Showing papers in "Trends in Analytical Chemistry in 2004"

Trends in quality in the analytical laboratory. II. Analytical method validation and quality assurance

Abstract: It is internationally recognized that validation is necessary in analytical laboratories. The use of validated methods is important for an analytical laboratory to show its qualification and competency. In this update on analytical quality, we place validation of analytical methodologies in the broader context of quality assurance (QA). We discuss different approaches to validation, giving attention to the different characteristics of method performance. We deal with the concepts of single-laboratory or in-house validation, inter-laboratory or collaborative study, standardization, internal quality control (IQC), proficiency testing (PT), accreditation and, finally, analytical QA (AQA). This article provides a good, complete, up-to-date collation of relevant information in the fields of analytical method validation and QA. It describes the different aspects of method validation in the framework of QA. It offers insight and direct help to anyone involved in any analytical methodologies, whether they are an academic researcher or in the industrial sector.

Developments in hollow fibre-based, liquid-phase microextraction

Abstract: The demand for automation in analytical liquid-liquid extraction (LLE) combined with organic solvent reduction or elimination has led to the recent development of liquid-phase microextraction (LPME) based on disposable hollow fibres. In this concept, analytes of interest are extracted from aqueous samples, through a thin layer of organic solvent immobilized within the pores of a porous hollow fibre, and into an acceptor solution inside the lumen of the hollow fibre. Subsequently, the acceptor solution is directly subjected to a final analysis by capillary gas chromatography (CGC), high-performance liquid chromatography (HPLC), capillary electrophoresis (CE), or mass spectrometry (MS) without any further effort. Hollow fibre-based LPME may provide high analyte pre-concentration and excellent sample clean-up, and it has a broad application potential within areas such as drug analysis and environmental monitoring. This review focuses on basic extraction principles, technical set-up, recovery, enrichment, extraction speed, selectivity, applications, and future trends in hollow fibre-based LPME.

Electrochemical sensors based on molecularly imprinted polymers

Abstract: Molecularly imprinted polymers (MIPs) are becoming an important class of synthetic materials mimicking molecular recognition by natural receptors. This review examines the literature on non-covalent MIP-based electrochemical sensors over the last 10 years. With insight into the different sensing phases, electrochemical transductions and integration strategies, we evaluate achievements and difficulties to date and assess future prospects.

Determination of pesticides and their degradation products in soil: critical review and comparison of methods

Abstract: Pesticides are applied widely to protect plants from disease, weeds and insect damage, and usually come into contact with soil, where they undergo a variety of transformations that provide a complex pattern of metabolites. This article reviews the most relevant analytical methods for determining pesticides and their transformation products in soils. We address some recent advances in sampling and sample-preparation technologies for soil analysis. We discuss and critically evaluate procedures, such as liquid extraction methods (pressurized liquid extraction or microwave-assisted extraction) and solid-phase based methods (headspace solid-phase microextraction, solid-phase microextraction or matrix-solid-phase dispersion). Analysis of pesticides is generally carried out by gas chromatography (GC) or liquid chromatography (LC) coupled to different detectors, especially to mass spectrometers (MSs). However, alternative and/or complementary methods, using capillary electrophoresis (CE), biosensors and bioassays have emerged recently. We also consider the advantages and the disadvantages of the various methodologies.

Determination of total organic carbon: an overview of current methods

Abstract: This article summarizes the most important and current methods for the determination of total organic carbon (TOC) in solid samples. The methods presented are chemical oxidation, combustion, acid treatment and ashing. We discuss the advantages of the different methods as well as problems that can be encountered during analysis. We give additional information on the detection techniques used for TOC determination and on the topic of volatile organic carbon (VOC) that deserves particular attention when carrying out TOC determinations, in particular with solid samples. We have compiled a concise survey of the literature covering 60 reports and tabulated the relevant analytical parameters.

