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papers from the latest issue:
Analytical and unconventional methods of cancer detection using odor
23 August 2012,
09:43:19
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry, Volume 38
Bogusław Buszewski, Joanna Rudnicka, Tomasz Ligor, Marta Walczak, Tadeusz Jezierski, Anton Amann
Finding a non-invasive, painless and simple screening method for early detection of cancer is a desirable goal. There is evidence that volatile organic compounds (VOCs) detectable in exhaled air and producing specific breath odor could be taken into consideration as possible cancer markers. Chemical analysis of VOCs in the breath that utilizes gas chromatography-mass spectrometry or an array of specific sensors (an electronic nose) could be useful for cancer screening. Preliminary reports show that canines, due to their extraordinary sense of smell and ability to perform well with operant conditioning, could also be used in the future as biological screeners for different forms of cancer. However, the question remains open whether specific VOCs or breath odors appear at very early (sub-clinical) stages of cancer disease or only at advanced stages of the disease during tumor decomposition.
Source:TrAC Trends in Analytical Chemistry, Volume 38
Bogusław Buszewski, Joanna Rudnicka, Tomasz Ligor, Marta Walczak, Tadeusz Jezierski, Anton Amann
Finding a non-invasive, painless and simple screening method for early detection of cancer is a desirable goal. There is evidence that volatile organic compounds (VOCs) detectable in exhaled air and producing specific breath odor could be taken into consideration as possible cancer markers. Chemical analysis of VOCs in the breath that utilizes gas chromatography-mass spectrometry or an array of specific sensors (an electronic nose) could be useful for cancer screening. Preliminary reports show that canines, due to their extraordinary sense of smell and ability to perform well with operant conditioning, could also be used in the future as biological screeners for different forms of cancer. However, the question remains open whether specific VOCs or breath odors appear at very early (sub-clinical) stages of cancer disease or only at advanced stages of the disease during tumor decomposition.
Highlights
► Carcinomas are a human health problem. ► Analytical methods for detecting potential markers for cancer in biological samples. ► Unconventional methods for detecting carcinoma, such as dogs’ sense of smell. ► Cancer detection using odor.Analytical methods based on exhaled breath for early detection of lung cancer
23 August 2012,
09:43:19
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry, Volume 38
M.D. Luque de Castro, M.A. Fernández-Peralbo
Lung cancer is among the most common malignancies and among the most difficult to treat, mainly due to the lack of symptoms, which means that the vast majority of tumors to be diagnosed are at an advanced stage. After reviewing the literature on this subject, with special emphasis on both canine smell and the potential of omics biomarkers for detecting lung cancer, we discuss the role of analytical chemists in the new steps to be taken for early detection. We also comment on the steps to be developed (from sampling to full validation of the biomarkers found).
Source:TrAC Trends in Analytical Chemistry, Volume 38
M.D. Luque de Castro, M.A. Fernández-Peralbo
Lung cancer is among the most common malignancies and among the most difficult to treat, mainly due to the lack of symptoms, which means that the vast majority of tumors to be diagnosed are at an advanced stage. After reviewing the literature on this subject, with special emphasis on both canine smell and the potential of omics biomarkers for detecting lung cancer, we discuss the role of analytical chemists in the new steps to be taken for early detection. We also comment on the steps to be developed (from sampling to full validation of the biomarkers found).
Highlights
► Canine scent for lung-cancer detection should involve analytical chemists. ► Biomarkers detect lung cancer in patients’ breath at very low concentrations. ► Proteomics and metabolomics are key to lung-cancer detection through breath.Electrospun nanofiber-based solid-phase extraction
23 August 2012,
09:43:19
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry, Volume 38
Samuel Chigome, Nelson Torto
The article discusses theoretical and experimental aspects of fabricating devices and developing methods for electrospun nanofiber-based solid-phase extraction (SPE). It seeks to encourage a better understanding of the use of electrospun nanofibers as a chromatographic sorbent bed. We base the discussion on fabricating six electrospun nanofiber-based SPE devices and evaluating their performance. We also categorize electrospun polymer nanofibers that are applicable as SPE sorbents as polystyrene type (relatively low mechanical strength) and nylon type (relatively high mechanical strength). We propose that the formats and the configurations of future electrospun nanofiber-based SPE devices may be guided by the mechanical strength of the polymer.
Source:TrAC Trends in Analytical Chemistry, Volume 38
Samuel Chigome, Nelson Torto
The article discusses theoretical and experimental aspects of fabricating devices and developing methods for electrospun nanofiber-based solid-phase extraction (SPE). It seeks to encourage a better understanding of the use of electrospun nanofibers as a chromatographic sorbent bed. We base the discussion on fabricating six electrospun nanofiber-based SPE devices and evaluating their performance. We also categorize electrospun polymer nanofibers that are applicable as SPE sorbents as polystyrene type (relatively low mechanical strength) and nylon type (relatively high mechanical strength). We propose that the formats and the configurations of future electrospun nanofiber-based SPE devices may be guided by the mechanical strength of the polymer.
