Inductively coupled plasma mass spectrometric detection for chromatography and capillary electrophoresis

Investigation of the Electrophoretic Mobility of the Actinides Th, U, Np, Pu, and Am in Different Oxidation States

The electrophoretic mobilities (μ_e) of the actinides Th and U-Am in different oxidation states (prepared in 1 M HCl and 1 M HClO₄) have been determined by capillary electrophoresis (CE)-inductively coupled plasma mass spectrometry (ICPMS) using 1 M acetic acid as the background electrolyte, which has proven to provide an excellent setup for trace analysis at environmentally relevant concentrations (1 × 10^-9 M). The values are independent of the respective acid solution. The μ_e of the Pu oxidation states +III to +VI have been measured. They agree with both the available literature data and the redox-stable analogues (Eu(III), Th(IV), Np(V), U(VI)) that have also been investigated. The trend in the μ_e for the actinides U-Pu was found to be An(III) > An(VI) > An(V) > An(IV). The μ_e values of Am(III) (μ_e(Am(III)) = 3.86 × 10^-4 cm²/(Vs)), U(IV) (μ_e(U(IV)) = 0.34 × 10^-4 cm²/(Vs)), and U(VI) (μ_e(U(VI)) = 1.51 × 10^-4 cm²/(Vs)) have been measured for the first time under these experimental conditions. Furthermore, the measured μ_e values show systematic trends that can be rationalized on the basis of the calculated species distribution of the actinides in 1 M acetic acid and the corresponding average effective charges (q_eff).

Selenium in wastewater: fast analysis method development and advanced oxidation treatment applications

Selenium, a ubiquitous non-metal in nature, is potentially toxic to natural ecosystems due to its bioaccumulation potential. Due to increased monitoring and enforcement of selenium regulations, the need to be able to measure and treat selenium efficiently has taken on an increased importance. The principal aqueous forms of inorganic selenium are selenite (Se(IV)) and selenate (Se(VI)). Selenate, due to its high mobility and lack of affinity to conventional adsorbents, is typically much more difficult to treat and remove. To address both measurement and removal, an analytical method is reported for quantification of selenium in wastewater (WW) using UV-Vis spectrophotometer followed by removal studies using advanced oxidation processes (AOPs). Malachite green and azure blue were selected for colorimetric analysis using UV-Vis. Malachite green indicator showed the best results for analysis. The reported UV-Vis method was applied to establish the effect of AOPs on selenium removal. It was noted that all of the AOP treated samples showed removal of selenium and it was established that the UV-Vis method has a lower limit of detection at 2 mg/L. Further, through this study, it was found that the chemical cavitation yield and selenium removal efficiency peaked at low frequency ultrasound of 40 kHz.

LC coupled to ESI, MALDI and ICP MS - A multiple hyphenation for metalloproteomic studies

A new multiple detection arrangement for liquid chromatography (LC) that supplements conventional electrospray ionization (ESI) mass spectrometry (MS) detection with two complementary detection techniques, matrix-assisted laser desorption/ionization (MALDI) MS and substrate-assisted laser desorption inductively coupled plasma (SALD ICP) MS has been developed. The combination of the molecular and elemental detectors in a single separation run is accomplished by utilizing a commercial MALDI target made of conductive plastic. The proposed platform provides a number of benefits in today's metalloproteomic applications, which are demonstrated by analysis of a metallothionein mixture. To maintain metallothionein complexes, separation is carried out at a neutral pH. The effluent is split; a major portion is directed to ESI MS while the remaining 1.8% fraction is deposited onto a plastic MALDI target. Dried droplets are overlaid with MALDI matrix and analysed consecutively by MALDI MS and SALD ICP MS. In the ESI MS spectra, the MT isoform complexes with metals and their stoichiometry are determined; the apoforms are revealed in the MALDI MS spectra. Quantitative determination of metallothionein isoforms is performed via determination of metals in the complexes of the individual protein isoforms using SALD ICP MS.

