bluuebunny/crossref_metadata_2025 huggingface dataset:
Capillary Electrophoresis of Peptides
Authors: Oda Robert P. , Strausbauch Michael , Landers James P.
Published: September 2006

The ability to resolve effectively peptides obtained by chemical or proteolytic cleavage is important in the structural investigation of proteins, whether it be minute amounts of protein isolated from a biological source or protein produced recombinantly for pharmaceutical use. Capillary electrophoresis (CE) can be used rapidly to resolve peptides electrophoretically in free solution with a selectivity that differs from that of other separation approaches. In this article, we provide a description of the instrumentation for CE and the fundamental principles driving peptide separation at low and high pH. Guidelines for method optimization of peptide injection and separation by CE are given along with a number of examples from the literature demonstrating the utility of CE for interrogating protein structure via CE‐based peptide and glycopeptide analysis.
Chromatography of Membrane Proteins and Lipoproteins
Authors: Zolla Lello
Published: September 2006

The available methods for the separation of membrane proteins and lipoproteins are sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS/PAGE), followed by immunoblotting, isoelectric focusing (IEF), capillary electrophoresis (CE) and high‐performance liquid chromatography (HPLC). In this article it is shown that HPLC techniques, given their wide versatility, relative ease of use, and high resolution, may be considered the most valuable tool for the characterization of virtually any hydrophobic protein. Moreover, HPLC is not a destructive technique and therefore proteins, once separated, are available for further analytical investigations. Application examples are described and comparisons with other methods are discussed.
Posttranslational Oxidative Modifications of Proteins
Authors: Schöneich Christian , Barrón Lorena B.
Published: September 2006

Specific oxidative modifications of amino acids in proteins are used to monitor the exposure of biological tissue to oxidative stress. This article introduces the most prevalent oxidative amino acid modifications which have been characterized in vivo and summarizes the analytical methodology for their identification and quantification.
Protein–Drug Interactions
Authors: Oravcová Jana , Lindner Wolfgang
Published: September 2006

Noncovalent (reversible) drug–protein binding interactions are an integral part of intermolecular recognition processes taking place in a cell or organ environment. Characterization of basic constraints of target protein binding site(s) (affinity, stoichiometry, specificity, saturability and stereoselectivity) for particular ligand(s) is an essential output of many different drug–protein binding studies. Nonlinear and stereoselective binding phenomena, including drug–drug (or enantiomer–enantiomer) interactions and their e.g. genetically or pathophysiologically determined variability, can be predicted in this way. In general, the methods used for drug–protein binding studies can be divided into separation (nonspectroscopic) and spectroscopic methods. Separation methods are particularly suitable for the quantitative determination of drug binding, whereas spectroscopic techniques are able to characterize the qualitative features of drug–protein complexes (e.g. conformational status/changes). The primary objective was to summarize the most relevant trends in separation techniques [affinity high‐performance liquid chromatography (HPLC) and affinity capillary electrophoresis (ACE)] employed in the framework of drug–protein/biopolymer binding assays and to compare them with so‐called conventional approaches (equilibrium dialysis (ED), ultrafiltration). Focused attention has been paid particularly to HPLC and capillary electrophoresis (CE) methods designed for drug–protein studies when so‐called “dynamic” and “secondary” equilibria are involved and created. A common feature of this strategy is to use binding protein(s) or interacting drug(s) without their covalent immobilization as mobile phase or background electrolyte (BGE) (buffer) additives. This offered a new, elegant tool for the separation of “bound” and “free” forms of interacting species in a “miniaturized free solution system” operating under nearly physiological conditions. Undoubtedly, it permits simplification of the experimental protocols where it is crucial to perform repetitive analyses under “the same starting conditions”, as e.g. the occupancy of binding sites is concerned.
Protein–Oligonucleotide Interactions
Authors: Gabrielsen Odd Stokke , Matre Vilborg , Bergholtz Stine
Published: September 2006

The specific binding of a protein to a nucleic acid is a first step in several central processes in a living cell. Sequence‐specific protein–DNA interactions are crucial for the functional read‐out of genetic information. Sequence recognition is the result of a concerted action of many weak chemical interactions of different types between the protein and its DNA target, including nonspecific electrostatic interactions, hydrogen bonding and van der Waals contacts. The precise complementarity of shape between the two macromolecules facilitates specific chemical recognition to be established. The electrophoretic mobility shift assay (EMSA) and several variants of footprinting are simple electrophoretic methods developed to study protein–DNA interactions. Because the specificity is determined by the nucleic acid sequence, the same methods can be exploited for a wide range of proteins simply by changing the sequence of the nucleic acid. EMSA detects sequence‐specific DNA‐binding activity in a protein sample as a separate migrating band in a nondenaturating gel. A footprinting method provides more detailed information on the precise location of a bound protein along the DNA fragment through the removal of specific bands in a pattern of cleaved fragments separated by electrophoresis. Both methods are highly sensitive due to the use of radioactively labeled oligonucleotides and can be performed with protein samples of low purity. When combined these methods are capable of providing a picture of the protein–DNA complex with a great deal of molecular detail, surpassed only by the more demanding methods of crystallography and nuclear magnetic resonance (NMR).
Carbamate and Carbamoyloxime Insecticides: Single‐Class, Multiresidue Analysis of
Authors: Honing Maarten
Published: September 2006

