bluuebunny/crossref_metadata_2025_split huggingface dataset:
Proton‐InducedX‐Ray Emission in Environmental Analysis
Authors: Ghermandi Grazia 
Published: September 2006

AbstractParticle‐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

AbstractVigorous 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

Abstract
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

AbstractInstrumental 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

Abstract
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.
Supercritical Fluid Extraction of Inorganics in Environmental Analysis
Authors: Ashraf‐Khorassani Mehdi , Taylor Larry T. , Combs Michael T. 
Published: September 2006

Abstract

Supercritical fluid extraction (SFE) of metal ions via in situ chelation and preformed metal chelates using pure or modified CO
2
from several matrices has been accomplished. To understand the extraction results better, the solubilities of different ligands and metal chelates have been measured in supercritical fluids (SFs). In most cases, fluorinated chelates have been found to possess higher solubility in the SF than nonfluorinated ones, which in turn can often enhance extraction efficiency. Metal chelate stability under supercritical conditions plays an important role in the extraction of metals. Also, the matrix has a major effect on extraction efficiency of both hydrated metal ions and metal chelates. In order to obtain sufficient extraction not only should solubility of the metal complex be considered, but also the overall stability of the complex is critical.
Supercritical Fluid Extraction of Organics in Environmental Analysis
Authors: Benner Bruce A. 
Published: September 2006

AbstractSupercritical fluids (SFs) possess several physical properties that make them attractive substitutes for conventional liquid solvents in analytical‐scale extractions. Molecular diffusivities of SFs are typically a factor of 10 greater (10−4vs 10−5 cm2 s−1) and their viscosities are a factor of 10 lower (10−4vs 10−3 N s m−2) than liquid solvents. These properties improve the rate of mass transfer of a solute from the matrix surface to the bulk extractions fluid – a transfer believed to be the rate‐limiting step of most extractions. Under optimized conditions, the improvements in mass transfer can enable a supercritical fluid extraction (SFE) to be completed in less than 1 h compared to ≥12 h for extractions involving conventional solvent techniques. The typical SFE also generates little solvent waste, compared to traditional extraction methods, but limitations have also emerged with respect to the efficiency of SFE as related to the sample composition (matrix effect). This review will discuss the progress made over the last 20 years in SFE as an alternative technique to liquid solvent extractions of environmental samples for the subsequent measurement of organic constituents.
Trace Organic Analysis by Gas Chromatography with Quadrupole Mass Spectrometry
Authors: Booth Matthew M. , Powell David H. 
Published: September 2006

Abstract
Gas chromatography (GC) with quadrupole mass spectrometry (MS) is one of the most powerful and widely used analytical techniques. This technology combines the high resolving power of GC with the excellent sensitivity and chemical‐structure‐informing power of quadrupole MS. The combination of these two techniques provides both the selectivity and sensitivity needed for qualitative and quantitative analysis of organic analytes at trace levels in a wide variety of matrices.
This article provides an overview of the development and combination of these two technologies. Types of quadrupole mass spectrometers that are commonly coupled to gas chromatographs are discussed. Both electron ionization (EI) and chemical ionization (CI) are reviewed. Sample preparation methods are discussed for air, water, and solids. The different approaches employed for highly volatile and semi‐volatile substances are presented. The use of chemical derivatives to improve sample response and various instrumental analysis considerations are also covered.
Aircraft‐Based Flux Sampling Strategies
Authors: Desjardins R.L. , MacPherson J.I. , Schuepp P.H. 
Published: September 2006

AbstractOne of the essential elements of plant growth is carbon dioxide assimilation and water vapor loss. Measuring the exchange of these gases can provide an accurate picture of plant growth, health, and ultimate yield. This report describes the instrumentation used on the Canadian flux aircraft and the type of data collected for measuring gas exchange over large areas. It presents flux measurements of carbon dioxide, sensible heat (H) and latent heat (LE) using the eddy‐covariance technique. This technique provides the most direct measurements of mass and energy exchange at the land–atmosphere interface. Flux measurements obtained over wetlands near James Bay, the boreal forest in northern Saskatchewan, grasslands in Kansas, agricultural crops in California, and over the city of Fresno in California are presented as examples of the potential of this technique to characterize transfer processes over complex ecosystems. The accuracy of aircraft‐based flux measurements is examined using data obtained with other aircraft during wing‐to‐wing formation flights and with several tower‐based systems during tower fly‐by. Finally, examples of the use of these data for interpreting satellite data and for characterizing the photosynthetic response of a wide range of vegetation are presented.
Chemical‐Sensing Networks: Satellite‐Based
Authors: Hahn John C. 
Published: September 2006

