Recent trends in atomic spectrometry with microwave-induced plasmas

The state-of-the-art and trends of development in atomic spectrometry with microwave-induced plasmas (MIPs) since the 1998s are presented and discussed. This includes developments in devices for producing microwave plasma discharges, with reference also to miniaturized systems as well as to progress in sample introduction for microwave-induced plasmas, such as pneumatic and ultrasonic nebulization using membrane desolvation, to the further development of gaseous analyte species generation systems and to both spark and laser ablation (LA). The features of microwave-induced plasma mass spectrometry (MIP-MS) as an alternative to inductively coupled plasma (ICP)-MS are discussed. Recent work on the use of microwave-induced plasma atomic spectrometry for trace element determinations and monitoring, their use as tandem sources and for particle sizing are discussed. Recent applications of the coupling of gas chromatography and MIP atomic spectrometry for the determination of organometallic compounds of heavy metals such as Pb, Hg, Se and Sn are reviewed and the possibilities of trapping for sensitivity enhancement, as required for many applications especially in environmental work, are showed at the hand of citations from the recent literature.     

Microwave plasma torch analytical atomic spectrometry

The microwave plasma torch (MPT), as a relative new source, has found extensive use in atomic spectrometry. In this review, the fundamental features and characteristics of the MPT are summarized and compared with other kinds of analytical atomic sources, such as the more popularly used inductively coupled plasma (ICP), the direct current plasma (DCP), as well as other kinds of microwave plasmas (MWPs). Since the MPT offers some attractive features, it has been used as an excitation source for atomic emission spectrometry (MPT-AES), including the atomic emission detection (AED) for gas chromatography (GC), liquid chromatography (LC) and supercritical fluid chromatography (SFC). Also, it has been used either as an ionization source for atomic mass spectrometry (MPT-AMS) or an atomization source for atomic fluorescence spectrometry (MPT-AFS). The historical development and recent improvements in these MPT atomic spectrometric techniques are evaluated with emphasis on the analytical advantages and limitations. In addition, the future research directions and the application prospects of MPT atomic spectrometry (MPT-AS) are discussed.     

Trends of development in plasma techniques for atomic spectrometric analysis: A review

Trends of development in atomic spectrometry with plasma sources for optical emission spectrometry and mass spectrometry are discussed, especially for inductively coupled plasmas and discharges under reduced pressure. Important fields of application such as materials analysis and environmental analysis with special reference to the speciation of traces of heavy metals are discussed.Introductory lecture at the Symposium on Plasma Techniques of the 1994 International Symposium on Microchemical Techniques, Montreux, May 16–20, 1994     

Trends in optical spectrochemical trace analysis with plasma sources

The state-of-art and trends in the development of optical spectrochemical trace analysis with inductively-coupled plasmas (i.c.p.), direct current plasmas (d.c.p.) and microwave-induced plasmas (m.i.p.) are discussed. Innovation in plasma optical emission spectrometry (o.e.s.) is shown ot lie in new sources such as the low-gas-consumption i.c.p., the air and helium i.c.p. as well as the toroidal m.i.p., which is operated at medium power and possibly with moleculary gases. Sample introduction has been improved by using new pneumatic nebulizers, flow injection, electrotheraml vaporization, hydride generation, direct sample insertion and direct solid sampling. Progress in the acquisition of spectral information is attained by high-resolution spectrometry, Fourier-transform spectrometry and by the use of multichannel detectors. D.c.p./o.e.s. is a mature technique for routin work and m.i.p./o.e.s. is a powerful tool for element-specific detection is chromatography. Plasma sources are also suitable atom reservoirs for atomic fluorescence spectrometry and for laser-enhanced ionization spectrometry. Trends in the figures of merit of optical plasma spectrochemical analysis are discussed.     

The development of microplasmas for spectrochemical analysis

Miniaturized microwave, high-frequency, and dc-powered microplasmas are discussed, with emphasis on the state-of-the-art and development trends. Specific atomic emission sources discussed include the microstrip microwave plasma operated in argon and helium at ca 10-30 W and below 1 L min(-1) gas at atmospheric pressure, the capacitively coupled microplasma, operated at 13.56 MHz, 5-25 W, and 17-150 mL min(-1) helium, the miniaturized inductively coupled plasma operated at several watts and reduced pressure, and dc glow-discharge plasmas on a chip, including a barrier-layer discharge as atom reservoir for atomic absorption spectrometry. Diagnostics for these sources are discussed and some of their figures of merit are compared with those of conventional sources. Current possibilities for introduction of gaseous samples are reported and scope for further development and outlook are both discussed.     

