Multielemental trace analysis of biological materials using double focusing inductively coupled plasma mass spectrometry detection

The analytical potential of double focusing-inductively coupled plasma-mass spectrometry (DF-ICP-MS) for total elemental analysis in clinical samples (serum, blood, urine and other biological fluids), tissues and food products is illustrated by reviewing typical applications recently published. Also, the use of DF-ICP-MS as specific detector for trace element speciation in biological samples is discussed. After adequate separation of interferences in the chromatographic column, low resolution measurements (R = 300) can be used to provide enhanced sensitivities of more than 100 times compared with quadrupole-inductively coupled plasma-mass spectrometry (Q-ICP-MS). This capability is extremely valuable in speciation studies. Also, the use of DF-ICP-MS at low resolution could provide very precise isotope ratio measurements for isotope dilution analysis due to the ‘flat topped’ peaks obtained at this resolution. Unfortunately, the literature on these last two issues is rather scarce so far, in spite of their extremely high analytical possibilities for biological research. Moreover, the bright future of DF-ICP-MS as a most powerful multielemental detector for trace element applications in biological systems will be highlighted. Apart from applications detailed above other important application fields can be envisaged. In particular, we will speculate on its possible use to confirm/establish ‘reference values’ of trace element content in ‘normal’ populations and so to help to diagnose health and disease status, related with trace element total content or their speciation in clinical specimens.     

Surveying selenium speciation from soil to cell—forms and transformations

The aim of this review is to present and evaluate the present knowledge of which selenium species are available to the general population in the form of food and common supplements and how these species are metabolized in mammals. The overview of the selenium sources takes a horizontal approach, which encompasses identification of new metabolites in yeast and food of plant and animal origin, whereas the survey of the mammalian metabolism takes a horizontal as well as a vertical approach. The vertical approach encompasses studies on dynamic conversions of selenium compounds within cells, tissues or whole organisms. New and improved sample preparation, separation and detection methods are evaluated from an analytical chemical perspective to cover the progress in horizontal speciation, whereas the analytical methods for the vertical speciation and the interpretations of the results are evaluated from a biological angle as well.     

Distribution and speciation of selenium in Lecythis ollaria plant

Selenium has been determined in different parts of the Lecythis ollaria (LO) plant (Venezuela) and the determination of its speciation has been achieved in fruit seeds. The study has been performed using different analytical techniques including inductively coupled plasma atomic emission spectrometry (ICP-AES), differential pulse cathodic stripping voltammetry (DPCSV), instrumental neutron activation analysis (INAA), high performance liquid chromatography (HPLC) and mass spectrometry (MS). Different parts of the plant (leaves, bark, capsules and seeds) were examined as well as the soil where LO was growing. Among different considered parts, seeds show the highest content in selenium (5 g kg⁻¹) which is dependent on the maturation extent of the fruit. In seeds, about half of the total selenium content is soluble in water while the remaining is involved in protein structure. In the aqueous fraction, the prevailing form of selenium appears to be seleno-cystathionine with much lower amounts of Se(VI) and Se(IV).     

Introduction to the EU-network on trace element speciation: preparing for the 21st century

The main objective of the EU-network is to bring together scientists with a background in analytical chemistry interested in speciation method development with potential users from industry and representatives from legislative bodies. The network started on 1/10/1997 for a duration of 2 years. A series of meetings are being organised to debate all the important questions for collecting information on environmental, food and occupational health aspects of speciation and to define possible future projects. The findings and conclusions will be summarised as a series of general papers that will be published in the open literature, recapitulating the essential information gathered to date, outlining the state of the art for each topic and recommending legislative actions. A first meeting was held in Überlingen, Germany on 5–6 December 1997. The representatives from industry explained their interest in the network and the participants from the academic and national institutes gave a state-of-the-art presentation of their research. Out of this, a program was compiled for the following meeting in Segovia from 16 to 20 March 1998. The topics dealt with were: organotin compounds in the environmental session; the speciation and bioavailability of trace element species (Cr, Fe, Se), the quality of the data and new legislation in the food session; and identification of inhaled particles and the search for bioindicators for exposure to Ni and Pt in the occupational health/hygiene session. In each session about half of the participants came from industry. The delegates agreed on a list of priorities in speciation analysis. A www-page has been created: hhtp://www. speciation 21.plymouth.ac.uk. Everybody interested in adding information to the page is requested to mail this to lpitts@plymouth.ac.uk     

Liquid chromatography-electrospray ionization tandem mass spectrometry for on-line characterization, monitoring and isotopic profiling of the main selenium-metabolite in human urine after consumption of Se-rich and Se-enriched food

