bluuebunny/crossref_metadata_2025 huggingface dataset:
Gas Chromatography/Mass Spectrometry
Authors: Palmer Peter T.
Published: September 2006

Gas chromatography/mass spectrometry (GC/MS) is perhaps the most widely used analytical technique for the analysis of complex mixtures. The power of this technique stems from the “marriage” of two powerful techniques into a hyphenated method. Gas chromatography (GC) is used to separate the components of a mixture based on their differing affinities for the stationary phase on the column. Mass spectrometry (MS) serves not only to detect and quantify the various species eluting off the column but also provides definitive information as to their identity. The most common GC/MS instruments employ a gas chromatograph with a split/splitless injector, capillary column, and either a quadrupole or quadrupole ion trap as a mass analyzer. A high degree of automation and a powerful data system are required for handling the large amounts of three‐dimensional (3‐D) data (time, mass‐to‐charge ratio, and intensity) that can be generated. The technique typically requires that the analytes in question have sufficient volatility to be amenable to GC. It is very sensitive, with detection limits typically in the picogram or even sub‐picogram range. It can be highly selective and allows for incredible flexibility with respect to the type and quality of the mass spectral data; the user may choose from a number of ionization modes and scan modes, and control mass range and mass resolution, and many other experimental parameters. Analysis speeds are relatively slow due to the time required for adequate chromatographic separation, but can be reduced to an order of a few minutes using fast GC techniques. GC/MS instrumentation is usually intended for benchtop operation in the laboratory, although a number of field‐portable instruments have been developed. The technique requires significant user expertise, knowledge of various means for compound identification and quantitation, and instrument tuning, maintenance, and upkeep.
High‐Resolution Mass Spectrometry and Its Applications
Authors: Jennings Keith R.
Published: September 2006

With the exception of the
12
C isotope of carbon which has a mass arbitrarily set equal to exactly 12 Da, all isotopes have unique nonintegral masses. The elemental composition of a sample can therefore often be inferred from an accurate measurement of the relative molecular mass of the sample. This requires that the mass resolving power (RP) of the instrument in use must be sufficiently high for the peak on which the mass measurement is based to be resolved from peaks arising from other components of closely similar mass. For samples of relative molecular mass below 500, an RP of 20 000 is often adequate, but for samples such as peptides and proteins an RP of several hundred thousand is often required.

The modes of operation, strengths and weaknesses of the several different types of mass analyzer currently available for the production of mass spectra of sufficiently high resolution are reviewed. Particular emphasis is placed on the use of mass spectrometry in the detection and identification of samples of biological origin for which its high sensitivity and specificity of information provided are of great importance. This article concludes with a brief review of the uses of high‐resolution mass spectrometry, in which the difficulties encountered in working with samples of very high relative molecular mass are discussed and an account is presented of the information to be gained from time‐dependent studies of H/D interchange at high resolution.
Inorganic Substances, Mass Spectrometric in the Analysis of
Authors: Taylor Howard E.
Published: September 2006

Mass spectrometry is an analytical technique used to measure the composition of a substance by isolating specific analyte components according to their individual atomic or molecular mass‐to‐charge ratios. Inorganic mass spectrometry is specifically used to determine the elemental and isotopic composition of the material being analyzed. The techniques are capable of the measurement of a range of concentrations from major components to ultratrace constituents.

Several instrumental approaches are used to separate and measure the abundance of component ions formed from the sample. These techniques include electron ionization mass spectrometry (EIMS), inductively coupled plasma mass spectrometry (ICPMS), thermal ionization mass spectrometry (TIMS) and spark source mass spectrometry (SSMS). These techniques utilize a variety of mass spectrometers including ion trap, quadrupole, magnetic sector and time‐of‐flight mass analyzers, depending on the type of sample being analyzed and the desired quality of the results. Often sample introduction techniques can be utilized to enhance the capabilities for solving specific analytical chemistry problems.
Literature of Mass Spectrometry
Authors: Down Stephen
Published: September 2006

The mass spectrometry (MS) literature is one of the major sources available for keeping up to date with new developments in the technique. There are different ways of reporting and presenting MS information, such as journals, abstracts and books, and several different means of distribution, including printed, diskette, CD‐ROM and the Internet.
Secondary Ion Mass Spectrometry as Related to Surface Analysis
Authors: Hanton Scott D. , Cornelio Clark Paula A.
Published: September 2006

Many important processes such as catalysis, corrosion, and adhesion depend on the elemental and molecular composition of the surface or interfacial region. The focus of this article is specifically surface applications of secondary ion mass spectrometry (SIMS). Conceptually, SIMS is a very simple technique consisting of a primary ion bombardment step, an energy transfer step, a particle desorption step, and an ion detection step. SIMS experiments are carried out in either a dynamic or a static mode. The two modes are distinguished on the basis of ion dose. Dynamic SIMS uses high primary ion beam doses and is generally used for elemental depth profiling. Static SIMS uses low primary ion beam doses (≤1 × 10
12
ions cm
−2
) and is generally used for the chemical characterization of surfaces. The major advantages of SIMS include high sensitivity (parts per million detection limits for some elements), the ability to obtain molecular information, isotopic analysis, lateral characterization (imaging), and analysis of low‐atomic‐number elements such as H and Li. These characteristics combine to make SIMS a very powerful analytical tool. The key disadvantages of SIMS are that the instrumentation is relatively expensive and that the data can be complex. Related analytical techniques for surface analysis include X‐ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), Scanning Auger Microscopy (SAM), and laser desorption mass spectrometry (LDMS).
Chemical Shifts in Nuclear Magnetic Resonance
Authors: Van Bramer Scott E.
Published: September 2006

