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.     

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.     

Arsenic speciation analysis

Nearly two dozen arsenic species are present in the environmental and biological systems. Differences in their toxicity, biochemical and environmental behaviors require the determination of these individual arsenic species. Considerable analytical progresses have been made toward arsenic speciation analysis over the last decade. Hyphenated techniques involving a highly efficient separation and a highly sensitive detection have become the techniques of choice. Methods based on high-performance liquid chromatography separation with inductively coupled plasma mass spectrometry, hydride generation atomic spectrometry, and electrospray mass spectrometry detection have been shown most useful for arsenic speciation in environmental and biological matrices. These hyphenated techniques have resulted in the determination of new arsenic species, contributing to a better understanding of arsenic metabolism and biogeochemical cycling. Methods for extracting arsenic species from solid samples and for stabilizing arsenic species in solutions are required for obtaining reliable arsenic speciation information.     

Solid phase extraction for the speciation and preconcentration of inorganic selenium in water samples: A review

Selenium is an essential element for the normal cellular function of living organisms. However, selenium is toxic at concentrations of only three to five times higher than the essential concentration. The inorganic forms (mainly selenite and selenate) present in environmental water generally exhibit higher toxicity (up to 40 times) than organic forms. Therefore, the determination of low levels of different inorganic selenium species in water is an analytical challenge. Solid-phase extraction has been used as a separation and/or preconcentration technique prior to the determination of selenium species due to the need for accurate measurements for Se species in water at extremely low levels. The present paper provides a critical review of the published methods for inorganic selenium speciation in water samples using solid phase extraction as a preconcentration procedure. On the basis of more than 75 references, the different speciation strategies used for this task have been highlighted and classified. The solid-phase extraction sorbents and the performance and analytical characteristics of the developed methods for Se speciation are also discussed.     

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。     

Determination of butyl- and phenyltin compounds in sediments by GC-FPD after NaBEt(4) ethylation

A reliable and rapid speciation method for the simultaneous determination of butyl- and phenyltin species in sediment samples has been developed. Two extraction procedures are compared: methanolic hydrochloric acid (at four different concentrations) and ethanoic acid leaching. Derivatization is carried out by the one-step ethylation/extraction procedure using the sodium tetraethylborate reagent directly in aqueous phase in the presence of an isooctane layer. Analysis is performed by capillary gas chromatography hyphenated to flame photometric detection (GC-FPD). Detection limits range from 0.5 to 1.5 ng(Sn) g(-1)(dry weight). Analysis of environmental samples and certified reference materials demonstrate the accuracy of the analytical method.     

Simultaneous speciation of mercury and butyltin compounds in natural waters and snow by propylation and species-specific isotope dilution mass spectrometry analysis

A robust method has been developed for simultaneous determination of mercury and butyltin compounds in aqueous samples. This method is capable of providing accurate results for analyte concentrations in the picogram per liter to nanogram per liter range. The simultaneous determination of the mercury and tin compounds is achieved by species-specific isotope dilution, derivatization, and gas chromatography–inductively coupled plasma mass spectrometer (GC–ICP–MS). In derivatization by ethylation and propylation, reaction conditions such as pH and the effect of chloride were carefully studied. Ethylation was found to be more sensitive to matrix effects, especially for mercury compounds. Propylation was thus the preferred derivatization method for simultaneous determination of organomercury and organotin compounds in environmental samples. The analytical method is highly accurate and precise, with RSD values of 1 and 3% for analyte concentrations in the picogram per liter to nanogram per liter range. By use of cleaning procedures and SIDMS blank measurements, detection limits in the range 10–60 pg L^–1 were achieved; these are suitable for determination of background levels of these contaminants in environmental samples. This was demonstrated by using the method for analysis of real snow and seawater samples. This work illustrates the great advantage of species-specific isotope dilution for the validation of an analytical speciation method—the possibility of overcoming species transformations and non-quantitative recovery. Analysis time is saved by use of the simultaneous method, because of the use of a single sample-preparation procedure and one analysis.     

Analytical Methods for Speciation of Organotins in the Environment

The growing awareness over the environmental fate of organotin compounds is reflected in the large number of analytical methods developed for their separation. Organotin compounds have varying degrees of toxicological properties, depending on the nature and number of alkyl groups bonded to the tin atom. Most of the analytical speciation methods applied to actual environmental media have involved prior derivatization to transform organotin compounds into volatile hydrophobic analytes amenable to separation and identification by gas chromatography coupled to a sensitive and selective tin-detector. Evidence exists that members of the same homologous series are related by environmental degradation pathways. Chemical treatment prior to analysis, or high temperatures associated with gas chromatography separation, may alter the relative amounts of organotins in samples and blur the true environment picture. To avoid species redistribution that may occur during derivatization or gas speciation analysis, methods based on liquid chromatography and supercritical fluid chromatography have been investigated. This review documents analytical methods for determination of tin and speciation of organotin compounds, in the hope that it will be of value to those interested in initiating a programme for assessing the impact of such species on the environment.     

