Analytical methodologies for aluminium speciation in environmental and biological samples – a review

It is recognized that aluminium (Al) is a potential environmental hazard. Acidic deposition has been linked to increased Al concentrations in natural waters. Elevated levels of Al might have serious consequences for biological communities. Of particular interest is the speciation of Al in aquatic environments, because Al toxicity depends on its forms and concentrations. In this paper, advances in analytical methodologies for Al speciation in environmental and biological samples during the past five years are reviewed. Concerns about the specific problems of Al speciation and highlights of some important methods are elucidated in sections devoted to hybrid techniques (HPLC or FPLC coupled with ET–AAS, ICP– AES, or ICP–MS), flow-injection analysis (FIA), nuclear magnetic resonance (²⁷Al NMR), electrochemical analysis, and computer simulation. More than 130 references are cited.     

环境与生物体系中铝形态分析技术的新进展

铝的形态分析是研究环境和生物体系中铝的毒性、生物有效性和传输机理的关键。从IUPAC2000，72，1453和Analyst2001，126(2)对元素形态概念的最新定义，在过去20年来，形态分析都是依据操作手段来进行“组形态”(group species)分析。然而，随着近5年来分析技术的发展，对铝的形态分析逐步达到了“单形态”(individual species)分析的水平。从以下两个方面对该领域的最新进展进行了评述，即：(1)组形态分析(fractionation)：离子交换、电化学分析和流动注射；(2)单形态分析(speciation)：联用技术、核磁共振和计算机拟合。     

Aluminium speciation in environmental samples: a review

Because of its toxic effects on living beings, Al may represent an environmental hazard, particularly under increased acidic conditions. Growing environmental concern over the presence of increased Al concentrations in soil solutions and fresh waters resulted in the development of numerous analytical techniques for the determination of Al species. Al has a very complex chemistry that is significantly influenced by pH. Different Al species are present in environmental solutions, and many of them are unstable. Contamination of samples and reagents by extraneous Al represents an additional problem in speciation of Al at trace concentrations. Due to these reasons quantitative determination of particular chemical forms of Al is still a very difficult task for analytical chemists. The most important analytical methodologies of the last decade and new trends for the speciation of Al in environmental samples are comprehensively reviewed here.     

Speciation analysis of aluminium(III) in natural waters and biological fluids by complexing with various catechols followed by differential pulse voltammetry detection

The biological effects of aluminium have received much attention in recent years. Speciation of Al is of basic relevance as it concerns its reactivity and bioavailability. A differential pulse voltammetry (DPV) procedure is proposed for speciation analysis of Al(III) in natural waters and biological fluids using six catechols (L-dopa, dopamine, epinephrine, norepinephrine, caffeic acid and o-benzenediol) as electroactive ligands. The decrease of the DPV anodic peak current for each catechol ligand is linear with the increase of Al concentration. This speciation analysis idea is based on the measurement of the complexation capacity, namely, different affinities of Al(III) for catechols and organic ligands under two pH conditions. The labile monomeric Al fraction (mainly inorganic aluminium) is determined at pH 4.6, while the total monomeric Al fraction is determined at pH 8.5. The principle for Al(III) speciation analysis by an electrochemical method is discussed. This sensitive and simple fractionation method is successfully applied to the speciation analysis of Al in natural waters and the results agree well with those of Driscoll's method. The speciation analysis of Al in biological fluids is also explored and the results are compared with those obtained by ultrafiltration and dialysis. Compared with other speciation protocols the electrochemical method possesses some remarkable advantages: rapidity, high sensitivity, cheap instrumentation and a simple operation procedure.     

