenarios.
397 citations
TL;DR: This review highlights different bioassays and recently developed biosensors based on acute toxicity measurements, with emphasis on the use of combined approaches involving chemical analysis for the characterization and identification of complex toxic wastewater effluents and sewage sludge.
Abstract: Toxicity testing has grown steadily in recent years, being a useful tool in environmental risk assessment. This review highlights different bioassays and recently developed biosensors based on acute toxicity measurements. Emphasis is placed on the use of combined approaches involving chemical analysis for the characterization and identification of complex toxic wastewater effluents and sewage sludge. Fractionation schemes that combine sample preparation and chemical analysis with biological measurements are presented and reviewed. Bioassay-directed chemical-analysis protocols involve solid phase extraction (SPE), followed by chromatographic techniques, such as liquid chromatography-mass spectrometry (LC-MS) or gas chromatography-mass spectrometry (GC-MS). Toxicity testing is carried out by either bioluminescence inhibition methods or a whole-cell bacterial biosensor. Other biological toxicity tests are also reviewed. Examples of using different bacterial acute toxicity assays are presented for phenols, polyethoxylate surfactants, linear alkyl benzene sulphonates (LASs), naphthalene and benzene sulphonates, polycyclic aromatic hydrocarbons (PAHs), pesticides and pharmaceutical drugs.
300 citations
TL;DR: In this article, a review describes current developments in the design and fabrication of disposable screen-printed sensors for the electrochemical determination of trace metals in biological, environmental and industrial samples.
Abstract: This review describes current developments in the design and fabrication of disposable screen-printed sensors for the electrochemical determination of trace metals in biological, environmental and industrial samples. Specific emphasis is placed on sensor-fabrication methods, operating details and performance characteristics for selected applications.
266 citations
TL;DR: An overview of the economic and social interest in the control of phthalate esters and in the availability of analytical methodologies for areas such as environmental and food analyses can be found in this paper.
Abstract: Excessive use of phthalate esters in industrial applications, mainly as plasticizers, has given rise to their persistent presence in consumer goods, and has raised numerous questions about their possible health effects or damage to the environment. This article presents an overview of the economic and social interest in the control of phthalate esters and in the availability of analytical methodologies for areas such as environmental and food analyses. It discusses potential contamination of the samples, usefulness of chromatographic techniques, generally after pre-treatment steps, and rare attempts to propose alternative techniques.
259 citations
TL;DR: Aptamers are artificial nucleic acid ligands that can be generated against amino acids, drugs, proteins and other molecules as mentioned in this paper, they are isolated from complex libraries of synthetic nucleic acids by an iterative process of adsorption, recovery and amplification.
Abstract: Aptamers are artificial nucleic acid ligands that can be generated against amino acids, drugs, proteins and other molecules. They are isolated from complex libraries of synthetic nucleic acids by an iterative process of adsorption, recovery and amplification. This review described the in vitro process to obtain aptamers (SELEX). It mentions the main characteristics of these molecules (i.e. affinity, specificity and stability). Moreover, it discusses advantages over antibodies. It reports potential applications of aptamers in analytical and diagnostic assays as biocomponents of biosensors (aptasensors) and allosteric ribozymes (aptazymes).
TL;DR: A review of 20 main compounds includes chelating agents and other compounds, such as the organophosphonates or polycarboxylates, which, by binding metal ions, also exhibit some complexing properties.