Combination of three analytical techniques for speciation of Al in environmental samples

An analytical scheme is proposed which combines three speciation techniques for determination of particular Al species in soil extracts and percolating waters. A cation-exchange fast protein liquid chromatography — inductively coupled plasma atomic emission spectrometry (FPLC-ICP-AES) procedure, a microcolumn chelating ion-exchange chromatography- atomic absorption spectrometry (MCC-ETAAS) technique and the 8-hydroxyquinoline spectrophotometric method (8HQ-spectrophotometry) were employed. The FPLC-ICP-AES procedure offers determination of Al³⁺ (retention time 4.5 min) and Al(OH)²⁺ species (retention time 4.0 min) which are separated from Al(OH)⁺ ₂ (retention time 1.5min). AlF²⁺ coelutes with Al(OH)²⁺ species, while Al(SO₄)⁺, AlF⁺ ₂ and negatively charged Al organic complexes coelute with Al(OH)⁺ ₂ species. The MCC-ETAAS technique enables determination of the sum of positively charged monomeric aqua- and hydroxy-Al species plus sulphate- and fluoro-Al complexes. Employing the 8HQ-spectrophotometry the sum of positively charged monomeric aqua- and hydroxy-Al species plus sulphato- and most of the labile organic Al species are determined. The sensitivities of these selected techniques were adequate for speciation of Al in the samples analyzed. On the basis of the specific selectivity of a particular technique various groups of Al species may be determined. Thus, the comparison of analytical data from complementary procedures provides more comprehensive information on Al species present in soil extracts and percolating waters.     

Improvement of quality control of speciation analysis using hyphenated techniques A decade of progress within the European Community

The awareness of a need for an improved control of environmental contamination levels has led to the development of new hyphenated techniques for the determination of a wide variety of chemical species (e.g., organotins, methyl-mercury, alkyl-lead compounds etc.). These techniques generally involve many analytical steps such as extraction, derivatisation, separation and detection which have to be carried out in such a way that the speciation is not changed during the abalytical process. The need for evaluating the method's performance has led the BCR programme of the European Commission (now Standards, Measurements and Testing programme) to conduct series of interlaboratory studies during the last decade. These projects followed a step-by-step approach for the evaluation of different steps of the analytical methods used, e.g., simple solutions to test the detection, cleaned extract to evaluate the separation, spiked samples to test the extraction and natural samples to evaluate the whole analytical procedures. These collaborative projects allowed most of the sources of errors related to either a technique or a laboratory to be detected and removed. This paper gives an account of discussions of possible errors occurring in speciation analysis and presents examples of technical scrutiny of hyphenated techniques using chromatography as applied to the determination of tributyltin, methyl-mercury and trimethyllead.     

Determination of butyl- and phenyltin compounds in biological material by gas chromatography-flame photometric detection after ethylation with sodium tetraethylborate

A reliable and rapid speciation method for the simultaneous determination of butyl- and phenyltin species in biological samples has been developed. Three extraction procedures are compared: enzymatic hydrolysis and solubilization by ethanoic and hydrochloric acids. Derivatization is performed by the one-step ethylation/extraction procedure using the sodium tetraethylborate reagent directly in the aqueous phase in the presence of an isooctane layer. Analysis is performed using capillary gas chromatography coupled to flame photometric detection. The detection limits are in the range of a few ng(Sn)/g. Analysis of the environmental samples and the certified reference material demonstrates the accuracy of the analytical method.     

Antimony in the environment as a global pollutant: a review on analytical methodologies for its determination in atmospheric aerosols

This review summarizes and discusses the research carried out on the determination of antimony and its predominant chemical species in atmospheric aerosols. Environmental matrices such as airborne particulate matter, fly ash and volcanic ash present a number of complex analytical challenges as very sensitive analytical techniques and highly selective separation methodologies for speciation studies. Given the diversity of instrumental approaches and methodologies employed for the determination of antimony and its species in environmental matrices, the objective of this review is to briefly discuss the most relevant findings reported in the last years for this remarkable element and to identify the future needs and trends. The survey includes 92 references and covers principally the literature published over the last decade.     

Sampling, sample treatment and quality assurance issues for the determination of phosphorus species in natural waters and soils

Phosphorus is an important macronutrient and the accurate determination of phosphorus species in environmental matrices such as natural waters and soils is essential for understanding the biogeochemical cycling of the element, studying its role in ecosystem health and monitoring compliance with legislation. This paper provides a critical review of sample collection, storage and treatment procedures for the determination of phosphorus species in environmental matrices. Issues such as phosphorus speciation, the molybdenum blue method, digestion procedures for organic phosphorus species, choice of model compounds for analytical studies, quality assurance and the availability of environmental CRMs for phosphate are also discussed in detail.     

