Showing papers in "Trends in Analytical Chemistry in 2008"
TL;DR: Recent advances in the development of aptamer-based biosensors and bioassay methods, most of which have employed electrochemical, optical and mass-sensitive analytical techniques are summarized.
Abstract: Nucleic-acid aptamers have attracted intense interest and found wide applications in a range of areas. In this review, we summarize recent advances in the development of aptamer-based biosensors and bioassay methods, most of which have employed electrochemical, optical and mass-sensitive analytical techniques. Aptamers exhibit many advantages as recognition elements in biosensing when compared to traditional antibodies. They are small in size, chemically stable and cost effective. More importantly, aptamers offer remarkable flexibility and convenience in the design of their structures, which has led to novel biosensors that have exhibited high sensitivity and selectivity. Recently, the combination of aptamers with novel nanomaterials has significantly improved the performance of aptamer-based sensors, which we also review in this article. In view of the unprecedented advantages brought by aptamers, we expect aptamer-based biosensors to find broad applications in biomedical diagnostics, environmental monitoring and homeland security.
1,192 citations
TL;DR: In this paper, the origins and the fundamentals of green analytical chemistry (GAC) are discussed, and the strategies and the tools available to make sample-pretreatment and analytical methods greener.
Abstract: We discuss the origins and the fundamentals of Green Analytical Chemistry (GAC), based on the literature published about clean, environmentally-friendly or GAC methods. We pay special attention to the strategies and the tools available to make sample-pretreatment and analytical methods greener. We consider that the main principles are to replace toxic reagents, to miniaturize and to automate methods, making it possible to reduce dramatically the amounts of reagents consumed and wastes generated, so reducing or avoiding side effects of analytical methods. We also consider on-line decontamination or passivation of wastes to be of special interest in making analytical chemistry sustainable.
806 citations
TL;DR: In this article, the authors review the fate and the ecotoxicology of emerging pollutants, especially focusing on their metabolites and transformation products (TPs) in the aquatic environment, including pharmaceuticals, hormones, perfluorinated compounds, byproducts of drinking-water disinfection, sunscreens or UV filters, benzotriazoles and naphthalenic acids.
Abstract: There has been a great effort to study the fate, the occurrence and the ecotoxicology of emerging pollutants in the aquatic environment. Recently, several articles have focused on degradation products of emerging pollutants and the study of their toxicological effects. We review the fate and the ecotoxicology of emerging pollutants, especially focusing on their metabolites and transformation products (TPs) in the aquatic environment, including pharmaceuticals, hormones, perfluorinated compounds, by-products of drinking-water disinfection, sunscreens or UV filters, benzotriazoles and naphthalenic acids. We describe analytical methodologies for the quantitative analysis of emerging pollutants, their metabolites, and their TPs in sewage and surface waters, and we give the results of monitoring surveys obtained from the application of these analytical methodologies.
793 citations
TL;DR: Quintana et al. as discussed by the authors discussed the major processes affecting the fate of OPEs in the environment, such as sorption, volatilization and biodegradation.
Abstract: Organophosphate esters (OPEs), in particular triesters, are high-production-volume chemicals used as flame retardants and plasticizers to protect or to enhance the properties of plastics, textiles, furniture and many other materials. The widespread usage, which may even increase due to the ban of brominated diphenylethers as flame retardants, and the diffusion from host materials result in continuous release of OPEs and their distribution through water, especially wastewater, and air, particularly associated with airborne particulate matter. This work highlights the occurrence of OPEs in wastewater, surface water and groundwater as well as indoor and outdoor air and particulate material. We discuss the major processes affecting the fate of OPEs in the environment, such as sorption, volatilization and biodegradation. Of the OPEs studied thus far, chlorinated tri(2-chloroethyl) phosphate (TCEP) and tri(chloropropyl) phosphate (TCPP) appear to be most recalcitrant and ubiquitous in water and air. We identified knowledge gaps concerning the fate of diesters and monoesters in the aqueous environment, the biodegradation of OPEs under less favorable conditions (sorbed to particles or under anoxic or anaerobic conditions) as well as the behavior of OPEs in the atmosphere and their potential for long-range transport. A second part, addressing analytical methods will published in the next issue [J.B. Quintana, R. Rodil, T. Reemtsma, M. Garci´a-Lopez, I. Rodri´guez, Trends Anal. Chem. (to be published in 27 (10) (2008))].
