bluuebunny/crossref_metadata_2025 huggingface dataset:
Microwave‐Assisted Techniques for Sample Preparation in Organic Environmental Analysis
Authors: Smith Frank E. , Xiong Guohua
Published: September 2006

This report describes innovative methods for sample pretreatment in organic environmental analysis that involve the use of microwave‐assisted techniques. The methods described include: microwave‐assisted extraction (MAE), focused microwave‐assisted Soxhlet extraction (FMASE), microwave‐assisted headspace analysis, microwave‐assisted derivatization (MAD), microwave‐assisted saponification (MAS) and microwave‐assisted decomposition. A brief history of the development of each technique is provided. Reference is made to literature published up to the beginning of 1999.
Microwave‐Enhanced Solvent Extraction of Organics in Environmental Analysis
Authors: Dean John R.
Published: September 2006

Microwave‐enhanced solvent extraction is a relatively new approach for the extraction of organic pollutants from solid environmental matrices. This approach uses microwave technology to heat organic solvent in contact with the sample in either a sealed (pressurized) or open (atmospheric) vessel. The major advantage of this approach over conventional extraction procedures, such as Soxhlet extraction, is the speed of the process. As well as the principles of microwave heating, the article also describes the instrumentation required to effect the extraction process. Finally, selected applications of microwave‐enhanced solvent extraction are described. Applications are divided into extraction from solid matrices and extraction from aqueous matrices. The specific analytes covered include the extraction of polycyclic aromatic hydrocarbons (PAHs), hydrocarbons, polychlorinated biphenyls (PCBs), pesticides and phenols from solid matrices; direct extraction of chlorinated benzenes from aqueous matrices; microwave elution of a range of analytes from solid‐phase extraction (SPE) media and, finally, volatile compounds, e.g. benzene, toluene, ethylbenzene and xylenes (BTEX) from aqueous samples. Finally, some recommended operating conditions for the extraction of analytes from solid matrices using pressurized microwave‐assisted extraction (MAE) are provided.
Organic Acids Analysis in Environmental Samples, Ion Chromatography for Determination of
Authors: Peldszus Sigrid
Published: September 2006

The analysis of environmental samples typically focuses on aliphatic short‐chain organic acids. The origin of these organic acids and the motivation for their analyses are unique for each type of matrix. Environmental sample matrices are very diverse and can range from air and atmospheric precipitation such as fog, rain or snow to wastewater, drinking water or landfill leachates and soil pore water. This diversity in matrix leads to substantial differences in organic acid concentrations and different organic acid distributions in the various types of environmental samples. Hence, the analytical techniques employed have to be adapted to the particular matrix under investigation.

Ion chromatography is one of the most commonly used techniques for organic acid analysis. Competing ion chromatographic methodologies are anion (ion)‐exchange chromatography (IC) and ion exclusion chromatography (ICE). The separation principles underlying each of these techniques are very different and may be used to their advantage. In IC, anions are separated by anion exchange processes between the cationic exchange groups on the resin and the eluent. Hence, inorganic anions and carboxylate anions may be analyzed at the same time (e.g. rain). Limitations of this technique set in when the inorganic anion concentration is much larger than the carboxylate concentration. As a consequence, inorganic anion peaks may mask or co‐elute with the analyte of interest. However, techniques have been developed to handle this problem, for example in drinking‐water analysis. The separation mechanism in ICE is much more complex than in IC involving Donnan exclusion, adsorption and steric exclusion. ICE is generally used for the separation of weak organic acids since strong organic acids elute in the system peak in the front of the chromatogram. Hence, large concentrations of strong inorganic anions, for example sulfate or chloride, will not interfere with the analysis of weak organic acids. However, organic acids with relatively low p Ka values may be difficult to separate from the system peak. In addition, weak inorganic acids such as carbonate have the potential to interfere with the analysis of certain organic acids if present in large enough concentrations.

Other techniques than ion chromatography have been used for organic acid analysis. Direct injections of samples into a gas chromatograph are very common for measuring volatile fatty acids (VFAs) in wastewater. More complex gas chromatography (GC) methods, which include concentration and derivatization steps, have been employed to analyze for specific types of organic acids such as dicarboxylic acids in rain. Capillary electrophoresis (CE) is a newer technique, which has not been used widely in routine analysis. However, speciality applications such as the determination of organic acids in a single raindrop show the potential of this type of methodology.
Organic Analysis in Environmental Samples by Capillary Electrophoresis
Authors: García‐Ruiz Carmen , Crego Antonio L. , Marina Maria L.
Published: September 2006

Capillary electrophoresis (CE) is an instrumental technique that employs narrow‐bore (10–100 µm ID, internal diameter) capillaries under the influence of a high‐gradient electric field to perform high‐efficiency separations. Different working modes of CE have been described. Capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC) have become the most popular modes of CE in environmental applications. Other kinds of electrokinetic chromatography (EKC) and other modes of CE like capillary electrochromatography (CEC) have also been used.

