Showing papers in "Trends in Analytical Chemistry in 1999"
TL;DR: Solid-phase microextraction (SPME) as mentioned in this paper is a sample preparation technique that minimizes the consumption of organic solvents and has been shown to be useful in analytical chemistry.
Abstract: In recent years, much attention in analytical chemistry has been paid to sample preparation techniques, especially those which minimise the consumption of organic solvents One of the most promising of these, solid-phase microextraction (SPME), is presented in both its theoretical and practical aspects Conditions which affect its performance are assessed, as are the problems which may arise from its use Finally, some typical applications are listed, highlighting the method's sensitivity and precision, and the range of samples where SPME can be used successfully
526 citations
TL;DR: In this paper, the introduction of polycyclic aromatic hydrocarbons (PAHs) into natural waters is considered in terms of both point and non-point source discharges to surface, ground and drinking water.
Abstract: The introduction of polycyclic aromatic hydrocarbons (PAHs) into natural waters is considered in terms of both point and non-point source discharges to surface, ground and drinking water. The occurrence of PAHs has been evaluated with regard to their concentrations in some aqueous samples and frequency of occurrence. In addition, an overview of the capabilities of the currently available analytical techniques is given along with requirements for achieving reliable analysis of PAHs in various environmental water samples.
437 citations
TL;DR: The development of analytical applications involving the electrochemical generation of chemiluminescence (ECL) in the last 5 years is reviewed in this article, where the mechanisms of common ECL reactions are summarised, and the potential advantages of ECL over conventional chemilUMinescence are discussed.
Abstract: The development of analytical applications involving the electrochemical generation of chemiluminescence (ECL) in the last 5 years is reviewed. The mechanisms of common ECL reactions are summarised, and the potential advantages of ECL over conventional chemiluminescence are discussed. The current limitations of the technique are considered along with how they are being addressed. Finally some pointers as to likely directions of future research are given.
317 citations
TL;DR: Membrane-based extraction techniques offer efficient alternatives to classical sample preparation techniques by making use of the advantages of liquid-liquid extraction, such as the possibility of tuning the selectivity by chemical means, and by avoiding the disadvantages of solvent consumption and the need for manual handling.
Abstract: Membrane-based extraction techniques offer efficient alternatives to classical sample preparation techniques by making use of the advantages of liquid–liquid extraction, such as the possibility of tuning the selectivity by chemical means, and by avoiding the disadvantages, such as solvent consumption and the need for manual handling. They permit high selectivity and high enrichment factors, as well as giving good possibilities for automation.
255 citations
TL;DR: In this article, the authors highlight the features of self-assembled monolayers (SAMs) which are applicable to enzyme immobilisation and the different immobilisation methods that can be used for constructing enzyme electrodes.
Abstract: Recently the bonding of enzymes to self-assembled monolayers (SAMs) of alkanethiols on gold surfaces has begun to receive attention as a method of constructing enzyme electrodes. This review highlights the features of SAMs which are applicable to enzyme immobilisation and the different immobilisation methods that can be used for constructing enzyme electrodes. An emphasis is placed on the ability of each method to produce reproducible enzyme electrodes and to give control over the molecular architecture of the sensor.
239 citations
TL;DR: Several useful applications of circular dichroism as a tool for analyzing properties of proteins are discussed and specific examples are given to illustrate each application.
Abstract: This review discusses several useful applications of circular dichroism as a tool for analyzing properties of proteins. The following topics are discussed: (1) protein–ligand interactions; (2) thermodynamics of protein folding; (3) conformational transitions and protein aggregation; (4) folding intermediates; (5) kinetics of protein folding. Specific examples are given to illustrate each application.
214 citations
TL;DR: Membrane-based extraction techniques offer efficient alternatives to classical sample preparation techniques as mentioned in this paper, and a number of examples from the fields of environmental and biomedical analysis are discussed, as well as the possibility of automated interfacing to chromatographic and other analytical instruments.
Abstract: Membrane-based extraction techniques offer efficient alternatives to classical sample preparation techniques. In this review a number of examples from the fields of environmental and biomedical analysis are discussed. High selectivity and enrichment factors, as well as the possibility of automated interfacing to chromatographic and other analytical instruments, are shown for quantitative analysis.
195 citations
TL;DR: In this article, the authors identify the factors of importance in the development of molecularly imprinted polymers for use in solid-phase extractions and summarizes the results obtained to date in the area of bioanalysis, pharmaceutical analysis and environmental analysis.
Abstract: This review identifies the factors of importance in the development of molecularly imprinted polymers for use in solid-phase extractions and summarizes the results obtained to date in the area of bioanalysis, pharmaceutical analysis and environmental analysis.
