Showing papers in "Trends in Analytical Chemistry in 2000"
TL;DR: In recent years, microwave assisted extraction has attracted growing interest as it allows rapid extractions of solutes from solid matrices, with extraction efficiency comparable to that of the classical techniques as mentioned in this paper.
Abstract: In recent years, microwave-assisted extraction has attracted growing interest as it allows rapid extractions of solutes from solid matrices, with extraction efficiency comparable to that of the classical techniques. In particular, numerous applications of this recent technique deal with the extraction of pollutants from environmental samples. This review gives a brief presentation of the theory of microwave and extraction systems, a discussion of the main parameters that influence the efficiency, and the main results on the applications to environmental matrices. Finally, the performance of this technique is compared to that from classical extractions (sonication and Soxhlet extraction) and recent techniques (supercritical fluid extraction and accelerated solvent extraction).
454 citations
TL;DR: This review aims to describe the present state-of-the-art of microsystems for use in miniaturised protein analysis, which will include both microarray- and microuidic- based microdevices.
Abstract: The field of genomics is being immeasurably altered by the introduction of microsystems in the guise of gene microarrays. There are a number of other microfabricated entities in the literature ranging from single chips for PCR to complete analysis systems. Developments in miniaturised protein analysis, though not as yet as revolutionary as some of those for DNA, are progressing. This review aims to describe the present state-of-the-art of microsystems for use in both these fields, this will include both microarray- (DNA or protein immobilised on chip) and microfluidic- (DNA or proteins being transported, processed and separated in a transport medium) based microdevices.
334 citations
TL;DR: In this article, details of the occurrence of the platinum group metals (PGM) in the Earth's crust and the composition of the principal minerals are presented along with data on supply and demand of PGM in different fields.
Abstract: Details of the occurrence of the platinum group metals (PGM) in the Earth's crust and the composition of the principal minerals are presented along with data on supply and demand of PGM in different fields. Trace level determination of the PGM requires preconcentration. Methods such as fire assay, chlorination, ion exchange, etc., are dealt with. Analytical techniques used for the determination of PGM such as spectrophotometry, atomic absorption, neutron activation methods, inductively coupled plasma atomic emission and inductively coupled plasma mass spectrometry (ICPMS) are discussed. The ICPMS technique, which has a leading role because of its high sensitivity, simultaneous multi-element capability and a fair degree of tolerance to interferences, is discussed in detail. The need for availability and use of certified reference materials of similar matrix and appropriate PGM content in obtaining reliable data is also discussed.
278 citations
TL;DR: In this paper, a brief review on the development and applications of optical and fiber-optic pH sensors in the 1990s is provided, including pH sensors based on conductive polymers, imaging fibers, microparticles and nanospheres.
Abstract: This article provides a brief review on the development and applications of optical and fiber-optic pH sensors in the 1990s. Various methods and materials for immobilization of pH indicators are surveyed. Different spectroscopic methods used for measurement with pH sensors are briefly discussed. Several special optical and fiber-optic pH sensors are reviewed, including pH sensors based on conductive polymers, imaging fibers, microparticles and nanospheres, as well as micron and submicron fiber-optic pH sensors, distributed fiber-optic pH sensors, pH sensors for high acidity and alkalinity, pH sensors with broad dynamic range and linear response, and CO2 and NH3 sensors based on pH indicators. Applications of fiber-optic sensors in environmental detection, biomedical research, medical monitoring and industrial process control are summarized.
259 citations
TL;DR: In this paper, the main types and areas of application of speciation analysis, and the use of sequential extraction in speciation studies are described, along with examples of their applications and the usage of various analytical techniques.
Abstract: The growing awareness of the strong dependence of the toxicity of heavy metals upon their chemical forms has led to an increasing interest in the qualitative and quantitative determination of specific metal species. Speciation has therefore become an important topic of present-day analytical research. This article describes the main types and areas of application of speciation analysis, and the use of sequential extraction in speciation studies. Brief characteristics of the basic types of speciation analysis, examples of their applications, and the usage of the various analytical techniques are also included.
257 citations
TL;DR: In this article, the basic experimental set-up is presented, and parameters influencing the extraction process are discussed, and the potential for replacing tedious classic extraction methods such as Soxhlet extraction is discussed.
Abstract: This review updates our knowledge on pressurised liquid extraction, PLE (also known as accelerated solvent extraction and pressurised fluid extraction) of persistent organic pollutants such as polynuclear aromatic hydrocarbons and polychlorinated biphenyls from environmental matrices. The basic experimental set-up is presented, and parameters influencing the extraction process are discussed. PLE can be used for a broad range of applications, and clearly has the potential for replacing tedious classic extraction methods such as Soxhlet extraction.