CE techniques have been considered as a good alternative for analyzing pollutants because of their high performance and versatility related to selectivity and range of application. In addition, CE is a powerful tool in the field of chiral separations and it is considered one of the so‐calledcleananalytical techniques. Although the main drawback of CE techniques in environmental analysis is their insufficient sensitivity for detecting trace‐level pollutants, some procedures have been developed in order to overcome this problem.
Pervaporation, Analytical
Authors: Luque de Castro M.D. , Gámiz‐Gracia L.
Published: September 2006

The use of pervaporation in analytical chemistry is a relatively new development. Pervaporation is a separation technique for the removal of volatile analytes or their volatile derivatives from the sample matrix. It can be defined as the integration of evaporation and gas diffusion in a single module. The volatile substances present in a heated donor phase evaporate through a porous membrane and the vapor condenses on the surface of a cool acceptor stream on the other side of the membrane. The temperature difference across the membrane is the driving force for the separation. An important characteristic of analytical pervaporation is the presence of a constant‐volume air gap between the sample in the donor chamber and the membrane, which hinders any contact between them, thus avoiding clogging and/or deterioration of the membrane.

Pervaporation can also be used for sample pretreatment, e.g. for solid samples where leaching and derivatization of the analytes are done simultaneously. In this article, the applications of analytical pervaporation that have been developed so far are discussed. Special attention is paid to its use as an alternative to gas diffusion, to liquid samples containing solids in suspension and/or corrosive, to solid samples in which a single analyte must be determined, to multideterminations, and to speciation studies. The integration of this separation technique with detection and the coupling of a pervaporator to a gas chromatograph (GC), which constitutes a valid alternative to headspace sampling, is also commented upon.
Phenols Analysis in Environmental Samples
Authors: Moeder Monika
Published: September 2006

Phenolic compounds are widely distributed in our ecosystems. In addition to naturally occurring phenols, the majority of toxic phenolic substances are released into the environment by industry and agriculture. As the manufacture and use of phenols requires qualitative and quantitative control, a wide variety of methods have been developed to determine phenolic compounds. In addition to coarse screening to rapidly obtain a general overview, many highly specialized techniques exist that are geared to individual analysis problems. The range of available methods extends from steam distillation and classic liquid–liquid extraction (LLE) as sample preparation combined with photometric or ultraviolet (UV) detection, to more sophisticated techniques such as liquid–solid extraction (LSE) including solid‐phase extraction (SPE) and solid‐phase microextraction (SPME) coupled to gas chromatography/mass spectrometry (GC/MS) and high‐performance liquid chromatography/mass spectrometry (HPLC/MS). This article describes the most suitable methods, taking account of special factors such as substance class, chemical properties, concentration range and accompanying matrices. Some new trends in phenol determination are also discussed in comparison with the established methods. The basic factors governing the selection of suitable analysis methods are also covered.
Polynuclear Aromatic Hydrocarbons Analysis in Environmental Samples
Authors: Fisher Michal , Schechter Israel
Published: September 2006

This chapter reviews conventional and novel methods of analysis of polynuclear aromatic hydrocarbons in environmental samples. Sampling and pretreatment techniques of air, soil and water are discussed, as well as various clean‐up and extraction methods. Most of the relevant polycyclic aromatic hydrocarbons (PAHs) separation techniques are reviewed. The principles and performance of the common PAH detection systems are presented. An introduction to novel analytical techniques, which will probably be introduced in the near future, is also provided.
Sample Preparation for Elemental Analysis of Biological Samples in the Environment
Authors: Subramanian Kunnath S.
Published: September 2006

This article focuses on biological sample preparation methods which are unique to each of the commonly used instrumental techniques used in trace element analysis. The biological samples covered are mainly of human and animal origin. The preparation methods considered span the entire gamut and include direct solid or liquid sample introduction involving dilution or matrix modification; dry ashing; wet oxidation including microwave digestion and high‐pressure ashing; deproteinization; and tissue solubilization. The instrumental techniques covered are flame atomic absorption spectrometry (FAAS), graphite furnace atomic absorption spectrometry (GFAAS), inductively coupled plasma atomic emission spectrometry (ICPAES), inductively coupled plasma mass spectrometry (ICPMS), X‐ray fluorescence (XRF) spectrometry, neutron activation analysis (NAA) and anodic stripping voltammetry (ASV). The choice of a given sample preparation method would be governed in general by the type of biological matrix, sample size and the type of instrumental technique used. The advantages and disadvantages of the various sample preparation methods have been emphasized for each of the instrumental techniques. Also, an attempt has been made to point out the optimum sample preparation method(s) suitable for the particular biological matrix and instrumental technique.
S
oxhlet and Ultrasonic Extraction of Organics in Solids
Authors: Webster G.R. Barrie
Published: September 2006

