bluuebunny/crossref_metadata_2025_split huggingface dataset:
Supercritical Fluid Chromatography in Clinical Chemistry
Authors: Graves Steven W. 
Published: September 2006

AbstractSupercritical fluid chromatography (SFC) employs a gas taken above its critical temperature and critical pressure to where it forms a supercritical fluid (SF). SFs have properties of both gases and liquids. They have lower densities and viscosities and higher diffusion coefficients than liquids, but they also have the solvating power of a liquid and can dissolve nonpolar and many polar compounds. As such, these favorable properties combine to make SFs an excellent mobile phase for column chromatography. The SFC technique is highly versatile in that it can be used with either packed columns (similar to high‐performance liquid chromatography (HPLC) columns with the same variety of stationary phases available) or open‐tubular columns (similar to gas chromatography (GC) columns and employing the same types of coatings) which can be interfaced with a very wide array of detectors. In addition, SFC avoids high temperatures during the chromatographic separation and in most cases the need to derivatize analyzed compounds. These features make SFC particularly well suited to the separation and assay of clinically important biomolecules. As SFC instruments have become commercially available, numerous applications have been explored in the areas of drug monitoring, toxicology, environmental contaminants, and the measurement of physiological biomolecules. Despite its potential, SFC enjoys limited use in clinical chemistry laboratories currently. Greater efforts are needed to improve sensitivity, standardize and validate assays, and work toward high‐volume throughput capabilities.
Atomic Spectrometry in Clinical Chemistry
Authors: Parsons Patrick J. 
Published: September 2006

AbstractAtomic absorption spectrometry (AAS) and atomic emission spectrometry (AES) are two closely related instrumental techniques that have many applications in many different fields. In clinical chemistry, these techniques are well established for the quantitative measurement of essential and nonessential elements found in body tissues and fluids. For most practical purposes, the elements that are routinely measured with modern commercial instrumentation include almost all of the metallic elements of the s, d and p blocks of the periodic table. The exceptions in the p block include the halogens, the noble gases and the elements C, H, N, O and S. Above atomic number 83 (Bi), only U is measured in absorption. With the emergence of commercial instrumentation for atomic mass spectrometry, e.g. inductively coupled plasma mass spectrometry (ICPMS) clinical chemists have another powerful tool with which to measure multielement composition of biological specimens at ultratrace concentrations, i.e. <10 µg L−1. With ICPMS, the halogens become detectable, along with B, C, N and Th. The coupling of ICPMS with separation technologies has opened new possibilities in clinical laboratory medicine in the field of speciation.In some areas of clinical chemistry, older atomic spectroscopy techniques are still considered the reference method for selected clinical applications, e.g. the determination of serum K and serum Na by flame atomic emission spectrometry (FAES). In other areas, flame atomic absorption spectrometry (FAAS) remains the method of choice for serum Mg and serum Cu because of its sensitivity, rapid throughput and the relatively low cost of instrumentation. Electrothermal atomic absorption spectrometry (ETAAS), while more complex than flame atomization methods, is the method of choice for applications such as blood Pb, serum Al and serum Se, where physiological concentrations are too low to be measured in the flame without laborious preconcentration efforts. Robust procedures for quality assurance (QA) and quality control (QC) are now well established within the clinical laboratory and cover the entire spectrum of clinical laboratory activities. These include preanalytical issues, personnel training and education, and also the appropriate use of certified reference materials (CRMs) for method validation purposes. Participation in proficiency testing (PT) programs and external quality assessment schemes (EQAS) for trace elements in biological fluids have also contributed to improved clinical laboratory performance. Despite the advent of ever more sensitive techniques and robust procedures, the quality of results is still only as good as the specimen collected. Contamination can occur at the preanalytical stage of the analysis and also during the analysis. Selection of the appropriate specimen is critical to obtaining meaningful clinical information about nutritional trace element status or exposure to toxic elements.
Ultraviolet/Visible Light Absorption Spectrophotometry in Clinical Chemistry
Authors: Upstone Stephen L. 
Published: September 2006

