Analytical methods for inorganic arsenic in water: a review

Inorganic arsenic, a term which encompasses both As (III) and As (V) species, constitutes the highest toxicological risk associated with arsenic in water in contrast to the organic arsenic species. Different determination methods of inorganic arsenic have been developed over 40 years providing timely and efficient risk assessments of inorganic arsenic contamination world wide. The current report gives an overview of more than 100 papers, regarding existing methods for analysis of As (III) and As (V) in water, including various spectroscopic, ICP and electrochemical techniques. Recent field portable analytical applications are also reviewed.     

Analytical methods for antimony speciation in waters at trace and ultratrace levels. A review

This review summarizes and discusses the analytical methods and techniques most frequently described in the literature for the determination of antimony species in waters (and possibly in other matrices) at ultratrace levels. The analytical methods for the separation and/or selective determination of Sb species fall into four main categories: 1. Chemical methods, which include such extraction techniques as: liquid-liquid and liquid-solid extraction, selective hydride generation and coprecipitation methods. 2. Chromatographic methods, which also includes a discussion of hyphenated techniques with different detectors. 3. Electrochemical methods based on the use of electrochemical detectors. 4. Kinetic methods The state-of-the-art of the main applications in waters and environmental samples and future trends are also reviewed. Received: 13 June 1997 / Revised: 29 September 1997 / Accepted: 3 October 1997     

Analytical methods for antimony speciation in waters at trace and ultratrace levels. A review

This review summarizes and discusses the analytical methods and techniques most frequently described in the literature for the determination of antimony species in waters (and possibly in other matrices) at ultratrace levels. The analytical methods for the separation and/or selective determination of Sb species fall into four main categories: 1. Chemical methods, which include such extraction techniques as: liquid-liquid and liquid-solid extraction, selective hydride generation and coprecipitation methods. 2. Chromatographic methods, which also includes a discussion of hyphenated techniques with different detectors. 3. Electrochemical methods based on the use of electrochemical detectors. 4. Kinetic methods The state-of-the-art of the main applications in waters and environmental samples and future trends are also reviewed.     

Analytical methods for the quantification of volatile aromatic compounds

The investigation of odorants is not an easy task, which needs to be undertaken in the context of fit-for-purpose quality systems. To date, great attention has been paid to determination of the volatile fractions of odorants, since they are responsible for the attributes of global flavor [i.e. a combination of olfactory (aroma) and gustatory (taste) sensations produced by chemicals]. This kind of determination can be carried out by analytical techniques [e.g., gas chromatography (GC) combined with mass spectrometry and/or olfactometric GC]. Methods complementary to GC analysis are available, allowing assessment of the olfactory impact by an electronic nose (e-nose) or a panel of selected individuals. Also, we consider some innovative analytical techniques to study the effects of odorants in food during consumption.     

Novel approaches for selenium speciation in foodstuffs and biological specimens: A review

Selenium is an essential element for human health. It has been recognized as an antioxidant and chemopreventive agent in cancer. Selenium is known to develop its biological activity via selenocysteine residue in the catalytically active centre of selenoproteins. The main source of selenium in human beings is the diet. However, in several regions of the world the content of selenium in diet has been estimated insufficient for a correct expression of the proteins. The beneficial effects of selenium on human health are strongly dependent on its chemical form and concentration. This review critically evaluated the state-of-the art of selenium speciation in biological matrices mainly focused in nutritional and food products. Besides the number of publications related to selenium speciation, isolation and accurate characterization and quantification of selenium species is still a challenge. Hyphenated techniques based on coupling chromatography separation with inductively coupled plasma spectrometry (ICP-MS) and its combination with molecular mass spectrometry (ESI-MS, ESI-MS-MS and MALDI-TOF) and isotopic dilution allow identification, quantification and structural characterization of selenium species. Particular attention is paid in the development of Se-enriched food and nutritional products and how the application of the techniques mentioned above is mandatory to get reliable results on selenium metabolisms in these particular matrices.     

Analytical methods for the determination of halogens in bioanalytical sciences: a review

Fluorine, chlorine, bromine, and iodine have been studied in biological samples and other related matrices owing to the need to understand the biochemical effects in living organisms. In this review, the works published in last 20 years are covered, and the main topics related to sample preparation methods and analytical techniques commonly used for fluorine, chlorine, bromine, and iodine determination in biological samples, food, drugs, and plants used as food or with medical applications are discussed. The commonest sample preparation methods, as extraction and decomposition using combustion and pyrohydrolysis, are reviewed, as well as spectrometric and electroanalytical techniques, spectrophotometry, total reflection X-ray fluorescence, neutron activation analysis, and separation systems using chromatography and electrophoresis. On this aspect, the main analytical challenges and drawbacks are highlighted. A discussion related to the availability of certified reference materials for evaluation of accuracy is also included, as well as a discussion of the official methods used as references for the determination of halogens in the samples covered in this review.