Soxhlet extraction is the removal and recovery of organic analytes from a permeable solid matrix by means of a solvent which is continually evaporated from a still‐pot and condensed in such a manner that it falls into and permeates through the matrix which itself is held in a permeable container in a siphonable chamber. Soxhlet extraction has been used for over 120 years (since 1879) and is commonly used as a benchmark for total extractable organic residues.

Ultrasonic extraction is the removal and recovery of organic analytes from a permeable solid matrix by means of a solvent which is energized by sound energy at frequencies in excess of those audible to the human ear. Energy may be introduced into the sample by means of an ultrasonic probe which is inserted into the sample or an ultrasonic bath into which the sample plus solvent is immersed. The ultrasonic energy may be strong enough to disrupt and pulverize the matrix, thus increasing the extractability of the analyte.

The operation of the Soxhlet extractor is intuitively easy to grasp. Extraction is viewed as being complete or close to complete.

Ultrasonic extraction is convenient and straightforward. Ultrasonic baths provide relatively reliable sources of extraction energy.

Soxhlet extraction is solvent intensive and requires laboratory facilities in which flammable and toxic solvents can be used safely. The glassware required is expensive and vulnerable to breakage. Cooling of the condenser of the Soxhlet apparatus requires a constant supply of cooling water. Residues are concentrated in the still‐pot and are thus vulnerable to thermal degradation. Only total residue can be extracted by Soxhlet extraction; little or no speciation is possible.

Ultrasonic extraction must be performed under conditions which protect the hearing of laboratory personnel. The ultrasonic generator may generate heat which may affect the extraction process. Ultrasonic probes become pitted when used for the extraction of abrasive matrices such as soil, thus changing the energy generated and affecting the extraction efficiency of the procedure. Ultrasonic baths provide less intense extraction energy. Extraction of total residue is the aim of ultrasonic extraction; little or no speciation is possible.
Sampling Considerations for Biomonitoring
Authors: Koeckritz Tim , Wappelhorst Olaf , Markert Bernd
Published: September 2006

This article looks at various factors involved in the first step in biomonitoring, namely the sampling process with special reference to heavy metal levels in living organisms and their interaction with terrestrial ecosystems. Because samples taken in the field naturally form the basis for the entire biomonitoring process, it is vitally important that the margin of error in this step is kept as low as absolutely possible. An important initial step is the decision about which organisms to use and where to gather them. It is important to consider factors such as chemical composition, relationship to the ecosystem involved and the number of individuals available, in addition to the abiotic and biotic factors which influence the amount of heavy metal the organism takes in from its environment, or its bioavailability (heavy metal accumulation is the practical example for biomonitoring used in this article).

How the samples are collected is as important as what is collected, and here various topics are covered, from choosing the most suitable organism(s), to deciding how many samples to take in order for them to be representative of the entire population at that site, to economic considerations. Although exact sampling methods vary according to the organisms involved and there are very few publications in this field, some basic guidelines are given to follow in any case, as well as references to the existing published guides.
Slurry Sampling Graphite Furnace Atomic Absorption Spectrometry in Environmental Analyses
Authors: Miller‐Ihli Nancy J. , Baker Scott A.
Published: September 2006

Slurry sampling graphite furnace atomic absorption spectrometry (GFAAS) is a powerful tool for the determination of trace elements in environmental samples owing to its high sensitivity, instrumental simplicity, and relatively low cost. In this technique, discrete aliquots of the slurry or suspension are deposited in a graphite tube and then electrically heated to produce atomic vapors. The absorption of the atomic vapor is measured, typically with a hollow cathode lamp (HCL) or electrodeless discharge lamp (EDL), to determine the amount of analyte present in the sample. To ensure that a representative portion of the slurry is injected into the furnace, the slurry must be stabilized or mixed immediately prior to analysis. Slurry sampling GFAAS detection limits (DLs) are typically in the range of 10−2to 1 part per million (pg absolute DLs). Precision (0.5–5%) and accuracy are also good, provided that proper guidelines for slurry preparation and instrument operation are followed, and samples are sufficiently homogeneous. An additional benefit of the technique is that matrix interferences are typically small; in fact, aqueous calibration standards are routinely used in the analysis of slurry samples. A limitation of slurry sampling GFAAS is that it is primarily a single‐element technique, although continuum source and sequential atomic absorption spectrometry (AAS) systems have been developed. Furthermore, the linear range is typically less than two orders of magnitude unless alternative wavelengths, or some other means of reducing sensitivity (e.g. minigas flow during atomization), are used. In addition, some environmental samples have to be ground if the sample is not in the proper form or if the analyte is not homogeneously distributed. Care must be taken during the grinding process to avoid contamination of the sample or fractional distribution of the analyte.
Soil Sampling for the Characterization of Hazardous Waste Sites
Authors: Schumacher Brian A. , van Ee J. Jeffrey , Englund Evan J.
Published: September 2006

