bluuebunny/crossref_metadata_2025 huggingface dataset:
Planar Chromatography in Clinical Chemistry
Authors: Jain Raka , Sherma Joseph
Published: September 2006

Planar chromatography (PC) like any other chromatographic technique is a multistage distribution process. It is a form of liquid chromatography in which the stationary phase is supported on a planar surface rather than a column. Separations in PC occur because of differential migration velocities through the sorbent layer in a fixed separation time. The sample zones are fixed in space at the completion of the separation, allowing off‐line monitoring. There are two planar techniques: paper chromatography and thin‐layer chromatography (TLC). In recent years, TLC has superseded paper chromatography owing to greater speed, versatility, and reproducibility. Improvements in techniques and equipment as well as the ready availability of high‐quality plates with uniform layers have extended and increased the use of TLC in clinical chemistry and other disciplines, offering quantitative as well as qualitative analysis. High‐performance thin‐layer chromatography (HPTLC), in particular, has developed to the extent that separation and quantitation can provide results that are comparable with other analytical methods such as high‐pressure liquid chromatography (HPLC). The widespread application of TLC is also due to the fact that it is simple, robust, and flexible, and has a large sample throughput. Furthermore, coupled spectroscopic methods (TLC/mass spectrometry (TLC/MS), TLC/Fourier transform infrared spectrometry (TLC/FTIR) etc.) have considerably enhanced the reproducibility of TLC.

TLC is often critically compared with column chromatography such as HPLC. This is a matter of endless dispute. Each technique has its own advantages and limitations. TLC is only inexpensive when qualitative results are needed. When reliable quantitative data are required, TLC is as expensive as column chromatography. In the authors' opinion, complementary rather than competitive chromatography offers the best solution to analytical requirements.
Urinalysis and Other Bodily Fluids
Authors: Free Helen M. , Free (deceased) Alfred H.
Published: September 2006

The chemical analysis of urine and other body fluids is an integral part of laboratory medicine today. Clinical chemistry measurements are made in laboratories ranging from large medical research/teaching centers to small rural physicians' offices, and with varying degrees of sophistication in all parts of the world. Indeed, the use of chemical tests at home is currently an important part of monitoring chronic conditions such as diabetes, and this aspect of chemical testing is expected to expand.

This article traces the historical methods of urine testing to provide information on health and disease, from crude visual examination in ancient times to modern techniques using sophisticated chemical instrumentation. The information obtained is useful in the diagnosis of disease, in monitoring the course of the treatment of disease, and in helping to maintain wellness in normal populations.

The chemical tests most widely used in urinalysis are described in some detail along with a discussion of the development of commercial tests leading to the evolution of the diagnostics industry. Chemical tests on other bodily fluids are briefly summarized.
Infrared and
R
aman Spectroscopy and Imaging in Coatings Analysis
Authors: Urban Marek W.
Published: September 2006

This monograph provides fundamental concepts utilized in infrared (IR) and Raman analysis of coatings as well as applications of attenuated total reflectance (ATR), reflection–absorption (RA), photo‐acoustic (PA), and IR/Raman imaging techniques. This choice of techniques is dictated by the fact that these techniques alone or their combination allow one to obtain a three‐dimensional molecular level representation of polymeric coatings, quantitative or semi‐quantitative analysis, surface/interfacial depth profiling, and determination of structure–property relationships in coatings. As a result, the effect of molecular level interactions/processes on macroscopic properties can be elucidated.
Mechanical Properties of Solid Coatings
Authors: Koleske Joseph V.
Published: September 2006

Coatings can be liquid or solid materials; they have been known and used from the time of early man and are of major importance for protecting and decorating the myriad of items in use today. These thin protective films are used to coat commercial and residential buildings (architectural coatings) and for many products in use today (industrial coatings). This article is concerned with the formation of coating films and the properties of these films. Static and dynamic mechanical properties, flexibility, toughness, adhesion, hardness, abrasion resistance, slip, chemical resistance, and stress within coatings are discussed and ways to investigate these characteristics are given. Some of the end‐uses and the relationship of coating properties to the uses are detailed.
Microscopy of Coatings
Authors: Rädlein Edda
Published: September 2006

Fundamental research on films and the development and optimization of coatings are not possible without high‐resolution imaging. This article describes the advantages and disadvantages of the newly introduced scanning probe microscopy (SPM) in comparison with well‐established microscopy techniques with light and particles [e.g. scanning electron microscopy (SEM) and transmission electron microscopy (TEM)], which are limited by the diffraction limit, i.e. 200 nm for conventional light microscopy and 4 nm for SEM. This limit does not hold for SPM, which uses near‐field interactions for imaging. Thus, even simple atoms or molecules can be resolved on well‐ordered structures by scanning tunneling microscopy (STM) or atomic force microscopy (AFM). Both possess an extremely good height sensitivity of 0.02 nm.1In the constant‐height operation mode, AFM can detect vertical forces as low as 10−15–10−4 N. Atomic resolution is not always possible or not always necessary for many practical applications; a lateral resolution of a few nanometers is sufficient. Besides the capability of achieving this value with ease, simple sample preparation, versatile environmental conditions and observation of reactions in situ are advantages of STM and AFM.