Abstract: Synthetic chelating agents are utilized in many industrial applications because of their capability of binding and masking metal ions. This review of 20 main compounds includes chelating agents and other compounds, such as the organophosphonates or polycarboxylates, which, by binding metal ions, also exhibit some complexing properties. It aimed to gather data about production, use, toxicity, entry into the aquatic environment, fate and environmental behavior. In spite of the low toxicity and metal mobilization values calculated for the measured or predicted environmentally observed concentrations, many of the investigated synthetic complexing agents, such as ethylene diamine tetra-acetic acid (EDTA), can be classified as environmentally relevant, since they are microbially poorly degradable and exhibit excellent water solubility. Thus they are not or only partially removed during drinking water treatment utilizing filtration and biodegradation steps. For other compounds that bind metal ions, such as the organophosphonates, adsorption is an important route of elimination from the water phase. The data available regarding concentrations of synthetic complexing agents in the aquatic environment has until now almost exclusively focused on the aminocarboxylates. The main examples are EDTA and nitrilo-tri-acetic acid (NTA), which are present in the low μg/L range in almost all anthropogenically influenced streams and rivers in industrialized countries, such as Germany. Concentration data regarding diethyl triamine penta-acetic acid (DTPA) and 1,3-propylenediamine tetra-acetic acid (PDTA) are quite scarce. Reported values of these compounds lie mostly in the detection-limit range 1–2 μg/L. DTPA concentrations found in sewage effluents of paper and pulp mills are in the mg/L range, while maximum concentrations reported for rivers are up to 72 μg/L. The predicted concentrations in surface waters for most of the investigated compounds are also in the lower μg/L range, e.g. for the organophosphonates between 0.25–2.5 μg/L. But until now, except for the aminocarboxylates, analytical methods do not exist for their quantification at these low concentrations. It is recommended that the entry of chelating and metal-binding agents into the water phase should be minimized by applying various measures. All industrial processes and productions dealing with poorly degradable chelating agents and compounds that bind metal ions should be used as little as possible, and their emission into the aquatic environment should be as low as possible. Wherever possible, substitution with compounds exhibiting better degradability should also be sought.
TL;DR: It is shown that the commonly applied leave-one-out cross-validation has a strong tendency to overfitting, underestimates the true prediction error, and should not be used without further constraints or further validation.
Abstract: Different methods of cross-validation are studied for their suitability to guide variable-selection algorithms to yield highly predictive models. It is shown that the commonly applied leave-one-out cross-validation has a strong tendency to overfitting, underestimates the true prediction error, and should not be used without further constraints or further validation. Alternatives to leave-one-out cross-validation and other validation methods are presented.
TL;DR: In this paper, a review of sample preparation techniques for forensic, clinical and pharmaceutical analysis, with special focus on in-tube solid-phase microextraction and related new techniques, is presented.
Abstract: Sample preparation is necessary to isolate the desired components from complex matrices, because most analytical instruments cannot handle the matrix directly. Recent trends in sample preparation include miniaturization, automation, high-throughput performance, on-line coupling with analytical instruments and reduction in solvent volume and time. This article reviews recent advances in sample preparation techniques for forensic, clinical and pharmaceutical analysis, with special focus on in-tube solid-phase microextraction and related new techniques.
TL;DR: The purpose of this review is to give an overview of the basic concepts of 2DE-based proteomics methodology, to discuss the advantages and limitations of the approach, and to highlight some recent advancements in 2de-based technology.
Abstract: Two-dimensional gel electrophoresis, mass spectrometry and bioinformatics are the key components of current proteomics technology. The purpose of this review is to give an overview of the basic concepts of 2DE-based proteomics methodology, to discuss the advantages and limitations of the approach, and to highlight some recent advancements in 2DE-based technology.
TL;DR: A brief overview of the methods available to measure free concentrations and will focus on negligible depletion-solid phase microextraction (nd-SPME) can be found in this article, including potential confounding factors, such as fouling, diffusion layer effects, and calibration.
Abstract: Measurement of free concentration is necessary to determine the effective or bioavailable quantity of a chemical, and is also a way of determining the binding affinity or partition coefficient of a compound. This review gives a brief overview of the methods available to measure free concentrations and will focus on negligible depletion-solid phase microextraction (nd-SPME). Theoretical as well as experimental details of the method are discussed, including potential confounding factors, such as fouling, diffusion layer effects, and calibration.