Capillary Electrophoresis-Inductively Coupled Plasma Mass Spectrometry

During the recent years, capillary electrophoresis (CE) has been fully established as a powerful tool in separation sciences as well as in element speciation. This road of success is based on the rapid analysis time, low sample requirements, high separation efficiency, and low operating costs of CE. Inductively coupled plasma mass spectrometry (ICP-MS) is known for superior detection and multielement capability. Consequently, the combination of both instruments is approved for analysis of complex sample types at low element concentrations which require high detection power. Also the diversity of potential applications brings CE-ICP-MS coupling into central focus of element speciation. The key to successful combination of ICP-MS as an (multi-)element selective detector for CE is the availability of a suitable and effective interface.Therefore, this chapter summarizes the most important and basic principles about coupling of capillary electrophoresis to ICP-MS. Specifically, the major requirements for interfacing are described and technical solutions are given. Such solutions include the closing of the electrical circuit from CE at the nebulization, the adoption of flow rates for efficient nebulization, the reduction of a suction flow through the capillary, caused by the nebulizer, and maintaining the high separation resolution from CE across the interface for ICP-MS detection. Additionally, detailed information is presented to determine and quantify the siphoning suction through the CE capillary by the nebulizer. Finally, two applications, namely, the manganese and selenium speciation in cerebrospinal fluid are shown as examples, providing the relevant operational parameter.

Evaluation of tetracationic salts as gas-phase ion-pairing agents for the detection of trivalent anions in positive mode electrospray ionization mass spectrometry

In previous studies, new electrospray ionization mass spectrometry (ESI-MS) approaches were developed for the highly sensitive detection of singly and doubly charged anions in positive mode ESI-MS by using specially synthesized dicationic and tricationic ion-pairing agents, respectively. By detecting the positively charged ion complex in the positive mode, limits of detection (LODs) for the anions can be lowered by several magnitudes. In this work, we used eighteen newly synthesized tetracationic ion-pairing agents, constructed with different geometries, linkages and cation moieties, for the detection of eighteen triply charged anions of different structural motifs. The LODs for these anions were from ten to several thousand times lower in the positive selective ion monitoring (SIM) mode than in the negative mode. These tetracationic agents also were shown to be useful for the detection of -1 and -2 anions. In addition, the LODs for -3 anions can be further lowered by monitoring the product fragments of the ion-pairing complexes in the single reaction monitoring (SRM) mode.

Environmental proteomics and metallomics

Monitoring environmental pollution using biomarkers requires detailed knowledge about the markers, and many only allow a partial assessment of pollution. New proteomic methods (environmental proteomics) can identify proteins that, after validation, might be useful as alternative biomarkers, although this approach also has its limitations, derived mainly from their application to non-model organisms. Initial studies using environmental proteomics were carried out in animals exposed to model pollutants, and led to the concept of protein expression signatures. Experiments have been carried out in model organisms (yeast, Arabidopsis, rat cells, or mice) exposed to model contaminants. Over the last few years, proteomics has been applied to organisms from ecosystems with different pollution levels, forming the basis of an environmental branch in proteomics. Another focus is connected with the presence of metals bound to biomolecules, which adds an additional dimension to metal-biomolecule and metalloprotein characterization - the field of metallomics. The metallomic approach considers the metallome: a whole individual metal or metalloid species within a cell or tissue. A metallomic analytical approach (MAA) is proposed as a new tool to study and identify metalloproteins.

Recent advances in mercury speciation analysis with focus on spectrometric methods and enriched stable isotope applications

This paper discusses some recent advances in spectrometric methods and approaches for mercury speciation analysis of environmental samples with focus on isotope dilution techniques for determination of mercury species' concentrations in gaseous samples and reaction rates in soils and sediments. Such analytical data is important inter alia in fundamental research on mercury biogeochemistry and for risk assessments of mercury-contaminated soils and sediments and for designing effective remedial actions. The paper describes how the use of enriched stable isotope tracers in mercury speciation analysis can improve the traceability and accuracy of results, facilitate rational method developments, and be useful for studying biogeochemical processes, i.e. rate of reactions and fluxes, of mercury species. In particular the possibilities to study and correct for unwanted species transformation reactions during sample treatment and to study "natural" transformations of species in environmental samples, or micro- and mesocosm ecosystems, during incubations are highlighted. Important considerations to generate relevant data in isotope tracer experiments as well as reliability and quality assurance of mercury speciation analysis in general are also discussed.