The planning for and collecting of samples at hazardous waste sites is nearly always the first step in any program that involves the analysis of real‐world soil samples. Knowledge of numerous different, yet related, topics, such as data quality objectives (DQO), sampling network design, quality assurance (QA)/quality control (QC), documentation, site characterization, sample collection, and sample handling and preparation, is essential to ensure the success of any program in obtaining accurate (non‐biased), precise, and representative soil samples. It is often quoted that during sample collection, 80% or more, for stable contaminants (e.g. heavy metals, polychlorinated biphenyls, polyaromatic hydrocarbons), ranging up to 99.9%, for less stable contaminants (e.g. volatile organic compounds (VOCs)), of the total measurement error associated with a sample occurs. Hence the goal of the program planner is to develop the most efficient sampling design that collects the desired samples while minimizing sample errors. If all of the aforementioned topics are not taken into account during the sample planning and collecting phases of the program, then no matter how good the analytical data may be, the data may lead to incorrect decisions with respect to the extent, distribution, and need for remediation of contaminants at a site.
Trace Organic Analysis by Gas Chromatography with Selective Detectors
Authors: Rosenberg Erwin
Published: September 2006

Selective detectors for gas chromatography (GC) allow one to detect selectively after gas chromatographic separation analytes that either contain certain elements or carry functional groups for which the detector is particularly selective (element‐selective detectors). Spectroscopic detectors are a class of selective detectors which, in the ideal case, may even allow the identification of the analytes through acquisition of molecule‐specific spectra. Selective detectors often allow the detection, quantitation or identification of analytes even in the presence of complex matrices and may thus significantly improve the selectivity of an analytical method.
Waste Extraction Procedures
Authors: Simmons Barton P.
Published: September 2006

Waste extraction procedures (EPs) were developed to identify wastes which have a potential for groundwater or surface water contamination. Procedures are used for both organic and inorganic substances to comply with specific regulatory requirements, for example, to identify wastes which are subject to regulation as hazardous wastes. In the United States, the toxicity characteristic leaching procedure (TCLP) is the most widely used procedure. Volatile organics are extracted using a zero‐headspace extractor, while semivolatile organics and inorganic substances are extracted using a bottle extractor. Because the typical batch EP does not measure a fundamental property of a waste, the result is highly dependent on steps in the protocol, particularly the choice of extraction solution. Although batch extraction tests like the TCLP are the most common procedures, other procedures using multiple pHs and multiple liquid : solid ratios have been developed to overcome the limitations of batch tests.
Water Analysis: Organic Carbon Determinations
Authors: Mopper Kenneth , Qian Jianguo
Published: September 2006

The determination of total organic carbon and dissolved organic carbon (TOC and DOC) is one of the most important parameters in water quality and environmental analysis today. TOC is composed of particulate organic carbon, DOC and volatile organic carbon, (POC, DOC and VOC). In most waters, DOC is the dominant component of TOC. POC consists of living and nonliving organic particles and can occasionally become quantitatively important. POC, DOC and VOC are operationally defined by the methods used to separate them. POC and DOC are usually separated from each other by filtration, which can introduce errors due to contamination and filter clogging. Other major errors in TOC and DOC analyses are related to contamination and losses during sampling, sample storage and sample manipulation. In particular, removal of inorganic carbon by either acidification with sparging or by acidification with evaporation to dryness results in variable loss of VOC.