Tailored materials for preconcentration or separation of metals by ion-imprinted polymers for solid-phase extraction (IIP-SPE)

Abstract: The development of new enrichment techniques and selective separation of closely related metals are two important frontier areas of research in analytical chemistry. Solid-phase extraction (SPE) or solid-liquid extraction (SLE) offers several advantages over other preconcentration or separation techniques. The introduction of ion-imprinted polymers (IIPs) in trace and ultratrace analysis provide vital breakthroughs in preconcentration or separation chemistry. The combination of the above two approaches results in IIPs for SPE (IIP-SPE) and has potential in trace and ultratrace analysis. With the preparation of tailor-made materials, IIP-SPE offers an approach to the recovery of valuable and rare metals from lean ores, minerals and dilute solutions and to the removal of toxic uranium and heavy metal pollutants from industrial wastes. This article takes stock of studies so far and outlines a future scenario in the rapidly developing and exciting area of IIP-SPE.

Analytical applications of the electrochemiluminescence of tris (2,2'-bipyridyl) ruthenium and its derivatives

Abstract: This article presents the state of the art of analytical applications of the electrochemiluminescence (ECL) of tris (2,2′-bipyridyl) ruthenium (Ru(bpy)32+) and its derivatives. In the last seven years, Ru(bpy)32+ ECL has attracted much interest from analysts and been successfully exploited as a detector of flow injection analysis (FIA), high-performance liquid chromatography (HPLC), capillary electrophoresis (CE), and micro total analysis systems (μTAS). Immobilization of Ru(bpy)32+ on a solid surface provides several advantages over the solution-phase ECL procedure, such as the simplicity of experimental design and cost-effectiveness. After a brief discussion of the mechanism of Ru(bpy)32+ ECL, we discuss its applications in FIA, HPLC, CE and μTAS and give special attention to the design of Ru(bpy)32+ ECL cells and some immobilization techniques of Ru(bpy)32+; we focus on papers published after 1997.

Selected drugs in solid matrices: a review of environmental determination, occurrence and properties of principal substances

Abstract: After intake, drugs absorbed by human or animal organisms are subject to metabolic reactions, such as hydroxylation, cleavage or glucuronation. However, a significant amount of the original or the metabolized substance leaves the organism via urine or feces. Thanks to improvements in analytical chemistry, many pharmaceutical compounds and endocrine disrupters are more easily detected in the surface-water and waste-water environmental compartments, at ppb concentrations. But what contaminates our solid environmental matrices? These substances can be eliminated by sorption or biodegradation but, at present, there is not enough data to allow evaluation of the behavior of the substances through the solid compartment, such as soil, sludge and bio-waste. This article provides an overview of the occurrence of pharmaceutical compounds in solid matrices on the basis of the quantities used, their physico-chemical properties and data from literature indicating the potential of the drug to persist in sediment, soil or sludge.

Supercritical fluid extraction: a critical review of its analytical usefulness

Abstract: We examine the evolution of supercritical fluid extraction (SFE) since 1990 in order to pinpoint the reasons for its rare implementation by routine analytical laboratories despite its high analytical potential. We identify various reasons, and we propose ways to overcome the shortcomings behind them. We also discuss the great analytical potential of SFE and justify its use for routine work.

Spectroscopic imaging and chemometrics: a powerful combination for global and local sample analysis

Abstract: Merging spectroscopic imaging and chemometrics enhances the outcomes of instrumental technology and data analysis. Multivariate exploratory and resolution methods can be adapted to image analysis and provide global and local information about pure compounds in an imaged sample. Knowing in detail how the chemical compounds are distributed over the scanned surface gives valuable information about essential issues in the manufacture and the characterization of products, such as evenness of composition and, therefore, homogeneity of the sample. The power to detect and to locate impurities is also greatly enhanced because these unwanted compounds could show locally large concentrations (and signals), even though their abundance on the surface is very low. The capabilities of this combination are shown in an example of pharmaceutical product control, where analysis of the end product requires chemical characterization and quantitative information at global and local levels. The approach used and the kind of information obtained is general and can be applied to the analysis of images in other fields.