Distribution and speciation of platinum group elements in environmental matrices

The use of platinum group elements (PGEs) as components of autocatalytic converters attached to motor vehicles has resulted in serious contamination of the environment by Pt, Rh and Pd in nanocrystalline forms. Trace concentrations of PGEs, particularly the major component Pt, in environmental samples have been measured by sensitive instrumental procedures. These data have raised further questions about the nature of Pt species in contaminated soils and in plants grown in them. The focus of attention is changing from accumulations of data expressing total concentrations to investigations of speciation. Application of analytical procedures for research on speciation has provided information concerning transformations of Pt compounds in contaminated soils, the uptake of Pt by plants and the nature of Pt compounds in vegetation. Determination of background levels of precious metals in clinical and environmental matrices has required the development of analytical methods which combine uses of minimal quantities of reagents, and as small a number of chemical operations as possible to yield very low procedural blanks. Sensitive instrumental methods based upon high resolution inductively coupled plasma mass spectrometry and adsorptive stripping voltammetry have proven to be valuable for this work.     

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。     

Methods for the determination of platinum group elements originating from the abrasion of automotive catalytic converters

Anthropogenic emission of platinum group elements (PGEs) from the abrasion of automotive catalytic converters into the environment has significantly increased. However, the concentration level of these PGEs (i.e. Pd, Pt, Rh) is still very low in the nature. Accordingly, their determination and speciation in various environmental compartments appears to be a challenging task for analytical chemists. The present review gives an overview of the analytical procedures documented in this particular field of analytical chemistry with a distinctive emphasis on spectrochemical methodology, it being the most sensitive and robust for accomplishing the above analytical task.     

Speciation analysis of heavy metals in natural waters: a review.

Metal speciation in natural waters is of increasing interest and importance because toxicity, bioavailability, environmental mobility, biogeochemical behavior, and potential risk in general are strongly dependent on the chemical species of metals. This paper provides an overview of the need for speciation of heavy metals in natural waters, the chemical and toxicological aspects of speciation, and the analytical procedures for separation and the different techniques for final determination that are used today. The trends and developments of speciation are also discussed. Finally, the case of chromium (Cr) was selected for a detailed presentation because the speciation of this metal has attracted a great deal of interest in view of the toxic properties of Cr(VI).     

Kinetic study of uranium speciation in model solutions and in natural waters using Competitive Ligand Exchange Method

Kinetic speciation of uranium in model solutions containing uranium and humic acid (HA) and in natural waters has been investigated by Competitive Ligand Exchange Method (CLEM). In alkaline freshwaters, most of uranium species were uranium-carbonate species, which were labile in the CLEM experiment. The uranium speciation of every sample was characterized either as “labile” or “non-labile” uranium complexes depending on the dissociation rate coefficients of the complexes. The results showed that as the U(VI)/HA ratio was decreased, the dissociation rate coefficients decreased and the labile fraction decreased as well. When the U(VI)/HA ratio was 0.1, the labile fraction of the U(VI)-HA increased with increasing pH; however, there was no pH effect on the dissociation of U(VI)-HA complexes at lower U(VI)/HA ratios. Chelex-100 had some limitations in its use for the study of dissociation of U(VI)-HA complex at very low U(VI)/HA ratios. By developing an analytical method and procedure for quantitative determination of kinetic parameters for the dissociation of uranium-HA complexes in model solutions and natural waters, this work has made a substantial contribution to analytical chemistry.     

Non-chromatographic hydride generation atomic spectrometric techniques for the speciation analysis of arsenic,antimony, selenium,and tellurium in water samples—a review

Hydride generation (HG) coupled with AAS, ICP–AES, and AFS techniques for the speciation analysis of As, Sb, Se, and Te in environmental water samples is reviewed. Careful control of experimental conditions, offline/online sample pretreatment methods employing batch, continuous and flow-injection techniques, and cryogenic trapping of hydrides enable the determination of various species of hydride-forming elements without the use of chromatographic separation. Other non-chromatographic approaches include solvent extraction, ion exchange, and selective retention by microorganisms. Sample pretreatment, pH dependency of HG, and control of NaBH₄/HCl concentration facilitate the determination of As(III), As(V), monomethylarsonate (MMA), and dimethylarsinate (DMA) species. Inorganic species of arsenic are dominant in terrestrial waters, whereas inorganic and methylated species are reported in seawater. Selenium and tellurium speciation analysis is based on the hydrides generation only from the tetravalent state. Se(IV) and Se(VI) are the inorganic selenium species mostly reported in environmental samples, whereas speciation of tellurium is rarely reported. Antimony speciation analysis is based on the slow kinetics of hydride formation from the pentavalent state and is mainly reported in seawater samples.