This article explains a variety of methods used to calculate
13
C and proton (
1
H) chemical shifts for alkanes, alkenes, aromatic compounds, and cyclic compounds. Additivity rules, which account for the effect of different functional groups, are used to calculate chemical shifts for a wide range of compounds. Example calculations are provided for each rule, to clarify the use and for comparison with experimental results. The chemical shifts calculated with these rules are typically accurate to ±10 ppm for
13
C nuclear magnetic resonance (NMR) and ±0.5 ppm for
1
H‐NMR.
Nuclear Magnetic Resonance Instrumentation
Authors: Neiss Thomas G.
Published: September 2006

A nuclear magnetic resonance (NMR) spectrometer is composed of a magnet, a sample probe, a transmitter and receiver, and a computer for instrument control and display of results. Magnets used in NMR spectroscopy are predominantly superconducting solenoid systems, in which a wire coil is immersed in liquid helium to render it superconducting. An electric current is passed through the coil and produces a static magnetic field proportional to the size of the current. The magnet has an open bore that has shim coils to compensate for imperfections in the magnetic field and in the sample probe coils. Liquid samples with a deuterated solvent are placed inside this coil.

An array of high‐power radiofrequency (RF) transmitter channels is also necessary to perturb the nuclear spin distribution from equilibrium through the use of strong RF pulses. A transmitter comprises an RF source, a phase modulator for determining pulse phases during an experiment, an amplitude controller and a solid‐state amplifier capable of pulses of up to several hundred watts. An excitation pulse tilts the net nuclear magnetization away from its equilibrium orientation parallel to the magnetic field axis, although it continues to precess around this axis. The precession induces a voltage in the probe coil that is tuned to the resonance frequency of the observed nucleus. One of the transmitters is part of a channel (known as a lock channel) that is dedicated to the detection of
2
H nuclei in deuterated solvents and is used to stabilize the magnetic field and permit the adjustment of field homogeneity. For both the observe and lock channels a high fidelity preamplifier and receiver are used to amplify and detect the signal and then route it to an analog‐to‐digital converter (ADC) and a noise filter system before converting it to a stored data file on a computer as a free induction decay (FID) signal. Software on the computer performs a Fourier transformation of the FID signal to convert the time base‐data into a frequency spectrum for interpretation.
Quadrupole Couplings in Nuclear Magnetic Resonance, General
Authors: Man Pascal P.
Published: September 2006

Nuclear magnetic resonance (NMR) spectroscopy is continually finding new applications. It enables the local symmetry to be probed at the atomic scale using the nuclear spins I of the compound under investigation. The nuclear spin is either a half‐integer (or odd) number or an integer (or even) number. The nuclei in the periodic table can be divided into two parts – spin‐$\def\tovr#1#2{{\scriptstyle{#1\over #2}}} \tovr{1}{2}$nuclei and spin larger than$\def\tovr#1#2{{\scriptstyle{#1\over #2}}} \tovr{1}{2}$nuclei. The spin larger than$\def\tovr#1#2{{\scriptstyle{#1\over #2}}} \tovr{1}{2}$nuclei are called quadrupole nuclei because they possess an electric quadrupole moment which interacts with the electric‐field gradient (EFG) generated by its surroundings. By extension, their spins are called quadrupole spins. Spin‐$\def\tovr#1#2{{\scriptstyle{#1\over #2}}} \tovr{1}{2}$nuclei are not sensitive to the EFG. Of the nuclei that possess a spin, 6% have integer quadrupole spins and 66% have half‐integer quadrupole spins.

This article focuses on the half‐integer quadrupole spins ($\def\tovr#1#2{{\scriptstyle{#1\over #2}}} {\hbox{I}} = \tovr{3}{2},\ \tovr{5}{2},\ \tovr{7}{2}$, and$\def\tovr#1#2{{\scriptstyle{#1\over #2}}} \tovr{9}{2}$) in single crystals and in powder compounds. Most of these spins are observable. As they are multi‐energy‐level systems (the number of energy levels is 2I + 1), multiple quantum (MQ) transitions occur during excitation of the spin system by a radiofrequency (RF) pulse sequence. As a result, quantum mechanical concepts are needed for an understanding of the spin dynamics and for interpretation of the results. In particular, the choice of pulse sequence and the experimental conditions, such as pulse duration, pulse strength, and phase cycling in the pulse sequence, depend on the strength of the EFG surrounding the nuclear spin.
Quadrupolar Nuclei in Solid‐State Nuclear Magnetic Resonance
Authors: Freude Dieter
Published: September 2006