540 citations
TL;DR: Some of the practical aspects pertaining to NMR-based quantitative metabolomics is described and some of the strengths, limitations and applications of this particular approach to metabolomics are highlighted.
Abstract: Nuclear magnetic resonance (NMR) spectroscopy can be used to both identify and quantify chemicals from complex mixtures. This can be done semi-automatically by comparing the mixture of interest to a library of reference spectra derived from pure compounds of known concentrations. This particular approach is now being exploited to characterize the metabolomes of many different biological samples in what is called quantitative metabolomics or targeted metabolic profiling. This review describes some of the practical aspects pertaining to NMR-based quantitative metabolomics and highlights some of the strengths, limitations and applications of this particular approach to metabolomics.
531 citations
TL;DR: Ambient desorption ionization mass spectrometry (MS) allows for the direct analysis of ordinary objects in the open atmosphere of the laboratory or in their natural environment as mentioned in this paper.
Abstract: Ambient desorption ionization mass spectrometry (MS) allows for the direct analysis of ordinary objects in the open atmosphere of the laboratory or in their natural environment. Analyte desorption usually accompanies the ionization step and these processes are often concerted, multi-step processes. Ambient desorption ionization methods typically require little or no sample preparation, offer a much simplified work flow and deliver unprecedented ease of use to MS analyses. Since the introduction of desorption electrospray ionization (DESI [Z. Takats, J.M. Wiseman, B. Gologan, R.G. Cooks, Science (Washington, D. C.) 306 (2004) 471]) in 2004 and the direct analysis in real time (DART [R.B. Cody, J.A. Laramee, H.D. Durst, Anal. Chem. 77 (2005) 2297]) in 2005, this new field of MS has developed rapidly. Numerous permutations of the various options for analyte desorption and ionization have been demonstrated. Desorption steps, such as momentum transfer, dissolution into ricocheting droplets and thermal desorption, have been combined with ionization steps, including ESI, atmospheric pressure chemical ionization and photo-ionization. The large number of possible combinations of desorption and ionization components that have already been applied is creating a proliferation of techniques and acronyms that is becoming ever more complex. Here, we provide a logical framework for the classification of these related experiments, based on the desorption and ionization processes involved in each.
514 citations
TL;DR: In this paper, the utility of various analytical strategies and techniques currently used for liquid chromatography coupled to mass spectrometry (LC-MS) is compared and compared. And current challenges in the application of LC-MS-based techniques for metabonomic analysis are described.
Abstract: In order to perform metabonomic investigations, it is necessary to generate comprehensive “global” metabolite profiles from complex samples, such as biofluids and tissues/tissue extracts. Analytical technologies based on liquid chromatography coupled to mass spectrometry (LC-MS) are destined to become a major source of global metabolite profiling data. Here, we describe and compare the utility of various analytical strategies and techniques currently used for LC-MS (capillary, high-performance and ultra-performance). We describe current challenges in the application of LC-MS-based techniques for metabonomic analysis.
321 citations
TL;DR: An overview of electrochemical sensors that employ nanomaterials and utilize electrochemical impedance spectroscopy for analyte detection can be found in this paper, where gold nanoparticles and carbon nanotubes (CNTs) are employed for impedance sensors.
Abstract: This article presents an overview of electrochemical sensors that employ nanomaterials and utilize electrochemical impedance spectroscopy for analyte detection. The most widely utilized nanomaterials in impedance sensors are gold (Au) nanoparticles and carbon nanotubes (CNTs). Au nanoparticles have been employed in impedance sensors to form electrodes from nanoparticle ensembles and to amplify impedance signals by forming nanoparticle-biomolecule conjugates in the solution phase. CNTs have been employed for impedance sensors within composite electrodes and as nanoelectrode arrays. The advantages of nanomaterials in impedance sensors include increased sensor surface area, electrical conductivity and connectivity, chemical accessibility and electrocatalysis.
316 citations
TL;DR: The use of carbon nanomaterials, mainly fullerenes and carbon nanotubes, as sorbents in the analytical process has been discussed in this article, where the authors present their use in the development of selective membranes.