生物和环境样品中硒元素的形态分析研究

金属组学是继基因组学/蛋白质组学和代谢组学后提出的一种新的组学,其研究重点在于对所研究的金属和类金属元素的各种存在形态进行分析。硒是生物环境中存在的一种重要的类金属元素。形态与浓度不同的硒化合物可能是生物体的必需元素,同时也可能导致中毒。本文对目前存在的硒元素形态分析方法的研究现状进行了总结,并对前景进行了展望。     

Recent advances in on-line coupling of capillary electrophoresis to atomic absorption and fluorescence spectrometry for speciation analysis and studies of metal-biomolecule interactions

Speciation information is vital for the understanding of the toxicity, mobility and bioavailability of elements in environmental or biological samples. Hyphenating high resolving power of separation techniques and element-selective detectors provides powerful tools for studying speciation of trace elements in environmental and biological systems. During the last five years several novel hybrid techniques based on capillary electrophoresis (CE) and atomic spectrometry have been developed for speciation analysis and metal-biomolecule interaction study in our laboratory. These techniques include CE on-line coupled with atomic fluorescence spectrometry (AFS), chip-CE on-line coupled with AFS, CE on-line coupled with flame heated quartz furnace atomic absorption spectrometry (FHF-AAS), and CE on-line coupled with electrothermal atomic absorption spectrometry (ETAAS). The necessity for the development of these techniques, their interface design, and applications in speciation analysis and metal-biomolecule interaction study are reviewed. The advantages and limitations of the developed hybrid techniques are critically discussed, and further development is also prospected.     

Speciation Analysis of Mercury in Water and Human Urine Using Gas Chromatography-Mass Spectrometry after Solid Phase Disk Extraction

In recent years, there has been growing interest in the field of mercury speciation analysis. Mercury speciation analysis of water or urine matrices are necessary for solving various environmental, biological or clinical problems. Due to the complexity of sample matrices and the low levels of mercury species, an extraction step, such as liquid-liquid extraction or solid phase cartridge extraction, is required for Hg speciation analysis to isolate and enrich analyte species from sample matrices. As a new experimental configuration, disks or membranes for solid phase extraction (SPE) have been utilized in recent years for the preparation of many different organic and environmental samples. However,the literature survey revealed that solid-phase disk extraction has received little attention in the field of elemental speciation analysis.     

Quantitative HPLC-ICP-MS analysis of antimony redox speciation in complex sample matrices: new insights into the Sb-chemistry causing poor chromatographic recoveries

In solution antimony exists either in the pentavalent or trivalent oxidation state. As Sb(III) is more toxic than Sb(V), it is important to be able to perform a quantitative speciation analysis of Sb's oxidation state. The most commonly applied chromatographic methods used for this redox speciation analysis do, however, often show a low chromatographic Sb recovery when samples of environmental or biological origin are analysed. In this study we explored basal chemistry of antimony and found that formation of macromolecules, presumably oligomeric and polymeric Sb(V) species, is the primary cause of low chromatographic recoveries. A combination of HPLC-ICP-MS, AFFF-ICP-MS and spin-filtration was applied for analysis of model compounds and biological samples. Quantitative chromatographic Sb redox speciation analysis was possible by acidic hydrolysis of the antimony polymers prior to analysis. Sample treatment procedures were studied and the optimum solution was acidic hydrolysis by 1 M HCl in the presence of chelating ligands (EDTA, citrate), which stabilise the trivalent oxidation state of Sb.     

Environmental specimen banking – Aspects of metal determination and distribution

Analytical investigations of metals within the present program of the German Environmental Specimen Bank (ESB) are briefly introduced. The focus is directed to challenges and opportunities which are provided by an ESB for analytical chemistry. Several aspects of instrumental approaches for environmental analysis, bioindication, speciation, data evaluation and quality assurance are discussed. Illustrative examples of ESB results are presented concerning metal concentrations in biological material, comparison of ecosystems and long-term tendencies.     

Overview of the methodology of nuclear analytical techniques for speciation studies of trace elements in the biological and environmental sciences

Recent achievements in speciation studies of trace elements in the biological and environmental sciences by nuclear analytical techniques, mainly molecular activation analysis, position-sensitive spectrometry with a variety of exciting sources, and synchronous radiation-based analytical techniques (although radioisotope or enriched stable isotope-based speciation techniques are also used), particularly in our laboratory, are outlined. In this paper the merits and drawbacks of the nuclear analytical techniques are discussed, as are reagent blanks, contamination, and artifacts.     