Solid‐state nuclear magnetic resonance (NMR) spectroscopy is mostly applied to1H or13C nuclei with the nuclear spin$\def\tovr#1#2{{\scriptstyle{#1\over #2}}} I = \tovr{1}{2}$, but about 100 of 130 NMR isotopes have$\def\tovr#1#2{{\scriptstyle{#1\over #2}}} I > \tovr{1}{2}$, and the electric quadrupole interaction strongly broadens the NMR signal in the solid‐state powder spectra. The perturbing effect of the electric quadrupole interaction is reduced at the higher magnetic fields which are available at present. In addition, approaches of the solid‐state NMR traditionally used in the study of spin‐$\def\tovr#1#2{{\scriptstyle{#1\over #2}}} \tovr{1}{2}$nuclei have been adapted for use with quadrupolar nuclei, and some techniques, e.g. double‐rotation (DOR) and multiple‐quantum transition in combination with fast spinning [multiple‐quantum magic‐angle spinning (MQMAS)], were recently developed for quadrupolar nuclei with half‐integer spins.

This article describes the basic theory, the line shape for first‐ and second‐order quadrupole broadened spectra with and without magic‐angle spinning (MAS) of the powder, the most important experimental techniques for the study of quadrupolar nuclei with half‐integer spins such as DOR, dynamic‐angle spinning (DAS), MQMAS, echo and nutation techniques, and some recent developments in deuterium NMR. Electric field gradient and chemical shift data for the most commonly studied quadrupolar nuclei with half‐integer spins,27Al,23Na, and17O, and a few references to recent solid‐state NMR studies of some other quadrupolar nuclei are given.
Scalar Couplings in Nuclear Magnetic Resonance, General
Authors: Lee Jo Woong
Published: September 2006

Indirect spin coupling refers to the magnetic interaction operative between a pair of magnetic nuclei in a molecule that is mediated by bonding electrons. The anisotropic part of this interaction averages out to zero when the internuclear vector connecting the two nuclei randomly changes its orientation in the isotropic fluid state as does the direct magnetic dipolar interaction between the same pair of nuclei which operates through space. The isotropic part, which is usually called the scalar spin coupling, survives such random modulations of the internuclear vector in the fluid state to give rise to splitting of the nuclear magnetic resonance (NMR) lines which would otherwise represent a mere collection of individual absorption lines corresponding to the chemical shift of each constituent spin. Adequate analysis of the multiplet structure of the NMR spectrum arising from a given set of nuclear spins can provide knowledge of the scalar coupling between each pair of nuclear spins which in turn yields a wealth of information on molecular structure as well as molecular processes occurring in the system.
Solid‐State Nuclear Magnetic Resonance: Spin‐1/2 Nuclei Other than Carbon and Proton
Authors: Wu Gang
Published: September 2006

Solid‐state nuclear magnetic resonance (NMR) spectroscopy is a powerful analytical technique with a wide range of applications in chemistry, biochemistry and materials science. Solid‐state NMR is amenable to studies of molecular systems that are not suitable either for liquid‐state NMR because of insolubility or for single‐crystal diffraction techniques because of poor crystallinity. Therefore, solid‐state NMR provides a natural connection between liquid‐state NMR and single‐crystal diffraction techniques. Furthermore, solid‐state NMR is the best way of studying the anisotropic nature of nuclear magnetic properties, thus potentially yielding more complete information about molecular structure and chemical bonding. This article provides an overview of the fundamental principles of solid‐state NMR with selected examples of chemical applications. Emphasis is placed on the fundamental information and practical aspects of solid‐state multinuclear NMR experiments for the following spin‐$\def\tovr#1#2{{\scriptstyle{#1\over #2}}} \tovr{1}{2}$nuclei:15N,29Si,31P,77Se,113Cd,199Hg,117Sn,195Pt,207Pb,57Fe,89Y,109Ag and183W. A brief introduction to the second‐order quadrupolar effect on spin‐$\def\tovr#1#2{{\scriptstyle{#1\over #2}}} \tovr{1}{2}$NMR spectra is also provided.
Solution Nuclear Magnetic Resonance: Spin‐1/2 Nuclei Other than Carbon and Proton
Authors: McGregor Mike
Published: September 2006

There are 22 spin‐$\def\tovr#1#2{{\scriptstyle{#1\over #2}}} \tovr{1}{2}$nuclei other than hydrogen and carbon, some with more than one spin‐$\def\tovr#1#2{{\scriptstyle{#1\over #2}}} \tovr{1}{2}$isotope. Four of these,15N,19F,29Si and31P, have been of major importance in chemistry and nuclear magnetic resonance (NMR) and are the subject of an extensive literature. Many spin‐$\def\tovr#1#2{{\scriptstyle{#1\over #2}}} \tovr{1}{2}$nuclides have had more specialized uses, such as3H,77Se,109Ag,113Cd,119Sn,125Te,129Xe,195Pt,205Tl, and207Pb. A few have been of limited use, generally due to poor sensitivity:57Fe,89Y,103Rh,169Tm,171Yb,183W,187Os and199Hg.

Spin‐$\def\tovr#1#2{{\scriptstyle{#1\over #2}}} \tovr{1}{2}$nuclei generally produce sharp spectral lines, which may allow a wealth of fine structure from spin–spin coupling to be observed. This coupling, along with chemical shift information and dipolar coupling information (nuclear Overhauser effect (NOE)) are used in a variety of ways to obtain structural information and solve chemical problems.

