bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fluorescence in Organized Assemblies
Authors: Hinze Willie L. 
Published: September 2006

AbstractThis article provides an overview of the general properties of organized assembly (ordered media) systems such as aqueous surfactant and bile salt micelles, lipid and surfactant vesicles (liposomes) and cyclodextrins (CDs) and summarizes their utilization to enhance the performance of analytical fluorescence measurements. In many instances, organic molecules and metal complex species, when included within a CD cavity or solubilized and bound to surfactant aggregates, exhibit enhanced fluorescence. This gives rise to improved detectability of such analytes. The altered microenvironment within the organized medium is capable of impeding the interfering action of other species (inorganic or organic) present in the sample matrix. This often can improve the selectivity of the analytical method. These benefits of improved sensitivity and selectivity arise from the compartmentalization, isolation and shielding of the excited singlet state of the guest analyte from quenching and nonradiative decay processes as well as prevent side reactions that otherwise can occur in bulk solution (or sample matrix). In addition, organic solvents or time‐consuming extraction steps can be avoided owing to the increased solubility of the nonpolar organic or inorganic reagents and/or analyte molecules in water in the presence of the organized medium; allowing for the use of an aqueous medium to perform the procedure. The possibility of conducting reactions and forming fluorescent organic or metal chelates in micellar (or other organized) media that are not observed in a bulk homogeneous solvent system serves to expand the scope of chemistries that one can consider using to design/develop new, unique and improved fluorescent assays. Numerous representative examples of fluorescent methods for determination of both organic and inorganic analytes are provided which serve to illustrate the advantages and benefits accrued from the use of the micelles, vesicles, liposomes or CDs in such procedures. Some experimental considerations and cautions to keep in mind when utilizing organized media are also delineated. An extensive reference section is provided so that the interested reader can easily refer to such for more detailed information on these systems and topics.
Near‐infrared Absorption/Luminescence Measurements
Authors: Swamy A.R. , Mason J.C. , Lee H. , Meadows F. , Baars M. , Strekowski L. , Patonay G. 
Published: September 2006

AbstractThe near‐infrared (NIR) region (600–1100 nm) offers several advantages in comparison with the conventional ultraviolet/visible (UV/VIS) region for spectroscopic measurements and detection. The lack of commercial instrumentation impeded the development of NIR techniques for years. The advent of inexpensive photodiodes and diode lasers used widely by the telecommunication industry gave the necessary impetus for development of analytical NIR techniques. This article describes the fundamental properties of NIR fluorophores and absorbers and provides a comparison with conventional UV/VIS dyes. The various analytical applications developed in the past decade that have utilized the advantages offered by this region are described with a particular emphasis on bioanalytical uses.
Absorption and Luminescence Probes
Authors: Acree William E. 
Published: September 2006

AbstractAbsorption and luminescence probes are molecules or ions whose spectral properties depend upon the chemical nature of the solubilizing media in the immediate vicinity of the probe molecule. Probe character is generally evidenced by the appearance of new spectral bands, shifts in the absorption or emission wavelengths, or by changes in emission intensities. Probe molecules have been used to determine solvent polarity and solvent acidity/basicity, pH, microviscosity, temperature and/or presence of specific ions/molecules. When combined with fluorescence lifetime measurements, absorption and luminescence probes can provide additional information regarding diffusion coefficients in probe excimer formation, fluidity in lipid vesicles, and rates of intermolecular collisions in quenching experiments.
Surface Measurements Using Absorption/Luminescence
Authors: Oldham Philip B. , Asanov Alexander N. , Rangnekar Vinay M. 
Published: September 2006