铝形态分析的研究进展

介绍了铝形态分析的意义,环境和生物体系中铝存在的形式,综述了铝形态分析时采用的连续静态浸提法、铝-试铁灵逐时络合比色光度法、酸碱电位滴定、电化学分析、色谱分析、核磁共振及计算机拟合等分析方法(1984—2009年间),引用文献65篇。     

金属有机配体分析方法及金属组学研究

环境和生物样品中金属与有机酸、氨基酸、多糖、蛋白质、DNA等形成的金属有机物是一系列生物金属。生物金属中参与金属离子配位的有机配基主要是含氧、硫、氮及磷的功能团。金属组学是整合生物金属中金属有机配体的结合形态及其生理功能活性的新概念。文中介绍了目前常用的金属有机配体的分析方法以及金属组学领域的研究技术,并展望了重金属富集和超积累植物的研究前景。     

Recent trends in nanomaterial-based microanalytical systems for the speciation of trace elements: A critical review

Trace element speciation in biomedical and environmental science has gained increasing attention over the past decade as researchers have begun to realize its importance in toxicological studies. Several nanomaterials, including titanium dioxide nanoparticles (nano-TiO₂), carbon nanotubes (CNTs), and magnetic nanoparticles (MNPs), have been used as sorbents to separate and preconcentrate trace element species prior to detection through mass spectrometry or optical spectroscopy. Recently, these nanomaterial-based speciation techniques have been integrated with microfluidics to minimize sample and reagent consumption and simplify analyses. This review provides a critical look into the present state and recent applications of nanomaterial-based microanalytical systems in the speciation of trace elements. The adsorption and preconcentration efficiencies, sample volume requirements, and detection limits of these nanomaterial-based speciation techniques are detailed, and their applications in environmental and biological analyses are discussed. Current perspectives and future trends into the increasing use of nanomaterial-based microfluidic techniques for trace element speciation are highlighted.     

毛细管电泳在形态分析中的应用

对近年来毛细管电泳（ＣＥ）与紫外检测器（ＵＶｄｅｔｅｃｔｏｒ）和ＣＥ与感应耦合等离子体质谱（ＩＣＰ－ＭＳ）联用在形态分析中的应用及其存在的一些问题加以评述。     

碲的形态分析进展

综述了近年来国内外碲的无机、有机形态分析进展。因碲在环境样品中的含量低、分散,存在形式较多,建立快速、准确的碲形态分析方法是值得进一步探讨的问题。     

毛细管电泳用于形态分析

一种元素的生物可给性、环境行为和迁移性在很大程度上取决于它的形态。如不同的键合形式或氧化态，因此，作为元素物种鉴别和含量测定的形态分析变得越来越重要。毛细管电泳作为一种分离分析技术有许多优点可以满足形态分析的要求。本文从样品的预处理、毛细管电泳的修饰、进样方式、分离模式和检测等几个方面评述了毛细管电泳在形态分析中的应用。     

CRMs for quality control of determinations of chemical forms of elements in support to EU legislation

The concern for the control of toxic chemical forms of elements in the environment is reflected by an increasing number of analyses performed by research and routine laboratories. The European Commission has recognised the need to include some of these species in the list of dangerous substances to be monitored, e.g. in the marine environment or in groundwater. However, in most cases, the specifications are far from being sufficient in respect to the chemical forms of the element to be determined. Furthermore, these determinations are in most cases based on multi-step analytical techniques which are often prone to errors (e.g. at the extraction, derivatization or separation steps). Certified reference materials (CRMs) certified for their content in chemical forms of elements are, therefore, necessary to ensure the accuracy of these measurements and hence the respect of the regulations. However, the lack of CRMs for speciation analysis hampers the quality control of determinations which in turn leads to an incomparability of data produced; so far the number of CRMs produced by international organisations, e.g. NIST (USA), NIES (Japan), NRCC (Canada) and BCR (Belgium), is very limited and concerns mainly compounds such as e.g. methyl-mercury and butyltin compounds in biological matrices or sediments. The Standards, Measurements and Testing Programme (formerly BCR) of the European Commission has started a series of projects for the improvement of speciation analysis in environmental matrices, the final aim of which being the production of a variety of environmental CRMs. The existing EU legislation involving chemical forms of elements is presented, the requirements for the preparation of CRMs for speciation analysis are discussed and an update of the most recent CRMs produced within the Standards, Measurements and Testing Programme (SM&T) is given.     