Differentially Ligand-Functionalized Microcantilever Arrays for Metal Ion Identification and Sensing

A microcantilever array sensor with cantilevers differentially functionalized with self-assembled monolayers (SAMs) of thiolated ligands is prepared by simultaneous capillary coating. This array is described for the detection of metal ions including Li+, Cs+, Cu2+, Co2+, Fe3+, and Al3+. Binding of the charged metal cations to the surface of the microcantilever sensors produces surface stress that causes bending of the cantilevers that is detected as tip deflection using an array of vertical cavity surface emitting lasers and a position-sensitive detector. Optimization studies of the nanostructured dealloyed surface were performed for SAMs based on their response to Cu2+ cations. Sensor performance experiments demonstrate good sensitivity toward metal ions, with limits of detection as low as 10(-8) molar. A multiplex capillary coating method for cantilever array creation is demonstrated and validated based on surface-enhanced Raman spectra obtained from adjacent cantilevers that were functionalized with different thiolated SAMs. The cantilever array coated with a range of thiolated ligands was exposed to the group of metal ions. The response characteristics of each metal ion show substantial diversity, varying not only in response magnitude, but response kinetics. A pattern recognition algorithm based on a combination of independent component analysis and support vector machines was able to validate that the sensor array response profiles produced enough information content that metal ions could be reliably classified with probabilities as high as 89%.

An overview of recent applications of inductively coupled plasma-mass spectrometry (ICP-MS) in determination of inorganic impurities in drugs and pharmaceuticals

The recent applications of inductively coupled plasma-mass spectrometry (ICP-MS) in determination of trace level inorganic impurities in drugs and pharmaceuticals have been reviewed. ICP-MS coupled with LC, GC and CE was used for speciation of heavy metals in pharmaceutical products. The review covers the period from 1995 to 2005 during which the technique was applied not only for determination of metallic impurities but also the assay of various trace elements in pharmaceuticals.

Hyphenation of ultra performance liquid chromatography (UPLC) with inductively coupled plasma mass spectrometry (ICP-MS) for fast analysis of bromine containing preservatives

Ultra performance liquid chromatography (UPLC) was coupled to inductively coupled plasma mass spectrometry (ICP-MS) for fast analysis of three bromine-containing preservatives, monitoring the 79Br and 81Br isotopes simultaneously. Due to the efficiency of the 1.7 microm column packing material, the resolution of the test substances was only slightly affected when the linear flow velocity was increased from 0.5 to 1.9 mm s(-1). However, the sensitivity of ICP-MS detection decreased when the linear flow velocity was increased from 0.5 to 1.9 mm s(-1). Analytical figures of merit were determined at an intermediate and at a high linear velocity. The precision was better than 2.2% R.S.D. and regression analysis showed that a linear response was achieved at both flow rates (R2 > 0.9993, n = 36). The analysis time was less than 4.5 min at a flow rate of 50 microL min(-1) and limits of detection and quantification were better than 3.3 and 11 microg BrL(-1), respectively. The analysis time was reduced to 2.7 min when the flow rate was increased to 90 microL min(-1) and limits of detection and quantification were better than 20 and 65 microg BrL(-1), respectively. The method was applied for quantitative analysis of bromine-containing preservatives in commercially available cosmetic products.

Modeling and separation-detection methods to evaluate the speciation of metals for toxicity assessment

There is an increasing appreciation for the importance of speciation in the assessment of metal toxicity. In this review, two approaches to speciation are discussed, with an emphasis on their application to biological samples. One approach is the direct separation and detection of metal species of toxicological interest. Various "hyphenated" techniques, consisting of a chromatographic system coupled to inductively coupled plasma-mass spectrometry (ICP-MS), are discussed. The chromatographic strategies employed for separation emphasize liquid chromatography (LC), but the increasing use of gas chromatography (GC) and capillary electrophoresis (CE) in speciation analysis is discussed. The second approach to speciation is the use of computer models to calculate the speciation of a metal ion within a complex mixture of ligands. This approach is applicable to systems in which the metal cation exchanges ligands rapidly, so that the sample represents an equilibrium mixture of metal complexes. These computational models are based on the equilibrium constants for the metal complexes and a series of mass balance equations and give the distribution of metal complexes in the original sample. This approach is illustrated using the speciation of Al(III) in serum as an example.