After a brief discussion of analytical techniques, the history, experimental practices, physical properties, relaxation properties, chemical shift referencing, applications and literature references for each nuclide are presented.
Z
eeman Interaction in Nuclear Magnetic Resonance
Authors: Dybowski Cecil
Published: September 2006

The Zeeman interaction is the physical phenomenon underlying the coupling of magnetic moments to magnetic fields. Its effects are detected in the features of spectra of samples taken while the sample is immersed in a magnetic field. Specifically, the features of nuclear magnetic resonance (NMR) spectra depend strongly on the coupling of nuclear spins to various sources of magnetic field.
Elastic Recoil Detection Analysis
Authors: Trocellier Patrick
Published: September 2006

In 1976, a Canadian group described in detail for the first time a new ion beam analytical method based on the elastic recoil of target nuclei collided with high energy heavy incident ions. In this case 25–40‐MeV35Cl impinged on a multilayer C or Cu (backing)/LiF or LiOH/Cu (30–150 nm)/LiF or LiOH and H, Li, O and F recoiled atoms were detected. These exemplified the main characteristics of elastic recoil detection analysis (ERDA): its sensitivity to depth distribution and its ability to detect light elements in heavy substrates. In 1979, the use of megaelectronvolt energy4He beams permitted the use of ERDA to be extended to depth profiling of hydrogen isotopes in the near surface region of solids.

ERDA has rapidly been revealed to be an excellent alternative to resonant nuclear reaction spectrometry for hydrogen determination in solids. Despite its less advantageous performance with respect to its lower depth resolution, lower analyzable depth, comparable sensitivity and more restricting irradiation and detection geometry, some ERDA features have made its development in ion beam analysis (IBA) laboratories worldwide easier; these are simultaneous access to1H and2H depth distributions, access to single‐ended Van de Graaff accelerators compared with tandem or cyclotrons, the ability to be combined with Rutherford backscattering spectrometry (RBS) and a less damaging effect on the investigated targets compared to those generated by heavy ions.

The development of detection devices and the analytical capabilities offered by high‐energy heavy ion‐induced ERDA in material sciences for profiling light, medium and large mass number elements give this method a wide area in which to progress as illustrated by discussions at ion beam‐related technique conferences.
Nuclear Reaction Analysis
Authors: Demortier Guy
Published: September 2006

Nuclear reaction analysis (NRA) is one among the numerous analytical techniques involving the irradiation of a material with energetic particles. In NRA methods we exclude any remnant radioactivity together with interactions leading to the scattering of the incident particle only: this last procedure leads to RBS (Rutherford backscattering spectroscopy) and ERD (elastic recoil detection).

In NRA the nature of the emitted particle used as an analytical signal is obviously different from that of the incident one. In order to avoid permanent radioactivity, the energy of the projectile is maintained at a sufficiently low value (below 6 MeV, easily available using a small accelerator). Consequently, due to the large coulomb barrier around heavy nuclei, only light nuclei may be easily identified (atomic mass less than or equal to 30).

After discussing the kinematics and fundamentals of the interactions, we present examples of applications in material sciences, archaeological and biological materials.
PIXE
(Particle‐Induced
X
‐Ray Emission)
Authors: Mandò P.A.
Published: September 2006

Particle‐induced X‐ray emission (PIXE) is the most popular among the ion beam analysis (IBA) techniques, which are based on the use of the specimen to be analyzed as a target for a beam of accelerated particles. The detection of the radiation induced by the beam bombardment is then used to discriminate and quantify the presence of the different elements in the specimen. In PIXE, what is exploited is in particular the X‐rays emitted from the target, whose energies are characteristic of the emitting atomic species. After a general, simple description of the main features of PIXE, with a short historical overview and a brief comparison to other X‐ray fluorescence (XRF) techniques, the article covers in greater depth all the specific aspects of this “nuclear” technique. The basic aspects of X‐ray emission from the atoms are first recalled; then, the extraction of quantitative compositional data from thin and thick specimens is explained, and a discussion is given of the excellent performance of PIXE in terms of minimum detection limits (MDLs), and of the factors affecting them. A technical description then follows of how proper beams for PIXE are produced and of the experimental set‐ups commonly used, with particular emphasis on the external‐beam arrangements. The X‐ray detector characteristics, the electronics for constructing the energy spectra, and the software processes for their deconvolution, leading to the extraction of quantitative data, are then briefly described. The last section surveys the main analytical applications of PIXE in various fields (environmental monitoring, biomedicine, earth sciences, cultural heritage), with no intent of exhaustiveness but rather with the purpose of focusing on when and why PIXE may be particularly suitable in each of them.
Radiochemical Neutron Activation Analysis
Authors: Heydorn Kaj
Published: September 2006

Radiochemical neutron activation analysis (RNAA) is a method for trace‐element determination based on the measurement of an indicator radionuclide, chemically separated from a neutron‐activated sample. Unlike instrumental neutron activation analysis (INAA) the RNAA is therefore not a nondestructive method, and at the same time the amount of work put into the analysis of each sample makes RNAA much more expensive than INAA. This is the cost that has to be paid for determining selected elements at much lower concentrations and superior accuracy, while maintaining matrix independence and most of the other excellent characteristics of INAA. One of these characteristics is the small self‐shielding during irradiation with neutrons, which opens the possibility of analyzing also large samples without any pretreatment.