The metabolism of selenium (Se) in the human body has yet not completely been unravelled and hence, an efficient method for characterization and on-line monitoring of the main Se-compound in human urine after consumption of Se-rich food was developed. Total Se-concentration in human urine after consumption of several Se-rich products was measured with inductively coupled plasma mass spectrometry (ICP-MS). The highest Se concentration in urine was observed after 4-10 h. The urine samples were brought onto a reversed phase column and the Se was detected by ICP-MS. Parameters for liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS-MS) measurements were optimized by using commercially available sugars, because it is known that some of the urinary metabolites contain a sugar moiety. In order to characterize the predominant Se-metabolite, it was necessary to extensively clean-up the sample and preconcentrate the species. The main metabolite was measured on its precursor ion on three different m/z according to three isotopes of Se. Relative peak surfaces matched the relative abundances of the isotopes. The product ions could be measured in a human urine sample in accordance to the product ions of the commercially available sugars. Moreover, the evidence of a selenosugar was demonstrated by the use of the Se-isotopes when measuring the product ions. LC-ESI-MS-MS was proven to be very efficient for the characterization of the main urinary Se-metabolite and can be used for on-line monitoring of the compound in urine samples. The method can be extended for clinical screening after consumption of Se-(en)rich(ed) food by use of the Se-isotopic profile and/or of the typical product ions of (methyl)-N-acetyl-hexosamines.     

Current trends in isolation, separation, determination and identification of isoflavones: a review

Isoflavones are natural substances which elicit a number of physiological effects in living organisms. The substances are synthesized in plant tissues as protective agents against biotic stress (i. e. bacterial infection). Isoflavones are also an important dietary constituent in human nutrition. Modern trends in studies of isoflavones in plant materials and foodstuffs and procedures for chemical analyses of isoflavones in human body fluids and plant tissues are discussed in this review. Highly effective extraction and purification techniques, i. e. solid-phase extraction, accelerated-solvent extraction, and Soxhlet extraction, are presented. Latest procedures in chromatographic separation of isoflavones that apply different types of sorbents are described. Immunochemical analysis, electrochemical sensing of isoflavones, and spectrometric and other analytical techniques and their applications are also mentioned. Special attention is paid to the highly selective and sensitive technique of mass spectrometry and its application for identification of isoflavones and their glucosides in plants. Studies of interactions of isoflavones with cell receptors and a number of biologically active substances such as DNA and proteins are described. The review does not intend to give a complete overview of the topics considered but rather to present modern and most recent methods used in studies of isoflavones.     

An Overview of the Analytical Methods for the Determination of Organic Ultraviolet Filters in Cosmetic Products and Human Samples

UV filters are a group of compounds commonly used in different cosmetic products to absorb UV radiation. They are classified into a variety of chemical groups, such as benzophenones, salicylates, benzotriazoles, cinnamates, p-aminobenzoates, triazines, camphor derivatives, etc. Different tests have shown that some of these chemicals are absorbed through the skin and metabolised or bioaccumulated. These processes can cause negative health effects, including mutagenic and cancerogenic ones. Due to the absence of official monitoring protocols, there is an increased number of analytical methods that enable the determination of those compounds in cosmetic samples to ensure user safety, as well as in biological fluids and tissues samples, to obtain more information regarding their behaviour in the human body. This review aimed to show and discuss the published studies concerning analytical methods for the determination of organic UV filters in cosmetic and biological samples. It focused on sample preparation, analytical techniques, and analytical performance (limit of detection, accuracy, and repeatability).     

Perspectives on analyses of nucleic acid constituents: the basis of genomics

The recent mapping of the human genome was a tremendous achievement made possible to a large degree by the development of analytical methods for sequencing purine and pyrimidine bases in nucleic acids. In the last 3 decades, the number of analyses of nucleic acids and their constituents by HPLC and capillary electrophoresis (CE) has exploded. These techniques have been used not only for genomics, but also for the determination of free nucleotides, nucleosides and their bases in body fluids and tissues. Although a large number of HPLC and CE papers have been published on nucleic acid constituent applications, relatively little has been written on the mechanisms of the separations. However, to optimize analytical conditions knowledgeably and rapidly, it is important to know why and how these separations occur and the factors that affect them. The HPLC methods for the analysis of nucleic acid constituents and the information available on some of the mechanisms of separation of nucleotides, nucleosides and their bases, as well as the analysis of these compounds by CE and the factors that affect these separations are discussed.     

