Showing papers in "Trends in Analytical Chemistry in 1998"
TL;DR: An overview of the development and application of surface-enhanced Raman scattering (SERS) techniques using metal-coated nanostructures on solid substrates is provided in this article.
Abstract: This article provides an overview of the development and application of the surface-enhanced Raman scattering (SERS) techniques using metal-coated nanostructures on solid substrates An introduction to theoretical principles of the SERS effect and the different SERS-active media is presented The focus is on nanostructured solid substrates and their practical applications in chemical, environmental and biomedical areas Specific examples of analytical techniques, instruments and sensors developed in the author's laboratory will be discussed to illustrate the usefulness and potential of the SERS techniques
543 citations
TL;DR: In this paper, the authors describe case studies of standardization approaches for single and sequential extraction procedures applied to soil and sediment analysis, in particular the strategy followed by the Standards, Measurements and Testing program (formerly BCR).
Abstract: Environmental studies on soil and sediment analysis are often based on the use of leaching or extraction procedures (e.g. single or sequential extraction procedures) which enable broader forms or phases to be measured (e.g. `bioavailable' forms of elements) and which are, in most cases, sufficient for the purpose of environmental policy. However, the lack of uniformity in the procedures used often hampers comparison of the results, owing to their `operationally defined' character. This implies that the `forms' of metals are defined by the determination of extractable elements, using a given procedure and, therefore, the significance of the analytical results is highly dependent on the extraction procedures used. The comparability of results can hence only be achieved if similar procedures are applied, which justifies efforts towards standardization. This article describes case studies of standardization approaches for single and sequential extraction procedures applied to soil and sediment analysis. In particular, the strategy followed by the Standards, Measurements and Testing program (formerly BCR) is fully described (feasibility study, interlaboratory studies and establishment of standardized protocols based on the results of tests and participants' experience).
465 citations
TL;DR: The biomarker vitellogenin (viteLLogenin-synthesis assay) is an appropriate tool for determining endocrine effects and of chemical pollutants in effluents and how these influence sex differentiation in fish.
Abstract: The increasing preponderance of females in fish populations has become a matter of concern not only for scientists but also for environmental authorities. For example, in the extensive waterways in Berlin, Germany, 70% of the fish population is female. A twofold question should be asked: is the biomarker vitellogenin (vitellogenin-synthesis assay) an appropriate tool for determining endocrine effects (European Commission 1996) and of chemical pollutants in effluents (Castillo et al. 1997), such as estradiols, phthalates, alkyl-phenols, and alkyl-ethoxylates, influence sex differentiation in fish?
307 citations
TL;DR: It has been demonstrated that the particles from up to nine different source types can be distinguished from each other simultaneously in the southern California atmosphere by this method.
Abstract: The contribution of the major urban air pollution sources to regional particulate air quality problems can be diagnosed by using organic molecular marker techniques. Distinctive organic compounds or compound groups that are present in the emissions from some source types but not others are used to quantify the presence of the effluent from different air pollution sources within atmospheric fine particle samples. The tracer compounds are measured in source samples and in atmospheric samples by gas chromatography–mass spectrometry. Some of the most valuable tracers include hopanes and steranes from petroleum use in motor vehicles; phytosterols, lignans, phenolic products from lignins, and diterpenoids from resins in wood smoke; cholesterol in meat charbroiling smoke; high-molecular-weight odd carbon number n-alkanes in the particles shed as leaves rub together in the wind, and iso- and anteiso-alkanes in cigarette smoke. To date it has been demonstrated that the particles from up to nine different source types can be distinguished from each other simultaneously in the southern California atmosphere by this method. In the future, new analytical methods will increase the family of tracer compounds, assist in the identification of markers for additional sources, and speed the chemical analysis process in the laboratory.
182 citations
TL;DR: In this paper, different types of sorbents for the solid phase extraction of polar organic pollutants from environmental water and the use of the new synthesized polymeric resins are discussed.