Commonly used TOC and DOC methods fall into two approaches: wet oxidation and high‐temperature combustion (HTC). In both approaches, organic matter is oxidized to CO
2
, which is then usually determined by nondispersive infrared (NDIR) absorbance. Two wet oxidation methods are in common use: wet chemical oxidation (WCO) and ultraviolet oxidation (UVO). In WCO, a strong chemical oxidant, usually persulfate, is added to the aqueous sample and the digestion is usually carried out batchwise in a reactor at an elevated temperature. In contrast, UVO digestion is commonly carried out in a quartz coil surrounding a mercury vapor lamp. Thus, UVO methods can be readily automated using flow‐injection systems. Two types of HTC methods are currently in use: dry combustion and direct aqueous injection. In dry combustion methods, the sample is acidified, dried and the residue is combusted at high temperature in a sealed tube, usually in the presence of a catalyst. This method is advantageous for the analysis of large samples. In direct aqueous injection HTC methods, samples are injected into a high‐temperature column (600–900°C), which usually contains a catalyst. In recent years, the latter method has become widely used for the analysis of seawater and other waters because it appears to have a greater oxidation efficiency and precision than most of the other methods, and it can be readily automated. However, automated HTC instruments have problems in the analysis of saline samples, in particular, salt deposits in the sample injection system, memory (or carry‐over) effects, and system blank evaluation. Recently, improvements in the HTC injection system and column design have addressed these problems.
X
‐Ray Fluorescence Spectroscopic Analysis of Liquid Environmental Samples
Authors: Russell Philip A.
Published: September 2006

X‐ray fluorescence (XRF) spectrometry is an instrumental technique used for multielement analysis. It is one of only three techniques available to the modern analyst, the others being mass spectrometry and optical emission spectroscopy, the latter usually being the inductively coupled plasma (ICP) variant. The determination of environmental sensitive elements in the range P–U in aqueous and/or organic matrices provides challenges to all multielement techniques. With recent improvements in instrumentation and methods design (simplified sample preparation compared with other techniques), XRF, in particular for highly contaminated liquid waste, is becoming the preferred technique. XRF is shown to give the most cost effective and best overall speed of analysis across a range of diverse matrix types. Potable drinking water to highly toxic industrial sludge/waste can be analyzed for either precise ultralow level (parts per billion) or screening purposes, respectively. Energy‐dispersive X‐ray fluorescence (EDXRF) has provided the best all‐round performance with the introduction of dedicated instruments and standard methods for the analysis of environmentally sensitive elements in all forms of liquid matrices.
Cone‐penetrometer‐deployed Samplers and Chemical Sensors
Authors: Doskey Paul V. , Cespedes Ernesto R.
Published: September 2006

The development of rapid, cost‐effective, accurate methods for environmental site characterization and monitoring has been a very active area of research during the past two decades. One approach that has recently received widespread attention involves the use of cone penetrometer technologies for in situ detection and mapping of environmental contaminants in subsurface soils and groundwater. The most recent technological developments include the incorporation of on‐line analytical and in situ chemical detection techniques into the cone penetrometer. This article describes a variety of sampling and chemical sensing technologies that have been or are currently being adapted to cone penetrometer systems for the detection of subsurface contaminants, including petroleum, oils, and lubricants (POLs), volatile organic compounds (VOCs), toxic metals, explosives/energetics, and radioactive wastes. For example, cone penetrometer devices that incorporate in situ isolation techniques to purge VOCs from groundwater eliminate the analysis of the sample media in the laboratory. A high level of agreement was found between an in situ purging technique and the conventional method of bailing a sample from a groundwater sampler, transferring the sample to a container, and analyzing the sample in the laboratory. Completion of a site characterization with this probe was estimated to require approximately 15% of the time needed for conventional methods, significantly reducing costs. The laser‐induced fluorescence (LIF) sensor, which measures POLs, represents the first and most mature cone penetrometer chemical detection technology. Technology evaluations estimated that costs of site characterizations using the LIF probe are approximately 50% lower than costs of site characterizations using conventional methods for collecting soil cores, subsampling the cores, and analyzing the subsamples in the laboratory.
Field‐portable Instrumentation
Authors: Goedert Michel G.
Published: September 2006

The analysis of gas and vapors in the field is an important part of the remediation process. The purpose of this article is to familiarize the reader with some of the analytical instruments available today to determine the composition of gaseous samples. Although this section deals with portable instruments, it was found necessary to mention on‐site measurements since this is an important part of field measurements. On‐site measurements are done with conventional analytical instruments operating from recreational vehicles. The samples have to be collected and the first part of this article gives an overview of some of the techniques, such as canister and solid adsorbents, used for this purpose. Identification of compounds collected on‐site or directly in the field can be done by gas chromatography (GC) and mass spectrometry (MS). A comprehensive description of the hardware used with these techniques is provided.

An important part of the portable section covers direct‐reading instruments such as gas sensors, electrochemical devices, ionization detectors and colorimetric detectors. These instruments provide only a limited amount of information and, most of the time, require a prior knowledge about the content of the sample. However, they are small, portable and cheaper than laboratory analytical instruments and therefore they have found a market.