Large quantities of modern pesticides such as theN‐methyl‐ and carbamoyloxime carbamates (over 1000 t of theN‐methylcarbamate carbaryl) are used for agricultural as well as for nonagricultural purposes. The European Union (EU)‐permitted concentration levels of these insecticides and their related transformation products in drinking water is 0.1 µg L−1, and the maximum for the total pesticide content has been set to 0.5 µg L−1. Many analytical procedures, focusing on sample pretreatment, column chromatographic separation, and sensitive detection, have been reported for the trace‐level determination of these compounds. This article surveys the application of these techniques, and their potential with regard to recovery, resolution, sensitivity, and robustness is discussed.

For example the reproducibility of results with a variety of carbamates from water samples or pretreated biological/soil samples is an essential criteria during the development of extraction procedures. The percentage of recovery influences the sensitivity of the total analytical method. Good results with solid‐phase extraction (SPE) are obtained with a C18/OH phase which is used on a routine basis by various analytical laboratories for the analysis of surface waters and vegetables. This technique is superior to liquid–liquid extraction (LLE) for reasons explained in this article. Chromatographic resolution is most effective, when gas chromatography (GC) is used. Unfortunately, thermal degradation of some carbamates in the injector takes place, making liquid chromatography (LC) the separation technique of choice despite the fact that some carbamates cannot now be separated. Capillary electrophoresis (CE) offers better separation efficiency but is still not a robust technique. Another way to solve the coelution problem is the application of mass spectrometry (MS). Utilizing the selected ion monitoring mode, coeluting compounds can be quantified. MS adds an extra separation step because ionized compounds are separated by the mass‐to‐charge ratio. Application of the ionspray (ISP) and the heated nebulizer (HN) interfacing techniques makes possible the quantification of carbamates at trace levels as low as 0.1 ng L−1in drinking water, without any sample preconcentration. Furthermore, MS also offers the ability to confirm the identity of the compounds. On‐line SPE in combination with liquid chromatography/mass spectrometry (LC/MS) or, better, liquid chromatography/tandem mass spectrometry (LC/MS/MS) is the best method for the quantification and structural confirmation of carbamate pesticides at concentration levels of 0.1 ng L−1or lower.
Gas Chromatography and Supercritical Fluid Chromatography with Selective Detection in Pesticide Analysis
Authors: Carrasco Pilar Bou , Bayona Josep M.
Published: September 2006

Pesticide determination by gas chromatography (GC) and supercritical fluid chromatography (SFC) techniques has been presented in this article. Instrumentation used in the different pesticide class analyses, such as injection (vaporizing, cold injection and large volume) and detection techniques (nitrogen–phosphorus detection, NPD; flame photometric detection, FPD; electron capture detection, ECD), and hyphenated systems (atomic emission detection, AED; mass spectrometry, MS; Fourier transform infrared, FTIR) used in GC and SFC determination of pesticides are presented. The figures of merit of each detection technique are outlined. Instrumental set‐ups which combine extraction and separation techniques are also presented. Stationary phases used in GC and the type of SFC columns used in the determination of pesticides are also reported. Finally, the application of recent GC developments in the determination of pesticides is mentioned.
Herbicides (New Generation): Imidazolinones, Aryloxyphenoxypropionic Acids/Esters, and Diphenylethers, Analysis of
Authors: Laganà Aldo
Published: September 2006

This article critically examines the existing methodologies including residue isolation and preconcentration, cleanup, chromatographic analysis, such as gas chromatography (GC), high‐performance liquid chromatography (HPLC), hyphenated techniques, such as gas chromatography/mass spectrometry (GC/MS) and high‐performance liquid chromatography/mass spectrometry (HPLC/MS), and some nonchromatographic techniques, such as immunoassay (IA), of herbicide residues in crops, food, and environmental samples. The main structural groups of herbicides discussed are imidazolinones (IMIs), aryloxyphenoxy propionic acids/esters, and diphenyl ethers (DPhEs).
s
‐Triazine Herbicides and Their Transformation Products, Multi‐Residue Analysis of
Authors: Crescenzi Carlo
Published: September 2006