Abstract
The physical and chemical characteristics of surfaces along with the structure and dynamics of molecules near surfaces or interfaces have recently become critically important. Surface measurements have provided important information concerning the properties of the surfaces and the surface/adsorbate interactions. The physical, chemical and biological sciences have benefited tremendously from these studies, with significant developments being made in the areas of diagnostic devices, optical devices, electronic devices and sensors.
The specific behavior of macromolecules at or near surfaces, interfaces, and membranes is currently of primary interest in the biological sciences. Important applications include: adsorption of blood proteins on biomaterials in thrombogenesis research; the binding to and triggering of living cells by hormones, neurotransmitters and antigens; cell adhesion to various surfaces; the mechanism of electron transport in mitochondrial and photosynthetic membranes; and also reaction rate enhancement with membrane receptors by nonspecific adsorption and surface diffusion of ligands. However, investigation of biomolecular behavior at surfaces and interfaces remains a difficult task. Most of the common analytical methods available for investigation of surfaces either lack the extent of surface selectivity required or demand relatively harsh sample handling that severely limits the biological relevance of any results obtained. This article specifically describes ultraviolet/visible (UV/VIS) absorption and photoluminescence techniques applicable to analysis of surfaces or thin films.
Data Reduction in Gas Chromatography
Authors: Eiceman G.A. , Gardea‐Torresdey J. 
Published: September 2006

Abstract
The data obtained from a gas chromatographic measurement provide the user with details on both the quantitative and the qualitative composition of the sample. This information is displayed in the chromatogram from which information also can be gleaned concerning the performance and quality of the measurement. Quantitative determinations require attention to the relative response of the detector. The assignment of identity of individual constituents is possible in a formal sense only with authentic standards and mass spectra though retention times or indices can be indicators of identity. These aspects of data reduction have been understood for several decades and chemical information can be extracted from a chromatogram with ease and convenience.
In recent years, advanced chemometrics methods have been applied to chromatographic data with intrinsic advantages for probing patterns and trends too subtle or too complex for simple inspection of chromatograms. These methods are rooted in tools such as multivariate analysis and neural network analysis. Such methods are being developed in the area of natural products analysis.
Hyphenated Gas Chromatography
Authors: Coleman W.M. , Gordon Bert M. 
Published: September 2006

AbstractHyphenated gas chromatography (GC) refers to not only the coupling of a GC to information‐rich detectors but also the coupling of the gas chromatograph to automated sample preparation techniques. Examples of information‐rich detectors include mass and infrared spectrometers, whereas automated sample preparation techniques include solid‐phase microextraction (SPME), large‐volume injection (LVI), purge and trap (PT), headspace (HS), and gas chromatographic approaches. The gas chromatographic approach involves the wedding of two gas chromatographs and is commonly referred to as multidimensional gas chromatography (MDGC). The union of the automated sample preparation techniques with MDGC and information‐rich detectors affords the capability for quantitative and qualitative analysis of a wide variety of sample matrices for analytes at parts per billion (ppb) concentrations. However, not every hyphenated configuration is worth considering, and careful matching of the hyphenated approaches is essential to obtain the maximum analytical benefits.
Instrumentation of Gas Chromatography
Authors: Eiceman G.A. 
Published: September 2006

Abstract
Instrumentation for gas chromatography (GC) comprises well‐defined components, each of which contributes to the overall chromatographic performance. Most of these components have reached a mature level of technical development after nearly 50 years of development. Nonetheless, advances are occurring in an evolutionary, not revolutionary, manner with sample handling and in refinements of detectors. One area of dramatic advance in GC instrumentation is the development of small, sophisticated, portable gas chromatographs. Each component of a gas chromatograph (columns excepted) is discussed below where principles and recent developments are emphasized.
Liquid Phases for Gas Chromatography
Authors: Snow Nicholas H. 
Published: September 2006

Abstract
In gas chromatography (GC) the liquid phase, also called the stationary phase, provides the medium in which the separation occurs. The magnitude of separation is given by the relative strengths of intermolecular interactions between analyte and stationary phase molecules, thus numerous liquids have been used over the years. The stationary phase can be coated onto a solid support and packed into a tube (packed column GC), or coated onto the wall of a capillary (capillary GC). Today, most GC analyses are performed using capillary columns.
Spectral Data, Modern Classification Methods for
Authors: Mallet Yvette L. , Coomans Danny H. , de Vel Olivier 
Published: September 2006