Abstract: Over time, new materials have been used and incorporated in a wide variety of analytical processes. This century, technology has produced novel nanomaterials with unique properties whose use has increased in analytical sciences. Carbon nanostructures are among these new nanomaterials. This overview reports on the use of carbon nanomaterials, mainly fullerenes and carbon nanotubes, as sorbents in the analytical process. After a brief description of their main characteristics, we present their use in the development of selective membranes. Next, we describe their role as sorbent materials and stationary phases in chromatography and provide relevant examples. We also comment on the presence of carbon nanoparticles as components of electrophoretic buffers to improve both resolution and sensitivity of separations. Finally, we briefly describe other applications in which the sorption capabilities of carbon nanostructures play a role.
302 citations
TL;DR: In this article, the authors reviewed the analytical methodologies used and assessed biotic and abiotic degradation mechanisms of these antibiotics, and briefly evaluated their potential toxicity in the environment, and the main goal of this article is to review those research studies in which both parent drugs and their respective metabolites have been considered together.
Abstract: Sulfonamide residues have been detected in all kinds of environmental water matrix. However, little attention has been so far paid to their metabolites and degradation products, and very few articles have included them in their analytical scope. The main goal of this article is to review those research studies in which both parent drugs and their respective metabolites have been considered together. We review the analytical methodologies used and assess biotic and abiotic degradation mechanisms of these antibiotics, and briefly evaluate their potential toxicity in the environment.
297 citations
TL;DR: This review summarizes recent advances in electrochemical biosensors based on carbon nanotubes (CNTs) and carbon nanofibers (CNFs) with an emphasis on applications of CNTs.
Abstract: This review summarizes recent advances in electrochemical biosensors based on carbon nanotubes (CNTs) and carbon nanofibers (CNFs) with an emphasis on applications of CNTs. CNTs and CNFs have unique electric, electrocatalytic and mechanical properties, which make them efficient materials for developing electrochemical biosensors.
We discuss functionalizing CNTs for biosensors. We review electrochemical biosensors based on CNTs and their various applications (e.g., measurement of small biological molecules and environmental pollutants, detection of DNA, and immunosensing of disease biomarkers). Moreover, we outline the development of electrochemical biosensors based on CNFs and their applications. Finally, we discuss some future applications of CNTs.
TL;DR: In this article, a review describes the processes undergone by these compounds once released into the environment and the instrumental methods based on chromatography and mass spectrometry reported in the literature for their determination in environmental samples.
Abstract: Organic ultraviolet (UV) filters are compounds used to absorb UV radiation and are increasingly being used as a result of growing concern about UV radiation and skin cancer. Their growing use may increase environmental contamination and exposure through the food chain. There is therefore major concern about the environmental fate and potential effect of organic UV filters used in beauty creams, hair sprays, shampoos, and other personal-care products, as well as those added to plastics and other materials to prevent degradation of polymers and pigments. This review describes the processes undergone by these compounds once released into the environment and the instrumental methods based on chromatography and mass spectrometry reported in the literature for their determination in environmental samples. We include concentrations found in the environment (e.g., water, soil, sediments, sludge and biota). The main focus is on metabolites, photodegradates and by-products of wastewater treatment.
TL;DR: Method improvements emphasize extraction procedures, evaluations of quality control of GC-MS in comparison to other techniques and approaches to data processing, and, integration of biological background knowledge aiding data interpretation remain.
Abstract: Gas chromatography coupled to mass spectrometry (GC-MS) is one of the most frequently used tools for profiling primary metabolites. Instruments are mature enough to run large sequences of samples; novel advancements increase the breadth of compounds that can be analyzed, and improved algorithms and databases are employed to capture and utilize biologically relevant information. Around half the published reports on metabolite profiling by GC-MS focus on biological problems rather than on methodological advances. Applications span from comprehensive analysis of volatiles to assessment of metabolic fluxes for bioengineering. Method improvements emphasize extraction procedures, evaluations of quality control of GC-MS in comparison to other techniques and approaches to data processing. Two major challenges remain: rapid annotation of unknown peaks; and, integration of biological background knowledge aiding data interpretation.
TL;DR: In this paper, the advantages and disadvantages of using the authentic analyte in a surrogate matrix and the use of a surrogate analyte on the authentic matrix are compared, and the authors highlight important aspects of validation of chromatographic methods for endogenous analytes.