Electrothermal atomic absorption spectrometry in the study of metal ion speciation

The literature on the use of electrothermal atomic absorption spectrometry (ETAAS) in the determination of metals in speciation studies of different samples is comprehensively reviewed. The methods of extraction, preconcentration, etc. in connection with speciation studies have been highlighted. The ETAAS programmes and other details of the developed methodologies are discussed. On critical examination it becomes obvious that chromium is the metal which has been analysed by most workers. Study of other metals falls in the following order: Pb, Sn, Cu, As, Al, Cd, Zn, Fe, Ni and Se. It is clearly evident that the major work on metal ion speciation has been carried out in natural water, followed by biological materials. There are also many reports on the speciation analysis of soil and sediment. Only a few papers have been published on metal speciation in airborne particulates. The analytical details of the developed methodologies have been examined in terms of limit of detection, precision and accuracy. Received: 27 December 1995 / Revised: 20 May 1996 / Accepted: 26 May 1996     

Current mass spectrometry strategies for selenium speciation in dietary sources of high-selenium

This document reviews the most relevant mass spectrometry approaches to selenium (Se) speciation in high-Se food supplements in terms of qualitative and quantitative Se speciation and Se-containing species identification, with special reference to high-Se yeast, garlic, onions and Brazil nuts. Important topics such as complexity of Se speciation in these materials and the importance of combining Se-specific detection and molecule-specific determination of the particular species of this element in parallel with chromatography, to understand their nutritional role and cancer preventive properties are critically discussed throughout. The versatility and potential of mass spectrometric detection in this field are clearly demonstrated. Although great advances have been achieved, further developments are required, especially if speciatedcertified reference materials (CRMs) are to be produced for validation of measurements of target Se-containing species in Se-food supplements.     

Electrothermal atomic absorption spectrometry in the study of metal ion speciation

The literature on the use of electrothermal atomic absorption spectrometry (ETAAS) in the determination of metals in speciation studies of different samples is comprehensively reviewed. The methods of extraction, preconcentration, etc. in connection with speciation studies have been highlighted. The ETAAS programmes and other details of the developed methodologies are discussed. On critical examination it becomes obvious that chromium is the metal which has been analysed by most workers. Study of other metals falls in the following order: Pb, Sn, Cu, As, Al, Cd, Zn, Fe, Ni and Se. It is clearly evident that the major work on metal ion speciation has been carried out in natural water, followed by biological materials. There are also many reports on the speciation analysis of soil and sediment. Only a few papers have been published on metal speciation in airborne particulates. The analytical details of the developed methodologies have been examined in terms of limit of detection, precision and accuracy. Received: 27 December 1995 / Revised: 20 May 1996 / Accepted: 26 May 1996     

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.     

Analytical techniques for determining biotin

Biotin is a vitamin of the B-complex, which plays an important biochemical role in every living cell. In the recent years, the interest in this vitamin has been rekindled, mainly due to its association with serious human disorders, such as the inherited syndrome multiple carboxylase deficiency, which can be successfully treated with biotin administration. Diagnosis of biotin deficiency as well as monitoring of biotin levels in biological fluids of patients receiving biotin treatment is crucial. Equally important is the determination of biotin levels in pharmaceutical preparations as well as in food and food supplement products, which constitute the main source of biotin in humans. Several analytical methods for measuring biotin in various samples, e.g. human fluids, pharmaceutical formulations, food material etc., have been reported in the literature. In this review, the most representative of these methods are presented, and their characteristics are evaluated.     

Recent applications of liquid chromatography–mass spectrometry to residue analysis of antimicrobials in food of animal origin

Residual antimicrobials in food constitute a risk to human health. Although epidemiological data on the real magnitude of their adverse effects are very scarce, they indicate that food could be an important vehicle for evolution and dissemination of antimicrobial-resistant bacteria. Public health agencies in many countries rely on detection by mass spectrometry (MS) for unambiguous identification of residues of antimicrobial agents in animal food products for human consumption. The introduction of relatively inexpensive and robust liquid chromatography (LC)–MS systems has given a strong impulse to the development of confirmatory methods for the above medicines in foodstuffs. The initial part of this review, after a brief introduction into the field of antimicrobials, is dedicated to the most important EU regulations and directives for control of residues of these substances in animal products. The main attention in this review is on the sample-treatment and MS detection systems in use today for analysing the most important classes of antimicrobials in various biological matrices (milk, animal tissues, eggs, and honey). As evidenced by this review, reversed-phase LC combined with tandem MS, usually triple-quadrupole MS (QqQMS), is currently the preferred technique in most residue analysis of a single-class of antimicrobials. A recently emerging analytical strategy is that of developing methods for detecting a large variety of veterinary drugs belonging to different classes, including pesticides (multi-class residue analysis). To do this, simple and generic extraction and separation techniques applicable to a broad range of compounds differing in physical and chemical properties have been adopted. Such methods are still based mainly on LC–QqQMS. Emerging alternative MS detection systems are time-of-flight MS, which provides accurate mass of the analyte(s), or Q–linear ion trap (IT) MS that eliminates some limitations of ITMS ⁿ .     