Abstract
This paper addresses preliminary system engineering for a disposable, remote, chemical‐sensing network. This network could interconnect a satellite hub, low‐earth orbiting (LEO) satellites, remote sensors, and a fiber optic (OF) interface that interlinks remote chemical sensors, situated underground in aquifers or directly beneath hazardous chemical/waste sites, with remote transmitter/receivers on the earth's surface. Some critical technical factors: orbital analysis, telemetry, data rates, data structures, digital modulation techniques, antennae selection, remote power considerations, satellite transponder access, and other hardware tradeoffs, are examined in an effort qualitatively to optimize the configuration of a wide area network (WAN). This paper demonstrates the viability of the proposed network, which is suited to the detection of hazardous chemicals in the atmosphere or underground.
Electrochemical Sensors for Field Measurements of Gases and Vapors
Authors: Cox James A. , Holmstrom Scott D. 
Published: September 2006

Abstract
Sensors that utilize signals produced by redox of a targeted species (analyte) at an electrode under controlled potential, the conductance changes produced by contact of a chemical species with an electrolyte, or a change in the equilibrium potential of an electrode upon contact with an analyte are being employed in studies of gaseous samples of environmental, biomedical, and industrial interest. Changes in the work function of chemically modified field effect transistors (FET) also is a strategy related to both conductivity and potentiometry. Electrochemical sensors are fundamentally advantageous over other types in that they directly convert information from the chemical to the electrical domain, rather than requiring another transducer. Yet, few have found commercial application. The common types that are employed for field measurements of gaseous samples include devices to quantify oxygen, hydrogen sulfide, sulfur dioxide, oxides of nitrogen, hydrogen cyanide, hydrogen chloride, and chlorine. The limitation is not sensitivity; by this measure electrochemistry is among the best of the analytical measurement methods. Amperometric sensors accrue selectivity by control of the electrode potential along with control of the process by which the analyte partitions from the gas to the electrolyte. The latter is the primary means by which conductivity and potentiometry systems achieve sensitivity. These methods are not as selective as those in which a chemical reaction is incorporated in the sensor. The most selective electrochemical sensors employ an enzymatic reaction as part of signal production, but these are applicable to only a few analytes, such as alcohols, of importance in the gas phase.
Field‐Based Analysis of Organic Vapors in Air
Authors: Berkley Richard E. 
Published: September 2006

Abstract
Volatile organic compounds (VOCs) exist in the vapor phase in ambient air at partial pressures ranging from less than 1 part per billion to a few parts per million. Some of them are toxic and potentially harmful to the environment and to human health. The threshold concentrations at which individual compounds become harmful is often not well defined, and less is known about mixtures. Accurate assessment of health risk requires analytical methods that are accurate, affordable, convenient, fast, and sensitive enough to detect each compound at a concentration below the threshold of harmful effect. The usual approach to identification and quantitation of them has been to collect samples and submit them to laboratory analysis. United States Environmental Protection Agency (USEPA) Method TO‐14 is a standard procedure for analyzing a group of 41 potentially harmful nonpolar and semipolar organic compounds, which is in widespread use and has been found to detect and measure target compounds reliably under most conditions. However, more rapid delivery of data is often needed, and samples can deteriorate during storage pending analysis. Alternative analytical methods that produce immediate data are needed. Analysis of samples at the time and place of collection has seldom been done because of the lack of suitable equipment and the vicissitudes of operating it under field conditions. Portable or field‐deployable gas chromatographs (PGCs) have, with cause, been regarded as less accurate than laboratory equipment, and a perception remains that analyses done in the field are less useful than those done in the laboratory. In fact, laboratory‐ and field‐based analyses each have inherent advantages and disadvantages, and using them together can finesse the disadvantages of both. A high‐speed gas chromatograph (GC) using a time‐of‐flight mass spectrometer (TOFMS) detector can mitigate the problem of delayed data.
Mobile Mass Spectrometry Used for On‐Site/In Situ Environmental Measurements
Authors: Matz Gerhard , Schröder Wolfgang , Kotiaho Tapio 
Published: September 2006