Portable instruments include miniaturized gas chromatographs and mass spectrometers. These instruments do not offer the high performance of their laboratory counterparts, but they give more information about the sample than direct‐reading instruments. The next step in process measurement sophistication is to combine these techniques. The most popular hyphenated technique is certainly the coupling of a gas chromatograph with a mass spectrometer, but there are also powerful and lesser‐known techniques such as GC combined with ion mobility spectrometry (IMS). IMS has found a market with military applications for the detection of chemical warfare agents. It offers less resolution than MS but operates at atmospheric pressure and is therefore truly portable. When combined with GC it offers some interesting features which will be described.
Microelectromechanical Systems Technology Applied to the Miniaturization of Field Instrumentation
Authors: Goedert Michel , Higdon William
Published: September 2006

This paper explores the miniaturization of analytical instruments using emerging microelectromechanical systems (MEMS) technology. MEMS provides an enabling technology base for miniaturization of many kinds. It has grown in parallel with the growth of the semiconductor industry since the discovery of silicon piezoresistance at the Bell Laboratories in the early 1950s, and borrows many principles and techniques from silicon “wafer fabs”. The technology is one of several that promises to revolutionize our lives in the 21st century.

We review some of the processes developed to fabricate MEMS parts and give examples of components developed with this technology. Finally, we describe how this technology has been used to develop a portable gas chromatograph (GC) and other chemical instrumentation for the detection of gases and vapors in the field. We show, with experimental results, how analytical instrumentation can benefit from MEMS technology.
Radon, Indoor and Remote Measurement of
Authors: Cua Florence T.
Published: September 2006

The existing radon and radon progeny measurement instruments are described in this article. The various methods and instruments used depend on whether radon or radon/thoron progeny or daughter products are being measured, the duration of the measurement, whether short‐term or long‐term and the type of radiation being detected (alpha, beta, or gamma). The modes of detection used include the following: activated charcoal radon monitors, electret ion chamber, registration of nuclear tracks in solid‐state materials, liquid scintillation, ionization chambers, scintillation detectors with zinc sulfide, ZnS(Ag), alpha particle spectrometers with silicon diodes, surface barrier or diffused junction detectors, and gamma‐ray spectrometry with NaI(Tl) scintillation crystals or germanium lithium (GeLi) semiconductor detectors, fiber optics sensors and glass. The advantages and disadvantages will be described for various portable instruments used for measuring radon, thoron, and their daughter products. Comparison studies among the radon monitors will be included.

The reader is referred in particular to George
1
and National Council on Radiation Protection (NCRP) Report 97
2
for additional information.
Adulteration Determination
Authors: Wilhelmsen Eric C.
Published: September 2006

Determining adulteration in food is accomplished by comparing analytical data with historical or control data. Without a proper reference set, the determination of adulteration is impossible. Adulteration is best shown by detecting a foreign component that is characteristic of a specific adulterant. Sometimes it is necessary to use deviations in a parameter, but typically these approaches are less sensitive owing to the natural variation in food. Often practitioners are interested in the more difficult converse, that is, authentication of a product or ingredient. In practice, authenticating a product or ingredient is equivalent to not finding any adulteration. Clearly, authentication is a negative, the absence of adulteration. It can never be entirely proven. The quality of a determination of authenticity is clearly linked to number and types of tests performed. The decision not to perform a test that yields additional information increases the potential of erroneously accepting a sample.

This proof of the negative challenge has led to competition between the practitioners of authentication and those who would adulterate their products or ingredients. This competition is readily apparent. Each time a useful new method has been introduced, previously undetected adulterations have surfaced. Unfortunately, the new methods generally do not supersede older methods and represent additional authentication costs. Fortunately, the vast majority of the food industry is not involved and generally cooperates in policing the marketplace.
Infrared Spectroscopy, Gas Chromatography/Infrared in Food Analysis
Authors: Mehrotra Ranjana
Published: September 2006

Infrared (IR) radiation is usually defined as that electromagnetic radiation whose frequency is between 20 and 14 500 cm−1. Within this region of the electromagnetic spectrum, chemical compounds absorb IR radiation provided there is a dipole moment change during a normal molecular vibration, molecular rotation, and molecular rotation–vibration or from combinations, differences and overtones of the normal molecular vibrations. The frequencies and intensities of the IR bands exhibited by a chemical compound uniquely characterize the material and its IR spectrum can be used to identify and quantify a particular substance in an unknown sample. IR spectroscopy in both the mid‐infrared (MIR) and near‐infrared (NIR) regions is emerging as a qualitative as well as quantitative analytical technique with great potential in a wide range of applied areas. The prime advantage of IR spectroscopy in food applications is that once the instrument has been calibrated, several constituents in a sample can be measured rapidly and simultaneously. No sample manipulation is required. It is also applicable to on‐line analysis in the food processing industries.
Near‐Infrared Spectroscopy in Food Analysis
Authors: Osborne Brian G.
Published: September 2006