Particularly for the lowest levels of trace elements RNAA provides several important advantages over alternative analytical methods:

the absence of a reagent blank, and

the corresponding insensitivity to contamination after activation

the controlled addition of carrier to avoid losses by adsorption etc., and

the corresponding possibility of determining chemical yield or recovery.

When carefully and thoughtfully carried out, RNAA qualifies as a so‐called definitive method, one of the reasons being its direct traceability to a comparator of the pure element to be determined.
Radiotracer Methods
Authors: Das Hendrik A.
Published: September 2006

Small amounts of radionuclides of suitable half‐life can be used to observe the kinetics of mass transport and isotopic exchange in the equilibrium distribution of a (micro‐)component between coexistent phases.

Quantitative assay of radioactivity is sensitive, precise and accurate and usually performed instrumentally. Though handling of radionuclides is restricted to authorized laboratories only, the combination of its potential and simplicity makes the radiotracer method an indispensable part of modern analytical chemistry.
Radiochemical Separation Schemes for Multielement Determination
Authors: Alfassi Zeev B.
Published: September 2006

Radiochemical activation analysis is a more laborious analytical method than instrumental analysis, but can be used to determine elements at lower concentrations. In most cases, the sample to be analyzed is separated into groups of elements rather than individual elements, so that the elements do not interfere with one another during the measurement of radionuclides content. Schemes for separation into multielement groups are given for metals, biological, geological and environmental samples.
Actinides and Other Alpha‐Emitters, Determination of
Authors: Vintró Luis León , Mitchell Peter I.
Published: September 2006

To assay an actinide or other α‐emitter at the low concentrations encountered in many environmental samples necessitates chemical separation of the actinide of interest from the bulk matrix, purification by the elimination of other interferants, mounting onto a suitable substrate for counting, and quantification by radiometric, mass spectrometric or other means. In this contribution, the chain of analysis from sampling to counting is critically reviewed and many of the most important pitfalls and sources of error are highlighted. Specifically, the pretreatment, preconcentration, separation and purification steps required for the assay of thorium, uranium, neptunium, plutonium, americium and curium in a wide range of environmental matrices are examined in detail. Emphasis is given to the need for appropriate radiochemical yield monitors and to the practical application of ion exchange, solvent extraction and extraction chromatography in the purification of these elements. This is complemented by a description of methods for the preparation of quality sources suitable for counting by α‐spectrometry, liquid scintillation α‐spectrometry and mass spectrometry. In addition, an overview is given of the operational principles and systems used in α‐radiometry and mass spectrometry, including a discussion of the practical limits of detection and quantitation achievable with these systems. Finally, the importance of traceability and good quality assurance in precision actinide assay is emphasized.
Mass Spectrometry of Long‐Lived Radionuclides
Authors: Sabine Becker H.J. , Dietze Hans‐Joachim
Published: September 2006

Inorganic mass spectrometric methods are powerful multielement analytical techniques for sensitive determination at the trace and ultratrace level, and for isotope ratio measurements in different materials (e.g. conducting, semiconducting and nonconducting solid samples; technical, environmental, biological, geological and water samples). An inorganic mass spectrometer consists of the following parts: the ion source for the evaporation, atomization and ionization of samples, the analyzer for the mass (and energy) separation of ion beams which are extracted from the ion source, and the ion detection system. The detection limits of solid‐state mass spectrometric techniques by thermal ionization mass spectrometry (TIMS), glow discharge mass spectrometry (GDMS), laser ablation inductively coupled plasma mass spectrometry (LA/ICPMS) for the direct analysis of solid samples were determined down to the sub‐nanogram per gram level. Resonance ionization mass spectrometry (RIMS) and accelerator mass spectrometry (AMS) are highly sensitive, selective ultrasensitive mass spectrometric techniques with detection limits up to 10
6
atoms.

Inductively coupled plasma mass spectrometry (ICPMS) has been applied as the most important and sensitive mass spectrometric technique with its multielement capability for the determination of long‐lived radionuclides in solid andaqueous samples, with detection limits the sub‐picogram per liter. Isotope ratios can be determined by ICPMS using single ion collectors and multicollectors with a precision of 0.02% and 0.006% relative standard deviation (RSD) respectively. This review discusses the most important inorganic mass spectrometric techniques and their application for the quantitative determination of long‐lived radionuclides in metals, alloys, and nonconductors, as well as in environmental, biological and geological samples, and radioactive waste materials. The application of these methods to isotope ratio measurements is also discussed.
Nuclear Detection Methods and Instrumentation
Authors: Tsechanski A.
Published: September 2006