Abstract
Ultraviolet/visible (UV/VIS) absorption spectroscopy has been used in the clinical laboratory for many years. The technique has appeal, as it is almost universal in its application. Although much of the routine work is performed using high‐throughput dedicated clinical analysis systems, absorption spectroscopy still has a place in most clinical laboratories.
This article discusses the range of application types for which absorption spectroscopy can be used and some examples of common analyses are given. The article also discusses the merits of various instrument types and discusses some more advanced spectroscopic techniques, such as derivative spectroscopy, to enhance the data measured by the spectrophotometer. Brief reference is also made to the use of reflectance in clinical analysis.
Nuclear Magnetic Resonance of Coating and Adhesive Systems
Authors: Brandolini Anita J. 
Published: September 2006

Abstract

The interaction of the magnetic moment of an atomic nucleus with a static magnetic field gives rise to nuclear magnetic resonance (NMR). Examination of NMR can reveal both the chemical structure and physical characteristics of a chemical system and this makes the technique particularly useful for the study of materials such as those encountered in coating and adhesive applications. No other spectroscopic technique can offer such a detailed description, both qualitative and quantitative, of molecular structure, including features such as stereochemistry, reaction kinetics and surface phenomena. Each nucleus has a distinct precession frequency, allowing different (e.g.
13
C,
1
H,
29
Si) to be observed within a sample. The technique does, however, suffer from a few drawbacks. First, it is not a particularly sensitive technique, and it is most readily applied to features that constitute at least a few percent of the sample. Second, sample preparation can be difficult; this can be especially true for coatings and adhesives materials, as will be discussed. The most detailed chemical information is obtained from the spectra of liquids or solutions, which precludes cross‐linked or cured materials. The spectra of solids, including cross‐linked and cured materials, must be studied using complex experimental approaches, and these often suffer from poor resolution.
Rheology in Coatings, Principles and Methods*Portions of this article are excerpted, by permission, from the chapter ‘Rheology and Viscometry’ by R.R. Eley, in the
Paint and Coatings Testing Manual: 14th Edition of the Gardner‐Sward Handbook
(1995), ASTM, 100 Bar Harbor Drive, West Coshocken, PA 19429‐2959.
Authors: Eley Richard R. 
Published: September 2006

Abstract

Rheology by definition is the study of the deformation and flow behavior of materials. An operational definition would be “the study of the response of certain materials to the stresses imposed on them”. Rheology seeks to understand the relationship between applied force, or stress, and the resulting deformation, particularly for materials showing nonsimple responses. Such a relationship expressed mathematically is termed a constitutive equation. Perhaps the most familiar such equation is Hooke's law for elastic solids, which states the linear relationship between the stress σ and the deformation or strain γ [Equation 1]:

where the modulus G is the constant of proportionality. However, rheology is primarily concerned not with the solid state but with the study of fluid behavior, and the simplest constitutive relation for a liquid is Newton's law [Equation 2]:

where the coefficient of viscosity or, more commonly, the viscosity η expresses the proportionality between stress and, now, not strain but the strain rate,

$\dot{\gamma}$

.

For the ideal, simple materials described above, G and η are called material constants because they are dependent only on the thermodynamic variables of temperature, pressure, and concentration, similar to a material property such as the density. However, rheology is not concerned with either Hookean solids or Newtonian liquids. It is rather concerned with materials whose constitutive relationships involve complex behavior. For such materials, G and η are no longer material constants but material functions. Their values will now depend on variables such as the magnitude of applied stress, strain, strain rate, and even the deformation history. In fact, for rheologically interesting materials, the behavior is somewhere between that of a Newtonian liquid and an elastic solid. Such materials are termed non‐Newtonian, and may display time‐dependent, plastic and viscoelastic behaviors.
Paints and industrial coatings, creams and lotions, inks, adhesives, ceramic slips, solder pastes, foods, medicines, etc. are representative of the range of materials whose commercial viability depends on having the correct rheology for the application. In turn, the required rheological properties must be defined with reference to the specific process at hand. This article introduces the science of rheology, with description of basic terms, models, and methods used. The mechanisms responsible for complex rheological behavior and the use of rheological measurements to understand and control the flow of materials are described. The emphasis is on coatings and coatings processes as points of reference, but the principles discussed apply to a wide range of materials and industrial products.
Automotive Emissions Analysis with Spectroscopic Techniques
Authors: Hirschberger Rainer 
Published: September 2006