Abstract: This article describes different types of sorbents for the solid-phase extraction of polar organic pollutants from environmental water and emphasizes the use of the new synthesized sorbents. The most important new sorbents are the chemically modified polymeric resins with functional groups such as acetyl, hydroxymethyl, benzoyl and o-carboxybenzoyl, and the highly crosslinked polymers. These sorbents are compared and their properties described. Recoveries for the most polar compounds are better when these new sorbents are used. Immunosorbents and molecularly imprinted polymers are new types of extraction sorbents which are specific for a group of compounds and they enable chromatograms with no matrix interference to be obtained when analyzing some polar compounds. The advantages and drawbacks of off-line and on-line procedures are also discussed, and solutions to their limitations are proposed.
180 citations
TL;DR: Differential mobility analyzers (DMAs) can classify a steady and narrowly monomobile stream of charged particles from a continuum spectrum of electrical mobilities as discussed by the authors, which has been widely exploited in aerosol research involving particles larger than some 10 nm.
Abstract: Differential mobility analyzers (DMAs) can classify a steady and narrowly monomobile stream of charged particles from a continuum spectrum of electrical mobilities. This feature has been widely exploited in aerosol research involving particles larger than some 10 nm. But high losses and low resolution due to Brownian diffusion have traditionally impaired DMA use for smaller particle sizes. These aerosol instruments have thus been poor competitors with time of flight drift tubes for mobility-based analysis of molecular ions and clusters. Recently, however, these problems have been overcome. Specially designed and run DMAs can now supply a pure and steady stream of molecular ions or clusters in a gas by classification from a complex ion mixture. The potential of such devices for investigations involving ions and nanoparticles is illustrated through various examples of recent work.
158 citations
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TL;DR: In this paper, the strengths and weaknesses of direct remote sensing, e.g., DIAL, LIDAR, and indirect sensing through fiber optics, are discussed, and details of different configurations, instrumentation, and mobile platforms for remote sensing are also given.
Abstract: Laser remote sensing is a fast developing area of laser spectroscopy with numerous applications. Strengths and weaknesses of direct remote sensing, e.g. DIAL, LIDAR, and indirect sensing through fiber optics are discussed. Details of different configurations, instrumentation, and mobile platforms for remote sensing are also given. Examples from environmental analytical spectroscopy, respectively process analysis, are covered for both types of remote sensing.
140 citations
TL;DR: In this paper, a new monolithic type of HPLC column, the SilicaROD™ column, is described, which permits the fast HPLC separation of compound mixtures within a few minutes.
Abstract: High performance liquid chromatography (HPLC) has become one of the most used methods for the analysis of compound mixtures in industry, especially for the quality control of products. Nowadays productivity is the major and dominant upcoming issue, i.e. the goal is to drastically reduce the analysis time and cost per analysis. The solution of the task is higher throughput and faster HPLC methods. Here we describe a new monolithic type of HPLC column, the SilicaROD™ column, which permits the fast HPLC separation of compound mixtures within a few minutes.
134 citations
TL;DR: Mid-infrared spectroscopy has recently been applied to the problem of food quality and some of the experimental and statistical approaches used and the results obtained are reported.
Abstract: Authenticity is an important food quality criterion. Rapid methods for confirming authenticity or detecting adulteration are increasingly demanded by food processors, consumers and regulatory bodies. Mid-infrared spectroscopy has recently been applied to this problem and this short review reports on some of the experimental and statistical approaches used and the results obtained. Implications for future applications are considered.
133 citations
TL;DR: The idea of using a laser-induced ''spark'' as a spectrochemical plasma source is extremely attractive and the potential advantages are now very well known: no sample preparation is needed; a sample of any phase may be examined, electrically conducting or not; remote measurements are possible; spatial information can be obtained; and rapid, simultaneous multi-element analysis is possible as discussed by the authors.