Element-selective detection for chromatography by plasma emission spectrometry

High-temperature argon and helium plasmas provide stable sources for emission spectroscopy. These plasmas have proven useful as a means of selective detection for column chromatography. This review is based on a survey of the literature from 1965, when the first communication on this topic appeared. The species for which liquid and gas chromatographic effluents are monitored include metal ions and elements not traditionally determined by atomic spectrometry such as C, H, N, P. 0, S, and the halogens. Applications to a wide variety of samples are discussed.     

Quantitative element analysis by isotope dilution in diode laser graphite furnace atomic absorption spectrometry

The paper reviews the application of the isotope dilution technique in optical atomic absorption spectrometry by use of a low-pressure graphite tube furnace as atomizer and diode lasers as radiation sources. The principles and the methodology to obtain accurate quantitative results despite of the occurrence of interferences are presented. The successful application of different Doppler-limited and Doppler-free spectrometric techniques is also presented. The perspectives but also the limitations of this new method are discussed.     

微波等离子体光谱技术的发展(二)

微波等离子体光源是一类重要的有较强激发能力的原子发射光谱光源,主要包括微波感生等离子体光源,电容耦合微波等离子体光源及微波等离子体炬光源。本文是微波等离子体光谱技术发展的第二部分,主要介绍了电容耦合微波等离子体光源及微波等离子体炬光源的结构原理和性能。并对它们的技术特点和进展进行评述。     

Current Developments in Optical Emission Spectrometry with High-Frequency and Microwave Induced Plasmas

The state-of-the-art and trends of development with the inductively coupled plasma (ICP) and microwave induced plasmas (MIP) as radiation sources for optical emission spectrometry arc presented. Especially techniques for sample introduction are discussed. Here special reference is given to the use of spark ablation as well as 10 direct sample insertion and slurry atomization for the direct analysis of powder samples. The development in MIP optical emission Spectrometry is shown to center on the improvement of the plasma sources, their characterization and their tailoring to various sampling techniques. Results of the use of pneumatic nebulization of liquids and electrothermal evaporation of dry solution residues will be presented.     

The use of plasma atomic spectrometric methods for the analysis of ceramic powders

The use of plasma atomic spectrometric methods for the analysis of high-purity refractory powders of Al₂O₃, SiC and ZrO₂ used in the production of advanced ceramics is discussed. Special reference is given to the use of combined procedures including sample decomposition and in the case of ZrO₂ to matrix removal as well as to the slurry technique as a direct method in atomic spectrometry with inductively coupled plasmas (ICP). Both the possibilities, limitations and analytical use of the slurry technique are discussed and shown to be related to the particle size of the powder; this should be below the 5–10 m level. The use of a Simplex method for the optimization of the slurry technique towards obtaining both the highest power of detection and calibration using solutions will be treated for the case of SiC. A critical evaluation of the use of ICP atomic emission and of ICP mass spectrometry is presented.     

Chemical vapor generation of noble metals for analytical spectrometry

As is apparent from the literature devoted to the analytical atomic spectrometry, chemical vapor generation (CVG) of noble metals by reaction with tetrahydroborate in acidic media may enhance the introduction of these elements into different atomic spectrometric sources. Recent developments in the CVG of noble metals species by reaction with tetrahydroborate in acidic medium are surveyed. Different aspects of this novel technique are discussed, including type of instrumentation used for the reaction, separation and transport of the species, effect of chemical and physical factors, identification of the species, and the efficiency of the process. Limitations and future prospects of the CVG technique are discussed.     

Diode laser atomic absorption spectrometry

The paper reviews the past 11 years of literature on the application of diode lasers in atomic absorption spectrometry with graphite furnaces (GF), plasmas and flames as atomizers. Experimental arrangements and techniques for powerful absorption measurements as well as the theoretical background are covered. The analytical possibilities of high-resolution spectroscopy, including Doppler-free techniques for isotope selective measurements and isotope dilution analysis are discussed and various applications of element-selective detection by diode laser atomic absorption in combination with separation techniques, such as liquid (LC) and gas chromatography (GC), and with laser ablation of solid samples, are presented.     

Atomic spectroscopy with surface wave plasmas

The use of microwave induced plasmas, particularly of surface wave plasmas, as detectors in atomic emission spectrometry for elemental analysis is reviewed. Surface wave plasmas have been produced at low HF power and used as gas chromatographic detectors. The analytical performances for the detection of non-metals with a Fourier transform spectrometer and a two-channel filter unit are reported. The excitation behavior of non-metals in helium-based mixed gas-plasmas has also be studied. In particular, the effect of power and of nitrogen concentration on the bromine emission has been systematically investigated. A nine-fold improvement of the detection limits for bromine can be obtained in a high power (900 W) helium-nitrogen (0.1-0.2%) plasma.     