AbstractQuantitative analysis of automotive emissions gives detailed information about a motor's combustion behavior and gives information about the contribution from traffic to air pollution. Following the introduction, which discusses the problems of exhaust gas analysis, section 2 covers the basics of the physical effects, that the different spectroscopic systems are based on. These physical effects are discussed especially with respect to gas analysis.Section 3 describes the functioning of different spectroscopic systems, the measuring procedures and different examples of exhaust gas analysis. Simple examples are used to illustrate the functioning of Fourier transform infrared (FTIR) and diode laser (DL) systems. The construction of a completely home‐made Raman polychromator is described in detail. Specific problem areas are pointed out. Selected examples of exhaust gas analysis show typical applications of the particular methods.Section 4 discusses the present and future potential of the systems described.
Optical Gas Sensors in Analytical Chemistry: Applications, Trends and General Comments
Authors: Rathgeb F. , Gauglitz G. 
Published: September 2006

AbstractCurrent concepts for optical gas sensors are reviewed. Different approaches for gas sensing such as intrinsic and extrinsic, direct and indirect sensing were taken into consideration. For each sensing approach reviewed here, a short principle description and recent applications are given. Several aspects governing the enrichment of gaseous analytes in sensitive layers are also discussed briefly.
Fourier Transform Infrared Spectrometry in Atmospheric and Trace Gas Analysis
Authors: Griffith David W.T. , Jamie Ian M. 
Published: September 2006

AbstractFourier transform infrared (FTIR) spectrometry is the dominant technique used to measure the infrared (IR) absorption and emission spectra of most materials, with substantial advantages in signal‐to‐noise ratio (S/N), resolution, speed and detection limits over conventional dispersive spectroscopy. In this application, FTIR spectrometry is used to measure the trace gas composition of the atmosphere. Applications to both clean and polluted air are described. Techniques include measurements over open paths in situ, sampling and measurement in closed cells in the field or laboratory and, briefly, remote sensing using the sun, sky or natural hot objects as an IR radiation source. The techniques are applicable to a very wide range of compounds, including labile or reactive species, and all species are measured simultaneously. Detection limits vary with the application but are typically of the order of parts per billion (nmol mol−1) in air.
Laser Absorption Spectroscopy, Air Monitoring by Tunable Mid‐Infrared Diode
Authors: Tacke M. , Wienhold F. , Grisar R. , Fischer H. , Lübken F.‐J. 
Published: September 2006

Abstract

Infrared (IR) spectroscopy is a proven tool for gas analysis, and tunable mid‐IR diode laser absorption spectroscopy is a special technique giving optimum sensitivity, selectivity and measurement speed for most molecules of interest. Molecules such as the NO
x
family (N
2
O, NO, NO
2
, HONO, and HNO
3
) can be detected selectively down to well below part per billion levels. The technique works well with all molecules having line spectra and thus is quite universal. It is conceptually simple and detects gases by repetitively scanning absorption lines, which is possible due to the narrow laser line width and easy laser tuning. The scanning procedures of diode laser spectroscopy optimally reduce background fluctuations. Basic operation principles are explained in the article.