Especially AFM has proved to be a useful technique for investigating coatings, because it is independent of conductivity and provides topographic data together with information on structure, local variations of mechanical properties and surface alterations in different media. However, some artifacts and restrictions have to be considered which can differ considerably from customary electron micrographs with comparable resolutions, such as onset overswing and tip convolution.

Microscopy helps in solving coating problems according to substrate quality, nucleation, wettability, thickness, roughness, microstructure, crystal phases (texture, orientation), lateral and vertical homogeneity, density, porosity, interfaces, adhesion, hardness, stress, scratch and abrasion resistance, tribology, wear and corrosion. Practical examples of microscopy results on these questions are presented together with suitable preparation methods and interpretation of artifacts.
Thermal Analysis of Coatings
Authors: Meyer Edwin F.
Published: September 2006

The thermal analysis of coatings involves measuring the response of a material when subjected to a thermal stimulus, sometimes in combination with a mechanical stress. The thermal stimuli used in the thermal analysis of coatings include linear temperature ramps, a sinusoidal modulation around a fixed temperature, the superposition of a linear ramp and a sinusoidal modulation, and a simple isotherm in which some property of the material is monitored as a function of time. The responses measured by the thermal analyst include: melting, crystallization, evaporation, degradation, stress relaxation, softening point, and glass transition, as well as physical properties such as the elastic and viscous moduli. These responses aid in the development, characterization, and determination of the proper application and bake conditions for a wide range of coatings.

In general, thermal analysis techniques are very sensitive and, for many applications, a sample mass of the order of 10 mg is sufficient. However, the assignment of a thermal event to a particular chemistry or morphology requires knowledge of the system being analyzed or another analytical technique. For example, thermal analysis can accurately determine the temperature and enthalpy of a crystalline polymer melt but it does not provide any other information as to the chemistry of the polymer. Assigning a cause to a thermal event becomes increasingly difficult as the nature of the material becomes more complicated. Such is the case with a fully formulated coating which contains a wide range of polymeric and oligomeric materials, as well as various additives. To determine which chemistry is responsible for a particular thermal transition, other analytical techniques are used, frequently in direct combination with the thermal analysis technique.
Airborne Instrumentation for Aerosol Measurements
Authors: Stefanutti Leopoldo , Borrmann Stephan
Published: September 2006

This paper gives a description of airborne and balloon‐borne instrumentation for the measurement of microphysical properties and the chemical composition of aerosol and cloud particles. Different techniques are described. In particular the instrumentation is subdivided into two broad categories: remote sensing instrumentation and in situ instrumentation. In the first category are instrumentation like cloud RADARs (radio detection and ranging), LIDARs (light detection and ranging), backscattersondes, limb and occultation aerosol detection devices. They can determine the microphysical properties of the aerosols and, only with complex a priori assumptions, their chemical composition. Among the in situ instrumentation, for example, optical particle counters (OPCs), condensation particle counters (CPCs) determine the microphysical properties of aerosols, while their chemical composition is determined by means of mass spectrometers, and the counterflow virtual impactor (CVI) technique associated with tunable diode laser and Lyman‐α spectrometers.
Differential Optical Absorption Spectroscopy, Air Monitoring by
Authors: Platt Ulrich
Published: September 2006

Differential optical absorption spectroscopy (DOAS) allows the quantitative determination of atmospheric trace gas concentrations by recording and evaluating the characteristic absorption structures (lines or bands) of the trace gas molecules along an absorption path of known length in the open atmosphere. The DOAS technique is characterized by the following: (1) measuring the transmitted light intensity over a relatively (compared to the width of an absorption band) broad spectral interval; (2) high‐pass filtering of the spectra to obtain a differential absorption signal and eliminating broad‐band extinction processes such as Rayleigh and Mie scattering (RS and MS); and (3) quantitative determination of trace column densities by matching the observed spectral signatures to prerecorded (reference) spectra by, for instance, least‐squares methods.

DOAS shares the advantages of most other spectroscopic techniques, including inherent calibration, sub‐parts per trillion (ppt) to ppt sensitivity and precision (1–10%), good specificity, wall‐less operation, and the capability for remote measurements. In particular, the concentration of very reactive species such as the free radicals OH, NO3, ClO, BrO, and IO are determined with DOAS. Other species of interest to atmospheric chemistry are also measurable such as SO2, CS2, O3, NO, NO2, HONO, NH3, CH2O, and most monocyclic aromatic hydrocarbons.