Abstract: At the Xth Colloquium Spectroscopicum Internationale, held at the University of Maryland in June, 1962, Fred Brech described his initial encouraging spectrochemical measurements using a ruby `maser'-induced plasma. The idea of using a laser-induced `spark' as a spectrochemical plasma source is extremely attractive and the potential advantages are now very well known: no sample preparation is needed; a sample of any phase may be examined, electrically conducting or not; remote measurements are possible; spatial information can be obtained; and rapid, simultaneous multi-element analysis is possible. For the past 35 years, laser-induced plasma spectroscopy has been widely studied during three obvious periods of growing and declining interest. The last five years have seen a renewed level of activity in the field, largely the result of ever improving detection technologies and increasingly reliable laser sources. It now appears likely that laser-induced plasma spectroscopy will find useful applications in elemental process monitoring and in portable semi-quantitative elemental analyzers. The fundamental matrix sensitivity of the technique may limit its use as a general-purpose analytical tool. This review examines selected literature of 1997.
127 citations
TL;DR: The matrix effects observed in several studies involving e.g. food, crop and environmental samples are briefly discussed in this article, where the procedures to eliminate the matrix interferences are discussed.
Abstract: Enzyme-linked immunosorbent assays (ELISAs) are the most extensively studied types of immunoassay and their application in pesticide residue monitoring is an area with enormous potential for growth. In comparison with classical analytical methods, ELISA methods offer the possibility of highly sensitive, relatively rapid, and cost-effective measurements. This review introduces the general ELISA formats used, focusing on their use in pesticide analysis. Identifying and studying the effects of interferences in immunoassays is an active area of research and we discuss the matrix effects observed in several studies involving e.g. food, crop and environmental samples. The procedures to eliminate the matrix interferences are briefly discussed.
TL;DR: In this paper, the authors describe the current achievements and limitations of laser ablation sampling for chemical analysis, including calibration and optimization, fractionation, sensitivity enhancements, mass loading, and particle transport.
Abstract: Laser ablation sampling provides significant benefits and capabilities for chemical analysis. It represents one of the most promising technologies for direct solid sample introduction. Despite the advantages, there are a number of issues that should be addressed to better understand and utilize this technology. Laser ablation itself is a complex process and is poorly understood, fundamentally. In this paper, we describe the current achievements and limitations in order to better understand and utilize laser ablation sampling for chemical analysis. Several current issues related to laser ablation sampling are discussed, including calibration and optimization, fractionation, sensitivity enhancements, mass loading, and particle transport.
TL;DR: In this article, a multivariate technique of principal components analysis (PCA) was applied to study two selected littoral ecosystems in the Gulf of Cadiz, which can be used successfully for contamination source assessments.
Abstract: The problem of identifying sources of anthropogenic pollutants in a local marine environment has been intensively studied during the last two decades. An approach is descibed for tracing anthropogenic pollutant sources, and for characterizing various geochemical and chemical processes related to contamination by anthropogenic heavy metals and surfactants in the marine coastal environment, which uses a multivariate technique of principal components analysis (PCA). This approach was applied to study two selected littoral ecosystems in the Gulf of Cadiz. The multivariate analysis approach can be used successfully for contamination source assessments. From this information, it was possible to identify current superficial sources of contamination and it might be possible to determine the areas where further toxicological testing is required.
TL;DR: The use of capillary electrophoresis (CE) for main component determinations, stoichiometric assays, analysis of vitamins and regulatory aspects of pharmaceutical analysis is discussed in this paper.
Abstract: Part I covered the use of capillary electrophoresis (CE) for main component determinations, stoichiometric assays, analysis of vitamins and regulatory aspects of pharmaceutical analysis. This second article examines the use of CE in the determination of drug-related impurities, chiral separations and the expanding use of capillary electrochromatography (CEC) within the pharmaceutical industry. Impurity determinations are probably the principal role of CE within pharmaceutical analysis and represent a challenge to both the selectivity and sensitivity capabilities of the technique. The main component and structurally-related impurities often have very similar chemical properties which place great requirements on the selectivity necessary. Detection limits of 0.1% area/area are widely accepted as a minimum requirement for a related impurity determination method and this is possible by CE. The use of a number of chiral selective electrolyte additives including proteins, carbohydrates, crown ethers and antibiotics are reviewed. Validation reports of chiral CE methods are discussed in comparison to high performance liquid chromatography methods. This review also examines the increasing use of CEC in the analysis of chiral compounds.