Abstract: Chromatographic methods are increasingly being used for the quantitative determination of endogenous compounds in biological samples. This article presents an overview of the specific issues, which have to be taken into account for the development, validation and application of these methods. The usual lack of analyte-free samples of the biological matrix implies that alternative strategies for calibration have to be followed. This article compares and discusses the advantages and disadvantages of two strategies – the use of the authentic analyte in a surrogate matrix and the use of a surrogate analyte in the authentic matrix. In addition, it highlights important aspects of the validation of chromatographic methods for endogenous analytes.
TL;DR: Examples of metabolic fingerprinting using direct MS analysis of complex mixtures with traditional and emerging ionization sources, spatially resolved metabolite profiling via MS imaging, metabolite profiles using chromatography coupled to MS, multi-dimensional chromatography paired to MS and ion-mobility MS are discussed.
Abstract: Mass spectrometry (MS) has secured a central role in metabolomics that is predicted to grow based upon continuous developments and improvements in MS technologies. This article reviews both current MS technologies incorporated into many metabolomics programs as well as emerging MS technologies that hold additional promise for the advancement of metabolomics. We discuss examples of metabolic fingerprinting using direct MS analysis of complex mixtures with traditional and emerging ionization sources, spatially resolved metabolite profiling via MS imaging, metabolite profiling using chromatography coupled to MS, multi-dimensional chromatography coupled to MS, and ion-mobility MS.
TL;DR: Nanomaterial-based biosensors for researchers new to the field are described, paying particular attention to metal nanoparticles and carbon nanotube (CNT)-based label-free approaches.
Abstract: With recent advances in nanotechnology, great progress has been made in biosensors based on nanomaterials, but there are still numerous challenges to overcome. We describe nanomaterial-based biosensors for researchers new to the field, paying particular attention to metal nanoparticles and carbon nanotube (CNT)-based label-free approaches. Label-free monitoring of biorecognition events provides a promising platform, which is simple, cost-effective, and requires no external modification to biomolecules. Using examples from recent reports, we illustrate the diversity of biological recognition events and the range of experimental techniques employed for metal-nanoparticle-based and label-free characterization.
TL;DR: An overview of the methods for nM nitrate and phosphate analysis in seawater can be found in this article, where a system comprising liquid waveguide capillary cells connected to a conventional segmented-flow autoanalyser and using miniaturized spectrophotometers is described.
Abstract: Over much of the world's surface oceans, nitrate and phosphate concentrations are below the limit of detection (LOD) of conventional techniques of analysis. However, these nutrients play a controlling role in primary productivity and carbon sequestration in these waters. In recent years, techniques have been developed to address this challenge, and methods are now available for the shipboard analysis of nanomolar (nM) nitrate and phosphate concentrations with a high sample throughput. This article provides an overview of the methods for nM nitrate and phosphate analysis in seawater. We outline in detail a system comprising liquid waveguide capillary cells connected to a conventional segmented-flow autoanalyser and using miniaturised spectrophotometers. This approach is suitable for routine field measurements of nitrate and phosphate and achieves LODs of 0.8 nM phosphate and 1.5 nM nitrate. © 2008 Elsevier Ltd. All rights reserved.
TL;DR: In this paper, the potential of ultra-performance liquid chromatography coupled with time-of-flight mass spectrometry (TOF-MS) for screening of non-target organic pollutants in water samples was demonstrated.
Abstract: We show the potential of ultra-performance liquid chromatography (UPLC) coupled to time-of-flight mass spectrometry (TOF-MS) for screening of non-target organic pollutants in water samples. The great accuracy and the resolution provided by a TOF analyzer allow the mass of any ionizable component in a sample to be accurately measured. Efficient screening applied to environmental samples should ideally detect as many pollutants as possible in one analytical run. This makes necessary the use of powerful chromatographic deconvolution software, which can manage the huge amount of MS data acquired after sample analysis so as to detect components in the sample. It is therefore feasible to compare the experimental data versus a home-made library (empirical and/or theoretical) that can contain hundreds of compounds relevant to the environment. When a compound is not found in the library, its deconvoluted accurate-mass spectra can be used to propose its elemental composition. We apply this strategy to several types of water samples and it has allowed detecting several pesticides (e.g., thiabendazole, imazalil, simazine and diuron) at low ppb levels. We also detected antibiotics (e.g., ofloxacin or ciprofloxacin) and drugs of abuse (e.g., benzoylecgonine, which is a cocaine metabolite). The home-made theoretical library contains more than 500 compounds, including many pesticides and transformation products, antibiotics and several drugs. UPLC-TOF-MS is an efficient technique for the rapid screening of multi-class organic pollutants in water that requires little sample manipulation. Full-acquisition MS data obtained by TOF-MS provide valuable qualitative information, which facilitates safe identification of many different compounds in samples.