AbstractA major concern which arises from the classification of spectral data, such as near‐infrared (NIR) spectra, is that the number of variables often exceeds the number of cases. In this instance each spectrum represents a case or observation, and each variable corresponds to the wavelengths at which a response (e.g. reflectance) is measured. Classification refers to the process of assigning a spectrum whose class identity is unknown into one of several predefined classes. There are two main strategies for combating the high‐dimensional (i.e. more variables than cases) scenario. One strategy is to use a high‐dimensional classifier, that is, one which is suited to the ill‐posed nature of the data. The second strategy is to reduce the number of variables by a feature extraction method and supply the variables to a low‐dimensional classifier, one which is suited to high observation‐to‐variable ratios. This article presents two high‐dimensional classification methods – regularized discriminant analysis (RDA) and penalized discriminant analysis (PDA). The low‐dimensional classifiers used include Bayesian linear discriminant analysis (BLDA), Bayesian quadratic discriminant analysis (BQDA), RDA and flexible discriminant analysis (FDA). Common stepwise selection routines are employed to investigate the effectiveness of the wavelet transform as a feature extraction technique. This includes implementation of the local discriminant bases (LDBs) algorithm and the adaptive wavelet algorithm (AWA).
Emission Spectroscopy, Infrared
Authors: Keresztury Gábor 
Published: September 2006

AbstractInfrared emission spectroscopy (IRES) is a branch of experimental infrared (IR) spectroscopy that can be considered as an alternative to the more commonly used IR absorption or reflection techniques for observing vibrational transitions in molecular systems. While these methods provide spectral data that are similar regarding their information content (structural, analytical), IRES may have definite advantages (or drawbacks) depending on the object to be studied.This article aims at giving an up‐to‐date account of the theory, instrumentation and laboratory practice of IRES. Following an introduction to the principles and nature of thermal radiation, the governing laws of IRES are outlined and analyzed in some depth, with the aim of defining the conditions for obtaining analytically meaningful IR emission spectra. Spectral distortions concomitant with the measurement of condensed‐phase samples and other sources of error are pointed out along with the procedures devised for their elimination. Various methods of excitation of thermal radiation and the instrumentation most often used in laboratory measurements of IR emission spectra are described, with emphasis on modern Fourier transform (FT) techniques and with an outlook to special applications like remote sensing and process monitoring. Attention is given to data manipulation and presentation of emission spectra in relation to quantitative evaluation of spectral data. Recent advances in sample handling techniques, for example allowing the measurement of optically thick samples or thin surface layers, are also reviewed, while reference is given to the original sources of literature in the field.
Gas Chromatography/Infrared Spectroscopy
Authors: Le Quéré Jean‐Luc 
Published: September 2006

AbstractGas chromatography/infrared (GC/IR) spectroscopy coupling combines the separation power of high‐resolution gas chromatography (HRGC) to the highly specific identification technique, infrared (IR) spectroscopy, based on the absorption of IR radiation by the molecules. Relying on different molecular properties, IR is an excellent complement to mass spectrometry (MS) in structural analyses. For volatile compounds, the coupling of gas chromatography/mass spectrometry (GC/MS) has been the universal basic technique for a long time. The advantages of Fourier transform infrared spectrometry (FTIRS) allowed the coupling of gas chromatography (GC) to an FTIR (Fourier transform infrared) spectrometer, ending with a powerful tool, gas chromatography/Fourier transform infrared spectrometry (GC/FTIRS). The first device developed to interface a gas chromatograph to an FTIR spectrometer was a flow‐through gas cell, known as the light pipe (LP), delivering vapor‐phase IR spectra of eluting solutes. Two other cryogenic devices which allowed mobile‐phase elimination by trapping the compounds eluting from the GC at sub‐ambient temperature have been developed: the matrix isolation (MI) interface operating at 11 K and the direct deposition (DD) window operating at 77 K. Each of these three types of interface has advantages and drawbacks that are discussed in terms of sensitivity and specificity. Some selected applications in selected domains of analytical chemistry, i.e. environment, flavor and fragrances, pheromones and fatty acids, are presented and discussed again in terms of sensitivity and specificity according to the interface type used. Finally some concluding remarks on technique developments for GC/FTIRS and related techniques combining chromatography with IR spectroscopy are given.
Infrared Reflection–Absorption Spectroscopy
Authors: Hollins Peter 
Published: September 2006