Highlights
► Electrospun nanofiber-based sorbents. ► Electrospun nanofiber-based solid-phase extraction (SPE) devices. ► Theoretical and experimental aspects of electrospun nanofiber-based SPE devices.Sample-preparation methods for pesticide-residue analysis in cereals and derivatives
23 August 2012,
09:43:19
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry, Volume 38
Miguel Ángel González-Curbelo, Antonio V. Herrera-Herrera, Lidia M. Ravelo-Pérez, Javier Hernández-Borges
Since the Neolithic Age, cereals have constituted an important part of the human diet, and they are now one of the foods most produced and consumed in the world. As a result, and because of the large population involved, food-safety issues are an important matter of concern and appropriate action is required. Pesticide-residue analysis, including method optimization, method development and monitoring programs are becoming increasingly important. The aim of this review article is to provide a general overview of the different sample-preparation methods published in the period 2006–11 covering the analysis of pesticides in cereal samples, including some of their derivatives, such as flour or cereal-based baby foods.
Source:TrAC Trends in Analytical Chemistry, Volume 38
Miguel Ángel González-Curbelo, Antonio V. Herrera-Herrera, Lidia M. Ravelo-Pérez, Javier Hernández-Borges
Since the Neolithic Age, cereals have constituted an important part of the human diet, and they are now one of the foods most produced and consumed in the world. As a result, and because of the large population involved, food-safety issues are an important matter of concern and appropriate action is required. Pesticide-residue analysis, including method optimization, method development and monitoring programs are becoming increasingly important. The aim of this review article is to provide a general overview of the different sample-preparation methods published in the period 2006–11 covering the analysis of pesticides in cereal samples, including some of their derivatives, such as flour or cereal-based baby foods.
Highlights
► Analytical methods used in the analysis of pesticide residues in cereals. ► Sample-pretreatment methods for the analysis of pesticide residues in cereals. ► Publications in 2006–11 for the analysis of pesticide residues in cereals.Advances in the determination of β-lactam antibiotics by liquid chromatography
23 August 2012,
09:43:19
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry, Volume 38
Francisco J. Lara, Monsalud del Olmo-Iruela, Carmen Cruces-Blanco, Carolina Quesada-Molina, Ana M. García-Campaña
β-lactam antibiotics have been the most widely used antimicrobial drugs for more than 80years and still constitute the most important group of antibiotics. Their extensive use in veterinary medicine practices as growth promoters, and chemotherapeutic and/or prophylactic agents causes numerous residues in foodstuffs which present a serious health hazard. For this reason, sensitive and specific methods for the quantification of these compounds in numerous matrices have been published. This article reviews the current status of the application of liquid-chromatography-based analytical methods in the analysis of β-lactam antibiotics. These methods are classified according to the different detection systems used: UV-visible spectrophotometry, mass spectrometry and other detection techniques such as fluorescence or chemiluminescence. We include applications in different fields (e.g., food, environmental, clinical and pharmaceutical).
Source:TrAC Trends in Analytical Chemistry, Volume 38
Francisco J. Lara, Monsalud del Olmo-Iruela, Carmen Cruces-Blanco, Carolina Quesada-Molina, Ana M. García-Campaña
β-lactam antibiotics have been the most widely used antimicrobial drugs for more than 80years and still constitute the most important group of antibiotics. Their extensive use in veterinary medicine practices as growth promoters, and chemotherapeutic and/or prophylactic agents causes numerous residues in foodstuffs which present a serious health hazard. For this reason, sensitive and specific methods for the quantification of these compounds in numerous matrices have been published. This article reviews the current status of the application of liquid-chromatography-based analytical methods in the analysis of β-lactam antibiotics. These methods are classified according to the different detection systems used: UV-visible spectrophotometry, mass spectrometry and other detection techniques such as fluorescence or chemiluminescence. We include applications in different fields (e.g., food, environmental, clinical and pharmaceutical).
