A microwave plasma cavity assembly for atomic emission spectrometry

Although inductively coupled plasmas (ICPs) are widely used for multielement analysis microwave induced plasma (MIP) offers a great potential for a variety of applications. Modifications to incorporate MIP into commercial ICP direct reading spectrometer systems have been developed. A direct reading échelle spectrometer is described which opens new possibilities for the successful construction of commercial MIP-AES systems with the potential to run all of the typical methods worked out for earlier ICP-AES applications. Use of flow injection techniques and automation to couple with in situ concentration will likely offer a further improvement in the analytical performance of this system. Due to the capabilities demonstrated by this spectrometer it appears that hybrid instruments will be increasingly important for future developments in optical spectrometry. This is particularly true for very demanding areas such as atomic emission spectrometry. The system could be readily commercialized.     

A microwave plasma cavity assembly for atomic emission spectrometry

Although inductively coupled plasmas (ICPs) are widely used for multielement analysis microwave induced plasma (MIP) offers a great potential for a variety of applications. Modifications to incorporate MIP into commercial ICP direct reading spectrometer systems have been developed. A direct reading échelle spectrometer is described which opens new possibilities for the successful construction of commercial MIP-AES systems with the potential to run all of the typical methods worked out for earlier ICP-AES applications. Use of flow injection techniques and automation to couple with in situ concentration will likely offer a further improvement in the analytical performance of this system. Due to the capabilities demonstrated by this spectrometer it appears that hybrid instruments will be increasingly important for future developments in optical spectrometry. This is particularly true for very demanding areas such as atomic emission spectrometry. The system could be readily commercialized.     

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.     

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.     

Determination of Minor Aluminum and Nickel in Brass Sample with Magnetic Field Enhanced Glow Discharge Optical Emission Spectrometry

Glow discharge atomic spectrometry, includes principally glow discharge optical emission spectrometry (GD-OES) and GD mass spectrometry, has been widely applied in direct solid sample determination and surface depth analysis. There have been numerous methods adopted to enhance the emission signal in a GD-OES without losing the advantage of narrow spectral lines by using what is known as boosted GD sources, especially microwave discharge and magnetic field enhanced techniques. The addition of a magnetic field to the GD volume is an attractive option because it does not require much modification to the original source configuration, in addition,the presence of magnetic field lengths the drift path of electrons from plasma region to the anode,and therefore strengthens the sputtering, excitation, and ionization processes that good for signal generation.     

Plasma-source mass spectrometry for speciation analysis: state-of-the-art

Current and emerging capabilities of plasma-source mass spectrometry (PS-MS) as it is employed for elemental speciation analysis are reviewed. Fundamental concepts and their advantageous aspects, experimental conditions, and analytical performance are described and illustrated by recent examples from the literature. Novel instrumentation, techniques, and strategies for inductively-coupled plasma mass spectrometry (ICP-MS), microwave-induced plasma (MIP) mass spectrometry, glow-discharge (GD) mass spectrometry, and electrospray ionization (ESI), among others, are described. The use of ionization sources that provide tunable ionization, others that can be modulated between different sets of operating conditions, and others used in parallel is also examined.     

Towards nanometric resolution in multilayer depth profiling: a comparative study of RBS, SIMS, XPS and GDOES

An increasing amount of effort is currently being directed towards the development of new functionalized nanostructured materials (i.e., multilayers and nanocomposites). Using an appropriate combination of composition and microstructure, it is possible to optimize and tailor the final properties of the material to its final application. The analytical characterization of these new complex nanostructures requires high-resolution analytical techniques that are able to provide information about surface and depth composition at the nanometric level. In this work, we comparatively review the state of the art in four different depth-profiling characterization techniques: Rutherford backscattering spectroscopy (RBS), secondary ion mass spectrometry (SIMS), X-ray photoelectron spectroscopy (XPS) and glow discharge optical emission spectroscopy (GDOES). In addition, we predict future trends in these techniques regarding improvements in their depth resolutions. Subnanometric resolution can now be achieved in RBS using magnetic spectrometry systems. In SIMS, the use of rotating sample holders and oxygen flooding during analysis as well as the optimization of floating low-energy ion guns to lower the impact energy of the primary ions improves the depth resolution of the technique. Angle-resolved XPS provides a very powerful and nondestructive technique for obtaining depth profiling and chemical information within the range of a few monolayers. Finally, the application of mathematical tools (deconvolution algorithms and a depth-profiling model), pulsed sources and surface plasma cleaning procedures is expected to greatly improve GDOES depth resolution.     