Triazine herbicides and some of their transformation products (TPs) are included in both the European Communities and United States Environmental Protection Agency (USEPA) priority list of pesticides. Owing to their widespread use and toxicity profile this family of herbicides is one of the classes of chemical pollutants that are more intensively monitored by water authorities. Many analytical methods for their determination have been published. A critical overview of these methods is presented in this paper. Conventional extraction techniques are generally nonselective and can lead to analytical interferences caused by coextracted components present in the environmental matrices. Parameters affecting extraction and problems in isolating s‐triazines, from water, soil, urine and food are discussed. The solid phase is particularly attractive because it may be coupled on‐line with chromatographic systems. Many extraction systems, in sorbent cartridge or disk format, have been developed in the last few years. Recently, interest has been growing in employing new highly selective materials such as molecularly imprinted polymers (MIPs) and immunosorbents to extract triazines from complex matrices. Strong cationic exchangers allow an effective clean‐up and are useful to improve the sensitivity of a method. Solid‐phase microextraction (SPME) is a new technique that can also be used for extracting analytes from water. This technique was successfully automated and coupled with liquid chromatography (LC). For solid matrices Soxhlet extraction is still widely used. Blending the sample in the presence of the solvent in high‐speed homogenizer machines or in an ultrasonic bath ensures complete sample disruption and a better extraction of pesticides. Microwave‐assisted solvent extraction, supercritical fluid extraction (SFE) and accelerated solvent extraction (ASE) are alternatives for conventional extraction procedures.

Both, gas chromatography (GC) and LC were successfully coupled with sensitive and selective detectors, but because of the legal implications, the analytical methods need sufficient specificity for testifying contamination. It has been recommended that analytical results indicating the presence of relevant concentrations should be confirmed by mass spectrometric methods. The use of chromatography with mass spectrometric detector and the most common interfaces (thermospray (TSP), electrospray (ES) and atmospheric pressure chemical ionization (APCI)) are illustrated. Rapid screening based on immunoassay and biosensor technologies are described. Finally some examples of recent applications are summarized.
Hydrocarbons: Gas Chromatography Procedures for On‐Line and Off‐Line Analysis
Authors: Klawun Christoph
Published: September 2006

The analysis of hydrocarbon mixtures originating from mineral oil sources using gas chromatography (GC) is compiled in this article and a general overview of GC and detectors, including hyphenated instrumentation, is given. The advantages and limitations of GC, as well as multidimensional GC are described in more detail from a standpoint of process GC, and the historical development of chromatography is put into perspective. Comprehensive tables of target analytes and methods offer access to all standard methods published by the American Society for Testing and Materials (ASTM) for hydrocarbon analysis with GC. Based on these tables, several subtopics are covered: gaseous and liquid hydrocarbons, heteroatom analysis, comprehensive and impurity analysis, natural gases, gasoline and fuel production, polymer feedstocks, hyphenated techniques, and bulk properties.
Metals, Nitrogen and Sulfur in Petroleum Residue, Analysis of
Authors: Robbins W.K.
Published: September 2006

When petroleum (i.e. crude oil) is distilled, a residual fraction containing molecules that do not volatilize is drawn off the bottom. This “resid” has an increased concentration of minor impurities, including sulfur‐, nitrogen‐, and oxygen‐bearing heterocyclics, soluble nickel and vanadium compounds and a variety of trace metals. These impurities both dominate the unique properties of the resid and play a major role in determining the refining processes necessary for its conversion to marketable products. This article introduces the common analytical techniques for the measurement of sulfur, nitrogen, nickel, vanadium, and trace metals in this challenging organic matrix.
Refractive Index Technology as a Real Time Viscosity Technique
Authors: Groetsch John G.
Published: September 2006

This article discusses productivity enhancement which involves using an on‐line digital process refractometer to determine the viscosity index (VI) of lube oil stocks. Since lube oils are Newtonian fluids, refractive index (RI) can be related to VI. A real‐time continuous measurement of the RI has eliminated sampling, improved product consistency, reduced waste and has helped to optimize the process.
Eluent Additives and the Optimization of High‐Performance Liquid Chromatography Procedures
Authors: Gilpin R.K. , Dudones L.P.
Published: September 2006

High‐performance liquid chromatography (HPLC) is one of several separation techniques that are based on the differential migration of an analyte (solute) through a fixed medium as the result of a driving force, the eluent. In the case of HPLC, the eluent is typically either a binary or ternary mixture of solvents and the stationary phase is most often a porous adsorbent or a chemically bonded phase attached to a porous substrate. The rate of migration of an individual solute and the separation between groups of solutes are governed by their interactions with the stationary phase. Thus, the optimization of an HPLC method involves the selection/adjustment of the physical and chemical parameters which control the rate of migration of the solute in such a fashion that baseline resolution is obtained between it and other co‐analytes or interfering compounds within the mixture. In doing this, given a series of closely related compounds, it is important to identify structural differences between solutes and to maximize the interactions with the stationary phase arising from them. This article considers the important physical and chemical aspects of the solute, eluent, and stationary phase in terms of chemical equilibria, solute structure, eluent conditions, operational parameters, and nonideal effects. Likewise, as several approaches may lead to acceptable analytical separations, other performance criteria such as simplicity, reliability, speed, and cost also are discussed in terms of arriving at the optimal method.
Mass Spectrometry in Pharmaceutical Analysis
Authors: Goodlett David R. , Gale David C. , Guiles Stacey , Crowther Jonathan B.
Published: September 2006