Highlights
► Critical review of analysis of β-lactam antibiotics by liquid chromatography. ► Detection modes and analytical applications of LC methods for β-lactam antibiotics. ► Advantages and drawbacks of sample preparation for LC of β-lactam antibiotics.Label-free detection in biological applications of surface-enhanced Raman scattering
23 August 2012,
09:43:19
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry, Volume 38
Xiao Xia Han, Yukihiro Ozaki, Bing Zhao
Surface-enhanced Raman scattering (SERS) is currently undergoing rapid development as an ultra-sensitive analytical technique in the biological field. Label-free and extrinsic SERS labeling are two independent approaches that are commonly used to detect biomolecules directly and indirectly. The label-free detection method is a direct, convenient method for the detection of biomolecules and is more reliable than extrinsic SERS labeling, but its major limitations are poor selectivity in some complex mixtures and poor sensitivity at relatively low sample concentrations. However, label-free, highly sensitive, selective detection of biomolecules based on SERS is possible. With the development of novel SERS-active substrates, Raman instruments, and methods for sample pretreatment, the label-free protocol is becoming increasingly powerful and promising. This review highlights recent developments in label-free SERS-based techniques for bimolecular detection, including direct biomolecule identification, biomolecule–ligand recognition via spectral differences among molecular bridges, and indirect phenolic molecule detection based on azo couplings.
Source:TrAC Trends in Analytical Chemistry, Volume 38
Xiao Xia Han, Yukihiro Ozaki, Bing Zhao
Surface-enhanced Raman scattering (SERS) is currently undergoing rapid development as an ultra-sensitive analytical technique in the biological field. Label-free and extrinsic SERS labeling are two independent approaches that are commonly used to detect biomolecules directly and indirectly. The label-free detection method is a direct, convenient method for the detection of biomolecules and is more reliable than extrinsic SERS labeling, but its major limitations are poor selectivity in some complex mixtures and poor sensitivity at relatively low sample concentrations. However, label-free, highly sensitive, selective detection of biomolecules based on SERS is possible. With the development of novel SERS-active substrates, Raman instruments, and methods for sample pretreatment, the label-free protocol is becoming increasingly powerful and promising. This review highlights recent developments in label-free SERS-based techniques for bimolecular detection, including direct biomolecule identification, biomolecule–ligand recognition via spectral differences among molecular bridges, and indirect phenolic molecule detection based on azo couplings.
Highlights
► Development of highly sensitive, biocompatible or reproducible SERS-active substrates. ► Development of SERS-based methods to probe native bimolecular structures. ► Development of methods for biorecognition based on SERS. ► Realization of SERS-based label-free indirect identification.Electrocatalysis, sensors and biosensors in analytical chemistry based on ordered mesoporous and macroporous carbon-modified electrodes
23 August 2012,
09:43:19
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry, Volume 38
Alain Walcarius
The past few years have seen an explosion in the use of ordered mesoporous carbon and, to lesser extent, templated macroporous carbon, as novel materials to design nanostructured electrodes devoted to sensing and biosensing. These materials offer attractive features that can be exploited in electrochemistry [e.g., good electronic conductivity, great porosity (high specific surface area, large pore volume and size) and widely open ordered structure]. After a brief presentation of these materials (template synthesis, characterization, properties and uses) and the ways to attach them to electrode surfaces (including their basic electrochemical behavior), we review their interest for electroanalytical purposes. We pay particular attention to applications in the fields of preconcentration electroanalysis, electrocatalysis, potentiometry and electrochemical biosensing, and to discussing the advantages of such templated porous carbons over other related nanostructured carbon materials.
Source:TrAC Trends in Analytical Chemistry, Volume 38
Alain Walcarius
The past few years have seen an explosion in the use of ordered mesoporous carbon and, to lesser extent, templated macroporous carbon, as novel materials to design nanostructured electrodes devoted to sensing and biosensing. These materials offer attractive features that can be exploited in electrochemistry [e.g., good electronic conductivity, great porosity (high specific surface area, large pore volume and size) and widely open ordered structure]. After a brief presentation of these materials (template synthesis, characterization, properties and uses) and the ways to attach them to electrode surfaces (including their basic electrochemical behavior), we review their interest for electroanalytical purposes. We pay particular attention to applications in the fields of preconcentration electroanalysis, electrocatalysis, potentiometry and electrochemical biosensing, and to discussing the advantages of such templated porous carbons over other related nanostructured carbon materials.