A description of the technique is given, and the various modes of operation and light‐path configurations are explained. The emphasis of this article is on the practical aspects of instrument design, components of DOAS systems, operation of DOAS instruments, and state‐of‐the‐art techniques for the evaluation of DOAS spectra and realistic determination of detection limits. Finally some examples of DOAS applications are given.
Diode Laser Spectroscopic Monitoring of Trace Gases
Authors: Tittel Frank K. , Petrov Konstantin P.
Published: September 2006

Modern diode laser spectroscopy is becoming an important and a more widely used tool for detection and measurement of trace gases. The change is driven by the recent advances in diode laser technology and diode laser frequency conversion techniques, which now push the limits of emission wavelength, output power, operating temperature, miniaturization, and cost. Basic features of the diode laser now find new, interesting, and unique use in well‐established laboratory and field applications related to trace‐gas detection, and in some instances even transform the traditional spectroscopic methods. It is the purpose of this chapter to familiarize the reader with the key elements of diode laser technology and analytical methods used in diode laser spectroscopy.
Laser‐Induced Breakdown Spectroscopy, Elemental Analysis
Authors: Yueh Fang‐Yu , Singh Jagdish P. , Zhang Hansheng
Published: September 2006

Laser‐induced breakdown spectroscopy (LIBS) is a laser‐based technique that can provide nonintrusive, qualitative and quantitative measurement of metals in various test environments. LIBS is an emission‐type technology that has been successfully applied to gas, liquid, and solid samples. The major advantages of LIBS compared to other analytical techniques is that no time‐consuming sample preparation is necessary. LIBS uses the plasma generated by a high‐energy laser beam to prepare and excite the sample in one step. It has the ability to perform multielement real‐time analysis. Its major disadvantage is that the excitation condition is sensitive to the fluctuation of environmental conditions as well as the laser energy, which can result in poor measurement precision. The small amount of sample material used in LIBS analysis also gives poorer sensitivity for some metals compared to inductively coupled plasma atomic emission spectrometry (ICPAES) and atomic absorption spectrometry (AAS).

The potential of LIBS to detect toxic metals in harsh environments was recognized in the early 1970s. Recent developments towards improving its analytical capability has led to more applications. This article reviews the analytical applications of LIBS with an emphasis on environmental monitoring. A brief review of some fundamental LIBS studies is also given. The analytical abilities of LIBS are compared with some spectroscopic techniques commonly used in the laboratory, such as AAS, ICPAES, and X‐ray fluorescence spectroscopy (XFS).
Laser Mass Spectrometry in Trace Analysis
Authors: Boesl Ulrich , Heger Hans‐Jörg , Zimmermann Ralf , Nagel Holger , Püffel Peter
Published: September 2006

Laser mass spectrometry (laser‐MS) in molecular trace analysis involves two analytical tools: Ultraviolet (UV)‐spectroscopy in the gas phase and time‐of‐flight mass selection. Both tools are combined by resonance‐enhanced multiphoton ionization (REMPI). This type of mass spectrometry is therefore called resonant laser‐MS in the following text. The special features of resonant laser‐MS are high selectivity, rapidity, multicomponent capacity, and adaptability for application to many different problems. Beneath the fundamental principle of this analytical technique (i.e. REMPI and time‐of‐flight mass selection) several options are described in this article, such as medium or high resolution of mass selection and UV‐spectroscopy. These options allow more or less sophisticated instrumentation and optimized adaptation to specific analytical problems. The reader will be introduced to the principles of resonant laser‐MS and then to its history and the state‐of‐the‐art of its application. This organization should help the reader to recognize the importance of the early experiments and of modern tendencies for application of laser‐MS in trace analysis. The large experimental and instrumental variety and the tables of numerous researchers and applications presented in section 3 may demonstrate the flexibility and growing acceptance of resonant laser‐MS. The examples presented, which illustrate the usefulness of resonant laser‐MS in practice, include on‐line trace analysis of emissions from combustion processes, e.g. from combustion engines or municipal incinerators. The article ends with a discussion of possible calibration processes, detection limits, and a summary of specific features.
Ultraviolet/Visible Light Detection and Ranging Applications in Air Monitoring
Authors: Wolf J.‐P.
Published: September 2006

Recent progress in light detection and ranging (LIDAR) and differential absorption light detection and ranging (DIAL) technology has allowed three‐dimensional (3‐D) mappings of concentrations of air pollutants to be obtained at the highest sensitivity (parts per billion) and over large distances (several kilometers). It is now possible to monitor on‐line spatial distributions of nitrogen oxides, sulfur dioxide, ozone, benzene, toluene, and aerosols. With the advent of new tunable all‐solid‐state laser systems, such as vibronic lasers and optical parametric oscillators (OPOs), LIDAR systems have furthermore reached the highest industrial standards in terms of reliability and ease of operation. An overview of results and capabilities of “all‐solid‐state” LIDAR/DIAL systems is presented. The examples of application include detailed urban studies performed in large cities (e.g. Berlin, Leipzig, Lyon, Stuttgart, Geneva, Athens, Seville), with special attention to the first direct access to smog formation processes and tropospheric ozone generation. Industrial applications are also numerous, such as site monitoring, identification of diffuse emissions, and evaluation of the impact of new emitters through plume dispersion studies. The use of LIDAR systems to validate numerical models is also discussed. The last section is dedicated to the calibration of the systems, intercomparison with standard analyzers, and legal aspects in terms of certification and new standards.
Luminescence in Environmental Analysis
Authors: Campiglia Andres D.
Published: September 2006