TL;DR: In this paper, an overview of organic compounds that contribute to the toxicity of paper-mill waters and effluents, their levels, toxicological characterization and the methodologies used for their analysis is given.
Abstract: Paper-mill effluents are characterized by the presence of color and suspended solids, bad smell, high concentration of nutrients that cause eutrophication of receiving waters, and high toxicity overall. This study attempts to give an overview of organic compounds that contribute to the toxicity of paper-mill waters and effluents, their levels, toxicological characterization and the methodologies used for their analysis. Families included are natural products, such as resin and fatty acids (wood extractives), additives used during paper-making, such as biocides, surfactants and phenolic compounds and by-products generated during bleaching, such as dioxins and furans. Several extraction methods, such as liquid-liquid extraction (LLE) or solid phase extraction (SPE) followed by gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-mass spectrometry (LC-MS) with atmospheric pressure chemical ionization (APCI) or electrospray (ESP) are described and method performance is discussed for each family of compounds. This study contributes to the characterization of the organic fraction of paper-mill effluents and highlights elimination strategies.
TL;DR: An overview of current data for these estimates is presented in this article, where the knowledge of the relative contribution of each contaminant to the total dioxin-like activity associated with environmental samples could aid in identifying the most important contributory pollutants.
Abstract: In recent decades, a great deal of emphasis has been placed on evaluating the toxic potency of dioxin in different environmental samples. The commonly named dioxin-like compounds (DLCs), such as polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs) and polychlorinated naphthalenes (PCNs), were studied to determine their relative toxic potency. Recently, some studies have indicated that another group of contaminants, the polycyclic aromatic hydrocarbons (PAHs), can dominate estimates of toxic equivalent quantity (TEQ) for samples containing PAHs and DLCs. Other emerging contaminants, such as brominated flame retardants (BFRs), especially polybrominated diphenyl ethers (PBDEs), also exhibit dioxin-like activities. The knowledge of the relative contribution of each contaminant to the total dioxin-like activity associated with environmental samples could aid in identifying the most important contributory pollutants. In this paper, an overview of current data for these estimates is presented.
TL;DR: In this article, the authors focus on the importance of unequivocally detecting emerging contaminants, as well as establishing their presence in the environment by accurate mass spectrometric measurement techniques, such as liquid chromatography coupled with tandem mass spectrametric (LC/MS/MS) and time-of-flight (TOF/MS).
Abstract: In this review, we focus on the importance of unequivocally detecting emerging contaminants, as well as establishing their presence in the environment by accurate mass spectrometric measurement techniques The environmental issue of emerging contaminants is tied to the analysis of wastewater samples using the new analytical methods of the last decade, especially liquid chromatography coupled to tandem mass spectrometry (LC/MS/MS) and time-of-flight mass spectrometric (TOF/MS) techniques Because of the high complexity of some environmental samples (ie wastewater and sludge samples), high-resolving power techniques are needed to provide additional structural information Thus, this paper focuses on LC/TOF/MS to analyze unknowns in the aquatic environment Emerging contaminants are defined as compounds that are not currently covered by existing regulations of water quality, that have not been previously studied, and that are thought to be a possible threat to environmental health and safety In particular, these compounds include pharmaceuticals, personal care products, surfactants, and pesticide degradates Unique types of structural information for these compounds are derived from TOF/MS and quadrupole (Q)-TOF/MS instruments for the analysis of emerging contaminants in water and sediments This review explains the unique features of these instruments and gives examples of their applications
TL;DR: A review of current developments in off-column and on-column approaches to trace enrichment in analysing real samples, and summarises the determination of pesticides residues by conventional CE as well as by the emerging techniques, such as CE-mass spectrometry (MS).
Abstract: Capillary electrophoresis (CE) is becoming an advantageous tool for determining pesticide residues in environmental matrices because of its simplicity and high separation efficiency. However, inadequate limits of detection (LODs) and a lack of selective detectors limit the technique. The present review gives an overview of current developments in off-column and on-column approaches to trace enrichment in analysing real samples, and summarises the determination of pesticides residues by conventional CE as well as by the emerging techniques, such as CE-mass spectrometry (MS). The usefulness of these approaches in environmental applications is documented.