195 citations
TL;DR: In this paper, a critical overview is presented of conventional methods (based on either organic solvent extraction or distillation) and new alternatives (including microwave-assisted extraction (MAE) as well as supercritical CO2 (SC-CO2) extraction and subcritical water extraction) for the isolation of essential oils from plants.
Abstract: Attention is drawn to the use of new and clean alternative methods for the isolation of essential oils from plants A critical overview is presented of conventional methods (based on either organic solvent extraction or distillation) and new alternatives (including microwave-assisted extraction (MAE) as well as supercritical CO2 (SC-CO2) extraction and subcritical water extraction) The advantages and disadvantages of each technique are reported and special emphasis is given to the use of continuous subcritical water extraction which emerges as clearly advantageous over conventional techniques (by avoiding the use of organic solvents and considerably shortening the extraction time, as well as increasing the efficiency) and recent techniques, such as MAE (by increasing the efficiency) and SC-CO2 extraction (by avoiding the co-extraction of cuticular waxes and lipids and the need for a sample drying stage prior to extraction)
182 citations
TL;DR: Molecular imprinting, which allows the formation of specific recognition sites in polymer matrices, is now applied widely for developing robust sensors for industry, diagnostics, and environmental analysis as discussed by the authors.
Abstract: Molecular imprinting, which allows the formation of specific recognition sites in polymer matrices, is now applied widely for developing robust sensors for industry, diagnostics, and environmental analysis. In these sensors, molecularly imprinted polymers are coupled with appropriate transducers for the quantitative detection. This article describes recent trends and some examples of sensors based on molecular imprinting.
179 citations
TL;DR: A review of the options available for immobilisation of biocomponents and signal generation using conducting polymer-based biosensors can be found in this article, where a range of biological moieties (enzymes, antibodies and even whole living cells) are incorporated into the polymer structure.
Abstract: Conductive electroactive polymers are materials discovered just on two decades ago. Originally heralded for their high conductivity/weight ratio, it is the unique chemical properties they possess that now arouse much attention. The ability to synthesise these materials under mild conditions enables a range of biological moieties (enzymes, antibodies and even whole living cells) to be incorporated into the polymer structure. The unique electronic properties then allow direct and interactive communication with the biochemistries incorporated to produce a range of analytical signals. This work reviews the options available for immobilisation of biocomponents and signal generation using conducting polymer-based biosensors.
TL;DR: Solid-phase microextraction (SPME) is a recent technique for sample preparation as mentioned in this paper, which has been used successfully to analyze environmental pollutants in a variety of matrices such as soils, water, and air.
Abstract: Solid-phase microextraction (SPME) is a recent technique for sample preparation. It has been used successfully to analyze environmental pollutants in a variety of matrices such as soils, water, and air. SPME is a solvent-free technique which has a number of advantages over more conventional sample preparation techniques such as liquid–liquid extraction (LLE) and solid-phase extraction (SPE). We describe the most recent developments in SPME and some which are being developed, including its coupling to HPLC and CE, the use of new fibers, and the automation of the entire SPME process and its application to field analysis. A summary is given of the most important parameters for applying this extraction technique to the analysis of environmental samples.
TL;DR: In this paper, several procedures using MIPs for solid phase extraction are reviewed along with the preparation and evaluation of a molecular imprinted polymers (MIP) for SPE of atenolol.
Abstract: Solid-phase extraction (SPE) has become the method of choice in many laboratories for the analysis of complex samples. Recently, highly selective extraction based on antibody columns or molecular imprinted polymers (MIPs) has been developed. To date biological antibodies have shown better specificity but MIPs are easier to produce. Several procedures using MIPs for SPE are reviewed along with the preparation and evaluation of a MIP for SPE of atenolol.
TL;DR: The potential of analytical techniques based on molecular imprinting is reviewed from the viewpoint of bio- and pharmaceutical analysis in this paper, where a literature study shows that molecularly imprinted polymers...
Abstract: The potential of analytical techniques based on molecular imprinting is reviewed from the viewpoint of bio- and pharmaceutical analysis. A literature study shows that molecularly imprinted polymers ...
TL;DR: In this article, tailor-made precolumn packings for HPLC integrated extractive clean-up of (bio)fluids are characterized by possessing a defined diffusion barrier and a biocompatible outer particle surface.
