Analytical Chemistry (analytical + chemistry)

Distribution by Scientific Domains


Selected Abstracts


Recent Updates of Chemically Modified Electrodes in Analytical Chemistry

ELECTROANALYSIS, Issue 13 2003
Jyh-Myng Zen
Abstract This review article updates recent developments in chemically modified electrodes (CMEs) towards analytical applications for the year of 2000,2002 with 179 references. The broad topics are subdivided into four main categories: i) physisorption/chemisorption, ii) covalently linked, iii) homogenous (uniform) multilayer and iv) heterogeneous (non-uniform) multilayer CMEs. The criteria for the preparation of CMEs in elecrocatalytic systems are clearly described in Section 1. Some of the encouraging results related to Au-nanoparticles for DNA detection and new ceramic carbon, carbon nanotubes, copper-plated screen-printed and Nafion/lead ruthenate pyrochlore CMEs for catalytic application were especially discussed in this review. [source]


Book Review: Eectrokinetec Phenomena: Principles and Applications in Analytical Chemistry and Microchip Technology.

ELECTROPHORESIS, Issue 6 2004
A. Guttman (Eds.), By A.S. Rathore
No abstracts. [source]


Thirty-fourth Annual Meeting of the Federation of Analytical Chemistry and Spectroscopy Societies (FACSS 2007), Memphis, TN, USA, 14,18 October 2007

JOURNAL OF CHEMOMETRICS, Issue 9 2008
Frank Vogt Guest Editor Journal of Chemometrics
No abstract is available for this article. [source]


Poster Session 3: Analytical Chemistry

JOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue S1 2008
Article first published online: 18 FEB 2010
No abstract is available for this article. [source]


Poster Session 1 , Analytical Chemistry

JOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue S1 2003
Article first published online: 18 FEB 2010
First page of article [source]


Poster Session 1 , Analytical Chemistry

JOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue S1 2002
Article first published online: 18 FEB 2010
First page of article [source]


A Biomimetic Potentiometric Sensor Using Molecularly Imprinted Polymer for the Cetirizine Assay in Tablets and Biological Fluids

ELECTROANALYSIS, Issue 18 2008
Mehran Javanbakht
Abstract Despite the increasing number of applications of molecularly imprinted polymers (MIPs) in analytical chemistry, the construction of a biomimetic potentiometric sensor remains still challenging. In this work, a biomimetic potentiometric sensor, based on a non-covalent imprinted polymer was fabricated for the recognition and determination of cetirizine. The MIP was synthesized by precipitation polymerization, using cetirizine dihydrochloride as a template molecule, methacrylic acid (MAA) as a functional monomer and ethylene glycol dimethacrylate (EGDMA) as a cross linking agent. The sensor showed high selectivity and a sensitive response to the template in aqueous system. The MIP-modified electrode exhibited Nernstian response (28.0±0.9 mV/decade) in a wide concentration range of 1.0×10,6 to 1.0×10,2 M with a lower detection limit of 7.0×10,7 M. The electrode has response time of ca. 20,s, high performance, high sensitivity, and good long term stability (more than 5,months). The method was satisfactory and used to the cetirizine assay in tablets and biological fluids. [source]


Electric field-enhanced transport across phase boundaries and membranes and its potential use in sample pretreatment for bioanalysis

ELECTROPHORESIS, Issue 5 2010
Pavel Kubá
Abstract Separation techniques, such as electrodialysis, electroextraction, electro-membrane extraction and extraction across phase interfaces, are reviewed and discussed as methods for sample cleanup and preconcentration. This survey clearly shows that electromigration of ionic species across phase interfaces, especially across supported liquid membranes, may be very selective and is strongly dependent on the chemical composition of these interfaces. Thus, electric field-enhanced transport across chemically tailored liquid membranes may open new perspectives in preparative analytical chemistry. This review offers comprehensive survey of related literature and discussion of the topic, which may stimulate interest of experts and practitioners in bioanalysis. [source]


Cover Picture: Fabrication of Stable Metallic Patterns Embedded in Poly(dimethylsiloxane) and Model Applications in Non-Planar Electronic and Lab-on-a-Chip Device Patterning (Adv. Funct.