TL;DR: In this article, the authors present progress to date of the SI-LOV approach as well as its applications in the automation and the micro-miniaturization of on-line sample pre-treatment.
Abstract: Termed the third generation of flow-injection analysis, sequential injection (SI)-lab-on-valve (LOV) has specific advantages and allows novel, unique applications – not least as a versatile front end to a variety of detection techniques. This review presents and discusses progress to date of the SI-LOV approach as well as its applications in the automation and the micro-miniaturization of on-line sample pre-treatment. Special emphasis is placed on using SI-LOV in conjunction with bead injection (BI) for on-line separation and pre-concentration of ultra-trace levels of metals by exploiting the renewable micro-column approach. With detection by ETAAS and ICP-MS, it is shown, as illustrated by recent results in the authors’ laboratory, that this methodology eliminates the problems encountered in conventional on-line column pre-concentration systems, improves the overall operational efficiency and yields the robustness necessary for routine assays. Also discussed is the future potential of the SI-LOV approach as a front end to various analytical protocols.
TL;DR: An overview of the methods currently in use to determine different compounds in beer samples can be found in this article, with a focus on the use of capillary electrophoresis (CE).
Abstract: Beer has been a popular beverage for thousands of years, and brewers often describe brewing as the oldest biotechnological process. Beer constituents comprise more than 800 compounds and many of them contribute to its flavor characteristics, such as bitterness, sweetness, acidity, hop character, carbonation, alcoholic and fruity or ester flavor, most of which are determined by capillary electrophoresis (CE). CE has recently emerged as a highly promising technique that consumes an extremely small amount of sample and is capable of rapid, high-resolution separation, characterization, and quantitation of analytes. An overview is presented of CE methods currently in use to determine different compounds in beer samples.
TL;DR: In this paper, an overview is given on the biological and analytical methodologies used, both individually and in combination, to determine estrogenicity and quantification for several EDCs present in sewage and surface-water matrices.
Abstract: The presence of numerous endocrine-disrupting compounds (EDCs) in surface waters and sediment has been primarily attributed to their incomplete removal in the sewage-treatment process. Determination of these chemicals is required in order to assess their environmental impact. An overview is given on the biological and analytical methodologies used, both individually and in combination, to determine estrogenicity and quantification for several EDCs present in sewage and surface-water matrices.
TL;DR: In this article, the separation capabilities of chiral selectors and criteria for their choice in terms of molecular size, charge, and the presence of specific functional groups or substructures in the analytes with a view to minimizing the number of trials needed are discussed.
Abstract: Capillary electrophoresis (CE) is an effective tool for the resolution of enantiomers, which is accomplished by supplying the background electrolyte with a chiral selector capable of discriminating between the enantiomers concerned. A large number of chiral selectors are currently available, especially prominent among which are cyclodextrins (CDs), chiral crown ethers, chiral surfactants, ligand-exchange complexes and linear polysaccharides. The most suitable chiral selector for each specific purpose is usually selected by trial and error, which is expensive and time-consuming. This article reviews the separation capabilities of chiral selectors and provides criteria for their choice in terms of molecular size, charge, and the presence of specific functional groups or substructures in the analytes with a view to minimizing the number of trials needed. Such criteria are summarized in tabular form and their application illustrated with selected examples.
TL;DR: In this article, the authors suggest guidelines that can be applied to a range of in-vivo microsensor applications for evaluation of analyte identification and improvement of selectivity.
Abstract: Microsensors are miniaturized analytical devices for making in-situ chemical measurements in biological systems with extraordinary temporal resolution. Their most severe limitation is chemical selectivity. Here, we suggest guidelines that can be applied to a range of in-vivo microsensor applications for evaluation of analyte identification and improvement of selectivity.