Validation of qualitative analytical methods

Abstract: VALIDACIO DE METODES DANALISIS QUALITATIVA La informacio quimica sobre la composicio duna mostra pot ser molt diversa: des de saber de quins analits es composa un cert material a saber exactament en quina quantitat shi troben o de quina forma hi son presents, si estan relacionats estructuralment entre ells, etc. Dacord amb tota aquesta varietat, els metodes analitics es classifiquen en dos grans grups: els metodes danalisi qualitativa i els metodes danalisi quantitativa. Segons les caracteristiques del problema analitic es triara un o altre tipus de metode danalisi. Quan lobjectiu es saber que hi ha en una mostra desconeguda, un metode qualitatiu sera el mes adequat. En els darrers temps, aquests metodes han estat objecte destudi, i sutilitzen avui dia, en molts camps daplicacio. Per exemple, en lanalisi daliments es habitual lus dun metode qualitatiu per determinar si un o mes analits es troben presents en la mostra per sobre o per sota duna determinada concentracio. Pero si linteres es saber la quantitat dun determinat component en una mostra, lopcio dun metode quantitatiu sera la mes adient. Aquesta tesi sha centrat en els metodes danalisi qualitativa pels nombrosos avantatges que presenten. Aquests metodes poden ajudar a destriar mostres en funcio de si aquestes presenten una quantitat dun cert analit al voltant dun valor de concentracio previament establert, abans de ser quantificades. Es a dir, sutilitzen com a pas previ a laplicacio del metode quantitatiu, implicant un estalvi de feina, de temps i de diners important si es tracta de quantificar contaminants, detectar adulteracions o qualsevol altra situacio en la que no es pugui sobrepassar una certa concentracio. En aquests casos nomes sha de quantificar la mostra que en el metode qualitatiu revela un resultat en el que es sobrepassa aquesta certa concentracio. En daltres ambits daplicacio, els metodes qualitatius estan perfectament integrats en el procediment estandard doperacions, pel que, llevat en situacions molt especifiques, un resultat positiu no necessita ser confirmat mitjancant una analisi posterior amb un metode quantitatiu. A mes de la importancia de triar un metode analitic adequat a cada problematica, cal destacar que es igual dimportant tenir fiabilitat sobre el resultat trobat i, per tant, sobre el metode emprat. Aixo vol dir que qualsevol metode analitic ha de tenir definits els seus requeriments i qualitats analitiques i que sha de comprovar que aquests parametres previament definits, realment tenen el valor que sels ha assignat. Daquesta confirmacio sen diu Validacio, i es una condicio indispensable per a poder emprar un metode analitic. Daquesta manera es poden garantir els resultats demanats pels clients/usuaris. A mes, des de laprovacio de la norma ISO 17025 aquesta comprovacio del metode analitic i dels seus resultats encara sha fet mes recomanable. Fins fa poc temps, la validacio de metodes analitics sha centrat en els metodes quantitatius. El resultat ha estat una serie de guies/pautes perfectament establertes dus molt comu. Pero no hi ha cap protocol general per a validar un metode qualitatiu. Amb aquesta tesi es vol contribuir a millorar aquesta situacio. Es comenca amb una revisio de les classificacions i de les definicions lligades a aquests metodes, a mes dun repas sobre quines institucions han fet esment daquest tema. Es segueix amb una proposta de classificacio daquests metodes i, finalment, es defineixen aquells parametres de qualitat que es consideren mes importants en la validacio. En les tres aplicacions practiques presentades es descriuen les caracteristiques intrinseques del metode danalisi qualitativa. Despres, es defineixen els parametres que sadequen millor als requeriments del metode i, finalment, es proposa un protocol de validacio que permet el seu establiment. El cas de la revisio de les classificacions i definicions emprades en aquest ambit, com en el cas de la presentacio de les contribucions corresponents a diferents institucions, shan traduit en dues publicacions que sadjunten en la tesi. Pel que fa a les aplicacions practiques, una delles tambe sinclou com a article publicat i les altres dues, sinclouen com a articles acceptats VALIDATION OF QUALITATIVE ANALYTICAL METHODS The chemical information about the composition of a sample can be of different nature: which species are in the sample, their concentration or if they are structurally related, etc. In order to fit any of these requirements, either a qualitative or a quantitative analytical method may be used. If the aim is to identify species, a qualitative method will suit the problem at hand. These types of methods have been recently studied and nowadays are being increasingly used in several fields of analysis. For example, it is common to use qualitative methods as far as food analysis is concerned. On the contrary, if the aim is to quantify one or more analytes of a sample, a quantitative method will be very useful. This thesis has focused on qualitative analytical methods because they provide several advantages and they are being increasingly used. These types of methods can screen samples according to the presence or absence of certain analytes with regard to a pre-set level of concentration. That is to say, they are used as a step before the quantitative method and results in lower analysis time and costs because analyte quantification is not required in all situations. There are some particular analysis fields where qualitative methods are used as routine methods. Therefore, analyte quantification is not always necessary. Moreover, it is also important to provide reliable results, that is to say, to assure that the method performs with reliability. Any analytical method must have its requirements and its analytical properties previously defined, and their values must be proven. To confirm that the requirements and the analytical properties are the right ones and to confirm that they have the right values is to validate the analytical method. This is a necessary condition to use an analytical method. In this sense, the reliability of the results given to the clients or to the users is assured. Moreover, the ISO Standard 17025 strongly encourages method validation. Method validation has focused on quantitative methods. Therefore and as a result, there are more standards or guidelines addressed to quantitative methods validation. These guidelines are commonly used by several communities of practitioners. However, there is no generally accepted standard or validation procedure addressed to qualitative methods. In this sense, this thesis aims to contribute with the development of several validation procedures. The starting point is to provide an overview as a result of a bibliographic search concerning qualitative methods validation. This overview includes the criteria existing for qualitative methods classification as well as the institutions committed the validation of these methods. After that, a classification of these methods is suggested and the most relevant performance parameters in the validation process are defined. The subsequent practical applications describe the intrinsic characteristics of the corresponding qualitative analytical method. After that, the performance parameters that best fit the requirements and the characteristics of the method are defined and, finally, a validation strategy is proposed. Bear in mind, that the strategy considers the intrinsic characteristics of the analytical method. The overview including relevant aspects such as qualitative methods classification, performance parameters definitions and the institutions committed to qualitative method validation, among others, are presented as two publications included in the thesis. Regarding the three practical applications, they are presented as three accepted papers.