CRMs for quality control of determinations of chemical forms of elements in support to EU legislation

The concern for the control of toxic chemical forms of elements in the environment is reflected by an increasing number of analyses performed by research and routine laboratories. The European Commission has recognised the need to include some of these species in the list of dangerous substances to be monitored, e.g. in the marine environment or in groundwater. However, in most cases, the specifications are far from being sufficient in respect to the chemical forms of the element to be determined. Furthermore, these determinations are in most cases based on multi-step analytical techniques which are often prone to errors (e.g. at the extraction, derivatization or separation steps). Certified reference materials (CRMs) certified for their content in chemical forms of elements are, therefore, necessary to ensure the accuracy of these measurements and hence the respect of the regulations. However, the lack of CRMs for speciation analysis hampers the quality control of determinations which in turn leads to an incomparability of data produced; so far the number of CRMs produced by international organisations, e.g. NIST (USA), NIES (Japan), NRCC (Canada) and BCR (Belgium), is very limited and concerns mainly compounds such as e.g. methyl-mercury and butyltin compounds in biological matrices or sediments. The Standards, Measurements and Testing Programme (formerly BCR) of the European Commission has started a series of projects for the improvement of speciation analysis in environmental matrices, the final aim of which being the production of a variety of environmental CRMs. The existing EU legislation involving chemical forms of elements is presented, the requirements for the preparation of CRMs for speciation analysis are discussed and an update of the most recent CRMs produced within the Standards, Measurements and Testing Programme (SM&T) is given.     

Considerations in the preparation of biological and environmental reference materials for use in the study of the chemical speciation of trace elements

Summary The role that information on chemical speciation can play in the selection of reference materials for the analysis of biological and environmental samples is reviewed. Some considerations that might go into the preparation of materials designed for chemical speciation studies are explored. Individual steps in the preparation of lyophilized serum and urine reference materials are examined in relation to changes that could occur in the chemical speciation of trace elements.     

Synthetic and structural carboxylate chemistry of neurotoxic aluminum in relevance to human diseases

The contact of Al(III) with biological components in human physiology has increased significantly over the years, due to a number of factors, prominent among which stands the rapid acidification of the environment and the concomitant introduction of that abundant metal ion in human biological fluids. As a result, pathophysiological aberrations in humans have arisen due to Al(III) (neuro)toxicity. Among the efforts targeting the elucidation of the factors responsible for Al(III) toxicity is the exploration of the requisite Al(III)-carboxylate chemistry in aqueous media, and its relevance to soluble, potentially bioavailable species capable of exerting toxic effects. A detailed synthetic, structural, and spectroscopic account of the Al(III)-carboxylate complexes, purported to exist as components in aqueous Al(III)-carboxylic acid speciation, is presented. The structures described are classified as mononuclear, dinuclear, trinuclear, tetranuclear, and polynuclear species, arising from various aqueous and non-aqueous Al(III)-carboxylate ligand reactions. Moreover, the solution chemistry and kinetic behavior of the so far reported complexes is given, with the specific aim of comparing their solid state and solution chemical and structural properties. In this sense, a comprehensive picture on the Al(III) speciation, in the presence of various physiological or biologically relevant carboxylate ligands, appears to emerge, which is expected to contribute to the understanding of Al(III) (neuro)toxicity and its consequence(s) in a multitude of human diseases. Carboxylate containing low and high molecular mass components stand prominent in their chemical preference to react with Al(III) in biological fluids. In this context, factors considered to influence the aqueous low molecular mass Al(III)-carboxylate chemistry, thus affecting the solubility and possibly the bioavailability of the resulting species, are discussed as potential research links to the ultimate manifestation of Al(III) toxicity at the cellular level.