Highlights
► Templated macro- and mesoporous carbon materials are attractive for electrochemistry. ► They offer good conductivity, great porosity, and widely open regular structure. ► They exhibit intrinsic adsorption and electrocatalytic properties. ► They have applications in chemical sensors and electrochemical biosensors. ► Possible advantages over related nanostructured carbons are discussed.Mercury-ion optical sensors
23 August 2012,
09:43:19
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry, Volume 38
Sherif A. El-Safty, M.A. Shenashen, Sherif A. El-Safty
The toxicity of mercury (Hg) to humans, including damage to the nervous system, is well known. Hg cannot be degraded into non-toxic compounds or other elements. It is released mainly through mining, industries, and fossil fuel combustion. Anthropogenic and natural activities, such as volcanoes, transform elemental Hg (Hg0) into its ionic form [Hg(II)], which bioaccumulates in biota and is biomagnified in the food chain, notably in aquatic environments. This critical report aims to control Hg(II)-ion toxicity through risk assessment, recognition, and removal via high-level waste management. We first discuss successful and up-to-date developments in different techniques, designs and studies that are potentially useful in enhancing the effectiveness of control of Hg(II)-ion toxicity. The key to designing optical nanosensors is to construct chromophore and fluorophore receptors as nanoscale platform scavengers with different functional characteristics (e.g., density, accessibility, and intrinsic mobility), which allow for easy, reliable signaling in continuous monitoring modes. We highlight a technique that depends on the use of engineered mesocage materials that have multidirectional cavities and microsized, particle-like monoliths to control the adsorption/detection of toxic metal ions, especially Hg(II) ions. With regard to proximal sensing, we consider controlled assessment processes that involve the evaluation of intrinsic properties (e.g., signal change, long-term stability, adsorption efficiency, extraordinary sensitivity, selectivity, and reusability). This study provides evidence that miniaturized mesosensor strips can revolutionize consumer and industrial markets with the introduction of ion-sensor strips.
Source:TrAC Trends in Analytical Chemistry, Volume 38
Sherif A. El-Safty, M.A. Shenashen, Sherif A. El-Safty
The toxicity of mercury (Hg) to humans, including damage to the nervous system, is well known. Hg cannot be degraded into non-toxic compounds or other elements. It is released mainly through mining, industries, and fossil fuel combustion. Anthropogenic and natural activities, such as volcanoes, transform elemental Hg (Hg0) into its ionic form [Hg(II)], which bioaccumulates in biota and is biomagnified in the food chain, notably in aquatic environments. This critical report aims to control Hg(II)-ion toxicity through risk assessment, recognition, and removal via high-level waste management. We first discuss successful and up-to-date developments in different techniques, designs and studies that are potentially useful in enhancing the effectiveness of control of Hg(II)-ion toxicity. The key to designing optical nanosensors is to construct chromophore and fluorophore receptors as nanoscale platform scavengers with different functional characteristics (e.g., density, accessibility, and intrinsic mobility), which allow for easy, reliable signaling in continuous monitoring modes. We highlight a technique that depends on the use of engineered mesocage materials that have multidirectional cavities and microsized, particle-like monoliths to control the adsorption/detection of toxic metal ions, especially Hg(II) ions. With regard to proximal sensing, we consider controlled assessment processes that involve the evaluation of intrinsic properties (e.g., signal change, long-term stability, adsorption efficiency, extraordinary sensitivity, selectivity, and reusability). This study provides evidence that miniaturized mesosensor strips can revolutionize consumer and industrial markets with the introduction of ion-sensor strips.
Highlights
► Mercury is well known as an environmental pollutant in air and water. ► Mercury pollution is widely recognized as a global issue. ► Risk assessment, recognition, removal and waste management of Hg2+ ions. ► Up-to-date developments in techniques for control of Hg2+ ion toxicity.Concept of (dis)similarity in data analysis
23 August 2012,
09:43:19
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry, Volume 38
Piotr Zerzucha, Beata Walczak
(Dis)similarity matrices (the Euclidean distance matrix included) can be used for unsupervised and supervised data analysis. In this review, we use four different data sets (real and simulated, with different dimensionalities and a different correlation structure) to demonstrate the performance of dissimilarity-based approaches [e.g., hierarchical clustering, dissimilarity-Partial Least Squares (dissimilarity-PLS) and Non-parametric Multiple Analysis of Variance (NP-MANOVA)]. Dissimilarity-PLS performs well for linear and highly non-linear data, both in regression and discrimination settings. NP-MANOVA allows for a fast randomization test of the statistical significance of the factors studied in the designed experiments. Dissimilarity-based approaches can be applied to data sets with numerous variables. However, if the studied data set contains numerous objects, a full dissimilarity matrix should be replaced with a dissimilarity matrix containing the distances of all of the objects to preselected “prototypes”. Although we focus on the Euclidean distance, any dissimilarity measure can be used in the approaches discussed, thus enlarging the areas of their application to different types of variable (e.g., nominal variables, and sensory data).