241 citations
TL;DR: The simplicity and adaptability of self-assembled monolayers (SAMs) and the control over biomolecule surface orientation suggest that SAMs will play an important role in the construction of artificial biomolecular recognition surfaces and particularly in the future development of biosensors.
Abstract: The recent developments in self-assembly technology applied to protein surface modification are described. The simplicity and adaptability of self-assembled monolayers (SAMs) and the control over biomolecule surface orientation suggest that SAMs will play an important role in the construction of artificial biomolecular recognition surfaces and particularly in the future development of biosensors.
228 citations
TL;DR: A brief overview of current developments in electrophoretic and chromatographic separation methods on microfabricated devices is given in this paper, highlighting some of the trends emerging from recent research results (published or pre-published before November 1999).
Abstract: Microchip-based separation techniques are essential elements in the development of fully integrated micro-total analysis systems, which are envisioned to become powerful instruments for obtaining and assessing analytical data in research, industry, and everyday life This article's goal is to give a brief overview of current developments in electrophoretic and chromatographic separation methods on microfabricated devices, and highlight some of the trends emerging from recent research results (published or pre-published before November 1999)
167 citations
TL;DR: In this article, the state-of-the-art of passive water sampling for long-term monitoring of organic pollutants in water is discussed, and the analytical costs (usually connected with expensive dynamic sample isolation and preconcentration techniques) can be reduced substantially.
Abstract: Commonly used monitoring systems usually record only pollutant concentrations at a specific point in time. Passive dosimetry, widely used to monitor air pollutants, can also be applied to monitor organic contaminants in water. Contrary to dynamic techniques, passive sampling is less sensitive to accidental extreme variations of the organic pollutant concentration in natural waters. A passive sampler can cover a long sampling period, integrating the pollutant concentration over time. Since only a few analyses are necessary over the monitoring period, analytical costs (usually connected with expensive dynamic sample isolation and preconcentration techniques) can be reduced substantially. Moreover, decomposition of the sample during transport and storage and/or changes during sample enrichment are also minimised. In this review, the present state of the art of passive water sampling for long-term monitoring of organic pollutants in water is discussed.
166 citations
TL;DR: The seemingly unlikely marriage between large mass spectrometers and small microchips is actually a good one as discussed by the authors, and the potential role of chip-mass spectrometry in proteomics and drug discovery is discussed.
Abstract: The seemingly unlikely marriage between large mass spectrometers and small microchips is actually a good one Microfluidic devices have been coupled to mass spectrometers using electrospray ionization interfaces Different interface designs and various integrated protein preparation and preconcentration procedures are reviewed The potential role of chip-mass spectrometry in proteomics and drug discovery is also discussed
165 citations
TL;DR: In this article, a review of the applications of instrumental techniques for the extraction of polycyclic aromatic hydrocarbons, polychlorinated biphenyls and pesticides from soils/sediments is presented.
Abstract: The extraction of organic pollutants from solid environmental matrices has traditionally been done using non-instrumental approaches, e.g. Soxhlet extraction. Recent developments have seen the possibility of extraction using instrumental techniques, namely, supercritical fluid extraction, microwave-assisted extraction and pressurised fluid extraction. This review considers the applications of instrumental techniques for the extraction of polycyclic aromatic hydrocarbons, polychlorinated biphenyls and pesticides from soils/sediments. Then, in order to assist the analyst to select the most appropriate technique (traditional versus instrumental techniques), a comparison of their analytical figures of merit is considered.
TL;DR: The multivariate curve resolution-alternating least squares (MCR-ALS) method has been shown to be a powerful tool in the analysis of metal complexation processes by a variety of voltammetric techniques as discussed by the authors.
Abstract: Voltammetry of metal ions in the presence of ligands is usually interpreted by means of hard-modelling approaches. Soft-modelling approaches have been scarcely applied to electroanalytical data, especially in comparison with their use in spectroscopy. In recent years, the multivariate curve resolution–alternating least squares (MCR–ALS) method, based on factor analysis, has been shown to be a powerful tool in the analysis of metal complexation processes by a variety of voltammetric techniques. In this article, an overview of the method and its applications is presented. For this purpose, either numerically simulated or experimental data corresponding to different characteristic systems are analysed. A very interesting feature of MCR–ALS is that, by using different constraints, both the pure voltammograms of the different electrochemical processes involved and the corresponding concentration profiles are easily obtained. This type of information cannot be reached by means of classical univariate data analysis techniques. From calculated concentration profiles, the model of complexation and the equilibrium stability constants are estimated.