Plasma-based mass spectrometry for simultaneous acquisition of elemental and molecular information

Chemical speciation studies are commonly accomplished by resorting to hyphenated analytical techniques, consisting of a powerful chromatographic separation technique coupled to a highly sensitive elemental spectrometric detector. However, in addition to this element-selective information, complementary molecular spectrometric tools are often required for a complete identification of macromolecules. Therefore, there is an increased research effort focused towards the development of integrated instruments to carry out the complete chemical speciation within a sample using a single instrument. An outline of recent developments in plasma-based mass spectrometric instrumentation for such comprehensive chemical speciation studies is here presented and their pros and cons detailed. In this context, the use of complementary techniques operating in parallel after splitting to a single chromatographic separation (dual sources) providing simultaneously elemental and molecular information is critically reviewed. Also, instrumental developments involving the use of stationary plasma sources operated in non-traditional modes (e.g. low pressure and low power) are also discussed. Moreover, the capabilities of tunable plasma-based ionization sources (allowing different ionization processes and, so, quasi-simultaneously providing elemental and molecular information with a single instrument) as a relatively simple and cheap approach are revised.     

Simultaneous determination of trace metals in sewage and sewage effluents by inductively coupled argon plasma atomic emission spectrometry

Inductively coupled plasma excitation sources are adapted for the simultaneous determination of multiple elements in sewage and sewage effluents by atomic emission detection. Digestion with aqua regia in test tubes is recommended for sample preparation. A typical comparison of lead in sewage by atomic emission (x) and atomic absorption (y) gave a least-squares fit of x = 0.98 y + 0.03 with a standard error of 0.5 mg l^-1 and a correlation coefficient of 0.996. More complete comparison data by the atomic emission and absorption techniques are presented for other elements.     

Standard dilution analysis of beverages by microwave-induced plasma optical emission spectrometry

In this work, standard dilution analysis (SDA) is combined with microwave-induced plasma optical emission spectrometry (MIP OES) to determine seven elements in coffee, green tea, energy drink, beer, whiskey and cachaça (Brazilian hard liquor). No sample preparation other than simple dilution in HNO₃ 1% v v⁻¹ is required. Due to relatively low plasma temperatures, matrix effects may compromise accuracies in MIP OES analyzes of complex samples. The method of standard additions (SA) offers enhanced accuracies, but is time-consuming and labor intensive. SDA offers a simpler, faster approach, with improved accuracies for complex matrices. In this work, SDA's efficiency is evaluated by spike experiments, and the results are compared to the traditional methods of external calibration (EC), internal standard (IS), and standard additions (SA). SDA is comparable to the traditional calibration methods, and it provides superior accuracies for applications involving ethanol-containing beverage samples. The SDA-MIP OES procedure is effective. Using only two calibration solutions, it may be easily automated for accurate and high sample throughput routine applications.     

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.     

气动雾化进样时微波等离子体炬作为激发光源的性能研究

以气动雾化进样研究了微波等离子体炬（ＭＰＴ）放电作原子发射光谱法激发光源的性能，包括ＭＰＴ的获得、操作参数的影响、样品引入及其分析性能，并与微波诱导等离子体进行了比较，证明ＭＰＴ放电作激发光源有良好的分析性能．     

A double plasma gas chromatography injector and detector

A direct-current, chip-based plasma has been used for gas sample injection in gas chromatography. A second identical plasma chip has been used as the excitation source for an optical emission detector. The first plasma is normally continually sustained during operation, causing continuous ionisation/fragmentation of the sample, whilst the second plasma records the optical emission downstream. For injection, the first plasma is briefly interrupted, introducing a "plug" of unmodified sample into the system. Injection plug sizes of between 5 and 50 [micro sign]l have been reproducibly obtained, although significantly smaller volumes may be possible with the use of smaller cross-section columns, lower flow rates and/or shorter plasma interruption times.     