TL;DR: This tutorial illustrates the main ideas of Genetic Algorithms and Evolutionary Strategies using a simple example, and general guidelines for the application of these algorithms are given.
Abstract: Evolutionary algorithms such as Genetic Algorithms and Evolutionary Strategies have gained wide popularity in the last decades. They have shown their ability to solve complex optimisation problems in a number of fields, including chemistry. In this tutorial, the main ideas are illustrated using a simple example, and general guidelines for the application of these algorithms are given. Pointers to available resources on the World Wide Web are given in the appendix.
TL;DR: In this paper, an in situ thermal hydrolysis and methylation (THM) step was incorporated into the pyrolysis analysis of whole bacteria, which reduced the sample preparation time from 60 min to less than 1 min.
Abstract: Pyrolysis mass spectrometry (Py–MS) can be used to profile methylated fatty acids from bacterial pathogens without a chromatographic step. An in situ thermal hydrolysis and methylation (THM) step incorporated into the Py–MS analysis of whole bacteria reduces the sample preparation time from 60 min to less than 1 min. Detection of four bacterial pathogens with a field-portable aerosol-sampling Py–ion trap MS using FAME profiles from whole bacteria is demonstrated with a total analysis time of less than 10 min/lipid profile.
TL;DR: In this article, a comprehensive view of the occurrence, biochemical effects and impact of organotin contamination on molluscs along the Catalan coast (Northwestern Mediterranean) is given, where chemical analysis of biota samples revealed that several years after legislation to reduce tributyltin (TBT) inputs, the concentration of this compound in mussels inhabiting Catalan harbours is still elevated.
Abstract: Organotin compounds are ubiquitous contaminants in the environment. The high biological activity of some compounds toward aquatic organisms leads to deleterious impacts in aquatic ecosystems. A comprehensive view is given of the occurrence, biochemical effects and impact of organotin contamination on molluscs along the Catalan coast (Northwestern Mediterranean). Chemical analysis of biota samples revealed that several years after legislation to reduce tributyltin (TBT) inputs, the concentration of this compound in mussels inhabiting Catalan harbours is still elevated. Likewise, levels of organotins outside the harbours are high enough to cause imposex in the commercial muricid Bolinus brandaris . The interaction of TBT with the molluscan cytochrome P450 and the consequences for the organism in terms of hormonal disruptions are discussed.
TL;DR: In this paper, the authors compared the microwave assisted extraction (MAE) and accelerated solvent extraction (ASE) techniques for the extraction and determination of chlorinated biphenyls (CBs) in soils and solid wastes.
Abstract: The extraction and determination of chlorinated biphenyls (CBs) in soils and solid wastes is an ongoing subject of study. This is an overview article that compares the microwave-assisted extraction (MAE) and accelerated solvent extraction (ASE) techniques. The extraction of CBs by ASE has been optimised taking into account the variation of pressure, temperature and extraction time by means of experimental design and the Simplex approach. The recoveries obtained under the optimum conditions are compared and discussed with those obtained from MAE and Soxhlet extractions.
TL;DR: In this article, the effect of solvent on analyte-additive interactions is discussed and compared to those additives that can change the analyte mobility through electrostatic or donor-acceptor interactions.
Abstract: This article reviews the recent developments in nonaqueous capillary electrophoresis and discusses the effect of the solvent on analyte–additive interactions. When nonaqueous solvents are used, solvophobic interactions are generally weaker than those in water; therefore, those additives that can change the analyte mobility through electrostatic or donor–acceptor interactions should be further explored.
Abstract: Single or sequential extraction procedures are often used for soil and sediment studies to determine forms or phases of elements (e.g. `bioavailable' forms of elements). The significance of the analytical results is highly dependent on the extraction procedures used, owing to the `operationally defined' character of these schemes which requires the adoption of standardized protocols. The first part of the present review discusses the aspects of standardization of leaching and extraction schemes as applied to environmental analysis. This second part focuses on the validation aspects of such procedures and describes the preparation and certification of soil and sediment reference materials certified for their extractable trace element contents, following standardized single and sequential extraction procedures.