An overview of the applications of photoluminescence techniques for the analysis of polycyclic aromatic compounds (PACs) in environmental samples is presented. The basic experimental procedures of several techniques, such as room‐temperature fluorimetry, low‐temperature phosphorimetry (LTP), micelle‐stabilized room‐temperature phosphorimetry (MSRTP), sensitized room‐temperature phosphorimetry (RTP), solid‐surface room‐temperature phosphorimetry (SSRTP), and Shpol'skii spectrometry at 77 K are provided. Analytical figures of merit, such as linear dynamic ranges (LDRs) of calibration curves, limits of detection, and relative standard deviations (RSDs), are compared. Basic spectrofluorimeters for direct laboratory analysis of organic pollutants and instrumental systems utilized for chromatographic detection are discussed. Emphasis to portable devices using laser excitation is given to illustrate the usefulness of photoluminescence techniques for field and remote analysis of contaminated sites. Specific examples of emerging technology developed in the author's laboratory are presented to illustrate recent advances in photoluminescence analysis of environmental samples.
Biological Samples in Environmental Analysis: Preparation and Cleanup
Authors: Barker Steven A.
Published: September 2006

The most difficult samples to analyze are those derived from biological sources. The analysis of biological samples requires the ability to extract and isolate a wide range of environmental pollutants from an even wider range of matrices, from simple bacteria to tissues and fluids from humans, from fungi to the complex tissues and structures of the plants and products that compose the food chain. These matrices comprise a variety of cells, connective tissues and fibers, fluids and related materials that introduce literally thousands of different organic and inorganic compounds to every analysis effort. In order to recognize and assess the nature and severity of pollution and its impact on humans as well as the flora and fauna that constitute our environment, highly efficient and selective methods for the extraction and cleanup of such samples must be developed. New developments in analytical science have been brought to bear on this problem, speeding the extraction and analysis process while making the resulting analyses more sensitive and selective. The present article examines the historical approach to the extraction and cleanup of biological samples for the analysis of pollutants, and reviews recent advances in technology and methodology that have proven applicable to this field.
Capillary Electrophoresis Coupled to Inductively Coupled Plasma‐Mass Spectrometry for Elemental Speciation Analysis
Authors: Wang Xiaoru , Lee Frank Sen‐Chun
Published: September 2006

Speciation analysis is a term commonly used to describe the analytical processes of identifying and measuring the different chemical forms of trace elements in the sample. Starting from the mid‐1980s, analytical techniques for elemental speciation analysis have been advancing at an accelerated pace owing to the rapid advancement in analytical instrumentation. Such advancement is especially evident in the development of hyphenated techniques, which involve the on‐line coupling of a species‐specific separation device with an elemental‐specific detection system. They are now well accepted as the methods of choice for speciation analysis because of their speed, sensitivity, specificity and resolution. Capillary electrophoresis/inductively coupled plasma mass spectrometry (CE/ICPMS) is one of the newest members of this family of hyphenated techniques which has found increasing applications in speciation analysis in recent years. Until today, chromatography has been the dominant separation technique in hyphenated techniques and the subject has been extensively reviewed. However, literature information on capillary electrophoresis (CE)‐based hyphenated techniques is much less available. In this chapter, the current status of CE/ICPMS will be reviewed with emphasis being placed on the interface design, analytical performance and applications of the different versions of the technique in speciation analysis.
Detection and Quantification of Environmental Pollutants
Authors: Gibbons Robert D.
Published: September 2006

With increasing concern over chemicals that are potential health hazards at low levels, determination of limits of detection and quantification have undergone considerable scrutiny. Most traditional detection limit (DL) estimators suffer from extensive statistical and/or conceptual limitations. In this article, traditional detection and quantification limit estimators are described and critically evaluated. Methods are categorized into decision limits, DLs and quantification limits. The methods are further categorized into single concentration design versus calibration design methodologies. While the single concentration design methods are useful for fixing ideas and clarifying definitions they are shown to be extremely limited in practice since dependence of variability on concentration can be neither estimated nor incorporated. Calibration‐based detection and quantification limit estimators are described, compared and contrasted. Discussion of nonconstant variance, multiple future detection decisions and simultaneous control of Type I and II errors is provided. The various methods are illustrated using real data and experimental design issues for DL studies discussed.
Dioxin‐Like Compounds, Screening Assays
Authors: Bunce Nigel J. , Petrulis John R.
Published: September 2006