Recent developments in nanomaterial optical sensors

Abstract: The application of nanomaterials in the field of optical sensors has become a new, growing area of interest in recent years. We review chemical sensors that apply the optical principles of nanomaterials to the determination of chemical and biochemical analytes. We mainly focus on the changes of spectral absorbance, photoluminescence (PL) and chemiluminescence (CL) phenomena induced by the interaction between nanomaterials and various analytes.

The use of micellar systems in the extraction and pre-concentration of organic pollutants in environmental samples

Abstract: Establishing simple, fast, low-cost, sensitive and selective analytical methods for extraction and determination of pollutants in the environment is one of the main lines of research in environmental chemistry. Recent studies have demonstrated that micellar systems (surfactant solutions) constitute a real alternative to organic solvents for use as extractants of organic pollutants from liquid and solid environmental samples. This article is an overview of the use of micellar systems in the extraction/pre-concentration of different organic pollutants. Specifically, it discusses the application of the cloud-point extraction (CPE) and microwave-assisted micellar extraction (MAME) methodologies to the extraction and pre-concentration of organic pollutants, such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), polychlorinated dibenzofurans (PCDFs), polychlorinated dibenzo-p-dioxins (PCDDs) and phenolic derivatives, from environmental matrices. These studies show the advantages of these optimised methodologies over the traditional extraction techniques.