Metal ion speciation and capillary electrophoresis: Application in the new millennium

Metal ions are essential for human beings at low concentrations but they are toxic or even carcinogenic at high concentrations. Many metallic ions are found in the environment in different species which are differentiated not only by their physicochemical forms but also by their diverse toxicities with respect to living organisms (speciation). CE has been used for metal ion speciation. The present review article describes the recent trends in metal ion speciation by CE. This article deals with the speciation of metal ions, optimization of the speciation (by independent and dependent variables), hyphenation of CE, validation of the methods, mechanisms of speciation, CE versus chromatography and conclusions.

Inductively coupled plasma mass spectrometry in separation techniques: Recent trends in phosphorus speciation

Inductively coupled plasma-MS (ICP-MS) and its combined use with molecular mass spectrometric techniques have become the most promising detection techniques in speciation studies. High sensitivity and element specificity of ICP-MS has the advantage of detecting trace amounts of the species of interest in complex matrices. This review is divided into two parts. In the first part, suitable use of ICP-MS either online or offline with currently used separation techniques such as HPLC, CE, and gel electrophoresis in speciation analysis is briefly discussed. In the second part, recent applications (1999-2005) of phosphorus speciation is presented to elucidate the importance of ICP-MS in separation methods and to illustrate its importance in nonmetal detection.

Capillary electrophoresis-inductively coupled plasma-mass spectrometry: A report on technical principles and problem solutions, potential, and limitations of this technology as well as on examples of application

This paper summarizes some basic principles of capillary electrophoresis (CE), inductively coupled plasma-mass spectrometry (ICP-MS), and coupling of both devices. Especially the interfacing is described in detail. A special focus is drawn to various interface developments reported in literature and technical problems, i.e., requirements to the interface setup and respective solutions. Nowadays, typically sheath flow-based interfaces are used. The sheath flow fulfills two requirements of hyphenation, (i) the closing of the electrical circuit of CE and (ii) the feeding of the used nebulizer with an adequate flow rate. In the beginning of CE-ICP-MS coupling predominantly home-made interface-nebulizer constructions were developed and tested for various speciation problems. Now increasingly such laboratory-constructed interfaces are left. Mostly commercial nebulizers are employed being combined with commercially available tee or cross fittings to connect the CE capillary to the electrode, the additional sheath flow, and the nebulizer. Due to the low sample amounts and low flow rates from CE, such nebulizers are typically low-flow nebulizers like, e.g., the microconcentric nebulizer (MCN) and the direct injection nebulizer (DIN). However, there are also reports on couplings using standard Meinhard systems. Still the control and reduction of a siphoning sucting flow and sufficient detection limits are the major problems in hyphenating CE to ICP-MS. Different solutions are reported on these problems and summarized here. Finally numerous applications are reported. Mostly, applications are performed on speciation of selenium, arsenic, metallothionein isoforms, mercury, or cobalt.

Separation of low-molecular mass organic acid–metal complexes by high-performance liquid chromatography

The solution speciation of metals is a critical parameter controlling the bioavailability, solution-solid phase distribution and transport of metals in soils. The natural metal-complexing ligands that exist in soil solution include inorganic anions, inorganic colloids, organic humic substances, amino acids (notably phytosiderophores and bacterial siderophores) and low-molecular mass organic acids. The latter two groups are of particular significance in the soil surrounding plant roots (the rhizosphere). A number of analytical methodologies, encompassing computational, spectroscopic, physico-chemical and separation techniques, have been applied to the measurement of the solution speciation of metals in the environment. However, perhaps with the exception of the determination of the free metal cation, the majority of these techniques rarely provide species specific information. High-performance liquid chromatography (HPLC) coupled to a sensitive detection system, such as inductively coupled plasma mass spectrometry (ICP-MS) or electrospray ionisation mass spectrometry (ESI-MS), offers the possibility of separating and detecting metal-organic acid complexes at the very low concentrations normally found in the soil environment. This review, therefore, critically examines the literature reporting the HPLC separation of metal-organic acid complexes with reference to thermodynamic equilibrium and kinetic considerations. The limitations of HPLC techniques (and the use of thermodynamic equilibrium calculations to validate analytical results) are discussed and the metal complex characteristics necessary for chromatographic separation are described.