A dioxin‐like compound (DLC) is a halogenated aromatic compound that has toxicological properties similar to those of the reference toxicant 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD). The DLCs include other halogenated dibenzo‐p‐dioxins and dibenzofurans (especially those that are chlorinated in the 2‐,3‐,7‐, and 8‐positions), and coplanar polychlorinated biphenyls (PCBs). They associate with the aryl hydrocarbon receptor (AhR) protein, and share some biological end‐points with TCDD, notably the induction of Phase 1 monooxygenase enzymes. Because DLCs normally occur as complex mixtures in environmental and biological samples, it is common to refer to the TCDD equivalent concentration [toxic equivalence (TEQ)], which is obtained by summing for each congener its actual amount or concentration by an empirical toxic equivalency factor (TEF). Conventional analysis of DLCs by gas chromatography/mass spectrometry (GC/MS) is cumbersome and expensive, and much attention has been given to developing bioassays that will yield a measure of the TEQ in a single determination. Many such bioassays are mechanism‐based, meaning that the assay end‐point is one of the steps along the pathway of the mechanism of action.

This article begins with an overview of bioassay methods in general, pointing out similarities and differences between chemical assays and bioassays, before describing particular assays that have been developed for DLCs. Among mechanism‐based assays, AhR binding assays are well established, and are useful because they include the dioxin‐like activity of both productive and unproductive compounds. In assays based on subsequent stages of the mechanism of action, unproductive substances can antagonize the responses of productive compounds, a phenomenon that is explicable in terms of target molecule antagonism, in which the AhR protein is the target molecule.

Immunoassays for DLCs have recently received much attention; although their spectrum of cross‐reactivity does not always correlate well with TEFs, there has been important recent progress in terms of the sensitivity and detection limit (DL) of these assays. Finally, early life stage bioassays are becoming increasingly important as research has revealed the toxicological effects of DLCs during development.
Dyes, Environmental Analysis of
Authors: Riu J. , Barceló D.
Published: September 2006

An overview of current analytical methodologies for the determination of dyes in environmental samples is presented. Conventional analytical methods involving liquid chromatography (LC) and mass spectrometry (MS) with thermospray (TSP) interface are reviewed as well as the newly developed methods using atmospheric pressure ionization (API) interfaces. The combination of capillary electrophoresis (CE) with MS as a new alternative for the analysis and confirmation of polar compounds (and particularly the sulfonated azo dyes) in environmental samples is also discussed. Finally, the extraction and preconcentration of dyes from water samples involving various solid‐phase extraction (SPE) cartridges are commented upon.
Flow‐Injection Techniques in Environmental Analysis
Authors: Burguera J.L. , Burguera M.
Published: September 2006

An overview is given on the most important applications of flow‐injection (FI) systems developed for environmental materials, highlighting their main basic components and modes. Also, the article systematically describes the different FI manifolds coupled to spectrometric or electrochemical (EQ) detectors used for the determination of analyte species to offer diverse solutions in the analysis of various samples.
Inorganic Analysis in Environmental Samples by Capillary Electrophoresis
Authors: Kim Yangsun
Published: September 2006

Capillary electrophoresis (CE) is a very useful technique which involves the separation of charged species (molecules) on the basis of their movement under the influence of an applied electric field in a capillary format. CE has been developed into rapid, highly effective techniques with extremely high separation power (105–107theoretical plates) and high mass sensitivity (femtomole to zeptomole amounts of substances in nanoliter to picoliter sample volumes) with high potential for separation in the analysis of environmental sample. CE has been compared with ion chromatography (IC) in the inorganic analysis of environmental samples since inorganic ions are usually separated by IC with suppressed conductivity detection. The advantages of CE compared to IC are speed, resolution, and the lack of a need for gradient elution. Operating costs are considerably lower, since ion‐exchange columns are usually expensive. In application, however, limitations imposed by the lack of detection sensitivity complicate the technique's use and impede its wide acceptance. However, as instrumental development continues (especially in detection mode and other techniques for manipulating sensitivity), this limitation will most likely be overcome and a diversity of inorganic species in real samples has already been proved to be amenable to the analysis by CE, and more can be expected in the years ahead.