TL;DR: A review of the literature on speciation analysis by high-performance liquid chromatography (HPLC) has been published in this paper, focusing on the analysis of mercury speciation.
Abstract: No previous reviews on speciation analysis by high-performance liquid chromatography (HPLC) have dealt solely with the analysis of mercury. The analytical methods are classified on the basis of the sample matrix analysed and deal with: standards and water, marine organisms, biomedical samples and sediments. The relevant technical information, column type, mobile phase, method of detection and detection limit, is presented in tabular form for each of the sample types. The majority of methods use reversed phase chromatography, usually with a buffer, organic modifier and some form of counter ion or complexing agent. Other aspects addressed in this review include sample preparation and instrumental methods of analysis. The review covers publications from 1986 to 1999.
TL;DR: A review of materials and fabrication methods commonly encountered for the production of such devices can be found in this article, where the focus is on the materials and methods frequently encountered for fabrication of micro-total analytical systems (μTAS).
Abstract: Over the last decade, microfabrication techniques have been reported for the production of devices in which fluidic manipulation and component separations of chemical and biological materials can be carried out. The term micro total analytical system (μTAS) is an accepted concept. However, it is perhaps the potential application of microfabricated devices in the wider context that has given added momentum to their development. In this review, the focus will be on the materials and fabrication methods frequently encountered for the production of such devices. Fluidic manipulation is achieved with either hydrostatic displacement pumps such as the syringe pump or electro-osmotic flow, which brings the added advantage of electrophoretic separations.
TL;DR: In this paper, a review of recent developments in analysis of aroma components in foods are reviewed, and the application of multivariate statistics is applied to compare the results from instrumental measurements to human perception requires careful control to ensure valid comparisons.
Abstract: Recent developments in analysis of aroma components in foods are reviewed. Aroma compounds are most closely associated with the volatile fraction of foods. Preliminary isolation remains an essential step in such procedures despite rapid developments in measurement techniques. Traditional methods of isolating volatile components have recently been complemented by solid phase microextraction. Gas chromatography (GC) and GC–mass spectrometry (MS) remain the dominant techniques for measurement of the extracted compounds although new electronic noses are promising techniques. Relating the results from instrumental measurements to human perception requires careful control to ensure valid comparisons. The application of multivariate statistics is important in this respect.
TL;DR: In this paper, the general composition of petroleum is discussed and also the relation between composition, product properties and processability, and the important role that comprehensive two-dimensional gas chromatography is expected to play in the near future in unraveling the composition of oil fractions.
Abstract: Because of the complex character of petroleum fractions and products, gas chromatography has played an important role as an analytical technique in this area since its introduction. For the majority of oil fractions classifying or group-type analyses are performed rather than determinations of all the individual constituents. The general composition of petroleum is discussed and also the relation between composition, product properties and processability. Compositional analyses for petroleum products are reviewed, especially in terms of multi-dimensional gas chromatography. The important role that comprehensive two-dimensional gas chromatography is expected to play in the near future in unraveling the composition of oil fractions is also discussed.
TL;DR: In this paper, the new development and application of this technique for speciation and analysis of mercury, arsenic and selenium are discussed, as well as its application for the determination of environmentally and biomedically important elements.
Abstract: Atomic fluorescence spectrometry is a very sensitive and selective method for the determination of a number of environmentally and biomedically important elements. The new development and application of this technique for speciation and analysis of mercury, arsenic and selenium are discussed here.
TL;DR: A review of micrometer scale reactors for chemical and biochemical applications can be found in this article, highlighting their inherent strengths and identifying areas where further development of a technology is poised to revolutionise significant areas of synthetic chemistry and biochemistry.
Abstract: Research into the fundamental and practical advantages of using micrometre scale reactors for chemical and biochemical applications is now growing at a considerable rate. This review tracks such developments, illustrating their inherent strengths and identifying areas where further development of a technology is poised to revolutionise significant areas of synthetic chemistry and biochemistry.
ENEA1
TL;DR: In the analysis of organotin compounds, derivatization is required in order to achieve more volatile compounds prior to the use of techniques based on GC separation as discussed by the authors, which can lead to an underestimation of their content in environmental samples.