Abstract: Tailor-made precolumn packings for HPLC integrated extractive clean-up of (bio)fluids are characterized by possessing a defined diffusion barrier and a biocompatible outer particle surface (restricted access materials, RAM). Only analytes of low molecular mass have free access to the binding centers at the inner pore surface, and thus can be retained and extracted selectively. These adsorbents allow the easy, inexpensive installation and economic operation of fully automated coupled-column systems for repetitive on-line solid-phase extraction (SPE), and the subsequent analytical separation of untreated (bio)fluids.
TL;DR: Molecular imprinting is a universal tool for the generation of artificial and robust recognition systems in the gas and liquid phases as discussed by the authors, which is suitable for trace analyses down to the ppb range.
Abstract: Molecular imprinting is a universal tool for the generation of artificial and robust recognition systems in the gas and liquid phases. Optical and mass-sensitive devices are suitable for trace analyses down to the ppb range. Imprinted polymers can be combined with pre-organized supramolecular hollows, which lead to further improvements in selectivity and sensitivity.
TL;DR: In this article, the advantages and disadvantages of various kinds of sorbents, ranging from conventional ones such as C 18 or polymerics, up to the most recent ones, such as immunosorbents (IS) or molecularly imprinted polymers (MIP), are highlighted.
Abstract: For the extraction and isolation of trace contaminants from complex environmental matrices new selective methods are required in order to achieve the low concentration levels imposed by the regulatory agencies, such as the CEE and US-EPA. Accordingly, several analytical methodologies involving the solid-phase extraction of traces of organic contaminants from environmental matrices, using different types of sorbents, are reviewed here. The advantages and disadvantages of the various kinds of sorbents, ranging from conventional ones such as C 18 or polymerics, up to the most recent ones such as immunosorbents (IS) or molecularly imprinted polymers (MIP), are highlighted. In addition, we report applications in the environmental field for the trace determination of pesticides and their degradation products, and polycyclic aromatic hydrocarbons (PAHs) in natural waters and sediments. Finally, an important feature of the development of new sorbent materials is their validation for assessing the high quality of the analytical procedures. In this respect, examples are given of the validation of immunosorbents by participation in inter-laboratory exercises, including the analysis of groundwater samples and certified sediment reference materials.
TL;DR: The requirements and procedures that may be used to obtain methods that have been validated `in-house', without full validation through collaborative trial, are outlined, pointing the way to international acceptance of such methods in future as the cost of carrying out full validation of methods through collaborative trials becomes prohibitory.
Abstract: The requirement for laboratories to use a `fully validated' method of analysis is now accepted or required in many sectors of analysis. Fully validated means that a method must have been assessed in a collaborative trial. The significance of these requirements is described because analysts will increasingly be required to justify their choice of method in the light of them. In addition, the requirements and procedures that may be used to obtain methods that have been validated `in-house', without full validation through collaborative trial, are also outlined in the article, these pointing the way to international acceptance of such methods in future as the cost of carrying out full validation of methods through collaborative trials becomes prohibitory.
TL;DR: It has become apparent that MIR can be used to address a wide range of issues and provide solutions for rapid analysis and on-line control and the authors predict that the use of MIR spectroscopy is likely to continue to increase and develop in the near future.
Abstract: This article deals with recent developments in the use of mid-infrared (MIR) spectroscopy for the analysis of foods. It has become apparent that MIR can be used to address a wide range of issues and provide solutions for rapid analysis and on-line control. In parallel with the new applications to food, which include new qualitative and quantitative applications and discriminant (classification) methods, there have been several technical advances in other fields that are set to impact on the food sector. New applications of transmission methods are described, which have been particularly successful for the analysis of oils and fats. Despite new advances in other sampling techniques, transmission methods have been quite widely employed. Diffuse reflectance has also been used with some considerable success, with new accessory designs and applications in food authentication using chemometric methods. However, the largest number of new applications and technical developments have used attenuated total reflectance (ATR). Novel ATR cells have been designed for high-temperature, high-pressure and a range of on-line applications. ATR has been used for a wide range of analytical application. The analysis of sugars in various systems has been particularly well studied. The authors predict that the use of MIR spectroscopy is likely to continue to increase and develop in the near future.
TL;DR: This review mainly covers the developments in PPFs used for bios sensor design since a previous review, and the role of dry-process-based PPFs in biosensor design has become increasingly more important.
Abstract: Biosensors are devices that use a biological reaction for detecting target analytes by generating a quantifiable electronic signal. They are powerful tools used in medical diagnostics, food-quality control and environmental monitoring. A typical biosensor is an integrated product, incorporating biological elements and transducers. It has been consistently shown that plasma-polymerized thin films (PPFs), created in a glow-discharge or plasma-in-vapor phase, have potential for use as the interface between the two components of biosensors. This review mainly covers the developments in PPFs used for biosensor design since that previous review [H. Muguruma, I. Karube, Trends Anal. Chem. 18 (1999) 62]. To date, transducers have been amenable to miniaturization, and the concept of biosensors has concomitantly expanded to encompass microchips, arrayed sensors and nanotechnology. The role of dry-process-based PPFs in biosensor design has become increasingly more important.