In this article, to understand how CE can be applied to separation and detection of inorganic ions of environmental sample, the basic principles underlying this technique and the operating parameters of CE for inorganic analysis of environmental samples are presented. For trace analysis of environmental samples, methods for manipulating the sensitivity and selectivity control for metal ions are discussed. Techniques such as the coupling of CE with inductively coupled plasma mass spectrometry (ICPMS) are also discussed. Specific applications in real world samples which have complex matrices as well as artificial samples or reference materials are offered to demonstrate the potential of CE in the analysis of environmental pollutants.
Ion‐Selective Electrodes in Environmental Analysis
Authors: Forster Robert J. , Keyes Tia E.
Published: September 2006

An ion‐selective electrode (ISE) is an electroanalytical sensor that produces a potential whose magnitude is dictated by the activity of a small number of ions. The signal is generated by selective partitioning of a charged analyte across the sample–electrode interface. These sensors allow a wide range of environmental pollutants to be detected and quantified rapidly, sensitively and selectively.1 The
ideal
ISE can be inserted into the sample and will display the result of the chemical analysis within a few seconds with high precision and selectivity. Often no sampling, dilution or reagent addition is required, and changes in the analyte concentration or activity can be displayed in real time. Beyond the classical glass pH electrode invented in the early 1900s, the field now includes electrodes with several selective membranes for both sensing analytes and eliminating interferences, as well as ion‐selective field‐effect transistors (ISFETs). These new sensing approaches have greatly extended the range of environmentally relevant molecules that can be measured, and sensors exist for environmental pollutants as diverse as atmospheric carbon dioxide and radionucleotides in highly acidic solutions.
Mercury Analysis in Environmental Samples by Cold Vapor Techniques
Authors: Anderson Kim A.
Published: September 2006

The accurate, precise, and automated determination of mercury in biological and environmental samples is complex, not only because of the various oxidation states of mercury (i.e. 0, I and II), but also because of biotic and abiotic methylation and the volatility of several forms of mercury(I and II). Mercury is unique among the metals because of its large vapor pressure at ambient conditions. Mercuric ions in solution can be reduced by tin(II), or sodium borohydride to produce volatile elemental mercury, referred to as the cold vapor process. The mercury is swept out of solution with a carrier gas (in the gas of sodium borohydride, the byproduct is hydrogen) into the cell (or torch) where the atomic absorption (or fluorescence, or emission) is measured. The cold vapor technique removes the mercury from the sample matrix, concentrates the mercury in the analytical sample into a small plug of carrier gas, and provides for a relatively long residence time. Detection limits vary depending on the instrument but are in the submicrogram to nanogram per liter range for atomic absorption spectrometry (AAS), atomic fluorescence spectrometry (AFS), and inductively coupled plasma atomic emission spectrometry (ICPAES).
Neutron Activation in Environmental Analysis
Authors: Randle Keith
Published: September 2006

After a brief historical survey of the role of neutron activation analysis (NAA) in environmental analysis there follows a section on the main types of NAA and their application to environmental problems and a table of ideal sensitivities is given. The rest of the article deals with NAA as it is applied to the main divisions of the environment. Each of these sections includes a short summary of the sampling requirements suitable for NAA. Section 3 deals with its application to biological samples and includes a brief discussion on standard reference materials (SRMs) in NAA. Applications to various types of biological material are discussed, ending with a survey of biomonitoring using NAA. The next section (the longest) is the analysis of water by NAA. This is mainly based on the preconcentration and postirradiation procedures currently used for the major types of water (seawater, surface water and underground water). A table of element concentrations in seawater and surface water illustrates the low limits of detection required to determine many trace elements by instrumental neutron activation analysis (INAA). Applications are discussed in the main body of the text. There then follows a section on the use of NAA in air particulate analysis for trace elements. The importance of PM10s (particles with aerodynamic diameter less than 10 µm) to human health and the reasons for concentrating on the analysis of these particles by NAA is discussed. Having discussed the main areas of NAA used there follows an application section. Large‐scale biomonitoring procedures are outlined, particularly those involving plant materials. The final section on major environmental divisions covers the use of NAA in analysis of soils and sediments together with the analysis of coal. This latter topic also includes on‐line analysis of coal using isotope sources. Finally, there is a discussion of speciation and the function of NAA in environmental speciation, particularly atmospheric and aqueous speciation analysis.
Nitroaromatics, Environmental Analysis of
Authors: Schmidt Torsten C. , Steinbach Klaus , Bütehorn Ulf
Published: September 2006

Nitroaromatic compounds (NACs) are important anthropogenic chemicals, which may enter all areas of the environment in significant amounts. Once there, they may be transformed, mainly via redox reactions. Most NACs and their transformation products are rather toxic, both in humans and ecosystems, and they are especially known for their carcinogenic potential. Thus, input and detrimental effects of NACs make environmental surveillance necessary, which in turn requires selective, sensitive, unbiased and robust methods suitable for the analysis of complex mixtures. These requirements are mainly fulfilled by the combination of an enrichment step with chromatographic separation and use of an appropriate detector. Official methods today use liquid–liquid extraction (LLE) or solid‐phase extraction (SPE), followed by high‐performance liquid chromatography (HPLC) with ultraviolet (UV) detection, or gas chromatography (GC) with electron capture detection (ECD). These methods are widely established and have been thoroughly tested in interlaboratory comparisons. However, new methods for extraction, separation and detection are emerging, which are superior in terms of the required characteristics, and thus may replace the existing methods in the future. Both standard methods and new developments for the environmental analysis of NACs are discussed in this article. Regarding the references given, priority was given to the most recent developments, and thus about 70% of the cited literature is less than five years old.
Optical Emission Inductively Coupled Plasma in Environmental Analysis
Authors: Tatro Mark E.
Published: September 2006