Abstract: In the analysis of organotin compounds, derivatization is required in order to achieve more volatile compounds prior to the use of techniques based on GC separation. Derivatization can be considered as one of the main critical steps in organotin analysis, since low yields of derivatization and losses of analytes can easily occur at this stage, and lead to an underestimation of their content in environmental samples. Furthermore, experimental conditions which are not perfectly under control may induce degradations, and alter the original speciation in the sample. Hydride generation, and alkylation by Grignard reagents or by NaBEt 4, are the derivatization methods usually applied for organotins. The advantages and disadvantages of these methods are reported. z2000 Elsevier Science B.V. All rights reserved.
TL;DR: The analytical chemistry of lipid peroxidation is reviewed with special attention to literature that has appeared in the last four years as mentioned in this paper, and the pathways of the cascade of reactions are first described and current analytical practice discussed.
Abstract: The analytical chemistry of lipid peroxidation is reviewed with special attention to literature that has appeared in the last four years. The pathways of the cascade of reactions are first described and current analytical practice discussed. Selected assays, classified by analyte, are then considered as indices of lipid peroxidation; these mainly involve ultraviolet and visible spectrophotometry, fluorescence and chemiluminescence.
TL;DR: The development of solid phase extraction (SPE) for environmental chemistry has progressed significantly over the last decade to include a number of new sorbents and new approaches to SPE as mentioned in this paper.
Abstract: The development of solid-phase extraction (SPE) for environmental chemistry has progressed significantly over the last decade to include a number of new sorbents and new approaches to SPE. One SPE approach in particular, the SPE disk, has greatly reduced or eliminated the use of chlorinated solvents for the analysis of trace organic compounds. This article discusses the use and applicability of various SPE disks, including micro-sized disks, prior to gas chromatography–mass spectrometry for the analysis of trace organic compounds in water.
TL;DR: The high temperature catalytic oxidation (HTCO)-discrete injection method for liquid samples is currently the preferred analytical technique for the determination of dissolved organic carbon (DOC) in natural water samples.
Abstract: The high temperature catalytic oxidation (HTCO)-discrete injection method for liquid samples is currently the preferred analytical technique for the determination of dissolved organic carbon (DOC) in natural water samples. This approach yields equivalent or greater amounts of DOC than wet chemical oxidation methods, is suitable for routine analyses and is stable for shipboard determinations. However, a limited understanding of evaluation criteria for instrument performance presents a number of analytical challenges. This article discusses current practical problems encountered in the (i) collection and handling, (ii) preservation, (iii) decarbonation and (iv) analysis of seawater samples and reviews recent improvements in HTCO systems. Particular reference is made to the issue of certified reference materials and the oxidation efficiency of the technique. Copyright (C) 2000 Elsevier Science B.V.
TL;DR: In this article, a review of the state-of-the-art column technology for enantioselective capillary electrochromatography (CEC) can be found.
Abstract: The current popularity of capillary electrochromatography (CEC) has led to an increasing number of studies on the development and evaluation of enantioselective CEC systems. These studies clearly demonstrate that the most prominent advantage of electrically driven separation methods, the vastly increased column efficiency as compared to pressure-driven chromatography, can also be experimentally achieved for the separations of enantiomers. In analogy to high-performance liquid chromatography (HPLC) and capillary electrophoresis (CE), several approaches have been used. The addition of a chiral selector to the mobile phase is the simplest method. Less erroneous and more elegant approaches are those that use open-tubular, conventional packed, and monolithic columns containing chiral stationary phases that stereoselectively interact with enantiomers. This review evaluates the new techniques and compares them to enantioselective HPLC and CE. Further, it describes the various concepts of enantioselective CEC and focuses on the current `state-of-the-art' column technology.
TL;DR: The Measurement and Testing Programme (formerly BCR) has undertaken projects focused on a variety of species (e.g. Sn, Se, As, Sb, Hg, Pb, Cr), which have been complemented by the studies of other authors as mentioned in this paper.
Abstract: The stability of chemical species in environmental samples is a critical factor during storage, owing to the interconversion and degradation processes which can occur in species characterisation. The preservation and stabilisation of these chemical species in the time interval between sampling and analysis is a difficult task and several studies have been developed to improve the quality of this aspect of speciation analysis. The Measurement and Testing Programme (formerly BCR) has undertaken projects focused on a variety of species (e.g. Sn, Se, As, Sb, Hg, Pb, Cr), which have been complemented by the studies of other authors. The procedures proposed are reviewed in detail and the influence of critical operational parameters for species stability, such as pH, temperature, light and the container material is considered. The problems are not yet completely solved, especially for complex solid matrices such as soils, sediments and biological tissues.