State-of-the art of selective detection and identification of I-, Br-, Cl-, and F-containing compounds in gas chromatography and liquid chromatography

This review article presents an overview of halogen-specific detection in gas chromatography (GC) and liquid chromatography (LC). Attention is primarily focused on the use of plasma emission spectroscopy and plasma mass spectrometry as detectors, but other halogen-selective detection principles are also mentioned. Different instrumental configurations are discussed both with respect to technical set-up and performance, the principal reasons for halogen-selective detection are highlighted, and recent applications are reviewed from areas such as environmental chemistry, petroleum characterization, and drug analysis.

Colored thin films for specific metal ion detection

This paper describes the investigation of chitosan and poly(allylamine) (PAH) for the creation of a multi-film, color-based dipstick for the detection of metal ions in solution. Thin, colored films of chitosan and PAH cross-linked with hexamethylene 1,6-di(aminocarboxysulfonate) (HDACS) are created where color is due to film thickness and optical interference effects. The films are investigated for their ability to selectively detect aqueous metal ions via changes in thickness and/or color. Chitosan-HDACS films were selective for Cr(VI) over all other metal ions tested including Cr(acac)3 and Cr(NO3)3 x 9H2O, and PAH-HDACS films were selective for Cu(II) and Cu(I) salts over all other metal ions tested. The irreversible, selective changes due to metal ion solutions were not caused by varying the pH. Potomac River water was also tested using the two films, with results indicating the presence of Cu(II) in the aqueous sample.

Environmental distribution, analysis, and toxicity of organometal(loid) compounds

The biochemical modification of the metals and metalloids mercury, tin, arsenic, antimony, bismuth, selenium, and tellurium via formation of volatile metal hydrides and alkylated species (volatile and involatile) performs a fundamental role in determining the environmental processing of these elements. In most instances, the formation of such species increases the environmental mobility of the element, and can result in bioaccumulation in lipophilic environments. While inorganic forms of most of these compounds are well characterized (e.g., arsenic, mercury) and some of them exhibit low toxicity (e.g., tin, bismuth), the more lipid-soluble organometals can be highly toxic. Methylmercury poisoning (e.g., Minamata disease) and tumor development in rats after exposure to dimethylarsinic acid or tributyltin oxide are just some examples. Data on the genotoxicity (and the neurotoxicity) as well as the mechanisms of cellular action of organometal(loid) compounds are, however, scarce. Many studies have shown that the production of such organometal(loid) species is possible and likely whenever anaerobic conditions (at least on a microscale) are combined with available metal(loid)s and methyl donors in the presence of suitable organisms. Such anaerobic conditions can exist within natural environments (e.g., wetlands, pond sediments) as well as within anthropogenic environmental systems (e.g., waste disposal sites and sewage treatments plants). Some methylation can also take place under aerobic conditions. This article gives an overview about the environmental distribution of organometal(loid) compounds and the potential hazardous effects on animal and human health. Genotoxic effects in vivo and in vitro in particular are discussed.

The determination of trace metal pollutants in environmental matrices using ion chromatography

A review is presented detailing the development of ion chromatography (IC) as a selective analytical tool for the determination of toxic metals and their organic species in many environmental sample matrices. A brief outline of ion chromatographic principles, together with an overview of the stationary phases used to separate metals, namely ion exchangers, modified ion pair sorbents and chelating ion exchangers, and the methods for detecting metal ions including hyphenation with spectroscopy and sample preparation schemes are also given, prior to a critical examination of developed methods for various metals including arsenic, chromium, cadmium, lead, mercury, beryllium, aluminium and uranium since 1990.