TL;DR: Immunosorbents are solid-phase extraction sorbents which are based upon molecular recognition using natural antibodies and allow a high degree of molecular selectivity as discussed by the authors, which can be combined with LC, in both off-line and online modes, thus providing a totally automated device.
Abstract: Immunosorbents are solid-phase extraction sorbents which are based upon molecular recognition using natural antibodies and allow a high degree of molecular selectivity. Extraction, concentration and isolation of complex aqueous environmental samples are possible in a single step from large volumes of sample. Immunoaffinity extraction can be combined with LC, in both off-line and on-line modes, thus providing a totally automated device. Its application to extracts from solid samples is solvent-free and simpler than any other clean-up procedures. The high degree of purification permits an efficient coupling with GC–MS or LC–MS. Single analytes can be targeted, and the cross-reactivity of the antibodies has been exploited with target groups of structurally related analytes, including metabolites. Several class-selective immunosorbents have been optimised for the trapping of groups of pesticides and priority industrial organic pollutants. Immunosorbents are robust, and validation studies using certified reference materials have demonstrated their reliability. They are in a more advanced stage than artificial molecularly imprinted materials, and are now moving from the laboratory stage to commercialisation.
TL;DR: The state of the art and the potential of sample screening systems (SSS) for the expeditious, reliable selection of samples to meet the requirements of customers and legislation is presented and discussed.
Abstract: The state of the art and the potential of sample screening systems (SSS) for the expeditious, reliable selection of samples to meet the requirements of customers and legislation is presented and discussed. The underlying procedures use simple equipment and operations and provide a yes/no binary response that occasionally requires confirmation. After a brief discussion of the distinction between `screening' and `analysis' and the principal features of analytical screening systems, the main aims and features of SSS are presented. Several classifications of these allow one to offer a general view of the topic. Representative examples are classified according to the complexity of the sample pretreatment required, and are used to demonstrate the impact SSS may have on analytical chemistry in the next century.
TL;DR: The use of platinum group elements (PGEs) as components of autocatalytic converters attached to motor vehicles has resulted in serious contamination of the environment by Pt, Rh and Pd in nanocrystalline forms.
Abstract: The use of platinum group elements (PGEs) as components of autocatalytic converters attached to motor vehicles has resulted in serious contamination of the environment by Pt, Rh and Pd in nanocrystalline forms. Trace concentrations of PGEs, particularly the major component Pt, in environmental samples have been measured by sensitive instrumental procedures. These data have raised further questions about the nature of Pt species in contaminated soils and in plants grown in them. The focus of attention is changing from accumulations of data expressing total concentrations to investigations of speciation. Application of analytical procedures for research on speciation has provided information concerning transformations of Pt compounds in contaminated soils, the uptake of Pt by plants and the nature of Pt compounds in vegetation. Determination of background levels of precious metals in clinical and environmental matrices has required the development of analytical methods which combine uses of minimal quantities of reagents, and as small a number of chemical operations as possible to yield very low procedural blanks. Sensitive instrumental methods based upon high resolution inductively coupled plasma mass spectrometry and adsorptive stripping voltammetry have proven to be valuable for this work.
TL;DR: In this paper, the latest developments in the application of microwave techniques to analytical chemistry are reviewed, including sample digestion, solvent extraction, sample drying, measurement of moisture, analyte desorption and adsorption, sample clean-up, chromogenic reaction, speciation and nebulization of analytical samples.
Abstract: The latest developments in the application of microwave techniques to analytical chemistry are reviewed. Some applications of microwave techniques to sample digestion, solvent extraction, sample drying, the measurement of moisture, analyte desorption and adsorption, sample clean-up, chromogenic reaction, speciation and nebulization of analytical samples are presented.
TL;DR: In this paper, the main difficulties found in the development and implementation of on-line immunosensors, as applied to the determination of organic pollutants such as pesticides, are discussed.
Abstract: The development of antibody-based sensors has grown steadily during recent years, and their use as routine instruments in pollution control programmes might become reality in the 21st century. The conversion from batch immunoassays to practical immunosensors has not been easy, owing to the sometimes different principles employed in these methodologies. In this review we illustrate the main difficulties found in the development and implementation of on-line immunosensors, as applied to the determination of organic pollutants such as pesticides. Some solutions to these problems are proposed, and their validities discussed critically.