Analysis and distribution of estrogens and progestogens in sewage sludge, soils and sediments

Abstract: This article focuses on solid samples and reviews the main findings so far concerning the source, the presence and the fate of estrogens and progestogens in the aquatic environment. We discuss the very few existing analytical methods for determination of estrogens and progestogens in environmental matrices (soils, sediments and sludge). Estrogens are continuously released in the aquatic environment mainly because treatment plants are unsuccessful in removing them. Studies show that estrogens and progestogens are easily distributed in the environment and are likely to accumulate in river sediments and in soils. However, it is not yet clear whether sorption or biodegradation processes play a major role in their elimination from the aquatic environment.

Analytical uses of ultrasound I. Sample preparation

Abstract: Ultrasound assistance is a growing trend in analytical chemistry. From the most basic use for cleaning to facilitating or making possible different steps of the analytical process – particularly those involved in sample preparation – ultrasonic devices are gaining the confidence of analytical chemists who use them for helping in steps ranging from sampling through to detection. In this first part of the article, we present an overview of the principles and the uses of these devices for improving, accelerating or automating sample preparation. We compare them with well-established alternatives and critically comment upon them.

Recent advances in the design of small molecule-based FRET sensors for cell biology

Abstract: Fluorescence resonance energy transfer (FRET) has been used extensively as the designing principle for fluorescent sensor molecules. One of the most significant advantages of designing sensor molecules with FRET modulation is that it can enable ratiometric measurement in living cells, which reduces artifacts from microscopic imaging system. We describe the design strategy for the development of small-molecule FRET sensor in terms of avoiding close contact of donor fluorophore and acceptor fluorophore in aqueous solution. Furthermore, we introduce a strategy to design FRET sensors with a modulating overlap integral of donor and acceptor.

Hydride generation – recent advances in atomic emission spectrometry

Abstract: This article presents recent advances in the hydride-generation (HG) technique hyphenated with different discharges of the atomic emission spectrometry (AES) [i.e. inductively-coupled plasma (ICP), microwave-induced plasma (MIP), direct-current plasma (DCP) and glow discharge (GD)], serving as excitation sources of hydride-forming elements. It surveys and discusses various aspects of vapour-phase introduction, comprising the instrumentation for performing the reaction, the influence of the chemical reaction conditions, the existence of chemical and non-chemical interference effects and the approaches to eliminating or lessening the interferences, as well as the analytical applications to real samples. In addition, it presents the latest trends in the technique, such as expansion of the scope to some transition and noble metals and the usage of organised surfactant-based media for the enhancement of the reaction properties.

Extraction and analysis of arsenic in soils and sediments

Abstract: The ability to extract arsenic (As) from soils and sediments, and analyze it with accuracy and precision, is of paramount importance, given the high risk that As, even in relatively low concentrations, poses to pore waters and biota. A large number of methods exist for extracting and analyzing total As, and As associated with a variety of operationally defined phase associations, in soils and sediments. We give an overview of methods used at present, and consider potential problems. We strongly recommend adoption of universal standard techniques and certified reference materials, especially for sequential extraction schemes.

DNA biochip arraying, detection and amplification strategies

Abstract: Research on DNA biochips is advancing rapidly and has yielded several commercial platforms. This review presents, critically comments upon and compares DNA-biochip-arraying methods and techniques. It also discusses methods for detecting and amplifying hybridization events. The review focuses on miniaturization of these systems for diagnostic applications of biochip technology.

Trends in quality in the analytical laboratory. I. Traceability and measurement uncertainty of analytical results

Abstract: Credibility of analytical data has never caught the public's eye more than today. The key principle for quality and reliability of results is comparability between laboratories and on a wider, international basis. In order to be comparable, analytical results must be reported with a statement of measurement uncertainty (MU) and they must be traceable to common primary references. This work focuses on traceability and uncertainty of results. We discuss different approaches to establishing traceability and evaluating MU. We place both concepts in the broader context of analytical method validation and quality assurance. We give up-to-date information in the framework of new, more exacting European and international standards, such as those from Eurachem/CITAC, IUPAC and ISO.