Multielemental speciation analysis of organometallic compounds of mercury, lead and tin in natural water samples by headspace-solid phase microextraction followed by gas chromatography–mass spectrometry

The development of a simple and rapid multielemental speciation method is described with the ultimate goal to simultaneously determine various organometallic compounds of mercury, lead and tin (inorganic mercury, methylmercury, trimethyllead, triethyllead, monobutyl-, dibutyl- and tributyltin) in natural water samples. The analytical method consists on the ethylation with NaBEt4, simultaneous headspace-solid phase microextraction (HS-SPME) of the derivatives and final gas chromatographic-mass spectrometric (GC-MS) analysis. After optimization of important process parameters, like SPME fiber coating, extraction time and extraction temperature, the analytical characteristics were evaluated. Detection limits in the low ng l(-1) level, linearity over three orders of magnitude and repeatability in the range of 3-20% were achieved for all compounds under study. The accuracy of the method in terms of average percentage recovery of the compounds in spiked river water and seawater samples was better than 90%. Finally, application of the proposed method to real natural aqueous samples enabled the simultaneous determination of all the compounds under study in seawater samples obtained from the marina area of Gijón (Asturias, Spain).

Dispersion effects of laminar flow and spray chamber volume in capillary electrophoresis–inductively coupled plasma-mass spectrometry: a numerical and experimental approach

Band broadening related to laminar flow and spray chamber dead volume is a potential problem in flow injection (FI)-inductively coupled plasma-mass spectrometry (ICP-MS). We studied these two dispersion effects with a sheath flow capillary electrophoresis (CE)-ICP-MS interface. A numerical model was used to simulate advection diffusion processes in the CE-capillary and dispersion in the spray chamber. Experimental results of FI with this CE-ICP-MS interface agree well with numerical modeling results. Dispersion due to laminar flow depends strongly on capillary diameter and analyte diffusion coefficient and to a lesser extent on laminar velocity and capillary length and typically amounts to one order of magnitude peak width increase. Three spray chambers of 5, 20 and 150 ml dead volume showed an increase in band broadening and peak tailing with increasing dead volume. The use of standard Scott-type spray chambers (>90 ml volume) increases peak widths by 5-10 s regardless of injection time. The use of a low dead volume spray chamber is recommended for experiments where resolution is critical. The modeling approach can be extended to the coupling of other flow injection techniques, like micro-LC and nano-LC with ICP-MS.

Elemental speciation studies--new directions for trace metal analysis

Elemental speciation is reviewed as a new approach to trace metals analysis. The importance of metal speciation relative to total metal analysis is considered. Various types of chromatographic separation methods using inductively coupled plasma-mass spectrometry (ICP-MS) detection are discussed. A brief introduction to the instrumental techniques is given, as well a discussion of coupling the instrumentation. Various chromatographies are included with an emphasis on liquid chromatography (LC). Gas chromatography (GC) and capillary electrophoresis (CE) are also discussed. Application examples contrast and compare the advantages and disadvantages of ICP- MS with other detection methods. Summary tables are included for two of the LC methods.

Element speciation definitions, analytical methodology, and some examples

This paper gives definitions related to element speciation and the reasons for the need for speciation. The problems focused on, involve sampling, sample preparation and storage, as well as changes in species information that occur during the use of various separation technologies. However, the potential and advantages of the separation methods in element speciation are also discussed. In addition, problems arising during element detection that are attributable to analytes or mobile-phase composition are outlined, as well as the pronounced advantages of detection by inductively coupled plasma-mass spectrometry (ICP-MS). The combination of the various separation systems with element- or molecule-specific detectors creates problems especially in element speciation. These difficulties are described along with recent developments for overcoming them or for improving their coupling efficiency. Finally, several elements for which the issue of speciation is important are discussed, with examples from some recent publications on arsenic, selenium and iodine speciation.

Comparative study on conventional and low-flow nebulizers for arsenic speciation by means of microbore liquid chromatography with inductively coupled plasma mass spectrometry

The performance of conventional and low-flow nebulizer systems with liquid chromatography in differentiating four arsenic species in urine was evaluated. Two low-flow (DIN and MCN) chamber assemblies and a conventional (CFN) nebulizer-spray chamber assembly were compared in the hyphenation of anion-exchange microbore liquid chromatography with inductively coupled plasma mass spectrometry. Under optimal analytical conditions, the detection limits of the four arsenic species were 0.2-0.6 ng ml(-1) for all the nebulizer systems tested. The chromatographic resolution was best in the case of DIN due to its minimal off-column dead volume and superior transport efficiency. Four arsenic species were determined in the certified reference materials NIST SRM 2670E and 2670N.