Nuclear detectors and associated electronics are among the most important components of analytical chemistry involving nuclear methods. Historically, the first and simplest particle detectors were gas‐filled counters using an electric field to collect the free charge carriers, electrons and ions, produced in the counter by ionizing radiation. These detectors include ion chambers, proportional counters and Geiger counters. The charge created at the proportional counter is directly proportional to the energy deposited in the detector by a nuclear particle and, therefore, this kind of detector can be used for energy measurements of nuclear radiation (nuclear spectrometry). The main disadvantage of gas‐filled detectors is their low efficiency for γ‐rays. This is because the gas detection medium is low in density. From this point of view, solid detectors are considerably more advantageous. Of these detectors, the scintillation counter is one of the earliest and most widely used detectors of nuclear radiation. It consists of a detection medium (inorganic or organic scintillator) and a photomultiplier tube (PMT). The incident particle enters the scintillator and interacts with its atoms, raising them to excited states. De‐excitation follows very rapidly by emission of light photons. The emitted photons are multiplied in the PMT, resulting in an output pulse of up to several volts. The high efficiency scintillation detectors are widely used in instrumental analytical chemistry including neutron activation analysis (NAA), both prompt neutron activation analysis (PNAA) and delayed neutron activation analysis (DNAA), and in X‐ray flourescence analysis (XRFA). Contemporary high‐resolution γ‐spectrometry is based on solid‐state ionization chambers. Only after the successful development of the technology for production of highly purified single crystals of germanium (Ge) and silicon (Si) did it become possible to develop Ge‐ and Si‐based solid‐state detectors by forming reverse‐biased junctions and cooling the semiconductor to liquid nitrogen temperature (77 K). The most prominent feature of the semiconductor detectors is their excellent energy resolution and availability of large crystals with relative efficiencies up to 120% compared with a standard NaI(Tl) detector. High‐resolution γ‐ray spectrometry is widely used in evaluation of γ‐emitting radioactive nuclides in various samples, in NAA, in a high‐sensitivity particle‐induced X‐ray emission (PIXE) method and others. Nuclear detectors provide a variety of information on detected radiation (energy, type of the radiation, timing data, etc.) in the form of electronic signals. To obtain this information, the signal must be processed by the appropriate nuclear electronic system, which includes power supply, preamplifier, main amplifier and multichannel analyzer (MCA) for digital processing of the analog signals.
Fourier Transform
R
aman Instrumentation
Authors: Edwards Howell G.M.
Published: September 2006

The physical basis of the instrumentation required for the recording of Raman spectra in the near‐infrared region of the electromagnetic spectrum using an interferometer and Fourier transform (FT) techniques is described. The advantages and disadvantages of the technique compared with the recording of Raman spectra in the visible or ultraviolet (UV) region are described. The impetus provided by the nondestructive nature of this analytical method, combined with the minimization of fluorescence and the ease of sample presentation to the spectrometer is illustrated with examples from archaeological science, environmental science, and biology; accessories such as a Raman microscopic and a remote sensing fibre‐optic probe are described with relevant applications in art conservation, materials analysis, processing and biomedical diagnostics. The potential for future applications of the technique in chemical, physical and biological sciences is outlined.
Raman Microscopy and Imaging
Authors: Andrew Jeremy J.
Published: September 2006

Raman microscopy and imaging couples the spatial resolution of optical microscopy with the spectral resolution and information content of Raman spectroscopy. Together, a powerful tool for the investigation of chemical, or molecular, heterogeneity is created. Raman microspectroscopy enables the nondestructive analysis of small quantities of sample and the identification of contaminants and inclusions in situ within a matrix – both of great importance and utility in forensic investigations. Perhaps more importantly, it has been recognized that the microheterogeneity of products has an influence on both product performance and appearance. In the analysis of complex, multiphase systems, optical microscopy contrast methods (the majority of which depend upon refractive index changes) are commonly employed to provide information on the structural organization of materials. However, information on the chemical organization of materials is then often based on conjecture. Raman microscopy is arguably the most easily applied of a family of techniques that use the innate spectral signatures of the components as a contrast element and hence provides a method for analyzing chemical heterogeneity in “real” systems.

Typically, the information that would be appropriate from an investigation of chemical heterogeneity would be:

the number of chemical components present;

the pure spectrum of each component;

spatially resolved concentration information for each individual component.

Raman microscopy and imaging provides a tool to determine these important factors in complex, multiphase systems. In its simplest form, the Raman microspectroscopy experiment requires a laser to be focused down to a diffraction‐limited spot on a sample and the inelastically scattered light is collected from that point and analyzed. This generates a Raman spectrum, which is indicative of the identity and quantity of the molecular species present in that sample volume. The limiting spatial resolution that can be obtained is of the order of 1 µm in the lateral plane and 2 µm in the axial plane, the microscopes used lending themselves to a confocal optical arrangement that provides this level of depth discrimination.

The information content is constrained to that available in the Raman vibrational spectra and so commonly molecules with distinct functional groups are clearly distinguished, whilst it is more difficult to distinguish specifically between molecules with very similar molecular structure and chemical functionality. It is also a commonly held belief that Ramaninvestigations are hampered by fluorescence interference, which obscures the Raman spectrum. However, with modern Raman microscopes there are few samples where this limitation becomes completely defeating.