ADVANCED FUNCTIONAL MATERIALS, Issue 4 2005
Mater.
Abstract A composite image is shown that highlights examples of device architectures that either incorporate or exploit polymer-embedded metallic microstructures. In work reported by Nuzzo and co-workers on p.,557, new applications of soft lithography, in conjunction with advanced forms of multilayer metallization, are used to construct these exceptionally durable structures. They are suitable for use in non-planar lithographic patterning, and as device components finding applications ranging from microelectronics to Lab-on-a-Chip analytical systems. This article describes the fabrication of durable metallic patterns that are embedded in poly(dimethylsiloxane) (PDMS) and demonstrates their use in several representative applications. The method involves the transfer and subsequent embedding of micrometer-scale gold (and other thin-film material) patterns into PDMS via adhesion chemistries mediated by silane coupling agents. We demonstrate the process as a suitable method for patterning stable functional metallization structures on PDMS, ones with limiting feature sizes less than 5,,m, and their subsequent utilization as structures suitable for use in applications ranging from soft-lithographic patterning, non-planar electronics, and microfluidic (lab-on-a-chip, LOC) analytical systems. We demonstrate specifically that metal patterns embedded in both planar and spherically curved PDMS substrates can be used as compliant contact photomasks for conventional photolithographic processes. The non-planar photomask fabricated with this technique has the same surface shape as the substrate, and thus facilitates the registration of structures in multilevel devices. This quality was specifically tested in a model demonstration in which an array of one hundred metal oxide semiconductor field-effect transistor (MOSFET) devices was fabricated on a spherically curved Si single-crystalline lens. The most significant opportunities for the processes reported here, however, appear to reside in applications in analytical chemistry that exploit devices fabricated using the methods of soft lithography. Toward this end, we demonstrate durably bonded metal patterns on PDMS that are appropriate for use in microfluidic, microanalytical, and microelectromechanical systems. We describe a multilayer metal-electrode fabrication scheme (multilaminate metal,insulator,metal (MIM) structures that substantially enhance performance and stability) and use it to enable the construction of PDMS LOC devices using electrochemical detection. A polymer-based microelectrochemical analytical system, one incorporating an electrode array for cyclic voltammetry and a microfluidic system for the electrophoretic separation of dopamine and catechol with amperometric detection, is demonstrated. [source]


Heteroscedastic controlled calibration model applied to analytical chemistry

JOURNAL OF CHEMOMETRICS, Issue 5 2010
Betsabé Blas
Abstract In chemical analyses performed by laboratories, one faces the problem of determining the concentration of a chemical element in a sample. In practice, one deals with the problem using the so-called linear calibration model, which considers that the errors associated with the independent variables are negligible compared with the former variable. In this work, a new linear calibration model is proposed assuming that the independent variables are subject to heteroscedastic measurement errors. A simulation study is carried out in order to verify some properties of the estimators derived for the new model and it is also considered the usual calibration model to compare it with the new approach. Three applications are considered to verify the performance of the new approach. Copyright © 2010 John Wiley & Sons, Ltd. [source]


Handling of Rayleigh and Raman scatter for PARAFAC modeling of fluorescence data using interpolation

JOURNAL OF CHEMOMETRICS, Issue 3-4 2006
Morteza Bahram
Abstract Fluorescence excitation-emission matrix (EEM) measurements are useful in fields such as food science, analytical chemistry, biochemistry and environmental science. EEMs contain information which can be modeled using the parallel factor analysis (PARAFAC) model but the data analysis is often complicated due to both Rayleigh and Raman scattering. There are several established ways to deal with scattering effects. However, all of these methods have associated problems. This paper develops a new method for handling scattering using interpolation in the areas affected by first- and second-order Rayleigh and Raman scatter in such a way that the interfering signal is, at best, removed. The suggested method is fast and requires no additional input other than specifying the scattering region. The results of the proposed method were compared with those obtained from common alternative approaches used for preprocessing fluorescence data before analysis with PARAFAC and were shown to be equally good for various types of EEM data. The main advantage of the interpolation method is in its lack of additional metaparameters, its algorithmic speed and subsequent speed-up of PARAFAC modeling. It also allows for using EEM data in software not able to handle missing data. Copyright © 2007 John Wiley & Sons, Ltd. [source]


A new maximum entropy-based method for deconvolution of spectra with heteroscedastic noise

JOURNAL OF CHEMOMETRICS, Issue 12 2004
Bĺrd Buttingsrud
Abstract Broadening of spectral lines combined with large and heteroscedastic noise contributions constitutes an important problem in analytical chemistry. Reduced interpretability and artefacts in further data analysis make deconvolution methods necessary. A new robust deconvolution method (RHEMEM) based on the principle of maximum entropy is proposed in order to effectively handle the presence of heteroscedastic noise. Other deconvolution methods such as Jansson's method, Fourier self-deconvolution and LOMEP are also studied with respect to their ability to handle heteroscedastic noise. A systematic simulation study is used to compare the performance of the new method with the reference methods. They are evaluated according to reconstruction performance, robustness and the ability to work without manual input. Copyright © 2005 John Wiley & Sons, Ltd. [source]