TL;DR: The main strength of nanopore sensing is that it implies the prospect of label-free single-molecule detection by taking advantage of the built-in transport-modulation-based amplification mechanism.
Abstract: Sensing with chemically-modified nanopores is an emerging field that is expected to have major impact on bioanalysis and fundamental understanding of nanoscale chemical interactions down to the single-molecule level. The main strength of nanopore sensing is that it implies the prospect of label-free single-molecule detection by taking advantage of the built-in transport-modulation-based amplification mechanism. At present, fabrication and application of solid-state nanopores are becoming the focus of attention because, compared with their biological counterparts, they offer greater flexibility in terms of shape, size, and surface properties, as well as superior robustness. A breakthrough in label-free nanopore sensing for real-world applications is therefore expected from implementing solid-state nanopores, an area that is still developing. Without claiming comprehensiveness, the focus of this review comprises recent results and trends in nanopore-based sensing (i.e. emerging technologies for fabricating solid-state nanopores, their chemical functionalization, and detection methods for quantitative analysis).
TL;DR: In this article, the authors highlight the features of both electricallyconducting and non-conducting organized layers, which are applicable to designing electrochemical sensors, and the methods applied to construct these novel nanomaterials.
Abstract: Recently, the field of highly-ordered mesoporous and macroporous thin films coated onto solid electrode surfaces has begun to receive attention due to their great interest for electrochemical analysis. This review highlights the features of both electricallyconducting and non-conducting organized layers, which are applicable to designing electrochemical sensors, and the methods applied to construct these novel nanomaterials. We emphasize methods based on use of self-assembled colloidal templates (e.g., surfactants or nanoparticles), around which the materials of interest are formed. We then describe their basic electrochemical behavior and discuss their possible use as electrochemical sensors and biosensors, mostly in the particular case of structured metallic layers, functionalized mesoporous silica films, and some other continuous three-dimensional ordered porous structures.
TL;DR: In this paper, the authors discuss HPLC methods for the determination of ascorbic acid and its oxidation product, dehydroascorbic acid (DHA) from the points of view of separation mechanism and detection technique.
Abstract: The potential role of ascorbic acid (AA) in biological systems has stimulated wide, multidisciplinary interest in this compound. Its determination is of interest in many fields (e.g., food, clinical, plant or pharmaceutical analysis). In the past few years, many methods, based on different analytical techniques, have been developed for the determination of AA and its oxidation product, dehydroascorbic acid (DHA). This review aims to make clear the differences, the progress, and the advantages and the disadvantages of individual approaches using high-performance liquid chromatography (HPLC). We discuss HPLC methods for the determination of AA and DHA from the points of view of separation mechanism and detection technique. Stability of these analytes is a key issue in obtaining reliable method validation, so we also included this aspect in the discussion.
TL;DR: A review of the latest analytical methods for the determination of organophosphate esters in water, air and particulate material (e.g., sediments and dust), covering various extraction and clean-up techniques, as well as their determination by gas chromatography-nitrogen-phosphorus detection (GC-NPD), GC-MS, and liquid chromatographyMS (LC-MS) is presented in this article.