TL;DR: In this article, a new method for HPLC which uses packing materials modified with a temperature-responsive polymer, poly( N -isopropylacrylamide), was developed.
Abstract: We have developed a new method for HPLC which uses packing materials modified with a temperature-responsive polymer, poly( N -isopropylacrylamide). The surface properties and functions of the stationary phases are controlled by the external temperature. In the proposed chromatographic system, the elution of target substances is controlled by only a small change in the column temperatures.
TL;DR: The matrix assisted laser desorption/ionisation-mass spectrometry (MALDI-MS) has been applied to a large number of analytical problems such as the analysis of proteins, glycoconjugates, polynucleotides and synthetic polymers as discussed by the authors.
Abstract: Since its invention in the late 1980s, matrix-assisted laser desorption/ionisation–mass spectrometry (MALDI-MS) has been applied to a large number of analytical problems such as the analysis of proteins, glycoconjugates, polynucleotides and synthetic polymers. This article explains briefly the principle of MALDI and the instrumentation required. The preparation and purification of samples on a microlitre scale prior to mass analysis are described. Examples are given of MALDI mass analysis using infrared and ultraviolet lasers (IR– and UV–MALDI-MS). Analytical applications of MALDI-MS to mass analysis of electroblotted proteins, to unambiguous protein identification, the de novo sequencing of polynucleotides, DNA mutant analysis for diagnostic purposes, and the analysis of non-covalent complexes, are addressed.
TL;DR: In this article, the harmonisation and standardization of methods for soils, composts and other wastes is needed for comparable and more comprehensive data for the different countries in the European Union.
Abstract: Composts are considered as organic soil improvement, however, with the introduction of organic substances from industrial or municipal wastes, they should be considered as secondary wastes. The harmonisation and standardization of methods for soils, composts and other wastes is needed for comparable and more comprehensive data for the different countries in the European Union.
TL;DR: The differences between academia and industry in the use of bioprocess monitoring are discussed, based on the key drivers determining implementation of analytical systems in each of these fields.
Abstract: Bioprocess monitoring capabilities are gaining increasing importance both in physiological studies and in bioprocess development. The present article focuses on on-line analytical systems since these represent the backbone of most bioprocess monitoring systems, both in academia and in industry. We discuss advantages and drawbacks of various of the most frequently used components (sampling units, flow systems and detection unit) and analytical techniques. The differences between academia and industry in the use of bioprocess monitoring are discussed, based on the key drivers determining implementation of analytical systems in each of these fields.
TL;DR: In this article, a more efficient use of data generated for regulatory purposes can be made by placing test data from quicker (concise) leaching procedures in context with the more elaborate characterization leaching procedure, which provides a basis for prediction of long term leaching behaviour by improving our understanding of the factors controlling release.
Abstract: For the management of wastes from large scale industrial processes and the decision to either dispose or utilize these materials, information on their environmental properties is needed. Leaching tests have been developed to assess such properties. These have been designed typically in relation to regulatory control, not as instruments for the management of wastes nor as an aid to improving the material properties for reuse. New methods have been designed to address this aspect, in which maximum benefit can be derived from knowledge of the systematic leaching behaviour of materials. The characterization information generated for specific wastes has a more general applicability than the current regulatory single step leaching test data. Since these more elaborate tests are more costly to perform and generally take more time to complete, quick tests are needed in process control. By placing test data from quicker (concise) leaching procedures in context with the more elaborate characterization leaching procedures, a more efficient use of data generated for regulatory purposes can be made. This extended information provides a basis for prediction of long term leaching behaviour by improving our understanding of the factors controlling release.
TL;DR: The shape selectivity of C30 alkyl chains is investigated in this paper, showing that at higher temperatures the capability of differentiating between different stereochemical isomers is lost, resulting in peak coelution.