Mass spectrometry (MS) applied to the biological sciences in the pharmaceutical industry covers a broad range of application topics, such as quantitative analysis of drugs in physiological fluids, qualitative analysis of noncovalent complexes, structural analysis to determine chirality and protein sequence analysis. Regardless of the application, electrospray ionization (ESI) is the primary ionization method for transfer of nonvolatile biologics like proteins and peptides into the gas phase for analysis. It is most often used as an interface between high‐performance liquid chromatography (HPLC) separation methods and MS. The ESI process converts analytes in solution to ions in the gas phase via electrostatic nebulization at atmospheric pressure. It is characteristic of ESI to produce multiply charged analytes in a concentration‐dependent manner that is sensitive to changes in solvent, pH and ionic strength. A high voltage is applied to a liquid containing analytes as they traverse a capillary, and when the liquid droplets exit this capillary at atmospheric pressure they are directed into the source region of a mass spectrometer where desolvation is completed. Ions are then focused by an electronic gradient across a series of lenses and separated by mass/charge (m/z) using various mass spectrometer designs. Currently, the two most popular mass separation devices are quadrupoles (either single or triple quadrupole (TQ)) and ion traps (ITs). Both types of mass spectrometers are used with ESI to achieve sensitivities as low as attomoles (10−18 mol) of analyte injected onto a microcapillary HPLC column. The type of analyte, as long as it is capable of accepting a charge (addition of H+or loss of charge in negative ion mode) is relatively transparent to ESI and so a diverse range of analyte classes with disparate molecular weights can be ionized, from peptides (500–5000 amu) to proteins (10 000–100 000 amu). Depending on the construction of the source, ESI can be carried out with reversed‐phase HPLC at flow rates from 200 nL min−1to 2 mL min−1and also with capillary electrophoresis. The ease of use of ESI compared to prior techniques like fast atom bombardment has made it very popular with biologists, chromatographers and chemists who might not otherwise have been interested in MS. In fact, for many scientists ESI has made MS almost as “user‐friendly” and thus accessible as an ultraviolet (UV)–visible detector for HPLC.
Vitamins: Fat and Water Soluble, Analysis of
Authors: Bates Christopher J.
Published: September 2006

The vitamins are a diverse group of compounds, both chemically and analytically, because they comprise a range of biomolecules whose common properties reside solely in the fact that they are essential dietary components, which are needed in relatively small amounts to sustain life and good health. In addition, the major analytical challenges that they present are derived from the facts that (1) there is a need to quantitate them in a wide range of biological matrices, which include both foods and body fluids (for status indices); (2) the concentrations that are present are usually very low, and the ratio to other components, which can be chemically very similar, is small; (3) they may be present in several or many chemically diverse, but biologically interconvertible, forms; (4) some of them are labile to heat, extremes of pH, degradative enzymes and so on and (5) there is no single analytical approach that can quantitate all of them together, within a biological matrix.

They have been divided, broadly, into fat‐ and water‐soluble groups, and each of these has been further subdivided, mainly on a functional basis. Historically, the B‐group vitamins were measured by various microbiological assays, and the others were measured (if at all) by semispecific colorimetric assays. Nowadays, there are several more‐powerful techniques available, which include high‐pressure liquid chromatography, with a range of detectors operating over a continuous range of selective modalities; radioimmunoassay (RIA) and enzyme‐linked immunosorbent assay (ELISA)‐based techniques, which use specific protein‐binding selectivities; enzyme reactivation techniques for certain B‐vitamin status assays, and so on. The use of mass spectrometry (MS) is gainingground and can be combined with several other separation techniques, such as gas–liquid chromatography (GLC), capillary electrophoresis (CE) and so on. Measurement of vitamins in simple pharmaceutical mixtures (vitamin supplements etc.) is now reasonably straightforward.

The technical advances that these methodologies represent have greatly broadened the horizons of the vitamin analyst, and have permitted even some of the more difficult biological matrices to be addressed. However, the unsolved challenges of accurate vitamin analysis show little sign of receding, and there are very few, if any, laboratories worldwide that are currently able to measure all of the known vitamins in all known biological matrices. This remains a major challenge and a goal for the twenty‐first century.
Inverse Gas Chromatography in Analysis of Polymers
Authors: Guillet James , Al‐Saigh Zeki Y.
Published: September 2006

This article describes the application of inverse gas chromatography (IGC) to the study of synthetic and natural polymers. The word “inverse” is used to indicate that the component of interest is the stationary phase, either as a finely divided powder or coating, dispersed on a suitable inert support and packed into a chromatographic column. The time required for a probe molecule to pass through the column gives a measure of the molecular interactions between the probe and the polymer which can be quantified with the help of chromatographic theory. Historically, most thermodynamic studies on polymers were carried out in dilute solution, but IGC provides information on condensed phases under conditions much more similar to those under which polymers are actually used.