TL;DR: It is anticipated that molecular imprints will find a prominent place in pharmaceutical research, not only as a tool to improve selectivity and sensitivity in analytical methods but also for selective extraction of drugs or intermediates from reaction media.
Abstract: The development of new selective analytical methods and sample enrichment techniques remains of interest. The implementation of molecular imprints in chemical analysis may offer advantages over existing methodologies. Criteria for the applicability of molecular imprints in separation methods, ligand-binding assays, sample pre-treatment and sensors are defined. Each analytical problem requires imprints with specific characteristics. Affinities can be comparable with those observed for antigen–antibody interactions, which enables application in ligand-binding assays and for sensors. However, for application in separation methods, moderate affinities, allowing fast mass transfer between the mobile and stationary phase, are essential to obtain highly efficient separations. For sample pre-treatment procedures a large range of affinities can be used; however, large sample volumes can only be processed with high affinity materials. The sample pre-treatment application directed to preconcentration looks the most promising. It is anticipated that molecular imprints will find a prominent place in pharmaceutical research, not only as a tool to improve selectivity and sensitivity in analytical methods but also for selective extraction of drugs or intermediates from reaction media. In an environmental context these imprints may be used for the analysis and/or removal of pollutants.
TL;DR: In this article, the chemistry of the ion-selective optode has been recognized as a highly selective ion-sensing methodology which involves the highly selective complexation between an ionophore and a primary ion.
Abstract: The chemistry of the ion-selective optode has recently been recognized as a highly selective ion-sensing methodology which involves a highly selective complexation between an ionophore and a primary ion. This simple methodology allowed the construction of several kinds of ion-sensing devices which enabled highly selective ion determination for analytical purposes. In this review, sensing devices are divided into the following four types with different analytical uses: (1) flow analytical devices (flow-through optode); (2) waveguide devices (waveguide optode); (3) sensing plate devices (sensing plate optode, film optode); (4) fiber-optic devices (fiber optode). The characteristics of each device are explained and discussed with experimental data, and the future prospects for ion-selective optode methodology are described.
TL;DR: In this article, the application of mass spectrometry to the analysis of plant phenols was examined and traces the chronological development of analyte ionisation methods were traced. But the present paper is focused on the use of ionization methods.
Abstract: Plant phenols embrace a considerable range of compounds and are defined as those substances derived from the shikimate acid pathway and phenylpropanoid metabolism. The present article examines the application of mass spectrometry to the analysis of these compounds and traces the chronological development of analyte ionisation methods.
TL;DR: In this paper, the possibilities of using high-temperature gas chromatography-mass spectrometry (HT-GC-MS) for the characterization of complex mixtures of organic contaminants present in industrial effluents is explored.
Abstract: The characterization of complex mixtures of organic contaminants present in industrial effluents is a well-known problem. The determination of individual target analytes depends very much on the analytical method used. In this article, the possibilities of using high-temperature gas chromatography–mass spectrometry (HT-GC–MS) are explored. In HT-GC–MS non-polar and medium-polarity phases can be operated at temperatures up to 370–420°C, allowing the analysis of high-molecular-weight compounds. So far, the applications of HT-GC have included the analysis of hydrocarbons up to C-100, lipids, sugars, and polyglycerols, but no data have been reported on the characterization of organic pollutants present in industrial effluents. The general sample handling approach reported here is based either on a sequential solid-phase extraction (SSPE) procedure, with a change of solvent composition in the elution from two different cartridges (C18 and Lichrolut EN), or on a toxicological fractionation. Effluent samples from tanneries, petrochemical plants, and textile industries are characterized, and the levels of the main organic pollutants identified are indicated. More than 50 compounds, including n-alkanes, phthalates, esters, acids, and phenols, were identified in the effluents studied.
TL;DR: A new procedure is proposed, which is totally consistent with the ISO approach in the sense that all the sources of error are identified, quantified and combined, but which is conceptually more similar to the `top-down' approach because of its holistic character.
Abstract: In this article, we critically describe the different approaches proposed so far for calculating uncertainty in chemical measurements: (1) the ISO approach, adapted for the analytical field by EURACHEM (commonly known as `bottom-up'), and (2) the Analytical Methods Committee approach (commonly known as `top-down'), based on interlaboratory information. We also propose a new procedure, which is totally consistent with the ISO approach in the sense that all the sources of error are identified, quantified and combined, but which is conceptually more similar to the `top-down' approach because of its holistic character. This new procedure estimates uncertainty from the information generated during the process of assessing accuracy.