Abstract: In comparison to conventional C18 phases, C30 phases exhibit superior shape selectivity for the separation of isomers of carotenoids and vitamins. To obtain this enhanced recognition capability the HPLC separation must be performed at a well-defined temperature. At higher temperatures the capability of differentiating between different stereochemical isomers is lost, resulting in peak coelution. This separation behaviour is primarily dependent upon the organisation of the C30 alkyl chains on the silica surface which can be visualised as two domains, the more ordered domain containing relatively rigid n-alkyl groups with trans conformations and the less ordered environment containing more flexible n-alkyl groups with gauche conformations. The ratio between trans vs. gauche conformations of the n-alkyl groups directs the shape selectivity of the C30 phase. The temperature-dependent interconversion of trans to gauche conformations can be monitored by temperature-dependent solid-state nuclear magnetic resonance (NMR) and suspended-state NMR measurements and visualised by molecular modelling calculations. Thus a direct correlation between chromatographic and physicochemical properties of C30 bonded phases is possible.
TL;DR: In this paper, the interfacing of flow injection analysis (FIA) with capillary electrophoresis (CE) is discussed. And the practical applicability of the FIA-CE technique has been demonstrated by the determination of small anions in, for instance, water, juice and milk samples.
Abstract: This article reviews the interfacing of flow injection analysis (FIA) with capillary electrophoresis (CE). Various sample pre-treatment procedures such as dialysis and gas diffusion can be fully automated as can the application of the electrokinetic injection principle for introduction of the treated sample into the CE system using a specially designed interface. The practical applicability of the FIA–CE technique has been demonstrated by the determination of small anions in, for instance, water, juice and milk samples. Sample throughput rates can reach 170/h and the repeatability is typically 2% (R.S.D.).
TL;DR: In this article, the use of ultrasonic extraction (UE) for heavy metals extraction in industrial hygiene applications is discussed. But, the authors focus on the industrial domain and do not consider the environmental domain, where UE has been underutilized for sample preparation purposes.
Abstract: Ultrasonic extraction (UE) is an effective method for the extraction of a number of heavy metals in environmental samples. In many cases, UE offers a means for quantitative recoveries of heavy metals. However, UE has been underutilized for sample preparation purposes in environmental analysis. Nevertheless, the use of UE for extraction of heavy metals in the industrial hygiene arena is increasing, with applications in the field as well as in the laboratory. In this article some examples of applications of UE to heavy metals extraction (for their subsequent determination) in environmental and industrial hygiene samples are presented. It is expected that the use of UE for sample preparation purposes in environmental analytical chemistry will become more widespread, owing to its simplicity, ease of use, speed, and enhanced safety when compared with other, more traditional sample preparation procedures.
TL;DR: Electrostatic ion chromatography (EIC) is a unique analytical method which separates ions on a bi-functional zwitterionic stationary phase using pure water as the mobile phase.
Abstract: Electrostatic ion chromatography (EIC) is a unique analytical method which separates ions on a bi-functional zwitterionic stationary phase using pure water as the mobile phase An introduction to this ion chromatographic method is given and new areas for the further development of the technique are discussed
TL;DR: Pervaporation is in principle a separation technique for the removal of volatile analytes or their volatile derivatives from the sample matrix but can also be used for sample pretreatment, e.g. for solid samples where leaching and derivatisation of the analytes are done simultaneously.
Abstract: The use of pervaporation in analytical chemistry is a relatively new development. Pervaporation is in principle a separation technique for the removal of volatile analytes or their volatile derivatives from the sample matrix but can also be used for sample pretreatment, e.g. for solid samples where leaching and derivatisation of the analytes are done simultaneously. The applications of analytical pervaporation that have been developed so far are discussed. Special attention is paid to its use as an alternative to gas diffusion, to its use with liquid samples containing solids in suspension or of a corrosive nature, as well as with solid samples for the determination of a single analyte or for multideterminations. Emphasis is given to the integration of the separation technique with detection and to the coupling of a pervaporator to a gas chromatograph, which constitutes a valid alternative to headspace sampling.