Liquid chromatography-inductively coupled plasma mass spectrometry

It is known that while many elements are considered essential to human health, many others can be toxic. However, because the intake, accumulation, transport, storage and interaction of these different metals and metalloids in nature is strongly influenced by their specific elemental form, complete characterization of the element is essential when assessing its benefits and/or risk. Consequently, interest has grown rapidly in determining oxidation state, chemical ligand association, and complex forms of a many different elements. Elemental speciation, or the analyses that lead to determining the distribution of an element's particular chemical species in a sample, typically involves the coupling of a separation technique and an element specific detector. A large number of methods have been developed which utilize a multitude of different separation mechanisms and detection instruments. Yet, because of its versatility, robustness, sensitivity and multi-elemental capabilities, the coupling of liquid chromatography to inductively coupled plasma mass spectrometry (LC-ICP-MS) has become one of the most popular techniques for elemental speciation studies. This review focuses on the basic principles of LC-ICP-MS, its historical development and the many ways in which this technique can be applied. Different liquid chromatography separations are discussed as well as the factors that must be considered when coupling each to ICP-MS. Recent applications of LC-ICP-MS to the speciation of environmental, biological and clinical samples are also presented.

CZE-ICP-MS separation of metallothioneins in human brain cytosols: comparability of electropherograms obtained from different sample matrices

Capillary zone electrophoresis, with its high resolution capability in the separation of different compounds, is well suited for the investigation of metal-containing proteins, especially when elemental detection is conducted using hyphenated inductively coupled plasma-mass spectrometry. A major problem in the separation of proteins in body fluids is caused by the effects of different sample matrix composition. The migration time of proteins varies significantly, depending on the nature of the matrix. Electropherograms are consequently difficult to compare and the peak identification is uncertain. Pre-analytical steps for the reduction of matrix compounds enhance the quality of the data, but the results are still unsatisfactory. This paper describes a technique for obtaining electropherograms that can be used for comparison purposes by correction of the data with the aid of time markers. A mixture of five substances (caesium chloride, arsenocholine, arsenobetaine, dimethylarsinic acid and monomethylarsonic acid) was added in a separate injection step. Ionic caesium eluted at the start of the separation and the other four markers appeared throughout and at the end of the electropherogram. All electropherograms were normalized to a reference run by recalculation of the time axis using the time markers. The method was applied to the analysis of human brain cytosols. Samples were separated after different pre-treatment steps and were compared, with special emphasis on the detection of the isoform metallothionein-3.

Analytical separations of lanthanides and actinides by capillary electrophoresis

The separation of lanthanide and actinide elements belongs to one of the most challenging tasks of the separation science, due to a great similarity in their physical and chemical properties. The electrophoretic separation can be accomplished in the presence of suitable complex-forming agents, from which alpha-hydroxyisobutyric acid (HIBA) has been used most often. In the most effective capillary electrophoretic mode--capillary zone electrophoresis (CZE)--a complete separation of lanthanide ions can be accomplished within a few minutes. Various electrophoretic methods can be relatively easily adopted for the determinations of individual lanthanide elements in certain kinds of technical materials, concentrates, precursors, etc., where the high speed and low costs of analysis characteristics of capillary electrophoresis (CE) may be advantageously exploited. Electrophoretic techniques may also be employed for speciation studies, especially for examinations of the behavior of actinides in the environment.

Elemental speciation by chromatographic separation with inductively coupled plasma mass spectrometry detection

Separation techniques coupled to inductively coupled plasma mass spectrometry (ICP-MS) is reviewed. ICP-MS technique is described briefly. Coupling of the different separation techniques are described, together with the most common applications used for each technique that has been described in the literature. An overview for the future of separation techniques coupled to ICP-MS with regard to elemental speciation is discussed.