Near‐infrared (NIR) spectroscopy is based on the absorption of electromagnetic radiation at wavelengths in the range 780–2500 nm. NIR spectra of foods comprise broad bands arising from overlapping absorptions corresponding mainly to overtones and combinations of vibrational modes involving CH, OH and NH chemical bonds. The concentrations of constituents such as water, protein, fat and carbohydrate can in principle be determined using classical absorption spectroscopy. However, for most food samples, this chemical information is obscured by changes in the spectra caused by physical properties such as the particle size of powders. This means that NIR spectroscopy becomes a secondary method requiring calibration against a reference method for the constituent of interest. As a consequence of the physics of diffuse transmittance and reflectance and the complexity of the spectra, calibration is normally carried out using multivariate mathematics (chemometrics).

NIR spectroscopy is used routinely for the compositional, functional and sensory analysis of food ingredients, process intermediates and final products.

The major advantage of NIR is that usually no sample preparation is necessary, hence the analysis is very simple and very fast (between 15 and 90 s) and can be carried out on‐line. One of the strengths of NIR technology is that it allows several constituents to be measured concurrently. In addition, for each fundamental vibration there exists a corresponding series of overtone and combination bands with each successive overtone band approximately an order of magnitude less intense than the preceding one. This provides a built‐in dilution series which allows several choices of absorptions of different intensity containing the same chemical information. Finally, the relatively weak absorption due to water enables high‐moisture foods to be analyzed.

The major limitation of NIR spectroscopy in food analysis is its dependence on less‐precise reference methods.
Nuclear Magnetic Resonance in the Analysis of Foodstuffs and Plant Materials
Authors: de Ropp Jeffrey S. , McCarthy Michael J.
Published: September 2006

Nuclear magnetic resonance (NMR) is an experimental technique based on the interaction between an applied magnetic field and nuclear magnetic moments in a sample. NMR provides information on material composition, molecular structure, physical structure, physical properties and dynamics of phase changes. NMR is a noncontacting and noninvasive measurement. NMR has been used for the routine analysis of foodstuffs and plant materials. NMR is used in the analysis of foods to detect moisture content, solid/liquid ratio in fats, adulteration of juices and characterization of texture. Applications of NMR to plant materials include observation and characterization of metabolites and ions, determination of pH and following changes of these over time. NMR is also used to determine structures of natural products isolated from plants. Magnetic resonance imaging (MRI) is used in both foodstuffs and plant materials to study morphology and also water transport, diffusion and variations of these under different conditions. The response of NMR is linear from the detection limits of approximately 10 ppb to 100%. The accuracy of the technique depends upon the signal‐to‐noise ratio (S/N), which is a function of the sample size, applied magnetic field strength, the radiofrequency (RF) coil, the spectrometer hardware and experimental parameters. Typical accuracy is 0.5% for composition and 1–5% for viscosity.
Nuclear Magnetic Resonance in Analysis of Plant Soil Environments
Authors: Fan Teresa W.‐M. , Lane Andrew N.
Published: September 2006

This article presents an overview of nuclear magnetic resonance (NMR) methods and their applications in probing the metabolic processes in plants and interaction between plants and soils. The basic principles of both solution‐ and solid‐state NMR are introduced, with an emphasis on useful parameters that can be employed for determining covalent structures and conformations of biomolecules and their environmental derivatives. Both one‐dimensional (1‐D) and two‐dimensional (2‐D) NMR techniques are described, and the advantages of improved resolution and information content for the 2‐D techniques are demonstrated. The substantial improvement in the sensitivity of inverse detection methods for detecting heteronuclei is also shown. Instrumental considerations as well as sample preparation requirements are described for in vivo and in vitro applications and analysis of small and macromolecules. Applications of multinuclear 1‐D and 2‐D NMR in plant metabolism and plant–soil interactions are illustrated. These include in vivo measurements of subcellular compartmentation, determination of metabolite concentrations, enzyme or exchange kinetics, in vitro analysis of plant tissue extracts and root exudates, use of stable isotope tracers for analysis of biochemical pathways, and structural and conformational characterization of natural organic matter (NOM) from soils and sediments. The relative advantages and disadvantages of solution‐ and solid‐state NMR techniques for analysis of plant–soil systems are discussed with examples from characterization of NOM, although 1‐D13C solid‐state methods have been of choice due to the polydispersive nature and low aqueous solubility of NOM. However, recent advances in 2‐D solution‐state methods are presented that provide valuable information on structure, conformation, and ligand binding of NOM, which is not practical by solid‐state methods. The limitations of NMR analysis for in vivo, in vitro and NOM are noted, along with a discussion on future prospects for NMR analysis in terms of spectral resolution and detection limits achievable.
Particle Size Analysis in Food
Authors: Robins Margaret M.
Published: September 2006