Abstract

Infrared reflection–absorption spectroscopy (IRAS, IRRAS) is an optical technique used to study thin (often submonolayer) films adsorbed on reflective substrates such as metals. Experimentally, it involves measuring the change in the reflectance spectrum of the substrate that accompanies adsorption. In order to maximize sensitivity, the reflection is usually performed at grazing incidence. On metal surfaces, the process is subject to an overriding selection rule which states that only those vibrational modes that have a component of their dipole change perpendicular to the surface can be detected: application of this metal surface selection rule (MSSR) often yields important information about adsorption geometry. Other advantages of the technique include its high sensitivity (<10
−4
monolayers in favorable instances), its ability to operate under high ambient pressures where other primarily electron‐based surface spectroscopies cannot be utilized, and the ease with which its results can be correlated with those from other vibrational spectroscopies, both surface‐ and bulk‐sensitive. A significant current disadvantage is the difficulty in studying low‐wavenumber vibrations, but this is being overcome by the development of more intense far‐infrared sources. Various acronyms for the technique have been employed – IRAS, IRRAS and Reflection–Absorption Infrared Spectroscopy (RAIRS) have all enjoyed wide currency. The last of these is perhaps the most widely used and is the form advocated by the International Union of Pure and Applied Chemistry (IUPAC).1, 2 Accordingly, it will be adopted in this article.
Quantitative Analysis, Infrared
Authors: Cadet Frédéric , de la Guardia Miguel 
Published: September 2006

AbstractIn this article, after reviewing the different mathematical methods used in quantification we will describe and discuss their respective advantages and inconveniences. First of all, different examples of applications of infrared (IR) spectroscopy, used with or without other analytical chemistry methods, will be presented. Some examples of direct quantitative analysis in food analysis will be reviewed: lipids (measurement of unsaturation degrees, lipids determination), carbohydrates, proteins (secondary structures, quantitative analysis). We will also focus on original examples of the use of IR spectroscopy combined with enzymes.Secondly, some examples of Fourier transform infrared (FTIR) analysis coupled with other analytical methods are reviewed in the following fields: FTIR quantification in pharmaceuticals, petroleum, paints and other industrial products and in the fields of health, environment, and trace compounds analysis.Finally, we will discuss the limitations and perspectives of IR spectroscopy for quantitative analysis. It appears that the most significant developments in the field of quantitative analysis will most probably come through progress in chemometrics and flow analysis (FA) (automation).
Vibrational Spectroscopy for the Analysis of Geological and Inorganic Materials
Authors: Busca Guido , Resini Carlo 
Published: September 2006