Wavelength selection with Tabu Search

JOURNAL OF CHEMOMETRICS, Issue 8-9 2003
J. A. Hageman
Abstract This paper introduces Tabu Search in analytical chemistry by applying it to wavelength selection. Tabu Search is a deterministic global optimization technique loosely based on concepts from artificial intelligence. Wavelength selection is a method which can be used for improving the quality of calibration models. Tabu Search uses basic, problem-specific operators to explore a search space, and memory to keep track of parts already visited. Several implementational aspects of wavelength selection with Tabu Search will be discussed. Two ways of memorizing the search space are investigated: storing the actual solutions and storing the steps necessary to create them. Parameters associated with Tabu Search are configured with a Plackett,Burman design. In addition, two extension schemes for Tabu Search, intensification and diversification, have been implemented and are applied with good results. Eventually, two implementations of wavelength selection with Tabu Search are tested, one which searches for a solution with a constant number of wavelengths and one with a variable number of wavelengths. Both implementations are compared with results obtained by wavelength selection methods based on simulated annealing (SA) and genetic algorithms (GAs). It is demonstrated with three real-world data sets that Tabu Search performs equally well as and can be a valuable alternative to SA and GAs. The improvements in predictive abilities increased by a factor of 20 for data set 1 and by a factor of 2 for data sets 2 and 3. In addition, when the number of wavelengths in a solution is variable, measurements on the coverage of the search space show that the coverage is usually higher for Tabu Search compared with SA and GAs. Copyright © 2003 John Wiley & Sons, Ltd. [source]


Horwitz's rule, transforming both sides and the design of experiments for mechanistic models

JOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES C (APPLIED STATISTICS), Issue 3 2003
Anthony C. Atkinson
Summary. The paper develops methods for the design of experiments for mechanistic models when the response must be transformed to achieve symmetry and constant variance. The power transformation that is used is partially justified by a rule in analytical chemistry. Because of the nature of the relationship between the response and the mechanistic model, it is necessary to transform both sides of the model. Expressions are given for the parameter sensitivities in the transformed model and examples are given of optimum designs, not only for single-response models, but also for experiments in which multivariate responses are measured and for experiments in which the model is defined by a set of differential equations which cannot be solved analytically. The extension to designs for checking models is discussed. [source]


Mass spectrometry-based metabolomics

MASS SPECTROMETRY REVIEWS, Issue 1 2007
Katja Dettmer
Abstract This review presents an overview of the dynamically developing field of mass spectrometry-based metabolomics. Metabolomics aims at the comprehensive and quantitative analysis of wide arrays of metabolites in biological samples. These numerous analytes have very diverse physico-chemical properties and occur at different abundance levels. Consequently, comprehensive metabolomics investigations are primarily a challenge for analytical chemistry and specifically mass spectrometry has vast potential as a tool for this type of investigation. Metabolomics require special approaches for sample preparation, separation, and mass spectrometric analysis. Current examples of those approaches are described in this review. It primarily focuses on metabolic fingerprinting, a technique that analyzes all detectable analytes in a given sample with subsequent classification of samples and identification of differentially expressed metabolites, which define the sample classes. To perform this complex task, data analysis tools, metabolite libraries, and databases are required. Therefore, recent advances in metabolomics bioinformatics are also discussed. © 2006 Wiley Periodicals, Inc., Mass Spec Rev 26:51,78, 2007 [source]


Mass spectrometry in bioinorganic analytical chemistry

MASS SPECTROMETRY REVIEWS, Issue 2 2006
Ryszard
Abstract A considerable momentum has recently been gained by in vitro and in vivo studies of interactions of trace elements in biomolecules due to advances in inductively coupled plasma mass spectrometry (ICP MS) used as a detector in chromatography and capillary and planar electrophoresis. The multi-isotopic (including non-metals such as S, P, or Se) detection capability, high sensitivity, tolerance to matrix, and large linearity range regardless of the chemical environment of an analyte make ICP MS a valuable complementary technique to electrospray MS and MALDI MS. This review covers different facets of the recent progress in metal speciation in biochemistry, including probing in vitro interactions between metals and biomolecules, detection, determination, and structural characterization of heteroatom-containing molecules in biological tissues, and protein monitoring and quantification via a heteroelement (S, Se, or P) signal. The application areas include environmental chemistry, plant and animal biochemistry, nutrition, and medicine. © 2005 Wiley Periodicals, Inc. Mass Spec Rev 25:255,289, 2006 [source]