Traceability of sediment analysis

Abstract: Chemical analysis of sediments provides an efficient tool for water-quality management. A basic sequence of measurements comprises three steps: sampling and sample preparation; grain size as a characteristic sediment feature; and, analytical procedures based on standardized extraction schemes and reference materials. These can be considered as an unbroken chain of comparisons. Further steps are split with regard to specific purposes: sediment-quality assessment, including biological effects; coupling of sediment-quality data with erosion-risk evaluation; chemical changes following resuspension of anoxic sediments; and, modeling of chemical sediment data. In the light of the economic value of these further steps for developing and executing far-reaching management plans, coordinated efforts should be made to improve their traceability (e.g., by organized dissemination of results from on-going research (ageing effects), official documentation of techniques and instruments in a relative new field (erosion effects), extension of standardized extraction schemes (anoxic sediments, capacity-controlling properties), and development of new reference materials (pore water)).

Derivatization and solid-phase microextraction

Abstract: The use of derivatization in the solid phase or in solution in analytical methods based on solid-phase microextraction (SPME) has made possible low detection limits (LODs) to determine substances with poor chromatographic behavior, high reactivity and/or volatility or thermal instability. The most common use of derivatization in SPME applications is the treatment of polar compounds to increase their recoveries from the sample matrix. The implementation of solid-phase derivatization procedures has permitted not only enhancement of recoveries, but also improvement in the separation, selectivity and/or sensitivity of analytical methods. This review covers analytical methods that involve derivatization and SPME.

Chemical and ecotoxicological guidelines for managing disposal of dredged material

Abstract: Different conventions around the world have produced guidelines for the disposal of dredged material (e.g., London Convention 1972 (LC) ( www.Londonconvention.org ); Oslo/Paris Convention (OSPAR) ( www.ospar.org ); and, the Helsinki and Barcelona Conventions). They suggest the use of different methodologies from physico-chemical to biological approaches to the management of different routes of disposal or uses of the dredged material. Most of these conventions propose methods based on a `weight of evidence' (WOE) approach. It consists from the beginning of a simple screening approach and progresses to more detailed assessments in cases where any initial management concerns cannot be discounted. Initial assessment considers factors relating to the dredged material, such as the particle-size characteristics of the dredged material, local and historic information, and its environment (e.g., surrounding industries, pollution sources, and collectors). If this information is insufficient to provide answers for the management proposed for it, then further data must be collected that involves chemical characterization of the dredged material. In some countries, these primary assessment processes also incorporate biological screening tests. If management decisions regarding sediment quality cannot be made from initial and primary assessments, direct measurements of toxicity and/or bio-accumulation and/or other case-specific studies may be required, until it is judged that sufficient information is available for a decision to be made about the disposal or use of the dredged material. We aim to review the different methodologies used for characterizing dredged material with an special focus on Spain, describing recent initiatives that include revision of some of the most common tests used to assess sediment quality and potential guidelines for the management of the disposal of dredged material.

Detection of gas-phase chemical warfare agents using field-portable gas chromatography–mass spectrometry systems: instrument and sampling strategy considerations

Abstract: Selection of sampling methods and GC–MS instrumentation for field analysis of dangerous chemicals should be based on desired performance. Using a combined, man-portable, GC–MS sampler, volatile compounds may be analyzed while in a contaminated atmosphere. Alternatively, a small solid-phase microextraction sampler allows analysis in a nearby clean area with stationary GC–MS instrumentation that offers advantages in sample throughput and the range of samples that may be analyzed.

Light at the end of the tunnel: recent analytical applications of liquid-core waveguides

Abstract: Optical chemical analysis systems are the most important tools to analytical chemists in need of sensitive measurement techniques. Liquid-core waveguides (Fig. 1) have proved to be an important innovation that has led to improvements in detection limits when incorporated into many types of optical analysis systems, especially UV–Vis absorbance, fluorescence and Raman measurements.