Abstract
The vibrational spectroscopies are those producing the entire (or part) vibrational spectrum of a sample, i.e. the collection of transition energies between its vibrational states. The simplest way to cause vibrational excitation is to allow the chemical species in its vibrational ground state to absorb an energy quantum from electromagnetic radiation of an appropriate energy, i.e. in the medium infrared (IR) or in the far infrared (FIR) regions. Transmission–absorption IR spectroscopy comprises the analysis of the quanta that are actually absorbed by a polyatomic chemical species and those that are not absorbed (so are transmitted). Other IR techniques relate to the analysis of the radiation that is emitted, diffused, or reflected by the sample. Another way to obtain part or all of the vibrational spectrum of a chemical species is to look at the inelastic scattering of beams other than IR radiation. Raman spectrometry is the analysis of the ultraviolet (UV), visible or near infrared (NIR) radiation that is scattered inelastically by the sample. Inelastic neutron scattering (INS) is the analysis of the energy of formerly monochromatic neutron beams after inelastic scattering by the sample. Analyses of the number and energies of the vibrational transitions of the sample, detected by each technique, yield information on the geometric (molecular and crystallographic) structure of the sample and on the strength and nature of the chemical bonds it contains.
Biopolymer Chromatography
Authors: Huber Christian G. 
Published: September 2006

Abstract
Biopolymers are biological macromolecules including peptides, proteins, nucleic acids, and polysaccharides whose physical and chemical properties differ considerably from those of small molecules. Biopolymer chromatography is a branch of liquid chromatography which is adapted to the specific requirements of biopolymers in order to obtain rapid and high‐resolution chromatographic separations of these molecules. Because of the low diffusion coefficients of biopolymers, special stationary phase configurations and surface modifications are necessary to permit sufficiently fast mass transfer kinetics between the mobile and stationary phase. Exploiting different molecular properties of the biopolymers, such as size, charge, hydrophilicity, hydrophobicity, the ability to form complexes with metal ions, or biological function, the most popular liquid chromatographic modes for biopolymer separation are size‐exclusion, ion‐exchange, normal‐phase, reversed‐phase, ion‐pair reversed‐phase, metal‐interaction, and affinity chromatography.
Because of their large size and the multitude of different functional groups present in biopolymers, more than one mechanism may be responsible for interaction with the stationary phase, resulting in enhanced selectivity due to mixed‐mode interactions. Adsorption at multiple sites results in very steep elution isotherms as a function of the mobile phase solvent strength. Therefore, elution with a gradient of increasing solvent strength is usually applied in biopolymer chromatography. The choice of a suitable chromatographic environment is of special importance ifthe native confirmation of a biopolymer, which is essential for its biological activity, is to be preserved for subsequent experiments. Generally, conditions that come close to the physiological environment are most appropriate.
The most important detection techniques for biopolymers are ultraviolet/visible absorbance detection, fluorescence detection, electrochemical detection, mass spectrometry, and low‐angle laser light scattering photometry. Miniaturization and multidimensional separation together with mass spectrometric detection allow the routine separation and identification of femtomole–attomole amounts of hundreds to thousands of different biopolymers contained in complex mixtures of biological origin.
Ion Chromatography
Authors: Pietrzyk Donald J. 
Published: September 2006

Abstract
Ion chromatography (IC), which is an important methodology within high‐performance liquid chromatography (HPLC), is a chromatographic separation/detection strategy that is applied to the determination of inorganic and organic analyte anions and cations. The methodology consists of three main components: (1) a low‐capacity ion‐exchange column, where the separation occurs; (2) a suppressor system, which reduces conductivity due to the mobile phase electrolyte; and (3) a conductivity detector, which is used to detect the analyte ions. Anionic analytes are separated on an anion‐exchange column and analyte cations are separated on a cation‐exchange column. IC, which is routinely applied in water, environmental, health, and food analysis, is a rapid, sensitive, and accurate method for the trace determination of complex mixtures of analyte ions, particularly analyte anions, where no other method offers similar advantages and scope of application.
Today, the term IC defines a broader group of methodologies applicable to the separation of analyte ions and now also defines the following strategies. Nonsuppressed IC of analyte anions and cations is possible. In addition, analyte ions can be separated with an ion interaction reagent (ion pair reagent) as a mobile phase additive and a reversed stationary phase column rather than an ion‐exchange column; this is often called ion interaction chromatography (IIC). Ion exclusion chromatography (IEC), which is a separation of weakly dissociated acid and base analytes on an anion exchanger, is also an important methodology within the field of IC.