Alternative techniques are well established and often allow detection of single components at lower system cost, but in general need specific sample pretreatment that makes the results often difficult to compare. Mass spectroscopy is an alternative multicomponent technique that reaches comparable selectivity, but only with preselection processes which induce calibration problems of their own, such as matrix‐dependent sensitivity. In order to give an insight into the capabilities of tunable mid‐IR diode laser absorption spectroscopy, three exemplary systems are treated in detail for air monitoring from airplanes, from rockets, and gas analysis of combustion exhaust. System parameters are explained, and system performance is compared with alternative techniques.
Laser‐ and Optical‐Based Techniques for the Detection of Explosives
Authors: Monts David L. , Singh Jagdish P. , Boudreaux Gary M. 
Published: September 2006

AbstractA wide variety of optical‐ and laser‐based techniques have been and are currently being investigated as means of identifying and characterizing explosive materials. These efforts are hampered by the very low volatility of explosive compounds at room temperature and their tendency to ignite at higher temperatures where their vapor pressures are beginning to reach a regime where the species can be readily detected. Traditional, condensed‐phase absorption spectroscopy (both infrared (IR) and ultraviolet/visible (UV/VIS)) requires larger samples than are frequently available and, although useful as confirmatory techniques, do not provide signatures that enable unique identification of species. The choice of nontraditional techniques for analysis of explosive materials is dependent upon the amount of sample available, the sample matrix, and sample‐imposed constraints upon the measurement. Raman spectroscopy can identify and quantify condensed‐phase explosive materials, but the detection limit depends upon substrate, excitation wavelength, and illumination area: limits of detection (LODs) vary from 0.05 ng for 2,4,6‐trinitrotoluene (TNT) on glass to 10 µg for nitroglycerin (NG) on silica gel. The other detection techniques considered require volatilization of either the explosive compound itself or more often of characteristic decomposition products, such as NO, NO2, or N2O. Using IR irradiation, researchers have demonstrated that photoacoustic spectroscopy (PAS) has detection limits ranging from 0.55 ppb (parts per billion) for vapor‐phase NG with 9 µm excitation to 220 ppm (parts per million) for vapor‐phase 2,4‐dinitrotoluene (DNT) with 6‐µm excitation. IR laser differential absorption detection of dissociation products NO, NO2, and/or N2O can achieve detection limits of a few picograms. Laser‐induced fluorescence (LIF) detection of the photofragments (typically NO) of explosive compounds yields detection limits in the tens to hundreds of ppb (by weight) range. Low LODs can be achieved using ion detection techniques: resonance‐enhanced multiphoton ionization (REMPI) spectrometry is capable of LODs for detecting vapor‐phase explosives compounds in the hundredths to tens of ppb range; ion mobility spectrometry (IMS) has vapor‐phase detection limits for common explosive compounds of typically 200 pg, but for some species can be significantly lower: for example, 1 pg for TNT.
Photoacoustic Spectroscopy in Trace Gas Monitoring
Authors: Harren Frans J.M. , Cotti Gina , Oomens Jos , Hekkert Sacco te Lintel 
Published: September 2006

AbstractSince ancient times people have searched for ways to understand processes occurring in the environment, atmosphere or living organisms. Study of the gaseous trace compounds present may shed new light on chemical reactions taking place in the atmosphere or biochemical reactions inside organisms such as plants, animals and human beings. This article presents photoacoustic spectroscopy as a sensitive, on‐line and noninvasive tool for monitoring the concentration of trace gases. Following a short introduction and a historic overview, attention is focused on the description of devices and equipment which determine the detection limits and selectivity. An overview is given of the current detection limits for photoacoustic detection. Applications are discussed with emphasis on environmental monitoring (in ambient air, car exhaust and stack gas emission), on medical applications and on biological applications (in postharvest physiology, plant physiology, microbiology and entomology).
Asbestos Analysis
Authors: Höfert Norbert , König Reiner 
Published: September 2006

Abstract
The comprehensive use of asbestos in approximately 3000 industrial applications in the past requires asbestos analysis at present and in the future. The different analysis methods range from simple and cost‐effective procedures in order to decide whether asbestos is present up to the expensive and time‐consuming determination of low fiber number concentrations of asbestos fibers including the identification of the fiber type using highly sophisticated measurement equipment.
The following survey discusses the most relevant objectives of asbestos analysis and the measurement techniques that are applied:

Ambient/indoor air measurements – low concentration range, fiber type usually not known, identification required – using transmission electron microscopy (TEM) in combination with energy‐dispersive X‐ray analysis (EDXA) and selected area electron diffraction (SAED), and using scanning electron microscopy (SEM) in combination with EDXA.