Techniques are described for determining particle size in food dispersions involving food particles ranging in size from 0.1 to 1000 µm, where the presence of the particles confers special properties such as texture, appearance or flavor release. Those foods of plant origin that are cellular in nature are outside the scope of this article, as their structure is not under the control of the food manufacturer. The techniques described are used to a greater or lesser extent on foods, and they are all methods in use in other industrial sectors. The techniques are classified according to their underlying physical principle. Summary tables are provided to act as quick reference guides for a potential user of the technique. After the detailed descriptions, the final section groups those techniques relevant to a specific type of dispersion.

The two most direct methods, microscopy and sieving, are discussed initially followed by three classes of optical technique, comparatively simple forward or back scattering, angular‐dependent light scattering and dynamic light scattering. The next technique to be addressed is the electrical sensing zone originally developed by Coulter. Sedimentation techniques follow: gravitational sedimentation, centrifugal sedimentation and field‐flow fractionation (FFF). All depend on the behavior of the particles in a force field that is balanced by viscous drag forces. The next two techniques are both acoustic in operation, either direct ultrasonic attenuation or electroacoustics. Finally, the novel applications based on nuclear magnetic resonance (NMR) are presented.
Pesticides, Mycotoxins and Residues Analysis in Food
Authors: Volante M. , Branca P.
Published: September 2006

This article will deal with methods for analyzing residues of pesticides and mycotoxins from molds in food. A general description of each topic is given directing the reader towards some key reviews, books or manuals published in the field with specific references added for more recent papers or topics of particular interest; techniques such as chromatography, spectrophotometry and immunochemical methods have been reviewed. In the first section sampling procedures are discussed, in the second section an overall description of the analytical methods used for pesticide residues in food is given with particular attention to multiresidue methods, in general those used most for assessing residue levels in crops at the international level, with consideration given to those less used methods dedicated to specific compound classes not covered elsewhere. The third section deals with mycotoxins with a brief description of the various mycotoxin types and some properties, followed by some discussion of analytical methods. The description of analytical techniques has been divided into extraction, cleanup and instrumental determination techniques for both pesticides and mycotoxins. Some tables of experimental data are also given.

The last section (four) deals with quality assurance aspects outlining the necessary steps, included interlaboratory trials, needed to validate a method and to assure reliability of the data.
Proteins, Peptides, and Amino Acids Analysis in Food
Authors: Dierckx Stephan , Boeve Karen , Van Camp John , Huyghebaert André
Published: September 2006

Proteins are an important fraction in most foodstuffs, ranging from 1.8% in roots and tubers up to about 25% in legumes.1However, in foods they are present in a complex multicomponent matrix also containing water, lipids, carbohydrates, and some minor components, all of which might interfere during the analysis of proteins in foods. A whole variety of analytical tools for protein analysis are available to the analyst2but not all of them are suitable for routine analysis procedures. This article will deal with some key analytical techniques in order to give an overview of possibilities and shortcomings of current techniques and some promising future trends. Well established methods are the Kjeldahl method, spectroscopy in the ultraviolet (UV), visible (VIS), and infrared (IR) ranges of the spectrum, chromatography, and conventional electrophoresis, while recent developments are to be found in the field of capillary electrophoresis (CE) and immunoassay. Since validation of methods and results are important features of today's analysis, some attention is paid to the availability and use of reference materials.
Proximate Assays in Food Analysis
Authors: Nielsen S. Suzanne
Published: September 2006

The proximate composition of foods includes moisture, ash, lipid, protein, and carbohydrate contents. These food components may be of interest in the food industry for product development, quality control (QC), or regulatory purposes. Analyses used may be rapid methods for QC or more accurate but time‐consuming official methods. Sample collection and preparation must be considered carefully to ensure analysis of a homogeneous and representative sample, and to obtain accurate results. Specific methods of analysis for moisture, ash, lipid, protein, and carbohydrate are described in this article, focusing on the principle of each method, application, and sources of error.
Sample Preparation Analytical Techniques for Food
Authors: Rothaupt Michael
Published: September 2006

Sample preparation is one of the important steps in flavor and food analysis. Thermal extraction (TE) of volatile substances simplifies sample preparation by separating volatile compounds from nonvolatile ones. A temperature vaporizing program allows additional prefractionation of the analytes. Solvent venting (SV) supports chromatography by removing a large amount of the solvent. SV also helps eliminate interfering and problematic ingredients from the sample. Sample preparation by supercritical fluid extraction (SFE) is compared to TE, with specific advantages and disadvantages being discussed.