AbstractThe potential of mass spectrometry (MS) and gas chromatography/mass spectrometry (GC/MS) techniques for on‐site analysis of compounds in a variety of matrixes such as air, water, soil and surfaces is discussed. The fundamental principles of operation including different mass separation procedures, modes of injection and separation methods for mixtures are presented here with a special emphasis on equipment suitable for measurement in the field. Commercially available systems as well as prototypes are described in detail. The power of MS and/or GC/MS analyses on‐site compared with conventional methods carried out in the laboratory is demonstrated in a detailed review of the literature dealing with measurement campaigns and experiences when applying mobile MS and GC/MS. In conclusion, mobile mass spectrometers have reached a high standard of quality and the operational areas in which they are utilized are likely to increase considerably in the future.
Solid‐State Sensors for Field Measurements of Gases and Vapors
Authors: Dickert Franz L. , Lieberzeit Peter A. 
Published: September 2006

AbstractRemote and in‐field analysis is developing into a crucial aspect of modern analytical chemistry. Chemical sensors, which are small measuring devices consisting of a recognition layer, a transducer and the measurement electronics, have proven to be highly suitable tools for this purpose. Although usually they are constructed for the detection of very limited amounts of chemical compounds and often do not reach the detection limits of modern analytical instruments, they show very desirable advantages: the systems are easy to operate, mostly rugged, small, good value and can be manufactured by established technological methods. Due to their size and ruggedness they can even be operated in harsh environments and often they can be constructed to be suitable for remote measurements, where several sensors are interrogated by a central analytical site.Devices being used include optical fibers, field effect transistors (FETs), electrochemical cells (be they potentiometric or amperometric) and mass‐sensitive components of all kinds. The chemically‐sensitive coatings range from bare transducer surfaces to dyes reacting with analyte or sterically‐specific binding sites (host–guest complexes etc.). A seeming drawback is the fact that only few sensors react specifically towards one defined component but normally show a sensitivity pattern towards chemically‐related substances. By using an array of several components followed by modern methods of data evaluation (such as neural networks) a group of analytes can be detected and characterized simultaneously. This article introduces device and recognition layer principles as well as covering field sensors published during the last one and a half decades based on all the different kinds of transducers and sensor layers. Some of the devices (such as the lambda probe) are already marketed, others are developed to a stage where field measurements have already been carried out, but which are not market‐ready.
Atomic Spectroscopy in Food Analysis
Authors: Baker Scott A. , Miller‐Ihli Nancy J. 
Published: September 2006

AbstractSince food is the primary source of essential elements for humans, the accurate and precise analysis of food materials is critical. The methods best suited to meet this task are atomic spectroscopic methods such as atomic absorption, atomic emission, and elemental mass spectrometry (MS). Methods commonly used in the generation of food composition data include flame atomic absorption spectrometry (FAAS), graphite furnace atomic absorption spectrometry (GFAAS), inductively coupled plasma atomic emission spectrometry (ICP/AES), and more recently, inductively coupled plasma mass spectrometry (ICP/MS). FAAS and ICP/AES offer similar detection limits (DLs) (ng mL−1levels), whereas, GFAAS and ICP/MS can provide sub‐ng mL−1detection capability. The choice of a method often depends on detection capability, but ease of use, speed of analysis, and cost must be considered. ICP/AES and ICP/MS offer the advantage of providing simultaneous multielement measurements, making them well suited for the analysis of large numbers of elements in food samples. If one or a few elements are to be determined, less expensive atomic absorption spectrometry (AAS) methods might be more suitable. The most critical stage in the development of analytical methods is sample preparation. Samples can be prepared using numerous procedures, but the most useful for a wide range of analytes and sample matrices are based on dry ashing or wet ashing of the sample. In addition to total element determinations, speciation measurements are important to determine the exact form of the element that is present in the sample. Since the bioavailability of an element is dependent on its chemical form (speciation), the development of reliable methods for identification and quantification of trace element species is critical. The coupling of chromatographic separation and atomic spectroscopic detection has proven useful for elemental speciation measurements.