Source:TrAC Trends in Analytical Chemistry, Volume 38
Piotr Zerzucha, Beata Walczak
(Dis)similarity matrices (the Euclidean distance matrix included) can be used for unsupervised and supervised data analysis. In this review, we use four different data sets (real and simulated, with different dimensionalities and a different correlation structure) to demonstrate the performance of dissimilarity-based approaches [e.g., hierarchical clustering, dissimilarity-Partial Least Squares (dissimilarity-PLS) and Non-parametric Multiple Analysis of Variance (NP-MANOVA)]. Dissimilarity-PLS performs well for linear and highly non-linear data, both in regression and discrimination settings. NP-MANOVA allows for a fast randomization test of the statistical significance of the factors studied in the designed experiments. Dissimilarity-based approaches can be applied to data sets with numerous variables. However, if the studied data set contains numerous objects, a full dissimilarity matrix should be replaced with a dissimilarity matrix containing the distances of all of the objects to preselected “prototypes”. Although we focus on the Euclidean distance, any dissimilarity measure can be used in the approaches discussed, thus enlarging the areas of their application to different types of variable (e.g., nominal variables, and sensory data).
Highlights
► (Dis)similarity matrices can be used for unsupervised and supervised data analysis. ► D-PLS method can be used for modeling non-linear problems. ► When working with dissimilarity matrices, it is very easy to identify X-outliers.Methods for the determination of biomarkers of exposure to emerging pollutants in human specimens
23 August 2012,
09:43:19
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry, Volume 38
Vicent Yusa, Xiaoyun Ye, Antonia M. Calafat
Biomonitoring is a very useful tool for assessing human exposure to environmental pollutants. This review discusses recent methods for the quantitative measurement of biomarkers of exposure to different classes of chemicals used in personal-care products (e.g., musk fragrances, preservatives, UV filters, and insect repellents) and consumer products (e.g., organophosphate flame retardants, phthalate esters, perfluorinated compounds, and industrial phenols). The measurements are mainly taken in urine, blood, and breast milk. We also discuss the different procedures commonly used for sample-pretreatment, extraction, and clean up, and chromatographic techniques currently used to determine these compounds. Finally, we present data on the main biomarkers occurring in different human specimens.
Source:TrAC Trends in Analytical Chemistry, Volume 38
Vicent Yusa, Xiaoyun Ye, Antonia M. Calafat
Biomonitoring is a very useful tool for assessing human exposure to environmental pollutants. This review discusses recent methods for the quantitative measurement of biomarkers of exposure to different classes of chemicals used in personal-care products (e.g., musk fragrances, preservatives, UV filters, and insect repellents) and consumer products (e.g., organophosphate flame retardants, phthalate esters, perfluorinated compounds, and industrial phenols). The measurements are mainly taken in urine, blood, and breast milk. We also discuss the different procedures commonly used for sample-pretreatment, extraction, and clean up, and chromatographic techniques currently used to determine these compounds. Finally, we present data on the main biomarkers occurring in different human specimens.
Highlights
► Biomonitoring is a useful tool for assessing human exposure to emerging pollutants. ► We report the methods for analysis of biomarkers of exposure to emerging pollutants. ► LC-MS/MS is the prevailing technique in determining biomarkers of emerging pollutants. ► We present data on the main biomarkers occurring in different human specimens.Isotopic methods give clues about the origins of trace metals and organic pollutants in the environment
23 August 2012,
09:43:19
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry, Volume 38
Philippe Négrel, Michaela Blessing, Romain Millot, Emmanuelle Petelet-Giraud, Christophe Innocent
Recent advances in techniques and methodologies in analytical chemistry help to address problems of environmental contamination. This is particularly true for isotope determinations of metals using multi-collector inductively coupled plasma mass spectrometry (MS) and on-line coupling of capillary gas chromatography and isotope-ratio MS, or compound-specific stable isotope analysis. We explore the methodologies and applications using the isotope signatures of inorganic or organic contaminants, which offer good potential for distinguishing potential sources within contamination plumes and possibly even estimating different source inputs at the catchment scale. Moreover, for organic pollutants, such methods provide unique information for deciphering their origin and studying degradation processes.
Source:TrAC Trends in Analytical Chemistry, Volume 38
Philippe Négrel, Michaela Blessing, Romain Millot, Emmanuelle Petelet-Giraud, Christophe Innocent
Recent advances in techniques and methodologies in analytical chemistry help to address problems of environmental contamination. This is particularly true for isotope determinations of metals using multi-collector inductively coupled plasma mass spectrometry (MS) and on-line coupling of capillary gas chromatography and isotope-ratio MS, or compound-specific stable isotope analysis. We explore the methodologies and applications using the isotope signatures of inorganic or organic contaminants, which offer good potential for distinguishing potential sources within contamination plumes and possibly even estimating different source inputs at the catchment scale. Moreover, for organic pollutants, such methods provide unique information for deciphering their origin and studying degradation processes.