Workplace air measurements – low to high concentration range, fiber type usually known, identification possibly required – using SEM, TEM, and phase contrast optical microscopy (PCOM).

Stationary source emission measurements using SEM, TEM, and PCOM.

Bulk material analysis – usually qualitative measurements; semiquantitative or quantitative results possible, if required – using SEM, TEM, infrared (IR) spectroscopy, PCOM, polarized light microscopy (PLM), and X‐ray diffraction (XRD).

Water analysis using TEM.
Atomic Fluorescence in Environmental Analysis
Authors: Cai Yong 
Published: September 2006

Abstract
Atomic fluorescence is a spectroscopic process which is based upon the absorption of radiation of a certain wavelength by an atomic vapor and subsequent radiational deactivation of the excited atoms toward the detection device. Both the absorption and the subsequent atomic emission processes occur at wavelengths which are characteristic of the atomic species present. Atomic fluorescence spectroscopy (AFS) is a very sensitive and selective method for the determination of a number of environmentally and biomedically important elements such as mercury, arsenic, selenium, bismuth, antimony, tellurium, lead, and cadmium. This technique has become one of the most important analytical tools for trace element analysis in environmental samples, such as mercury, owing to its advantages over other methods in terms of linearity and detection levels. Several books and a number of book chapters and review articles have been published dealing with the theory and instrumentation of AFS. This article will provide up‐to‐date AFS information regarding its application in environmental analysis.
Cyanogen Chloride and Cyanogen Bromide Analysis in Drinking Water
Authors: Xie Yuefeng , Hwang Cordelia J. 
Published: September 2006

Abstract

Cyanogen chloride (CNCl) (CAS
506‐77‐4
) is a common disinfection by‐product DBP formed in chloraminated waters. Cyanogen bromide (CNBr) (CAS
506‐68‐3
), the brominated analog of CNCl, is formed in chloraminated or ozonated waters that are high in bromide. Both CNCl and CNBr are labile in drinking water. They undergo degradation reactions at high pHs or in the presence of free chlorine or sulfite. Because of its potential health effects, CNCl was included in the United States Environmental Protection Agency (USEPA) Information Collection Rule (ICR). Aqueous standards for CNCl are generally prepared with pure CNCl gas. They can also be prepared with chlorinated or chloraminated cyanide (CN
−
) solutions. Aqueous standards for CNBr are prepared with commercially available CNBr. For sample preservation, ascorbic acid is commonly used to quench the residual chlorine or chloramines. Acid is often added to lower the pH to prevent possible hydrolysis degradation. There are three methods for analyzing CNCl and CNBr in drinking water samples: purge‐and‐trap gas chromatography/mass spectrometry (PT GC/MS), headspace gas chromatography/electron‐capture detection (GC/ECD), and micro liquid–liquid extraction gas chromatography/electron‐capture detection (LLE GC/ECD). All three methods are capable of analyzing microgram per liter levels of CNCl and CNBr in drinking water, and all three give similar method performance, including accuracy, precision, spiking recovery, and method detection limit. The PT GC/MS method is a modification of the USEPA Method 524.2, which requires the use of specialized instrumentation. Because of CNBr's low vapor pressure and high water solubility, the analysis of CNBr also requires a heated purge. Headspace GC/ECD method is a relatively simple and rapid analytical method. As the samples are prepared individually, the method requires a full‐time analyst to prepare and inject each sample. However, this analytical procedure can be automated using a commercially available headspace autosampler. In general, micro LLE GC/ECD is a well developed and common procedure for DBP analysis. The micro LLE GC/ECD method, originally developed for CNBr analysis, has been further developed for both CNCl and CNBr analysis in drinking water. The sample injection generally is automated with a common gas chromatography (GC) autosampler.