Recent advances in bioelectrochemical detection of E. coli bacteria in saline buffers and spiked real samples using traditional and nanostructured active substrates

A rapid and cost-effective method to specifically identify and quantify pathogenic Escherichia coli (E. coli) bacteria in aqueous samples and food products is highly recommended to avoid the degradation of human health that can unfortunately lead to fatal cases. To overcome these borderline situations, portable and easy-to-use screening devices are needed for the non-expert public and confirmed by medical personnel/physicians who can quickly guide/prescribe antibiotic treatments. In such a context, nanotechnologies are very promising and useful tools due to the remarkable optical, chemical and physical properties of biocompatible nanomaterials deposited or synthesized on traditional solid electrodes that greatly improve the detection limit and the selectivity of nanostructured-based biosensors. With this in mind, this review summarizes the latest advances in the bioelectrochemical detection of E. coli and its related products using different biosensor configurations in saline buffers and spiked real samples, namely food products (milk, fruits, vegetables), body fluids (blood, urine, swine feces) and river water.     

人体微量元素硒营养

硒是人体必需的微量元素。环境系统中的硒含量差异较大，缺硒现象普遍。利用天然食品摄取硒营养是安全，有效，可行的途径。     

Fast determination of the functional peptide soymetide in different soybean derived foods by capillary-high performance liquid chromatography

The determination of bioactive peptides derived from food sources is gaining special attention in last years, due to their ability to promote health and their potential to reduce the risk of chronic diseases. In this work, a new analytical methodology has been developed enabling for the first time the determination of soymetide, a new immunostimulating peptide derived from soybean, in different soybean derived foodstuffs. Capillary-HPLC was employed for peptide separation after accelerated tryptic digestion of soybean proteins. Two different capillary-HPLC columns were tested and chromatographic separation was optimized in each case. The use of a 300 μm fused-core technology C18 column enabled a suitable separation of soymetide from the other peptides in less than 18 min. Different analytical characteristics of the method were evaluated: selectivity, linearity, accuracy, precision, limit of detection and quantitation, and stability. The developed method was applied to the determination of soymetide content in different soybean dairy-like products for human consumption (powdered milks and infant formulas).     

Advantages of hydride generation interface for selenium speciation in waters by high performance liquid chromatography-inductively coupled plasma mass spectrometry coupling

This paper focuses on the analytical performance improvement of the coupled technique HPLC-ICPMS using on-line collision/reaction cell technology for selenium elemental and speciation analyses at the ng (Se) l(-1) level in aquatic environment. Collision/reaction cell operating parameters were optimised, resulting in selected conditions of 5.5 ml min(-1) H(2) and 0.5 ml min(-1) He mixture. The detection limits obtained were around 5 ng (Se) l(-1) for total analysis, and between 7 and 15 ng (Se) l(-1) depending on the species for speciation analysis. The capability of UV irradiation-hydride generation interfacing to increase detector sensitivity was also evaluated for speciation analysis. The detection limits obtained were in the range 2-8 ng (Se) l(-1) depending on the species. Moreover, such interface allowed to prevent bromine introduction to the ICPMS which is particularly convenient for selenium trace analysis in natural waters as (80)Se is preserved free from BrH interferences. The developed method was validated using certified water with low selenium content (TM Rain 95, NWRI, Canada) and applied to the analysis of different waters.     

Microextraction techniques in the analysis of food flavor compounds: A review

Food flavor compounds due to the complexity of food as a matrix, and usually their very low concentrations in a product, as well as their low odor thresholds, create a challenge in their extraction, separation and quantitation. Food flavor volatiles represent compounds of different polarity, volatility and chemical character, which determine method of extraction for their isolation from food. Microextraction techniques, mainly SPME and SBSE have been used for food flavor compounds analysis for two decades. Microextraction methods other than SPME and SBSE are seldom used despite their analytical potential. The review discusses the nature of food flavor compounds, and different approaches to food flavor analysis. It summarizes the use of microextraction methods in food flavor compounds analysis based on papers published in the last 5 years, and discusses the potential of microextraction methods in this field.     

Chemical speciation by sequential injection analysis: an overview

The simplicity of the sequential injection (SIA) manifold and its low need for maintenance makes it an ideal tool in speciation. As miniaturization and reduction of reagent consumption are also ultimate goals in chemical sensing, it is useful to review the use of combined injection and programmed flow as a central issue in designing SIA systems with chemical sensors and structurally simplified chemical analysers. This overview gives an insight into the current state, analytical scope and performance characteristics of sequential injection systems as analytical tools for speciation. The suitability of SIA for speciation analysis is illustrated by the methods used in the conduits of sequential injection systems for the chemical conversion of different chemical forms into detectable chemical species. Configurations of the basic sequential injection speciation analysis systems were designed around a multi-syringe-time-based-injection system with one detector, direct and indirect speciation of different forms using a single detector including diode array detection and direct speciation of different forms using multiple detection.

Examples showing the use of SIA for the simultaneous determination or speciation of metal ions, inorganic anions and organic compounds are given with some recent results from our research groups.