Bestimmung von Elementspuren im ng- und pg-Bereich durch optische Emissionsspektrometrie mit He-MIP-Anregung nach elektrolytischer Abtrennung im Graphitrohr und nach-folgender elektrothermischer Atomisierung

This article deals with the determination of traces of elements in the ng and pg range by emission spectroscopy with a He-MIP excitation after electrolytic preconcentration in a graphit tube followed by electrothermal atomization. A multi-stage combined procedure is described for the sensitive and reliable determination of trace elements in high-purity metals. Electrolytically depositable elements such as noble metals, copper, as well as bismuth, cadmium, iron, cobalt, zinc, and others are preconcentrated from acidic solutions with concentrations ? 0.05 ng ml^?1 after the decomposition of the sample if the matrix elements are not deposited. The electrolyte is cycled through a small cylindrical cathode of pure graphite on the inner wall of which the elements are deposited. The graphite tube is coupled directly to the quartz capillary of a microwave induced helium plasma (MIP). After electrothermal atomisation the trace elements are determined by emission spectrometry. Different types of MIP excitation sources are investigated. The MIP with the TM₀₁₀ microwave resonator shows optimal properties. For the determination of the trace elements in niobium and beryllium detection limits near 1 ng g^?1 and relative standard deviations between 6.5 and 15% are obtained.     

Diagnostics of an RF Plasma Flash Evaporation Process Using the Monochromatic Imaging Technique

The high densities and high gas temperature of rf plasmas at pressures near 1 atm are favorable for the development of plasma sources capable of evaporating solid precursors in the plasma zone. In the cooler region downstream of the plasma, the evaporated material condenses to nanoparticles and/or coatings. The complete evaporation of precursors injected into a thermal plasma depends on plasma and precursor parameters and is studied in this paper. Since many parameters contribute to the evaporation, fast experimental techniques are necessary to carry out a systematic study of the evaporation process. The monochromatic imaging technique applied in this work uses an intensified CCD camera with optical filters for the detection of characteristic plasma emission lines. The high spatial and temporal resolution of this technique results in a detailed picture of plasma emission and particle evaporation for different process parameters. These results are compared to model calculations for particle evaporation.     

On-Line Preconcentration and Simultaneous Determination of Cu and Mn in Water Samples Using a Minicolumn Packed with Sisal Fiber by MIP OES

An on-line preconcentration system for the simultaneous determination of Copper (Cu) and manganese (Mn) in water samples was developed and coupled to a microwave-induced plasma optical emission spectrometer (MIP OES). The flow injection system was designed with a minicolumn packed with sisal fiber (Agave sisalana). A multivariate experimental design was performed to evaluate the influence of pH, preconcentration time, and eluent concentration. Optimal conditions for sample preparation were pH 5.5, preconcentration time was 90 s, and HCl 0.5 mol L⁻¹ was the eluent. The main figures of merit were detection limits 3.7 and 9.0 µg L⁻¹ for Cu and Mn, respectively. Precision was expressed as a relative standard deviation better than 10%. Accuracy was evaluated via spiked recovery assays with recoveries between 75–125%. The enrichment factor was 30 for both analytes. These results were adequate for water samples analysis for monitoring purposes. The preconcentration system was coupled and synchronized with the MIP OES nebulizer to allow simultaneous determination of Cu and Mn as a novel sample introduction strategy. The sampling rate was 20 samples/h. Sisal fiber resulted an economical biosorbent for trace element preconcentration without extra derivatization steps and with an awfully time of use without replacement complying with the principles of green analytical methods.     

A possibility of element specific detection in HPLC by means of MIP-AES coupled with hydraulic high pressure nebulization

An interface for coupling hydraulic high pressure nebulization (HHPN) with microwave induced plasma (MIP) atomic emission spectrometry (AES) is described. An appropriate spray chamber and aerosol desolvation system has been constructed for matching the HHPN generated aerosol flow with the loading capacity of toroidal argon and cylindrical helium MIP sources. The system has been optimized for aqueous solutions. Nanogram amounts of metals and nonmetals could be detected by the HHPN-MIP-AES technique developed. The HHPN devices are directly compatible with HPLC solvent flow, therefore they can be directly coupled with HPLC separations in aqueous media.     