Several approaches to the generation of Raman images (images where the contrast is based on the chemical or molecular heterogeneity) have been established and are discussed in detail. A comparison is made between these different Raman imaging approaches and also with different spectral imaging methods.
Raman Scattering, Fundamentals
Authors: Popp Jürgen , Kiefer Wolfgang
Published: September 2006

An introduction of the fundamentals of linear and nonlinear Raman spectroscopy is given. The Raman effect is the result of inelastic light scattering. A small amount of the photon energy of the incident light wave is modulated by the molecular scattering system. An energy transfer occurs as a result of the coupling between the incident radiation and the quantized states of the scattering system. Depending on the coupling, the incident photons either gain or lose energy. The light, which has less energy than the incident laser light, is named Stokes–Raman scattering, and the radiation, which has more energy, is referred to as anti‐Stokes–Raman scattering.

In the case of the coupling between strong laser fields and molecular vibrations the observation of nonlinear Raman effects such as hyper‐Raman scattering, stimulated Raman scattering (SRS), coherent anti‐Stokes–Raman spectroscopy, the Raman gain spectroscopy, etc., is possible.

Apart from theoretical aspects of Raman spectroscopy an introduction into the instrumentation of linear and nonlinear Raman techniques is provided. For linear Raman spectroscopy two alternate approaches are described: dispersive Raman and Fourier transform Raman (FT‐Raman) spectroscopy. Special Raman techniques such as micro‐Raman spectroscopy and difference Raman spectroscopy are discussed.

In addition, a review of the instrumentation of several nonlinear Raman methods which are based on the second‐order (χ(2)) and the third‐order nonlinear susceptibility (χ(3)) is given. These methods include coherent anti‐Stokes–Raman scattering (CARS), stimulated Raman gain spectroscopy (SRGS), inverse Raman scattering (IRS), photoacoustic Raman spectroscopy (PARS), and ionization‐detected stimulated Raman spectroscopy (IDSRS).
Differential Scanning Calorimetry and Differential Thermal Analysis
Authors: Riga Alan , Collins Ricardo
Published: September 2006

The importance of thermal analysis methods in thermal and material science has proved awesome. Differential thermal analysis (DTA) and differential scanning calorimetry (DSC) have had a great impact on material science by enabling the measurement of a great number of physical and chemical properties. These techniques have allowed elucidation of endothermic and exothermic processes at temperatures ranging from very low (−120°C) to high (DSC 600°C and DTA 1800°C).
1–6
Some of the physical properties measured by these thermal analytical methods include melting transitions, crystallization temperatures, enthalpy of fusion and crystallization, specific heat capacity, liquid crystal transitions, vaporization, sublimation, solid–solid transitions, thermal conductivity and the glass transition temperature.
7–14
Chemical properties monitored by DSC and DTA are dehydration, decomposition, oxidative reactions, solid state reactions, chemisorption, combustion, polymerization, curing and catalyzed reactions.
15–19

In DTA, the temperature difference between the substance and a reference material is measured as a function of temperature, while the substance and reference material are subjected to a controlled temperature program.
20

In DSC, the difference in energy input into a substance and a reference material is measured as a function of temperature, while the substance and reference material are subjected to a controlled temperature program.
21
Two modes, power compensation DSC and heat flux DSC, can be distinguished, depending on which method of measurement is used.
22,23

The following is a review of DSC and DTA and their role in thermal science. The root of thermal analysis is the determination of heat and temperature. Heat is a macroscopic quantity and has its origin in molecular motion.
24
DTA measures the temperature difference between a sensitive reactive material and an inert reference as a function of time and temperature. DTA measurements provide information about transition temperatures as well as kinetic time‐based phenomena and thermodynamic properties. DSC is a step above DTA in that it measures quantitative heats of reaction and transitions. Both thermal methods can differentiate first order thermodynamic changes like fusion, and second order thermodynamic changes like a glass transition temperature, T

g

. This chapter will focus mainly on fundamentals, instrumentation and applications of DSC.
Thermogravimetry
Authors: Dunn Jeffrey G.
Published: September 2006

Thermogravimetry (TG or TGA) is a technique in which the mass of a substance is measured as a function of temperature whilst the substance is subjected to a controlled temperature program.1, 2 Commonly materials can be heated or cooled in the temperature range from −160 to 1600°C at rates of fractions of a degree per minute up to 100°C min
−1
. Sample sizes are from 10–100 mg, although apparatus is available which can take larger sample masses. Different atmospheres can be used, from inert gases such as nitrogen, to reactive gases such as oxygen, hydrogen and vapors. The sensitivity of the apparatus is usually in the microgram range, with an accuracy of ±1% and a similar level of precision. The results obtained from TG experiments are subject to a variety of experimental variables, and an understanding of the effects of these is essential to a correct interpretation of the results. TG can be used to study any physical or chemical reaction which gives a mass change, and includes absorption and desorption of gases, sublimation and vaporization, the thermal decomposition of a wide range of materials from inorganic compounds to polymers, the reaction between a gas and a solid, and solid–solid reactions. TG has also been widely used to carry out kinetic studies on solid materials, with the aim of determining the reaction model and the kinetic parameters of activation energy (
E
) and frequency factor (
A
). However, considerable care is required in the interpretation of the results obtained.
Absorption Techniques inX‐Ray Spectrometry
Authors: Kawai Jun
Published: September 2006

X‐ray absorbance depends on the wavelength of the X‐rays, atomic number, chemical environment, and concentration of analyte. X‐ray absorption spectrometry is a technique for analyzing the chemical environment of an element in an unknown material. This method is closely related to photoelectron spectroscopy, Auger electron spectroscopy, and X‐ray fluorescence spectroscopy.