Abstract: Increasing usage of several organophosphate esters (OPEs), as well as their systematic presence indoors and in water samples, requires development of appropriate analytical procedures to understand their environmental distribution and to identify their transformation and degradation by-products. We review the latest analytical methods for the determination of OPEs in water, air and particulate material (e.g., sediments and dust), covering various extraction and clean-up techniques, as well as their determination by gas chromatography-nitrogen-phosphorus detection (GC-NPD), GC-mass spectrometry (GC-MS) and liquid chromatography-MS (LC-MS). Besides phosphoric acid triesters, we also consider diesters and monoesters. We discuss thoroughly the merits and the limitations of these methodologies. We also highlight some challenging issues in the determination of OPEs (e.g., the need of certified reference materials, isotopically-labeled surrogates of the congeners causing the greatest concern, and standards for the phosphoric acid diesters and monoesters. Finally, we point to potential future trends in the analytical determination of OPEs. A previous review covering the environmental occurrence and fate of OPEs was published in the last issue of this journal [T. Reemtsma, J.B. Quintana, R. Rodil, M. Garcia-Lopez, I. Rodriguez, Trends Anal. Chem. 27 (2008)].
TL;DR: The state of the art in solid-state ECL of tris(2,2′-bipyridyl)ruthenium [Ru(bpy)32+] has received considerable attention.
Abstract: Electrochemiluminescence (ECL) of tris(2,2′-bipyridyl)ruthenium [Ru(bpy)32+] has received considerable attention. By immobilizing Ru(bpy)32+ on an electrode surface, solid-state ECL provides several advantages over solution-phase ECL, such as reducing consumption of expensive reagent, simplifying experimental design and enhancing the ECL signal.
This review presents the state of the art in solid-state ECL of Ru(bpy)32+. It briefly covers the mechanism of ECL of Ru(bpy)32+, some recent developments in fabrication of solid-state ECL sensors, analytical applications of ECL and alignment of ECL with capillary electrophoresis (CE), microchip CE, flow-injection analysis, high-performance liquid chromatography. It also indicates the outlook in this field.
TL;DR: HAIEMs are well matched to global and interactive aspects of the non-linear dynamic complex systems ofCHMs, and offer the possibility of evaluating whole systems of CHMs.
Abstract: This overview covers current strategies for the analysis of Chinese herbal medicines (CHMs) with holistic approaches and integrated evaluation models (HAIEMs). We start by discussing the analytical techniques used in HAIEMs for research on CHMs, including gas chromatography, liquid chromatography, and capillary electrophoresis. We also describe application of HAIEMs for quality control, elucidation of the properties of absorption, distribution, metabolism and excretion, and metabonomics evaluation of CHMs. HAIEMs are well matched to global and interactive aspects of the non-linear dynamic complex systems of CHMs, and offer the possibility of evaluating whole systems of CHMs.
TL;DR: The possibilities of different algorithms in the global study of homogeneity in pharmaceutical samples that may confirm different stages in a blending process are explored, and new possibilities in cluster analysis and MCR-ALS in image analysis are presented.
Abstract: Near-infrared spectroscopy chemical imaging (NIR-CI) is a powerful tool for providing a great deal of information on pharmaceutical samples, since the NIR spectrum can be measured for each pixel of the image over a wide range of wavelengths. Joining NIR-CI with chemometric algorithms (e.g., Principal Component Analysis, PCA) and using correlation coefficients, cluster analysis, classical least-square regression (CLS) and multivariate curve resolution-alternating least squares (MCR-ALS) are of increasing interest, due to the great amount of information that can be extracted from one image. Despite this, investigation of their potential usefulness must be done to establish their benefits and potential limitations. We explored the possibilities of different algorithms in the global study (qualitative and quantitative information) of homogeneity in pharmaceutical samples that may confirm different stages in a blending process. For this purpose, we studied four examples, involving four binary mixtures in different concentrations. In this way, we studied the benefits and the drawbacks of PCA, cluster analysis (K-means and Fuzzy C-means clustering) and correlation coefficients for qualitative purposes and CLS and MCR-ALS for quantitative purposes. We present new possibilities in cluster analysis and MCR-ALS in image analysis, and we introduce and test new BACRA software for mapping correlation-coefficient surfaces.
TL;DR: Methods for generating and interpreting metabolic profiles based on nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry (MS) and multivariate chemometrics are summarized.
Abstract: Metabonomics can now be regarded as a central pillar in top-down systems biology. We summarize methods for generating and interpreting metabolic profiles based on nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry (MS) and multivariate chemometrics. We describe recent developments for information recovery from complex data sets, including integration of NMR and MS results and trans-omics correlations.
TL;DR: The potential of PARAllel FACtor analysis 2 (PARAFAC2) is shown, a model capable of handling three-way data and does not assume that the elution profiles of each factor are invariant across samples, to solve several problems derived from experimental conditions in GC-MS datasets.