Using this technique, melting, glass and other solid‐phase transitions can be studied and quantified. Degrees of crystallinity can be determined in an unambiguous procedure without calibration by other methods. Solubility, permeability and diffusion constants can be determined for probe molecules. IGC is also used extensively in determining the permeability of additives such as antioxidants in polymers, as well as thermodynamic quantities such as activity coefficients, heats of solution, Flory–Huggins interaction parameters (χ), and solubility parameters. Surface areas can be measured at any desired temperature by the determination of the adsorption isotherms of suitable probes. Measurements on polymer blends can yield important information on polymer–polymer interactions and can be used to predict the compatibility of the components over a wide range of temperatures. The use of finite concentration IGC provides a rapid method of determining the density of crosslinks in rubber‐like polymers.

Almost any commercial gas chromatograph can be easily modified to carry out IGC experiments by procedures described in this report. The method provides a wealth of information of both fundamental and practical importance in the study of polymeric materials.
Neutron Scattering in Analysis of Polymers and Rubbers
Authors: Bucknall D.G.
Published: September 2006

The neutron is in many ways an ideal probe for the investigation of the structure and dynamics of materials. Elastically scattered neutrons can be used to determine the structure of the sample from the atomic to macromolecular length scales, whilst dynamic information describing the vibration, rotation and translation of these molecules is obtained from inelastically scattered neutrons. The use of isotopic substitution provides an easy route to highlighting whole or parts of a molecule in the neutron scattering experiment. Isotopic labeling has been extensively used in polymer studies owing to the large difference between hydrogen and deuterium. The combined use of neutrons often with isotopic labeling schemes has provided a wealth of detailed information about polymer materials, which could not be derived so easily by other methods.
Positron Annihilation Spectroscopy of Polymers and Rubbers
Authors: Bartoš Josef
Published: September 2006

Positron annihilation spectroscopy (PAS) is a common name for a set of techniques based on measurements and analysis of the annihilation characteristics of a positron e+and its bound form with an electron e−, so‐called positronium (e+e−) ≡ Ps. PAS includes three basic techniques:

Positron annihilation lifetime spectroscopy (PALS)

Angular correlation of annihilation radiation (ACAR)

Doppler broadening spectroscopy (DBS).

These techniques measure the time of emission, energies and momenta of positron–electron annihilation photons, respectively. PALS measures positron and positronium lifetimes and their relative intensities, giving information about the structural–physical properties of condensed materials such as metals, ceramics and polymers, while ACAR and DBS provide information about the electron momentum and energy distribution in a material. The first technique is the most developed and it serves to characterize the microstructural features of the disordered phase of condensed matter, such as defects or free‐volume holes.
Size‐Exclusion Chromatography of Polymers
Authors: Trathnigg Bernd
Published: September 2006

Size‐exclusion chromatography (SEC) is a standard technique for determining molar mass averages and molar mass distributions (MMDs) of polymers. Sometimes the termsgel permeation chromatography (GPC) or gel filtration chromatography (GFC) are also used, but SEC should be preferred, because this term describes the mechanism much better: polymer molecules are separated according to their hydrodynamic volumes (which can be correlated with molar mass), with the larger size molecules exiting first followed by the smaller. Molar masses are determined either from a calibration or using molar mass sensitive detectors. In the case of copolymers, the knowledge of chemical composition along the MMD is required, which can be obtained from combinations of different concentration detectors. As the hydrodynamic volumes of different polymers are typically somewhat different, molecules with different chemical composition and different molar mass will be eluted in the same slice of the chromatogram. Obviously, a discrimination between such molecules requires a two‐dimensional separation, in which one dimension may be SEC, and the other one a chromatographic technique, which separates according to chemical composition rather than molar mass, such as liquid adsorption chromatography (LAC), liquid chromatography at the critical point of adsorption (often also called liquid chromatography under critical conditions, LCCC), supercritical fluid chromatography (SFC), temperature rising elution fractionation (TREF), etc.

In the lower molar mass range, mass spectroscopy competes with SEC. The most frequently used technique is matrix‐assisted laser desorption/ionization time‐of‐flight mass spectroscopy (MALDI/TOF/MS), which cannot, however, provide quantitatively accurate MMDs. Due to its excellent resolution in molar mass, it can be combined with chromatographic techniques in order to increase the reliability of the analysis.
Supercritical Fluid Chromatography of Polymers
Authors: Ute Koichi
Published: September 2006