A possibility of element specific detection in HPLC by means of MIP-AES coupled with hydraulic high pressure nebulization

An interface for coupling hydraulic high pressure nebulization (HHPN) with microwave induced plasma (MIP) atomic emission spectrometry (AES) is described. An appropriate spray chamber and aerosol desolvation system has been constructed for matching the HHPN generated aerosol flow with the loading capacity of toroidal argon and cylindrical helium MIP sources. The system has been optimized for aqueous solutions. Nanogram amounts of metals and nonmetals could be detected by the HHPN-MIP-AES technique developed. The HHPN devices are directly compatible with HPLC solvent flow, therefore they can be directly coupled with HPLC separations in aqueous media.     

Time‐Resolved Synchrotron Radiation Excited Optical Luminescence: Light‐Emission Properties of Silicon‐Based Nanostructures

The recent advances in the study of light emission from matter induced by synchrotron radiation: X‐ray excited optical luminescence (XEOL) in the energy domain and time‐resolved X‐ray excited optical luminescence (TRXEOL) are described. The development of these element (absorption edge) selective, synchrotron X‐ray photons in, optical photons out techniques with time gating coincide with advances in third‐generation, insertion device based, synchrotron light sources. Electron bunches circulating in a storage ring emit very bright, widely energy tunable, short light pulses (<100 ps), which are used as the excitation source for investigation of light‐emitting materials. Luminescence from silicon nanostructures (porous silicon, silicon nanowires, and Si–CdSe heterostructures) is used to illustrate the applicability of these techniques and their great potential in future applications.     

Critical comparison of sources and detection methods in atomic spectrometry

Summary Over the past three decades, the nature of atomic spectrometric analysis has changed dramatically. In the 1960's, flame and furnace atomic absorption were dominant, with furnace techniques gradually achieving prominence. In contrast, the 1970's witnessed the introduction of the inductively coupled plasma (ICP) and the direct current plasma (DCP). Although the ICP is still the most frequently used excitation source, the decade of the 1980's has seen a resurgence of interest in the glow-discharge lamp (GDL) and the microwave-induced plasma (MIP). Today, novel sources are continually being introduced, supported by combinations of gas mixtures and operated alternatively at DC, microwave or radio frequencies. These advances must be assessed against the backdrop of more unconventional atom-formation techniques that involve the use of high-powered lasers, rare-gas sputtering systems, or tandem (coupled) sources.In a similar vein, modes of detection have changed significantly over the past 30 years. While chemical flames and furnaces were the atom reservoirs of choice, atomic absorption was favored, in large measure because of its simplicity. In contrast, in the period of the 1970's, the attributes of the ICP made emission spectrometry the most attractive, in large part because of its straightforward adaptation to simultaneous multielement approaches. The most common configurations for such emission-based measurements were the direct-reading spectrometer, borrowed from earlier arc and spark days, and the slew/scan arrangement, in which desired spectral regions were scanned slowly, but regions of less interest bypassed hastily. In both systems, it was recognized that background correction was becoming increasingly important.In the 1980's, we have come to realize that other detection techniques might ultimately prove superior to a conventional emission measurement. For example, plasma-source mass spectrometry has already demonstrated detection limits several orders of magnitude lower than can be achieved routinely by emission. Similarly, atomic or ionic fluorescence, excited by a laser source, has been shown capable of detecting as little as a few thousand atoms. Ultimately, techniques such as resonance ionization spectrometry are appealing, despite their complexity, since they are capable of detecting even a single atom.Adding to this rather complicated situation is the question of how emission might best be detected if it is the measurement of choice. The traditional direct-reading and slew/scan approaches are convenient and well established. However, they lack the ability to detect a complete atomic-emission spectrum, a feature offered long ago by a photographic film or plate. Now, such capability exists in multichannel electronic readout devices, of either the linear or two-dimensional variety. The advent of charge-coupled devices (CCD), charge-injection devices (CID) and integrated linear photodiode array packages (PDA) makes it possible to consider replacing single-channel detectors with an electronic analog of the photographic plate. Similarly, the use of Fourier-transform spectrometry, produced by means of a moderate-resolution interferometer, affords the option not only of simultaneous multielement analysis, but also of simultaneous monitoring of background levels, accurate registration of atomic-emission wavelengths, and relatively rapid scan speeds.In this paper, a few of the more attractive alternatives in this apparently bewildering array of options will be outlined. The most attractive of the options will be compared with each other in an attempt to assess not only what the most attractive current choices are in atomic spectrometric analysis but also what the future might bring.