The ability of the ICP/AES (inductively coupled plasma/atomic emission spectroscopy) system to perform multielement trace metal analysis of environmental samples provided commercial laboratories with the needed incentive to enter into the business of trace metal analysis. Previously, trace metals were typically analyzed using colorimetric techniques, which were both cumbersome and subject to interferences, or flame atomic absorption techniques, which although almost interference free, were labor intensive owing to their one element at a time analytical mode. Even the furnace atomic absorption technique, for years the standard bearer of low‐level trace metal analysis, is giving way to axial viewed ICP/AES techniques.

Taking the USEPA (United States Environmental Protection Agency) SW‐846 solid waste analysis manual as an example, this article reviews the methods used for the preparation of samples and the ICP/AES analysis of the prepared samples for trace metals in environmental matrices. The review includes a detailed overview of the quality control (QC) requirements for environmental ICP/AES analysis.
Polychlorinated Biphenyls Analysis in Environmental Samples
Authors: van Bavel Bert , Tysklind Mats , Lindström Gunilla
Published: September 2006

The analysis of polychlorinated biphenyls (PCBs) in a wide variety of environmental samples is discussed, starting with the more traditional methodology and moving on to more recent developments that are expected to continue in the twenty‐first century. Several detection techniques, including gas chromatography (GC) coupled with electron capture detection (ECD) and mass spectrometry (MS), are described in the first part of this article. The use of MS as a detection technique is discussed in detail, from both a qualitative and a quantitative point of view. To a large extent the detection technique used determines the sample pretreatment and clean‐up, and in later paragraphs column clean‐up on adsorbents is discussed, including fat removal, alumina column chromatography and planar separation on carbon. A new methodology for the analysis of PCBs in environmental samples is also described. Both speed of analysis using gas chromatography/time‐of‐flight mass spectrometry (GC/TOFMS) and environmentally friendly analysis using supercritical CO
2
are discussed in detail. In the last section several aspects of quality assurance/quality control (QA/QC) are discussed using an international intercalibration study as an example.
Proton‐InducedX‐Ray Emission in Environmental Analysis
Authors: Ghermandi Grazia
Published: September 2006

Particle‐induced X‐ray emission (PIXE) is an analytical method based upon X‐ray spectrometry. In the vast majority of applications, a proton beam is used to eject inner‐shell electrons from atoms in a solid specimen (target). When the resulting vacancies are filled by outer‐shell electrons, characteristic X‐rays whose energies identify the particular atom are emitted.

Proton PIXE is performed by a small particle accelerator (the most widely used is the Van de Graaff machine at a 2–3 MV voltage, more recently also small tandem accelerators), that provides a beam of protons. The beam emerging from the accelerator, stabilized and directed by electrostatic and magnetic steering elements in a high vacuum line, enters the specimen chamber through suitable collimators. The X‐ray detection system, housed in the chamber, is generally a Si(Li) device, that combines the advantage of high efficiency in the X‐ray energy region of interest (usually 2–20 keV) with a good energy resolution.

A typical PIXE spectrum consists of characteristic X‐ray peaks superimposed on a background due to bremsstrahlung radiations and nuclear reactions induced by the beam. The area of each peak is related directly to the concentration of the corresponding element in the specimen. Various software codes have been developed to deconvolute spectra and to accurately calculate peak areas.

PIXE intrinsic detection limit (DL) is not very much below 1 ppm (mg kg−1) in a given matrix. It offers its maximum sensitivity in two atomic number (Z) regions: 20 < Z < 35 and 75 < Z < 85. Measurement errors are in the order of 10%, depending mainly on the target preparation procedure and on the slight variability of the proton flux.

The PIXE technique allows fast (few minutes), nondestructive, highly sensitive simultaneous determinations of a wide group of elements (12 ≤ Z ≤ 85), without large variations in sensitivity among different elements. The total element concentration is measured by PIXE, independent of different oxidation states. Adequate sample preparation procedures may be required in environmental PIXE applications since solid targets have to be exposed to the particle beam. Thin targets are preferable, in order to minimize matrix effects. For thin samples and for light‐element matrices, PIXE has superior sensitivity compared to X‐ray fluorescence (XRF). In heavy‐element matrices XRF is preferable. DLs for inductively coupled plasma atomic emission spectroscopy (ICPAES) may be lower than for PIXE (depending on the sample dilution factor), but the topic of interferences is much more complex for ICPAES than for PIXE.
Quality Assurance in Environmental Analysis
Authors: Clark Malcolm J.R.
Published: September 2006