Sulfur-specific detection of impurities in cimetidine drug substance using liquid chromatography coupled to high resolution inductively coupled plasma mass spectrometry and electrospray mass spectrometry

The use of liquid chromatography coupled to sector field inductively coupled plasma mass spectrometry (SF-ICP-MS) for the specific detection of sulfur-containing compounds is described. In the sulfur-containing drug substance cimetidine, structurally related impurities well below the 0.1% mass fraction level relative to the main drug substance could easily be detected. The structure of most of the impurities was confirmed by electrospray mass spectrometry (ESI-MS), and thus, the complementarity of the two techniques for drug analysis is shown. The limit of detection by SF-ICP-MS for cimetidine in solution was approximately 4-20 ng x g(-1), but it was blank-limited.

Metal speciation using capillary electrophoresis--inductively coupled plasma atomic emission spectrometry and polytetrafluoroethylene capillaries

A capillary electrophoresis--inductively coupled plasma atomic-emission spectrometry (CE-ICP-AES) system using a polytetrafluoroethylene (PTFE) capillary has been developed. The CE-ICP interface was a modified concentric nebulizer. The PTFE capillary (50 microm internal diameter) was used as the central capillary of the nebulizer. Using the PTFE capillaries, the solution flow rate induced by the carrier gas flow was smaller than that of glass capillary. Solution flow was mainly induced by the CE electric field. Baseline separation of Ba2+/Mg2+ ion pair using simple buffer solution of 0.014 M sodium acetate was reported. Separation and correlation of metal species in metallothioneins (MT-1 and MT-2 in MT) of rabbit liver using the CE-ICP system were also discussed.

Trace analysis of heavy metals in groundwater samples by ion chromatography with post-column reaction and ultraviolet-visible detection

Groundwaters originating from local and regional aquifers surrounding ash deposits produced by a coal-fired power plant were collected. These water samples were chemically analyzed for quantifying their heavy metal composition at trace levels. A highly sensitive analytical technique based on ion chromatography with a UV-Vis detector and under isocratic eluent flow-rate conditions was used. In order to quantify the major heavy metals (Pb, Cu, Cd, Co, Zn and Ni), three ionic separation column systems were evaluated: (1) a cationic column (HPIC-CS2, Dionex) tested with two eluents (10 mM oxalic acid-7.5 mM citric acid; and 40 mM D-tartaric acid-12 mM citric acid); (2) an anionic column (HPIC-AS4, Dionex) evaluated with 25 mM oxalic acid as eluent: and (3) a bifunctional ion-exchange column (Ionpac CS5, Dionex) which was also tested with two eluents (6 mM pyridine, 2,6-dicarboxylic acid; and 50 mM oxalic acid/95 mM lithium hydroxide). The lowest detection limits achieved with the Ionpac CS5 column and the 50 mM oxalic acid-95 mM lithium hydroxide eluent enabled the heavy metal analysis in groundwater samples to be reliably performed. Details of this comparative study, including the ion chromatography procedure selected and its application to heavy metal analysis of groundwater samples, are presented in this work.

Element selective detection for supercritical-fluid chromatography

This manuscript describes the use of Supercritical-Fluid Chromatography (SFC) with plasma spectrometric detection for the analysis of organometallics. An introduction on the principles and characteristics of Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) is included, along with a discussion about requirements for coupling SFC to plasma detection and the different approaches for interfacing SFC to ICP. The last part of this review paper provides a comprehensive description of SFC-ICP applications for the analysis of organometallics containing iron, silicon, tin, chromium, arsenic, lead, mercury and antimony.

Investigation of Cr(III) hydrolytic polymerisation products by capillary electrophoresis-inductively coupled plasma-mass spectrometry

The development of a new method for the determination of Cr(III) hydrolytic polymerisation products using capillary electrophoresis-inductively coupled plasma mass spectrometry (CE-ICP-MS) is described. The results indicate that CE-ICP-MS can be used to separate and detect monomeric and polymeric Cr(III) species. The various species migrate through the capillary at a rate proportional to their equilibrium distribution, which is dictated by the solution pH, metal ion concentration and ageing period. In general, the data suggest that the relative mobility follows the order trimer>dimer>monomer. The experimentally determined speciation shows a good qualitative agreement with that described in the literature. Independent confirmation of the presence of polymeric Cr(III) species was performed by ionspray mass spectrometry.