The mobile phase in supercritical fluid chromatography (SFC) is a substance raised above its critical temperature and pressure which exhibits greater solvating properties together with reduced viscosities and higher diffusivities than its liquid state. The eluting power of supercritical mobile phase can be varied widely by controlling pressure, temperature and composition. Thus, SFC offers many advantages over high‐performance liquid chromatography (HPLC) in the characterization of polymers and oligomers. SFC of polymeric substances has been operated so far in the three modes of chromatography: adsorption chromatography for the separation of oligomer homologs, size‐exclusion chromatography (SEC) for the determination of molecular weight distribution, and adsorption chromatography at critical conditions for the characterization of functionality type distribution. The combination of SFC with supercritical fluid extraction (SFE) is useful for the analysis of polymer additives, such as stabilizers and plasticizers, in an industrial polymer material. SFC is compatible with most conventional HPLC and gas chromatography (GC) detectors, and can also be interfaced with infrared (IR) spectroscopy and mass spectrometry (MS), etc.
Thermogravimetry of Polymers
Authors: Price Duncan M. , Hourston Douglas J. , Dumont Fabrice
Published: September 2006

Thermogravimetry (TG) is the study of the relationship between a sample's mass and its temperature. It can be used to study any physical (such as evaporation) or chemical process (such as thermal degradation) that causes a material to lose volatile gases. Polymers have different thermal stabilities and thus the qualitative “fingerprint” afforded by TG in terms of temperature range, extent and kinetics of decomposition provides a rapid means to distinguish one polymer from another using only milligram quantities of material. Experiments are most commonly carried out under conditions where the temperature is increased in a linear fashion with time or the sample is held isothermally at an elevated temperature, although more sophisticated temperature profiles are occasionally used for compositional and kinetic analysis. Processes which do not result in a change in sample mass are not detected by TG. Therefore simultaneous measurements by differential scanning calorimetry (DSC) are useful. Volatile decomposition products may be detected and identified (e.g. by infrared (IR) spectrometry or mass spectrometry (MS)) in order to elucidate the mechanism of mass changes. TG is used for quantitative compositional analysis of polymers, lifetime prediction and kinetic studies, making the technique invaluable in all stages of polymer development, fabrication and component testing.
Flow and Sequential Injection Analysis Techniques in Process Analysis
Authors: Aldstadt Joseph H. , Olson Don C. , Wolcott Duane K. , Marshall Graham D. , Stieg Scott W.
Published: September 2006

The principles of flow injection analysis (FIA) and sequential injection analysis (SIA) are described as applied to industrial process monitoring. A brief history is followed by an overview of the fundamentals of FIA and SIA, with emphasis on injection methods and membrane‐assisted sample processing approaches. A discussion of the design of process instruments focuses on simplicity, maintainability, and software development. Hardware issues affecting autosamplers, fittings, pumps, and valves are also discussed. Issues affecting method development, quality control, and method validation are examined using specific examples from the chlor‐alkali and phosphate rock industries. The design and operation of on‐line sample interfaces is then described in detail. Applications in the major industrial areas are used as examples – chemical, biotechnology, manufacturing, and environmental. Finally, strengths and weaknesses are delineated and prospects for the future are presented.
Infrared Spectroscopy in Process Analysis
Authors: Coates John P. , Shelley Paul H.
Published: September 2006

Infrared (IR) instruments have been in use as important measurement and analysis tools for process monitoring and production control for more than half a century. They range in complexity from the simplest filter‐based photometers to opto‐mechanically complicated devices, such as Fourier transform infrared (FTIR) instruments. Simple nondispersive infrared (NDIR) instruments are in common use for systems where one to a few main analytes are involved. For more complex measurement situations it is necessary to record more spectral information, and often full‐spectral analyzers are used. Of the main analytical instrument techniques, IR analysis is the most versatile, where all physical forms of a sample may be considered – gas, liquids, solids and mixed phase materials. A wide range of sample handling options exists, and many of these may be adapted to either near‐line/at‐line production control or on‐line process monitoring applications. Instrumentation used within a manufacturing environment usually requires special packaging to protect the instrument from the environment, and to protect the operating environment from the instrument. This places special constraints on the way that an instrument is designed and the way that it performs. Often, it is necessary to utilize special technologies, normally not required for laboratory instruments, to meet the performance objectives. For most practical installations within a production environment it is a normal requirement for the final instrument to comply with local manufacturing and electrical safety codes. The range of applications of IR spectroscopy is extremely broad and the technique can play an important role in virtually all industries for manufacturing quality and production control, and for environmental monitoring.
Near‐Infrared Spectroscopy in Process Analysis
Authors: Goldman Don S.
Published: September 2006

Near infrared (NIR) is a spectroscopic method based upon the absorption of light in the wavelength region between 700 nm and 2500 nm due to vibrations of molecular functional groups in the sample. These spectral features arise from overtones and combinations of the fundamental molecular vibrations of these groups that occur in the infrared (IR) at longer wavelengths. NIR is rich with features arising from vibrations of CH, OH and NH.

NIR spectra are acquired by determining the absorbance, A, of light over a continuous range of wavelengths in spectrophotometers or at several specific wavelengths in fixed‐filter photometers. Absorbance is defined by Equation (1):

where I is the signal from the sample relative to the signal from a reference, I

o

. The reference can be an empty transmission sample cell for liquids, or it can be a broadband spectral reflector, such as a white ceramic, for reflectance measurements of solids.