Chemical information in the chemical shift and line shape of XANES (X‐ray absorption near‐edge structure) spectra is described. The history and theory of EXAFS (extended X‐ray absorption fine structure) are discussed in relation to other experimental techniques. Data analysis methods, databases, software packages, instrumentation, and synchrotron radiation facilities for X‐ray absorption analysis are overviewed. Alternative methods such as electron energy loss spectroscopy (EELS), self‐absorption effect, extended X‐ray emission fine structure (EXEFS), X‐ray Raman scattering, diffraction anomalous fine structure (DAFS), β‐environment fine structure (BEFS), and inverse photoemission spectroscopy (IPES) are also described.
Structure Determination,
X
‐Ray Diffraction for
Authors: Chung D.D.L.
Published: September 2006

X‐ray diffraction is a widely used experimental method for materials analysis. The scope of materials analysis that can be provided by X‐ray diffraction includes crystalline phase identification, lattice parameter measurement, grain size measurement, and texture analysis. In particular, crystalline phase identification is a basic form of materials analysis that is critically important for metals, ceramics, and other crystalline materials. In contrast, elemental analysis, as provided by X‐ray spectroscopy, atomic absorption, etc., provides information on the composition but not the phases. Because a material frequently consists of more than one phase, the composition of the multiphase mixture is not the same as the composition of an individual phase. A true understanding of a crystalline material cannot be obtained until one knows what phases are present in the material. Even if two phases have the same composition, their difference in crystal structure can make them have very different electrical, magnetic, thermal, mechanical, or chemical properties.
Total Reflection
X
‐Ray Fluorescence
Authors: Wobrauschek Peter , Streli Christina
Published: September 2006

Total reflection X‐ray fluorescence (TXRF) analysis is an energy‐dispersive (ED) X‐ray fluorescence (XRF) technique using a special excitation geometry. The narrow collimated beam impinges at grazing incidence on a special sample carrier. This is a flat polished quartz plate on which the sample is deposited. The most significant advantages of TXRF over conventional XRF analysis are the improved detection limits achieved by inherent signal increase and reduced background. Detection limits are in the picogram range for X‐ray tube excitation and even down to femtograms for excitation using synchrotron radiation (SR). The main application is the analysis of some microliters of a liquid sample deposited and dried on the quartz reflector or of some microliters of slurry or microgram grains of solid samples. The most widely used application is the quality control of contaminations on Si wafer surfaces. The detection limits demanded by the semiconductor industry can be reached today using X‐ray tube excitation, but metrology shows that in the future SR is required or special preconcentration techniques. Straight TXRF is the only analytical technique offering nondestructive and spatial resolved analysis. A special ED detector with an ultrathin window is suitable for the detection of low atomic number,
Z
elements (C upwards) using TXRF. Another promising application is the characterization of thin layers on a reflecting surface or implanted atoms in Si by variation of the incidence angle and measurement of the fluorescence signal. It is possible to determine the elements forming the layer, the layer thickness and its density. For thin layered samples as well as implantations, thickness, depth and depth profile for implanted atoms can be evaluated by comparing experimental results with theoretical models.
Energy Dispersive,X‐Ray Fluorescence Analysis
Authors: Lindgren E. Selin
Published: September 2006

Energy‐dispersive X‐ray fluorescence (EDXRF) is an analytical method for qualitative as well as quantitative determination of elements in a sample, independent of their chemical form. It is built on the fact that elements that are irradiated with energetic X‐rays have a certain probability of emitting characteristic X‐rays, the energies of which are unique for each element. In the energy‐dispersive systems, the emitted X‐rays are detected by their energies. Use of the EDXRF technique has accelerated since the 1960s as a result of the development of solid‐state detectors, nuclear electronics and small computers. EDXRF is multielemental and nondestructive and can be applied to large as well as small samples of different composition and character. If conditions are optimized, minimum detection limits (MDLs) can be below the nanogram level for small laboratory instruments and into the femtogram region for more advanced instrumentation [total reflection X‐ray fluorescence (TXRF), synchrotron radiation].

EDXRF spectrometers exist at many degrees of sophistication, ranging from advanced laboratory instruments to small portable instruments for field observations. They can be designed for analysis of bulk material or for scanning and elemental mapping of small areas.

Typical applications for EDXRF are analysis of agricultural material, medical samples, archaeological and historical objects and environmental samples such as soil, ores, water and aerosol particles.
Sample Preparation for
X
‐Ray Fluorescence Analysis
Authors: Injuk Jasna , Van Grieken René
Published: September 2006

This article is a comprehensive review of sample preparation methods for various kinds of samples prior to X‐ray measurement. Not only are commonly used methods presented but also included are some specific techniques for certain kinds of materials, with emphasis on more recent applications and developments.