Development of new analytical methods for selenium speciation in selenium-enriched yeast material

A sequential extraction allowing the discrimination of water-soluble and non-soluble selenium fractions has been developed to evaluate the availability of selenium (Se) in an Se-enriched yeast candidate reference material. The fractionation of selenium-containing compounds in the extracts was achieved on preparative grade 200 Superdex 75 and columns. It showed that water-soluble selenium is present in several fractions with a large mass distribution. Low-molecular- (< or = 10,000) and high-molecular-mass selenocompounds (range 10,000-100,000) were considered separately for further experiments. The analytical approach for low-molecular-mass selenocompounds was based onanion-exchange HPLC with on-line inductively coupled plasma (ICP) MS for quantitative analysis. Selenocystine, selenomethionine, selenite and selenate were quantified in the fractions isolated in preparative chromatography. The study revealed the existence of various unidentified Se species in yeast material. The Se-containing proteins in the yeast material have been further separated and selenium quantified by the combination of gel electrophoresis and electrothermal vaporization-ICP-MS. This new approach allows the separation of the proteins with high resolution by sodium dodecylsulfate-polyacrylamide gel electrophoresis and the sensitive determination of selenium in the protein bands.     

石油饱和烃分子组成分析方法综述

高效利用石油资源和生产高质量石油产品要求从分子水平认识石油化学组成,而饱和烃作为石油中最主要的一类组分,其分子组成分析是石油化学研究的重要课题.总结了石油饱和烃的分子组成分析方法并简要介绍其应用,主要包括基于气相色谱技术的单体烃分析方法和基于质谱技术的分子/族组成分析方法.针对石油饱和烃的质谱电离技术,总结了各方法的技...     

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.     

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.     

Non-chromatographic atomic spectrometric methods in speciation analysis: A review

In recent years, knowledge of the different chemical forms of the elements has gained increasing importance. There has been significant progress in methods that hyphenate chromatographic separations with atomic spectrometry. These hyphenated methods can provide the most complete information on the species distribution and even structure. However, they can be lengthy, relatively costly and difficult to bring to the routine. On the other hand, it is important to remember that chromatographic techniques represent only a minor part of the separation procedures available and, in certain cases, the application of basic chemistry to sample treatments can give quantitative information about specific chemical forms. In this sense, non-chromatographic procedures can provide methods that offer sufficient information on the elemental speciation for a series of situations. Moreover, these non-chromatographic strategies can be less time consuming, more cost effective and available, and present competitive limits of detection. Thus, non-chromatographic speciation analysis continues to be a promising research area and has been applied to the development of several methodologies that facilitate this type of analytical approach. In view of their importance, the present work overviews and discusses different non-chromatographic methods as alternatives for the speciation analysis of clinical, environmental and food samples using atomic spectrometry for detection.     

Preconcentration of selenium compounds on a porous graphitic carbon column in view of HPLC-ICP-AES speciation analysis

The retention of organic selenium compounds on a porous graphitic carbon stationary phase was investigated. Different acids were studied as mobile phases to elute selenocystamine, selenoethionine, selenomethionine and selenocystine. Detection was achieved using inductively coupled plasma-atomic emission spectrometry to provide selenium-specific and sensitive detection. The separation of the four species was carried out using methanoic acid. An important on-column preconcentration was obtained when solutes were injected in nitric acid or trifluoroacetic acid (TFA) media. The large injection volume employed (2,500 µL) allowed us to reach low relative detection limits (2–6 µg/L). The method, employing TFA as injection solvent and methanoic acid as the eluent was found to be robust with respect to different matrices spiked with selenocompounds.     

Development of extraction methods for speciation analysis of selenium in aqueous extracts of medicinal plants

Advanced extraction methods have been developed for direct speciation of dissolved inorganic and organic selenium (Se) species in aqueous extracts of medicinal plants (MPs). The inorganic species of Se (SeIV and SeVI) were separated from organic forms by adsorbing inorganic Se on alumina, while the organic Se was not retained. The retained inorganic Se species was eluted with 10 mL 0.2 M HCl. The total inorganic Se species was determined after prereduction of SeVI into SeIV with concentrated HCl. The SeIV in the eluent and total inorganic Se species were then complexed with diethyldithiocarbamate. The resultant complexes were entrapped in the nonionic surfactant Triton X-114. The total Se, organic Se, total inorganic Se, and SeIV species were determined by electrothermal atomic absorption spectrometry with a modifier. The SeVI concentration was obtained by subtracting SeIV from total inorganic Se contents. The main factors affecting the methodologies were investigated in detail. Under the optimized experimental conditions, the LOD for SeIV was 50 microg/L. Among dissolved inorganic and organic Se species in aqueous extracts of MPs, organic Se species were present in the range of 74-84%, SeIV 3.62-7.47%, and SeVI 12.4-18.57% of total Se contents.     