Steroid estrogen determination in sediment and sewage sludge: a critique of sample preparation and chromatographic/mass spectrometry considerations, incorporating a case study in method development

Abstract: Steroid estrogens have been identified in the solid matrices of unit treatment processes in sewage treatment works (STWs) and in sediments of watercourses that receive effluent. This article discusses the sample preparation and analytical considerations necessary for reliable determination and the need to evaluate for possible matrix interferences during method development. Complementing this is a case study highlighting the potential for analyte transformation during sample preparation and the phenomena of ion suppression when utilising LC/MS ESI with a comparison of method recoveries by GC/MS. We discuss the use of LC/MS/MS and TOF instruments; however, at present, their use in environmental analyses appears to be limited because of their capital costs.

Robustness of models developed by multivariate calibration. Part I: The assessment of robustness

Abstract: Monitoring products for quality assurance in real-time during industrial processes has become of great importance in recent years Infrared spectroscopic (IRS) techniques combined with multivariate calibration methods are primarily used for on-line analysis, in situ sensors or automatic sampling In order to ensure the correct use of these methods for routine industrial use, all the mechanical and the environmental conditions need to be taken into account, as well as the introduction of time delays and signal bias during sampling This requires a robustness study of the IRS measurement and the calibration model used In this review, we focus on both identifying the “robustness” used for multivariate calibration and the different methods applied to evaluate this robustness, especially with regard to the IRS technique used in industry We also present and discuss various criteria intended for robustness assessment

Long-wavelength fluorophores: new trends in their analytical use

Abstract: Interest in the analytical use of long-wavelength fluorophores (LWFs) is growing, as shown by the numerous articles published recently in different areas, such as immunoassay, liquid chromatography (LC), capillary electrophoresis (CE) and sensors. This article provides an overview of the usefulness of cyanines, oxazines, rhodamines, ruthenium(II) complexes and other compounds to improve selectivity in fluorimetric determinations. It includes the advantages and the limitations of their applications, mainly in the field of biological analysis.

Reference materials: terminology and use. Can't one see the forest for the trees?

Abstract: The use of reference materials (RMs) and the regular participation in proficiency testing (PT) schemes have become fundamental pillars of assuring and controlling the quality of analytical data in terms of precision and accuracy, thus proving the competence of analytical laboratories. In recent times, many terms describing non-certified reference materials (non-certified RMs) have emerged, often the result of confusing use with characteristics. Depending on the use of a material, a certain number of characteristics (e.g., homogeneity and assigned value) must be demonstrated. This article reviews the main types of application of RMs and describes the main material characteristics needed to fulfill the corresponding purposes. Based on this, it summarizes minimum requirements for certain uses.

Biomarkers as tools to assess sediment quality. Laboratory and field surveys

Abstract: The traditional approach to assessing sediment quality involves chemical analysis. However, this is not sufficient to ensure safe disposal of dredged material or to determine the impact on biota of sediment contamination. The toxic effect on flora and fauna is related to the bioavailability of contaminants. Because of the potential transfer of contaminants along food chains, not only the local habitat can be affected, but also organisms at higher trophic levels. The consumption of seafood may lead to adverse effects on human health. Biomarkers are useful tools as early warnings to determine exposure to contaminants and the effect of contaminants on organisms before the damage becomes irreversible. They may link the bioavailability of compounds with their concentrations at target organs and intrinsic toxicity. Nevertheless, other confounding factors must be taken into account when the results are interpreted. We review different biomarkers used to determine the quality of marine sediment and dredged material. Also, we consider evaluation of the use of biomarkers in environmental risk assessment (ERA) and links between laboratory and field surveys. We integrate available information to determine the validity of the different biomarkers, their relevance for assessing contaminated sediments and the suitability of the methodology. We consider the results in a tiered approach to testing at levels characterizing toxic effects and validating in situ changes.