Abstract: Gas chromatography combined with mass spectrometry (GC-MS) is an important technique for identification and quantification of analytes in multifactor systems. Nevertheless, the experimental sources of variability related to GC-MS (e.g., column and flow-meter ageing, changes in certain characteristics or properties of the stationary phase, and changes in temperature, experimental conditions or preparation of standards or chemicals) may cause variations (e.g., elution time, baseline drifts, unexpected overlapping of peaks, or non-Gaussian peaks). Several approaches have been proposed to handle these problems, with the standardization of peak areas using internal standards being one of the most efficient techniques. However, such a solution is not sufficiently versatile when deviations from the ideal are more pronounced. Since a mass spectrum can be obtained at each elution time during chromatographic separation, GC-MS data of several samples can be considered a three-way structure. PARAllel FACtor analysis 2 (PARAFAC2) is a model capable of handling three-way data and, unlike the PARAFAC model, does not assume that the elution profiles of each factor are invariant across samples. This, coupled with its uniqueness property, allows PARAFAC2 to solve several problems derived from experimental conditions in GC-MS datasets. In this article, we aim to show the potential of PARAFAC2 for solving common GC-MS problems, using GC-MS data from wine samples to illustrate the solutions.
TL;DR: Biocompatibility, biodistribution, biodegradation, inflammation and interference with cells and normal functioning of organs, among other factors, will determine the toxicity of engineered inorganic nanoparticles and carbon nanostructures, and therefore the extent of their use.
Abstract: Biocompatibility, biodistribution, biodegradation, inflammation and interference with cells and normal functioning of organs, among other factors, will determine the toxicity of engineered inorganic nanoparticles and carbon nanostructures, and therefore the extent of their use. Recent examples in the literature show that engineered inorganic nanoparticles and carbon nanostructures, which may incidentally or intentionally enter into contact with living organisms, normally, at realistic doses, do not cause acute toxic effects. However, their prolonged interaction with living organisms may disrupt normal activity leading to malfunctioning and diseases. Indeed, observed nanoparticle-biological interactions, which can be used to detect and to manipulate biological states and therefore heal damaged organs, could also lead to environmental and human health hazards. In this scenario, how those nanostructures enter and are distributed inside the body is critical.
TL;DR: A review of the most significant liquid chromatography electrospray ionization (LC-ESI-MS) methods for determining pesticide residues in foodstuffs is provided in this paper.
Abstract: Pesticide testing in foodstuffs is a challenging application for mass spectrometry (MS), since it implies simultaneous trace analysis of hundreds of compounds belonging to a many classes, preferably undertaken in one fast run. The appearance and the use of new, more polar pesticides has prompted the use of liquid chromatography electrospray ionization MS (LC-ESI-MS) instead of gas chromatography. Currently, large-scale multi-residue methods (LSMRMs) (i.e. covering over 80 analytes) for pesticide analysis are developed using LC with tandem MS (LC-MS 2 ) with triple quadrupole mass analyzers or LC with time-of-flight MS (LC-TOF-MS). The present article provides a review of the most significant MRMs for determining pesticide residues in foodstuffs. We discuss the main features of LC-MS 2 and LC-TOF-MS instruments, including recently introduced advances in instrumentation. In addition, we describe the advantages and the pitfalls of these methods, together with examples of the application of LC-TOF-MS and LC-MS 2 to large-scale screening, identification and quantitation of pesticides in foodstuffs.
TL;DR: New developments in affinity capillary electrophoresis, electrospray ionization mass spectrometry (ESI-MS and phasetransfer methods), which are particularly adaptable, use very small quantities of material, and do not place severe requirements on the spectroscopic properties of the binding partners are covered.
Abstract: Many methods for determining intermolecular interactions have been described in the literature in the past several decades. Chief among them are methods based on spectroscopic changes, particularly those based on absorption or nuclear magnetic resonance (NMR) [especially proton NMR ((1)H NMR)]. Recently, there have been put forward several new methods that are particularly adaptable, use very small quantities of material, and do not place severe requirements on the spectroscopic properties of the binding partners. This review covers new developments in affinity capillary electrophoresis, electrospray ionization mass spectrometry (ESI-MS) and phasetransfer methods.