Atomic spectrometric detectors for flow-injection analysis

The distinction between liquid chromatography and flow injection analysis is discussed in terms of the underlying concepts, the performance characteristics and the hardware involved. For the last aspect, attention is focused on the role of the detector and the development of spectroscopic detectors for these techniques is discussed. The limitations of atomic spectrometric detectors are discussed for the three most widely used techniques, flame atomic absorption spectrometry, plasma spectrometry and electrothermal atomisation atomic absorption spectrometry, and the recent literature concerned with the use of these techniques for chromatographic detectors is summarized. The use of flow-injection methods to extend the capabilities of the techniques, particularly as far as detection limits and matrix interferences are concerned, is discussed. These topics are illustrated by a detailed review of relevant papers from 1988 and 1989. It is concluded that there is a considerable sustained research effort in this field.     

Atomic spectroscopy with surface wave plasmas

The use of microwave induced plasmas, particularly of surface wave plasmas, as detectors in atomic emission spectrometry for elemental analysis is reviewed. Surface wave plasmas have been produced at low HF power and used as gas chromatographic detectors. The analytical performances for the detection of non-metals with a Fourier transform spectrometer and a two-channel filter unit are reported. The excitation behavior of non-metals in helium-based mixed gas-plasmas has also be studied. In particular, the effect of power and of nitrogen concentration on the bromine emission has been systematically investigated. A nine-fold improvement of the detection limits for bromine can be obtained in a high power (900 W) helium-nitrogen (0.1–0.2%) plasma.     

A close-up of three microwave plasma sources in view of improved element-specific detection in liquid chromatography

Progress in the features of three types of microwave plasmas is discussed, in view of the development of successful methods for atomic spectrometric element-specific detection in liquid chromatography. For the low-power microwave induced plasmas the development of the toroidal plasma in a TM010 cavity according to Beenakker is mentioned as the break-through for the introduction of wet aerosols. Capacitively coupled microwave plasmas (CMP), which can be operated with helium, argon and even air as working gases, are robust and allow obtaining of detection limits for Fe, Cr, Ni and Co in aqueous solutions in the 0.02 to 0.06 μg/ml range and in light oils, as an example of organic liquids, between 0.08 and 0.13 μg/ml. Special attention should be given to the microwave plasma torch (MPT) in which aerosols from aqueous as well as from organic solutions produced by a Légère nebulizer can be introduced without desolvation. Here, detection limits for Cd, Cr, Li and Pb range from 0.02 to 0.5 μg/ml. For the case of chromium dissolved as dithiocarbamate complex in an acetonitrile/H₂O mixture (2:1), its detection limit is 0.12 μg/ml, being already below that obtained with UV spectrophotometry. The limits of detection achieved with the sources discussed in the case of atomic emission spectrometry show the prospective for further development.     

Element-selective detection in liquid and gas chromatography by diode laser absorption spectrometry

An element-selective detector for chromatography based on atomic absorption spectrometry with semiconductor diode lasers is described. The analytical utility of the technique is demonstrated by speciation examples of HPLC and GC employing analytical flames and plasmas to atomize.     

Electrolytic sample pretreatment in atomic spectrometry: A review

The use of electrolysis in analytical atomic spectrometry is reviewed. Topics such as electrodeposition for analyte enrichment, electrochemical sample pretreatment and hydride generation are discussed. The use of batch and flow-through electrochemical cells is compiled and critically evaluated. Flow-through cells with porous working electrodes were found to provide the best performance for analyte enrichment.     

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

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

Determination of Lead,Cadmium and Mercury in Surface Marine Sediments and Mussels

Abstract

Lead, cadmium and mercury were determined in sediments and mussels, and the ability of these indicators to record metal variations in coastal marine environment is described in this work. The results of an extended investigation of the status of three gulfs at Northern Greece are given, regarding the content of these metals in surface sediments and Mytilus galloprovincialis. The samples were collected during a four-year period. The total concentration of the above heavy metals was determined after digestion of the samples by suitable mixtures of acids, including nitric, perchloric and hydrofluoric acid. The digestion was carried out in a steel pressurised bomb with closed teflon vessels. Lead and cadmium were determined by means of electrothermal atomic absorption spectrometry (ETAAS), and mercury by cold vapour atomic absorption spectrometry (CVAAS). The results were statistically evaluated by analysis of variance, and emphasis was given to annual, seasonal and spatial sources of variation. The annual changes during the last four years and the spatial distribution of heavy metals load is also discussed.