Highlights
► Advances in analytical chemistry methodologies address pollution. ► Isotope signatures provide valuable information to decipher the origin of pollutants. ► Isotope signatures provide valuable information to study degradation processes. ► We review of isotope methodologies and applications for studying pollution.Model-population analysis and its applications in chemical and biological modeling
23 August 2012,
09:43:19
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry, Volume 38
Hong-Dong Li, Yi-Zeng Liang, Dong-Sheng Cao, Qing-Song Xu
Model-population analysis (MPA) was recently proposed as a general framework for designing new types of chemometrics and bioinformatics algorithms, and it has found promising applications in chemistry and biology. The goal of MPA is to extract useful information from complex analytical systems, so as to lead to better understanding and better modeling of chemical and biological data. To give an overall picture of MPA, we first review its key elements. Then, we describe the theories and the applications of selected methods that focus on the two fundamental aspects in chemical and biological modeling: outlier detection and variable selection. We highlight the key common principles of these methods and pinpoint the critical differences underlying each method.
Source:TrAC Trends in Analytical Chemistry, Volume 38
Hong-Dong Li, Yi-Zeng Liang, Dong-Sheng Cao, Qing-Song Xu
Model-population analysis (MPA) was recently proposed as a general framework for designing new types of chemometrics and bioinformatics algorithms, and it has found promising applications in chemistry and biology. The goal of MPA is to extract useful information from complex analytical systems, so as to lead to better understanding and better modeling of chemical and biological data. To give an overall picture of MPA, we first review its key elements. Then, we describe the theories and the applications of selected methods that focus on the two fundamental aspects in chemical and biological modeling: outlier detection and variable selection. We highlight the key common principles of these methods and pinpoint the critical differences underlying each method.
Highlights
► Model-population analysis is a framework for chemometrics/bioinformatics algorithms. ► We address model-population analysis (MPA) approaches to outlier detection. ► Model-population analysis is used in variable selection/biomarker discovery.Recent developments in solid phase extraction in elemental speciation of environmental samples with special reference to aqueous solutions
23 August 2012,
09:43:19
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry, Volume 38
Debasis Das, Utpal Gupta, Arabinda K. Das
The literature on the use of solid-phase extraction (SPE) as a tool for trace-element speciation is highly significant. Among methods of pretreatment, SPE is unique because of its effectiveness, robustness, speed and, above all, its “greenness”. We illustrate the combination of SPE with highly sensitive detection methods for accurate measurements of chemical species at extremely low concentrations in environmental samples with special reference to aqueous solutions. We examine the analytical strategies for speciation of elements in terms of limits of detection.
Source:TrAC Trends in Analytical Chemistry, Volume 38
Debasis Das, Utpal Gupta, Arabinda K. Das
The literature on the use of solid-phase extraction (SPE) as a tool for trace-element speciation is highly significant. Among methods of pretreatment, SPE is unique because of its effectiveness, robustness, speed and, above all, its “greenness”. We illustrate the combination of SPE with highly sensitive detection methods for accurate measurements of chemical species at extremely low concentrations in environmental samples with special reference to aqueous solutions. We examine the analytical strategies for speciation of elements in terms of limits of detection.
23 August 2012,
09:43:19
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry
Francisco Pena-Pereira, Regina M.B.O. Duarte, Armando C. Duarte
In this work, we provide an overview of the different strategies employed for achieving the immobilization of metallic and metal-oxide nanomaterials on solid substrates for analytical purposes. We describe significant strategies employed for obtaining solid surfaces with attached metallic nanoparticles (MNPs), and report on surfaces used for immobilization of MNPs, and their characteristics. Finally, we discuss representative applications of metallic and metal-oxide nanomaterials in different areas of analytical chemistry (localized surface-plasmon-resonance sensors, surface-enhanced Raman scattering substrates, electrochemistry, microextraction coatings, analytical separations, and quartz-crystal-microbalance sensors.
Source:TrAC Trends in Analytical Chemistry
Francisco Pena-Pereira, Regina M.B.O. Duarte, Armando C. Duarte
In this work, we provide an overview of the different strategies employed for achieving the immobilization of metallic and metal-oxide nanomaterials on solid substrates for analytical purposes. We describe significant strategies employed for obtaining solid surfaces with attached metallic nanoparticles (MNPs), and report on surfaces used for immobilization of MNPs, and their characteristics. Finally, we discuss representative applications of metallic and metal-oxide nanomaterials in different areas of analytical chemistry (localized surface-plasmon-resonance sensors, surface-enhanced Raman scattering substrates, electrochemistry, microextraction coatings, analytical separations, and quartz-crystal-microbalance sensors.