Absorbance is usually linearly related to concentration, following Beer's Law (Equation 2):

where ɛ represents the molar extinction coefficient and C is the concentration of the species, and l is the optical pathlength of light through the sample. For a particular species and fixed experimental set‐up, ɛ and l are constants. Letting a constant, k = (ɛl)
−1
, then (Equation 3):

A principal advantage of process NIR over IR is the ability to use fiber optics to transmit light between the instrument and the sample over considerable distance. This permits the instrument, a potential source of ignition, to be placed in safe areas where no flammable vapors exist. Only the fiber optic probe in contact with the sample and the optical fibers that connect to the instrument need be placed in the hazardous location. A disadvantage of process NIR is the characteristics of the spectra, which are typically comprised of broad, overlapping peaks in comparison to IR spectra. This often requires the use of sophisticated data analysis methods that place additional demands upon vendors to provide stable NIR instruments and upon manufacturers to have highly‐trained staff, often at the PhD level, for calibration model development, implementation and maintenance.
X‐ray Photoelectron Spectroscopy, Paper Surface Analysis By
Authors: Pamidimukkala Krishna M.
Published: September 2006

X‐ray photoelectron spectroscopy (XPS) also popularly known as electron spectroscopy for chemical analysis (ESCA) involves the irradiation of a solid surface in ultrahigh vacuum with monoenergetic soft X‐rays. The X‐rays cause electrons of an atom to be ejected and to be ionized as photoelectrons. The number of electrons and their kinetic energies are then measured. The energy of the emitted electron is very characteristic of the atom from which the electron originated and its environment. The XPS spectrum is a plot of the number of emitted electrons per energy interval versus their binding energies. Quantitation can be achieved either by fundamental parameter calculation or comparison with appropriate standards. In the pulp and paper industry, XPS has successfully been used to study migration of binder in coated paper, the surface chemistry of pulps and its effect on the properties of the final products; the adhesion between paper and polymer, toner or ink; and the chemical additives on the paper surface.

As with most analytical instrumentation, XPS has its limitations and disadvantages and is often used in conjunction with other, complementary techniques such as SIMS (secondary ion mass spectrometry) and FTIR (Fourier transform infrared) spectroscopy for the identification of organic compounds on paper surfaces. XPS is surface sensitive which renders it useless if the underlying cause of the problem might be other than surface related. XPS provides only semiquantitative information. A more precise quantification of the elements is possible, but requires exhaustive calibration.
Elevation Modeling and Displacement Mapping using Radar Interferometry
Authors: Massonnet Didier
Published: September 2006

Topographic modeling consists of producing a digital description of the relief of a given area. This description is generally given on a regular grid in two coordinates. The product consists of the value of the altitude of the terrain for each position of the grid, with respect to a reference shape such as an ellipsoid (approximation of the shape of the Earth) or the geoid (shape of the potential of gravity at sea level). The grid itself is defined in a cartographic or a geographic coordinate system. Common systems include the Universal Transverse Mercator (UTM), Lambert or, alternatively, coordinates in latitude/longitude. Topographic data are used in a variety of applications, from the correction of geometric distortion in remote sensing images to the prediction of the volume of materials to be removed in public works. Their applications include military uses, such as collision avoidance for low‐flying aircraft or missiles, or civilian ones, such as optimal positioning of transmitters to cover an area for mobile communications. Radar interferometry is a promising technique for producing topographic maps on a large scale. It makes use of the very peculiar features of the images produced by synthetic aperture radar (SAR) instruments placed on board satellites. Used in differential mode, this technique can also produce a unique product: the map of the displacements which occur in a given area between two passes by a radar satellite. Again, the data can be organized as a digital file placed on a grid similar to the ones used for topographic mapping. However, in the case of displacement measurement, the useful piece of data placed on each node is the displacement experienced by the node, expressed in appropriate units of length. As for each new technique, there are a number of points to take care of before interpreting the data. The purpose of this article is to describe the radar data, both historically and technically, and to detail their two main applications in topography and displacement mapping. The main issues of the interpretation and the availability of the data are covered. Finally, we compare the performance of radar interferometry with other techniques, in both domains, and we try to outline its future.
Global Land Databases for Environmental Analyses
Authors: Loveland Thomas R.
Published: September 2006

Global land databases present the area, spatial extent, location, and patterns of land characteristics. Land cover, the natural and artificial materials on the land surface, is the most widely available and used land data theme, but soils and elevation global databases are also found. These land data sets are key inputs to many global and regional environmental models and provide a means to parameterize key landscape processes used in studies of climate and meteorology, atmospheric chemistry, ecological dynamics, hydrology, and resource management.
Metal Analysis, Sampling and Sample Preparation in
Authors: Deak Charles K.
Published: September 2006

This article deals with sampling and sample preparation for the chemical analysis of metals. It discusses the types of samples, their definitions, purposes, and requirements. Sampling of various types, shapes, and forms of metals ranging from liquid molten steel to scrap metals is described, along with ways of rendering a sample homogeneous. The various methods of making a sample suitable for the required analytical procedures are explained in the sample preparation section. This section discusses melting of samples in various types of laboratory melting furnaces and machining samples for use in all types of determinations using various techniques such as optical emission spectroscopy (OES), X‐ray fluorescence spectroscopy (XRF), atomic spectroscopy, thermal analyses, wet chemistry and so on. Discussion also centers around dissolving and fusing samples to convert them into a solution which is required by wet chemical, atomic spectroscopy, and other procedures.