Vigorous and thorough programs of quality assurance (QA) are vital to ensure that environmental analysis studies yield results which are trustworthy, scientifically credible, and of known quality commensurate with their intended use. Mistakes in any step of the environmental analysis process can result in a substantial increase in random and nonrandom errors. Poor design of an environmental analysis program or failure to adhere to good scientific practices (GSP) for every step of the environmental analysis process can result in compromised or even meaningless results. Therefore, a holistic approach must be taken to ensure adequate QA is implemented for each and every step of the environmental analysis process, from initial study design through final information reporting. However, there is a substantial economic cost toincorporate QA on such a thorough and comprehensive basis. Therefore, QA efforts are unlikely to succeed unless management is committed to the value of these efforts. Increased recognition of the importance of QA, plus broadened international adoption of harmonized standard QA methodologies, has substantially improved the reliability of environmental analyses. QA ensures that environmental monitoring results are compatible with project goals, are comparable between different agencies, and maintain a high degree of scientific credibility. The key elements of QA programs include comprehensive planning, defined data quality objectives (DQOs), thorough training of personnel, standard operating procedures, detailed documentation, timely resolution of problems, regular reporting, routine independent audits plus regular challenges of study elements.
Sample Preparation for Environmental Analysis in Solids (Soils, Sediments, and Sludges)
Authors: Kimbrough David Eugene
Published: September 2006

The purpose of the analysis of environmental contaminants, such as pesticides, organic solvents, and toxic elements, in solids is to provide the basis for certain environmental decisions. Thus, the needs of the end user of the analytical procedures are the guide to understanding sample preparation. Two common goals for end users are regulatory compliance and data comparability, which is why it is very common to use standardized analytical procedures. There are two steps in the analysis of solids, the separation of analytes of interest from the rest of the sample and then the instrumental analysis of the analytes. The first step is the topic of this article. More than any other medium, solids are subject to severe matrix effects. The sample matrix is the portion of the sample not of interest except to the extent it affects the analysis of the portion that is of interest. Matrix effects can include reactions that prevent the separation of the analytes from the sample matrix or the inclusion of nontarget materials that interfere with the instrumental analysis. Other issues with sample matrix include heterogeneity and moisture content. A heterogeneous sample can give unrepresentative results and the moisture content can change over time and lead to variable results. These issues are often dealt with by drying and homogenization. The two most common types of analyte that require sample preparation are elements (e.g. copper and lead) and nonvolatile organic compound (NOC) (e.g. pesticides and polychlorinated biphenyls (PCBs)). Acid digestion is the most common sample preparation for elemental analysis. The acid must be aggressive enough to break the bonds between the analyte and the matrix and it must yield a form of the element soluble in the acid. NOCs are generally extracted from the sample matrix by organic solvents. The extraction solvent must be more soluble to the analyte than the sample matrix and the solvent must be able to penetrate into the sample matrix in order to solubilize the analyte. Thus the correct selection of acids and extraction solvents is the key to successful extraction
Soil Instrumental Methods
Authors: Carter M.R. , Curtin D. , Gregorich E.G.
Published: September 2006

Instrumental methods play an important role in the analysis of soil material. Soil is composed of mineral, organic, water, and air components. Analytical methods are required that characterize the fitness or quality of soils to perform various functions, such as providing a medium for plant growth, recycling waste products, and regulating and storing water, energy, and nutrients. The objective of this article is to describe the basic concept and approach to laboratory analysis of soil, and to outline the application of techniques used in the analysis of soil quality properties. Emphasis is placed on soil sampling and sample preparation, followed by a description of the possible instrumental methods available for the analysis of the chemical, biochemical, and physical properties of soil.
Solid‐Phase Microextraction in Environmental Analysis
Authors: Pawliszyn Janusz
Published: September 2006

Solid‐phase microextraction (SPME) uses a small volume of sorbent dispersed typically on a surface of small fibers to isolate and concentrate analytes from a sample matrix. After contact with the sample, analytes are absorbed or adsorbed by the fiber phase (depending on the nature of the coating) until an equilibrium is reached in the system. The amount of an analyte extracted by the coating at equilibrium is determined by the magnitude of the partition coefficient of the analyte between the sample matrix and the coating material. After the extraction step, the fibers are transferred, with the help of the syringe‐like handling device, to an analytical instrument, for separation and quantitation of target analytes. This technique is able to integrate sampling, extraction and sample introduction in a simple way, facilitating on‐site monitoring. The additional advantages include elimination of solvents from the sample preparation step and convenient introduction of extracted components into the analytical instrument. Applications of this technique to date include environmental, industrial hygiene, process monitoring, clinical, forensic, food and flavor, fragrance and drugs, in laboratory and on‐site analysis.