Highlights
► We reviewed analytical aspects of immobilized metallic nanomaterials. ► We discussed the strategies used to obtain nanoparticle-covered surfaces. ► We described the surfaces employed for immobilization of nanoparticles. ► We provided analytical applications of metal nanoparticles attached to surfaces.Gold nanoparticle-based optical probes for sensing aminothiols
23 August 2012,
09:43:19
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry
Qunyan Xiao, Huiling Gao, Chao Lu, Qipeng Yuan
Measurement of biological aminothiols (e.g., cysteine, homocysteine and glutathione) is important for clinical diagnosis. There is growing interest in the fabrication of optical nanoprobes due to their high sensitivity, low cost, low-power requirements and high biocompatibility. We give a general overview of the different strategies for gold nanoparticle (AuNP)-based optical probes for sensing aminothiols, including colorimetric, fluorescent, resonance-light scattering, chemiluminescent and surface-enhanced Raman scattering techniques. This review also summarizes these optical probes in terms of analytical performance, and discusses possible solutions to overcome some critical challenges facing these methods.
Source:TrAC Trends in Analytical Chemistry
Qunyan Xiao, Huiling Gao, Chao Lu, Qipeng Yuan
Measurement of biological aminothiols (e.g., cysteine, homocysteine and glutathione) is important for clinical diagnosis. There is growing interest in the fabrication of optical nanoprobes due to their high sensitivity, low cost, low-power requirements and high biocompatibility. We give a general overview of the different strategies for gold nanoparticle (AuNP)-based optical probes for sensing aminothiols, including colorimetric, fluorescent, resonance-light scattering, chemiluminescent and surface-enhanced Raman scattering techniques. This review also summarizes these optical probes in terms of analytical performance, and discusses possible solutions to overcome some critical challenges facing these methods.
Highlights
► Recent advances using gold-nanoparticle-based optical probes for aminothiols. ► Gold nanoparticles as colorimetric probes for aminothiols. ► Gold nanoparticles as fluorescent probes for aminothiols. ► Gold nanoparticles as resonance-light scattering probes for aminothiols. ► Gold nanoparticles as chemiluminescent probes for aminothiols.Tree-based ensemble methods and their applications in analytical chemistry
23 August 2012,
09:43:19
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry
Dong-Sheng Cao, Jian-Hua Huang, Yi-Zeng Liang, Qing-Song Xu, Liang-Xiao Zhang
Large amounts of data from high-throughput analytical instruments have generally become more and more complex, bringing a number of challenges to statistical modeling. To understand complex data further, new statistically-efficient approaches are urgently needed to: select salient features from the data; discard uninformative data; detect outlying samples in data; visualize existing patterns of the data; improve the prediction accuracy of the data; and, finally, feed back to the analyst understandable summaries of information from the data. We review current developments in tree-based ensemble methods to mine effectively the knowledge hidden in chemical and biology data. We report on applications of these algorithms to variable selection, outlier detection, supervised pattern analysis, cluster analysis, tree-based kernel and ensemble learning. Through this report, we wish to inspire chemists to take greater interest in decision trees and to obtain greater benefits from using the tree-based ensemble techniques.
Source:TrAC Trends in Analytical Chemistry
Dong-Sheng Cao, Jian-Hua Huang, Yi-Zeng Liang, Qing-Song Xu, Liang-Xiao Zhang
Large amounts of data from high-throughput analytical instruments have generally become more and more complex, bringing a number of challenges to statistical modeling. To understand complex data further, new statistically-efficient approaches are urgently needed to: select salient features from the data; discard uninformative data; detect outlying samples in data; visualize existing patterns of the data; improve the prediction accuracy of the data; and, finally, feed back to the analyst understandable summaries of information from the data. We review current developments in tree-based ensemble methods to mine effectively the knowledge hidden in chemical and biology data. We report on applications of these algorithms to variable selection, outlier detection, supervised pattern analysis, cluster analysis, tree-based kernel and ensemble learning. Through this report, we wish to inspire chemists to take greater interest in decision trees and to obtain greater benefits from using the tree-based ensemble techniques.