Occurrence and chemical speciation analysis of organotin compounds in the environment: A review

Environmental concerns regarding organotin compounds have increased remarkably in the past 20 years, due in large part to the use of these compounds as active components in antifouling paints [mainly tributyltin (TBT)] and pesticide formulations [mainly triphenyltin (TPhT)]. Their direct introduction into the environment, their bio-accumulation and the high toxicity of these compounds towards “non-target” organisms (for example: oysters and mussels) causes environmental and economic damage around the world. As a consequence, the presence and absence of organotin compounds is currently monitored in a range of environmental matrices (e.g., water, sediment and shellfish) to examine the utility of controls meant to regulate the level of contamination as required in some EC Directives and the Water Framework Directive 2000/60/EC. To evaluate the environmental distribution and fate of these compounds and to determine the effectives of legal provisions adopted by a number of countries, a variety of analytical methods have been developed for organotin determination in the environment. Most of these methods include different steps such as extraction, derivatisation and clean up. The aim of the present review is to evaluate the environmental distribution, fate and chemical speciation of organotin compounds in the environment.     

Review on metal speciation analysis in cerebrospinal fluid-current methods and results: a review

The large number of patients suffering from neurodegenerative diseases like Alzheimer's disease and Parkinson's disease motivates many research groups worldwide to investigate pathogenic factors and molecular mechanisms of these diseases. Recent studies and reviews indicate that metals are involved in these neurodegenerative processes in case their homeostasis in the brain is disturbed. Important is that the focus of these recent studies is on essential metals like Fe, Cu, Zn and Mn, but not on the well-known neurotoxic metals like Hg and Pb. Key issues for understanding metal induced neurotoxic effects are the transport processes across the neural barriers, the metal binding forms (species) and their interactions with neuronal structures. Total metal concentrations in cerebrospinal fluid were published in several studies for controls and patients, but the amount of reliable data sets is not yet sufficient for clear definition of normal and elevated levels. The need for more detailed information on metal species in CSF is highlighted in this review. However, studies on element speciation analysis, that means identification and quantification of the various binding forms of metals in cerebrospinal fluid, are rare. The major reasons therefore are difficulties in accessing cerebrospinal fluid samples, the non-covalent nature of many metal species of interest and their rather low concentrations. In spite of this, several applications demonstrate the potential of hyphenated techniques as additional diagnostic tools for cerebrospinal fluid analysis. This review shows the importance of trace element analysis and more specifically of element speciation in cerebrospinal fluid for an improved understanding of pathologic mechanisms promoting neuro-degeneration. Respective analytical techniques are also highlighted. Additionally, biochemical assays for selected high molecular mass metal species are summarized and critically discussed. Moreover additional potential techniques like direct non-invasive methods as well as mathematical modelling approaches are considered. Data on total concentrations of numerous elements in CSF as well as speciation information of elements such as Al, As, Ca, Cd, Cu, Fe, Mg, Mn, Hg, Pb, Se and Zn in CSF are summarized.     

Analytical methodologies for chromium speciation in solid matrices: a survey of literature

The analytical literature about chromium speciation in solid samples has been surveyed. From 451 articles published on the speciation of chromium from 1983 to 1997, the methodologies to do speciation in solids after sample pretreatment are discussed, through consideration of the types of samples and their dissolution, the analytical techniques employed for chromium measurement, and the figures of merit of the 86 papers reported in the Analytical Abstracts data base.     

Analytical methodologies for chromium speciation in solid matrices: a survey of literature

The analytical literature about chromium speciation in solid samples has been surveyed. From 451 articles published on the speciation of chromium from 1983 to 1997, the methodologies to do speciation in solids after sample pretreatment are discussed, through consideration of the types of samples and their dissolution, the analytical techniques employed for chromium measurement, and the figures of merit of the 86 papers reported in the Analytical Abstracts data base. Received: 6 February 1998 / Revised: 6 March 1998 / Accepted: 7 March 1998     

Analytical strategies for the detection of sulfide: a review

The detection of sulfide, particularly hydrogen sulfide, has long held the attention of the analytical community and, as such, a large number of protocols have arisen. Built around a core of reactions, some of which are highly specific to sulfide, there is considerable scope for exploitation across a number of instrumental platforms. Such flexibility may provide options for alleviating potentially intractable matrix effects through switching to an alternative detection methodology. This review details the need for sulfide measurements and describes the basis of many of the current approaches to sulfide detection. The collation of information from a broad range of sources, covering the major approaches, has been achieved and the salient points of each technique presented and critically appraised. The various peculiarities of the systems are compared and contrasted and a summary of the analytical characteristics (matrix, methodology and detection range) from each has been constructed.