Nitrite anions induce nitrosative deamination of peptides and proteins

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2006
Haiteng Deng
In the present study, reactions of sodium nitrite with proteins/peptides were characterized with mass spectrometry. The reaction generates two major products: replacement of the amino group by a hydroxyl group and formation of an alkene derivative by loss of a NH3 group at the N-terminus and the side chain of lysine residues of proteins/peptides. The reaction proceeds rapidly in weak acidic solution and at 37°C in the presence of a millimolar concentration of nitrite, demonstrating that nitrite induces nitrosative deamination in proteins and peptides. The facile nitrite-induced modification of amino groups of protein/peptides changes the chemical nature of proteins and may have various applications in peptide synthesis, analytical chemistry, and protein engineering. It also provides information to enhance our understanding of functions of nitrite ions in biology and food preservation. Copyright © 2006 John Wiley & Sons, Ltd. [source]


Electrospray ionization mass spectrometric characterization and quantitation of xanthine derivatives using isotopically labelled analogues: an application for equine doping control analysis

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2004
Mario Thevis
Isotope-dilution mass spectrometry has been employed successfully in numerous fields of analytical chemistry enabling the establishment of fast and reliable procedures. In equine sports, xanthine derivatives such as caffeine and theobromine are prohibited, and doping control laboratories analyze horse urine specimens regarding these illicit performance-enhancing drugs. Theobromine has to exceed a threshold level of 2,,g/mL, hence a robust and reliable quantitation is required. Stably deuterated theobromine and caffeine were synthesized by the reaction of xanthine or theobromine with iodomethane-d3 in the presence of N -methyl- N -trimethylsilyltrifluoroacetamide or potassium carbonate in acetonitrile, respectively. Both compounds were characterized by nuclear magnetic resonance spectroscopy and electrospray ionization tandem mass spectrometry, and a robust and fast assay for the qualitative and quantitative analysis of theobromine in equine urine samples was validated. Urine specimens were extracted by means of solid-phase extraction cartridges, and concentrated extracts were analyzed by liquid chromatography interfaced to a triple-quadrupole mass spectrometer. In addition, the dissociation behavior of deuterated analogues to caffeine and theobromine allowed proposals for fragmentation routes of xanthine derivatives after atmospheric pressure ionization and collisionally activated dissociation. Copyright © 2004 John Wiley & Sons, Ltd. [source]


Wissenschaftliche Photographie als visuelle Kultur.

BERICHTE ZUR WISSENSCHAFTSGESCHICHTE, Issue 3 2005
Die Erforschung und Dokumentation von Spektren
Abstract This paper discusses facets of 19th-century scientific photography as a visual culture. The example of spectral research and documentation is particularly well suited, because prismatically diffracted light from the sun or from luminous gases was one of the most frequently examined phenomena of that century. The results were significant not only for physics but also for analytical chemistry and astrophysics. The spectrum also served as an ideal test object for checking the effectiveness of a wide array of photochemically sensitizable surfaces to the various color regions. Scientific photography became the most important experimental technique in the infrared and ultraviolet. H. A. Rowland's spectrum charts are discussed as an example of the transition from comprehensiveness in documentation to fetishism. The discussion of the Lippmann process, one of the first methods of color photography, addresses the associated training of the eye. Issues of authenticity and the much averred ,mechanical objectivity" are raised with regard to retouching. The overriding theme of visual science cultures leads furthermore to unanticipated interdependencies with other scientific fields, such as geography, and draws the importance of practitioners into the foreground. [source]


Prostaglandins, bioassay and inflammation

BRITISH JOURNAL OF PHARMACOLOGY, Issue S1 2006
R J Flower
The formation of the British Pharmacological Society coincided almost exactly with a series of ground-breaking studies that ushered in an entirely new field of research , that of lipid mediator pharmacology. For many years following their chemical characterisation, lipids were considered only to be of dietary or structural importance. From the 1930s, all this changed , slowly at first and then more dramatically in the 1970s and 1980s with the emergence of the prostaglandins (PGs), the first intercellular mediators to be clearly derived from lipids, in a dynamic on-demand system. The PGs exhibit a wide range of biological activities that are still being evaluated and their properties underlie the action of one of the world's all-time favourite medicines, aspirin, as well as its more modern congeners. This paper traces the development of the PG field, with particular emphasis on the skilful utilisation of the twin techniques of bioassay and analytical chemistry by U.K. and Swedish scientists, and the intellectual interplay between them that led to the award of a joint Nobel Prize to the principal researchers in the PG field, half a century after the first discovery of these astonishingly versatile mediators. British Journal of Pharmacology (2006) 147, S182,S192. doi:10.1038/sj.bjp.0706506 [source]