TL;DR: In this article, the importance of matrix pretreatment, sample extraction, clean-up and fractionation of PCBs from food matrices is discussed, with emphasis on MS methods, together with the limitations of these techniques.
Abstract: Polychlorinated biphenyls (PCBs) are highly persistent, lipophilic and bioaccumulative toxic industrial contaminants formed as a result of human activities Most of its uses have been banned since the late 1970s This article describes the importance of matrix pretreatment, sample extraction, clean-up and fractionation of PCBs from food matrices It reviews detection techniques, such as cGC, for these congeners and their enantiomers, using different columns and detectors, with emphasis on MS methods, together with the limitations of these techniques It also discusses other methods, such as MEKC, immunoassays and bioassays, as applied to the detection of PCBs in foods
TL;DR: In this article, the potential for using other phenomena and materials where supramolecular assemblies are involved, such as coacervation, hemimicelles/admiceLLes and amphiphilic-templated mesoporous silicas, for the extraction/concentration of organic compounds.
Abstract: Supramolecular assemblies have been used largely in analytical extraction and concentration schemes. Their ability to form a phase with regions of different polarities, acidities and viscosities, where solutes of very different structure can be solubilized, has encouraged this use. At present, the basis, characteristics and scope of extraction techniques, such as cloud point, are well established. However, they have not been accepted in routine analysis, despite the demonstrated advantages of surfactant-mediated separations over other conventional extraction techniques. This article deals with the challenges in making these extraction techniques competitive and explores the potential for using other phenomena and materials where supramolecular assemblies are involved, such as coacervation, hemimicelles/admicelles and amphiphilic-templated mesoporous silicas, for the extraction/concentration of organic compounds.
TL;DR: In this paper, the use of organized surfactant molecular assemblies, such as micelles, reversed micells and microemulsions, in analytical solution chemiluminescence is steadily increasing because it can change luminescent characteristics and result in greatly improved analytical performance, in terms of selectivity, sensitivity and experimental convenience.
Abstract: The development of new or enhanced analytical methodologies based on the use of microheterogeneous systems is a very active area of current research. The use of organized surfactant molecular assemblies, such as micelles, reversed micelles and microemulsions, in analytical solution chemiluminescence is steadily increasing because it can change luminescent characteristics and result in a greatly improved analytical performance, in terms of selectivity, sensitivity and experimental convenience. This review focuses on how micelles, reversed micelles and microemulsions may be used to improve the quality of chemiluminescent analytical procedures and gives some applications of these microheterogeneous chemiluminescent systems.
TL;DR: In this article, a review of the accepted techniques for the speciation of arsenic in biological tissues and the need for quality assurance of speciation analyses is discussed, focusing on the use of certified reference materials.
Abstract: Arsenic is an ubiquitous element. Its toxicity, environmental mobility and accumulation in living organisms usually depend on the form in which the element is present. Information on the chemical forms is important for understanding the role of the element present as well as revealing its environmental cycle. This requirement stimulates the need for information on the speciation of arsenic and the development of suitable analytical methodology. It is well known that seafood can contain considerable quantities of naturally-acquired arsenic and developments in speciation have focused on seafood samples.
It seems that the major arsenic species in fish, crustaceans and molluscs have the tetraalkylarsonium structure (R4As+) and the species in marine algae and bivalves have the trialkylarsine oxide structure (R3AsO). However, the concentrations are still low enough to require a sensitive analytical method based on the isolation, identification and quantification of the individual arsenic-containing species.
This review will discuss the accepted techniques for the speciation of arsenic in biological tissues and the need for quality assurance of speciation analyses. Quality control will be discussed, focusing on the use of certified reference materials. As well as validation of methods, reference-material certification involves the participation of several laboratories, enabling the evaluation of state-of-the-art analytical techniques.
The certification process of a candidate oyster-tissue reference material for different chemical species of elements (including arsenic species) is discussed.