Highlights
► Decision tree can do automatic stepwise variable selection and complexity reduction. ► Decision trees can cope effectively with complex chemical data. ► Tree-based ensemble approaches could be applied to solve various chemometric problems.Wireless sensors and sensor networks for homeland security applications
23 August 2012,
09:43:19
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry
Radislav A. Potyrailo, Nandini Nagraj, Cheryl Surman, Hacene Boudries, Hanh Lai, Joseph M. Slocik, Nancy Kelley-Loughnane, Rajesh R. Naik
New sensor technologies for homeland security applications must meet the key requirements of sensitivity to detect agents below risk levels, selectivity to provide minimal false-alarm rates, and response speed to operate in high throughput environments, such as airports, sea ports, and other public places. Chemical detection using existing sensor systems is facing a major challenge of selectivity. In this review, we provide a brief summary of chemical threats of homeland security importance; focus in detail on modern concepts in chemical sensing; examine the origins of the most significant unmet needs in existing chemical sensors; and, analyze opportunities, specific requirements, and challenges for wireless chemical sensors and wireless sensor networks (WSNs). We further review a new approach for selective chemical sensing that involves the combination of a sensing material that has different response mechanisms to different species of interest, with a transducer that has a multi-variable signal-transduction ability. This new selective chemical-sensing approach was realized using an attractive ubiquitous platform of battery-free passive radio-frequency identification (RFID) tags adapted for chemical sensing. We illustrate the performance of RFID sensors developed in measurements of toxic industrial materials, humidity-independent detection of toxic vapors, and detection of chemical-agent simulants, explosives, and strong oxidizers.
Source:TrAC Trends in Analytical Chemistry
Radislav A. Potyrailo, Nandini Nagraj, Cheryl Surman, Hacene Boudries, Hanh Lai, Joseph M. Slocik, Nancy Kelley-Loughnane, Rajesh R. Naik
New sensor technologies for homeland security applications must meet the key requirements of sensitivity to detect agents below risk levels, selectivity to provide minimal false-alarm rates, and response speed to operate in high throughput environments, such as airports, sea ports, and other public places. Chemical detection using existing sensor systems is facing a major challenge of selectivity. In this review, we provide a brief summary of chemical threats of homeland security importance; focus in detail on modern concepts in chemical sensing; examine the origins of the most significant unmet needs in existing chemical sensors; and, analyze opportunities, specific requirements, and challenges for wireless chemical sensors and wireless sensor networks (WSNs). We further review a new approach for selective chemical sensing that involves the combination of a sensing material that has different response mechanisms to different species of interest, with a transducer that has a multi-variable signal-transduction ability. This new selective chemical-sensing approach was realized using an attractive ubiquitous platform of battery-free passive radio-frequency identification (RFID) tags adapted for chemical sensing. We illustrate the performance of RFID sensors developed in measurements of toxic industrial materials, humidity-independent detection of toxic vapors, and detection of chemical-agent simulants, explosives, and strong oxidizers.
Highlights
► Brief summary of chemical threats of importance to homeland security. ► Origins of the most significant unmet needs in existing chemical sensors. ► Specific requirements and challenges for wireless chemical sensors and networks. ► New approach to selective wireless chemical sensing. ► New sensors for toxic materials, chemical agent simulants, explosives and oxidizers.Analytical methods developed using chemiluminescence- resonance-energy transfer based on nanomaterials
23 August 2012,
09:43:19
Publication year: 2012
Source:TrAC Trends in Analytical Chemistry
Xiangyi Huang, Jicun Ren
Chemiluminescence-resonance-energy transfer (CRET) is non-radiative energy transfer from a chemiluminescent donor to a suitable acceptor molecule. Although the CRET phenomenon was observed some time ago, there are very few applications of conventional CRET due to its poor energy-transfer efficiency and the limited number of energy acceptors. Recently, significant progress in CRET was made, due to the introduction of some nanomaterials as energy acceptors (e.g., quantum dots, gold nanoparticles and grapheme). The energy-transfer efficiency is greatly improved by using nanomaterials as energy acceptors, and nanomaterial-based CRET is currently used successfully in immunoassays, DNA and microRNA analysis, small-molecule detection and cell imaging. Nanomaterial-based CRET provides a new strategy to design optical sensors and develop analytical methods. In this review article, we first introduce recent advances in the nanomaterial-based CRET and some typical CRET modes, then we summarize key applications, and, finally, we discuss future prospects.
Source:TrAC Trends in Analytical Chemistry
Xiangyi Huang, Jicun Ren
Chemiluminescence-resonance-energy transfer (CRET) is non-radiative energy transfer from a chemiluminescent donor to a suitable acceptor molecule. Although the CRET phenomenon was observed some time ago, there are very few applications of conventional CRET due to its poor energy-transfer efficiency and the limited number of energy acceptors. Recently, significant progress in CRET was made, due to the introduction of some nanomaterials as energy acceptors (e.g., quantum dots, gold nanoparticles and grapheme). The energy-transfer efficiency is greatly improved by using nanomaterials as energy acceptors, and nanomaterial-based CRET is currently used successfully in immunoassays, DNA and microRNA analysis, small-molecule detection and cell imaging. Nanomaterial-based CRET provides a new strategy to design optical sensors and develop analytical methods. In this review article, we first introduce recent advances in the nanomaterial-based CRET and some typical CRET modes, then we summarize key applications, and, finally, we discuss future prospects.
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