TL;DR: Digital imaging was investigated as a potential means of processing high density dot arrays for analytical purposes to return numerical values for the red, green and blue components of the colour of each dot.
Abstract: Digital imaging was investigated as a potential means of processing high density dot arrays for analytical purposes. Using a high resolution digital camera, a colour image of the dot array was taken and subsequently processed using in-house developed National Instruments LabVIEW® software to return numerical values for the red, green and blue components of the colour of each dot.
TL;DR: The status of supercritical fluid extraction as an analytical technique for treatment of solid samples is discussed in this article, where its most significant advantages are its preconcentration effect, cleanness and safety, quantitativeness, expeditiousness and simplicity.
Abstract: The status of supercritical fluid extraction as an analytical technique for treatment of solid samples is discussed. Its most significant advantages are its preconcentration effect, cleanness and safety, quantitativeness, expeditiousness and simplicity. Its limitations include the difficulty of extracting polar analytes, owing to the non-polar character of the CO2 which is used, the different recoveries obtained from spiked and natural samples, and the frequent need for clean-up steps after extraction. A critical discussion is given of these factors, as well as possible solutions and new alternatives such as the use of sub- and supercritical water and accelerated solvent extraction.
TL;DR: Specific biomarker proteins have been identified and the feasibility of using reference spectra, reference cultures or protein databases for taxonomic identification of bacteria by MALDI–MS has been demonstrated.
Abstract: In the few years since the first reports that characteristic proteins could be desorbed directly from bacterial cells using MALDI, the use of mass spectrometry to investigate bacteria, bacterial proteins and the bacterial proteome has advanced rapidly. The effects of experimental parameters are understood sufficiently that reproducible spectra can be obtained in different laboratories and bacteria can be characterized by genus, species or strain. Specific biomarker proteins have been identified and the feasibility of using reference spectra, reference cultures or protein databases for taxonomic identification of bacteria by MALDI–MS has been demonstrated.
TL;DR: Advantages of microdialysis performed in vivo compared to traditional sampling methods are discussed and analytical considerations are discussed with a focus on practical aspects of micro dialysis.
Abstract: Microdialysis sampling is used to monitor the pharmacokinetics and distribution of drugs and endogenous compounds in vivo. This article discusses advantages of microdialysis performed in vivo compared to traditional sampling methods. In addition, analytical considerations are discussed with a focus on practical aspects of microdialysis. Recent advances and applications of in vivo microdialysis with emphasis on pharmacokinetics are described.
TL;DR: Capillary CEC columns are generally classified into three types: packed, open-tubular, and continuous-bed or monolithic as mentioned in this paper, and the advantages and disadvantages of each column type are discussed in detail.
Abstract: Column technologies for capillary electrochromatography (CEC) are reviewed. To achieve high efficiency, the inner diameters of open-tubular and packed columns should be less than 25 and 200 μm, respectively. To obtain acceptable separation speed under typical CEC conditions (e.g. 30 kV, 1 mm s−1 electroosmotic flow velocity, and 2–4×10−8 m2 V−1 s−1 electroosmotic mobility) the column lengths for open-tubular and packed columns should be less than 120 and 60 cm, respectively. Capillary CEC columns are generally classified into three types: packed, open-tubular, and continuous-bed or monolithic. The various column preparation procedures and the advantages and disadvantages of each column type are discussed in detail.
TL;DR: In this paper, the authors proposed a method for the mass fabrication of amperometric biosensors using rigid conducting carbon-polymer composites, which can not only act as reservoirs of the biological material but also contain catalysts, mediators and cofactors that improve the response of the resulting electrochemical sensors.
Abstract: Rigid conducting carbon–polymer composites are ideal for the construction of electrochemical sensors. The plastic nature of these materials makes them modifiable, permitting the incorporation of fillers before they are cured. A great number of biological materials can be immobilised by blending them with these composites to form new biocomposite materials. These biocomposites not only act as reservoirs of the biological material but may also contain catalysts, mediators and cofactors that improve the response of the resulting electrochemical biosensors. One of the outstanding features of these conducting biomaterials is their rigidity, resulting in a high mechanical stability over time. Furthermore, the sensing surface can be renewed by a simple polishing procedure. The proximity of the redox centres of the biological material and the conducting sites on the sensing surface favours the transfer of electrons between electroactive species. This may in some cases permit the regeneration of the biological component without using cosubstrates and mediators. These biocomposites are prepared easily and they show improved electrochemical characteristics. This is very attractive for the mass fabrication of amperometric biosensors.