Sampling and analysis of fasteners (regulated in the United States), and instances in which the sample or the analysis is or may be involved in litigation are also included.
Proximal Probe Techniques
Authors: Wiesendanger Roland
Published: September 2006

Proximal probe techniques are based on sharp tips which are brought within a small distance of a sample to be investigated by means of a stepper motor. The various interactions of these probe tips with the sample, which might be of mechanical, electrical, magnetic, optical or thermal origin, can be used to probe the sample's properties locally and to control the separation between tip and sample surface.

If the distance dependence of a particular type of interaction is strong, the distance control based on that interaction is very sensitive to small changes in tip–sample separation. By scanning the probe tip over the sample surface while keeping the interaction strength constant using a feedback loop, the surface contours can be followed by the tip with high accuracy. By monitoring the vertical position of the tip as a function of the lateral position, a three‐dimensional image of the sample surface is obtained. The motion of the tip both laterally and vertically with respect to the sample surface can be realized with subatomic accuracy by means of piezoelectric drives.

In contrast to electron microscopy and vacuum‐based surface analytical methods, proximal probe techniques can be operated in air and in liquids in addition to in vacuum. Therefore, proximal probe techniques offer great potential for investigations of solid–liquid interfaces or for in vivo investigations of biological specimens. Furthermore, proximal probe techniques can be operated in a wide temperature range (from millikelvin up to more than a 1000 K) and under extreme conditions (e.g. in high magnetic fields or high‐pressure conditions). The most attractive feature of proximal probe techniques is, however, that they combine ultrahigh spatial resolution (down to the atomic scale) with high‐resolution spectroscopic measurements so that detailed information about the physical, chemical or biological state of the sample can be extracted. Limiting factors are the finite size and often ill‐defined state of the probe tips and the limited information depth of proximal probe techniques. It has also found to be difficult to identify elemental species based solely on proximal probe measurements although chemical‐selective imaging even down to the atomic scale is nowadays routinely achieved.
Inductively Coupled Plasma/Optical Emission Spectrometry
Authors: Hou Xiandeng , Jones Bradley T.
Published: September 2006

Inductively coupled plasma/optical emission spectrometry (ICP/OES) is a powerful tool for the determination of metals in a variety of different sample matrices. With this technique, liquid samples are injected into a radiofrequency (RF)‐induced argon plasma using one of a variety of nebulizers or sample introduction techniques. The sample mist reaching the plasma is quickly dried, vaporized, and energized through collisional excitation at high temperature. The atomic emission emanating from the plasma is viewed in either a radial or axial configuration, collected with a lens or mirror, and imaged onto the entrance slit of a wavelength selection device. Single element measurements can be performed cost‐effectively with a simple monochromator/photomultiplier tube (PMT) combination, and simultaneous multielement determinations are performed for up to 70 elements with the combination of a polychromator and an array detector. The analytical performance of such systems is competitive with most other inorganic analysis techniques, especially with regards to sample throughput and sensitivity.
Soft Modeling of Analytical Data
Authors: de Juan A. , Casassas E. , Tauler R.
Published: September 2006

In this contribution different methods for soft modeling data analysis are reviewed. Soft modeling approaches attempt the description of a system without the need of an a priori model postulation, physical and/or chemical. The goal of these methods is the explanation of data variance using the minimal or softer assumptions about data. Most of these soft modeling approaches are based on factor analysis (FA) decompositions of experimental data matrices. These decompositions are done by pure mathematical means and allow the identification of the number of data variance sources, their qualitative and, eventually, quantitative estimation. Results of soft modeling data analysis are useful to validate hard modeling results and also for investigation of complex chemical systems. In this contribution, the soft modeling data analysis methods described can be applied to one data matrix or to several data matrices (three‐way data sets). The purpose of these methods are mainly exploratory analysis and resolution of mixture data sets. Within the lattergroup, special attention is devoted to multivariate curve resolution (MCR) techniques and their extension to three‐way data analysis. Three examples of application are given covering the chromatographic coelution of mixtures of pesticides using liquid chromatography/diode‐array detection (LC/DAD), the infrared (IR) spectral data analysis from multiple runs of an industrial process and the interpretation of thermodynamic and conformational transitions of polynucleotides using spectrometric titrations.