Signal Formation in Laser-Enhanced Atomic Ionization Spectrometry with Laser Sampling into the Flame

The results of the observation of ionization signals in the laser-ablation sampling of solid samples into the flame were reported. The signals exhibited two maxima. The first, nonselective, maximum, which appeared immediately after the pulse of the volatilization laser, is due to thermions formed in the laser plasma. The second, selective (analytical), signal appeared after the pulse of the optical excitation laser. The nonselective signal may interfere with the detection of the analytical signal. The dependence of both signals on parameters such as the height of the cathode and the height of signal observation above the burner and the time delay between the laser pulses was studied. The optimal conditions for the detection of signals in laser-enhanced atomic ionization spectrometry were found.     

Tungsten devices in analytical atomic spectrometry

Tungsten devices have been employed in analytical atomic spectrometry for approximately 30 years. Most of these atomizers can be electrically heated up to 3000 °C at very high heating rates, with a simple power supply. Usually, a tungsten device is employed in one of two modes: as an electrothermal atomizer with which the sample vapor is probed directly, or as an electrothermal vaporizer, which produces a sample aerosol that is then carried to a separate atomizer for analysis. Tungsten devices may take various physical shapes: tubes, cups, boats, ribbons, wires, filaments, coils and loops. Most of these orientations have been applied to many analytical techniques, such as atomic absorption spectrometry, atomic emission spectrometry, atomic fluorescence spectrometry, laser excited atomic fluorescence spectrometry, metastable transfer emission spectroscopy, inductively coupled plasma optical emission spectrometry, inductively coupled plasma mass spectrometry and microwave plasma atomic spectrometry. The analytical figures of merit and the practical applications reported for these techniques are reviewed. Atomization mechanisms reported for tungsten atomizers are also briefly summarized. In addition, less common applications of tungsten devices are discussed, including analyte preconcentration by adsorption or electrodeposition and electrothermal separation of analytes prior to analysis. Tungsten atomization devices continue to provide simple, versatile alternatives for analytical atomic spectrometry.     

单一稀土元素检测方法的新近进展

本文对1999～2004年间有关单一稀土元素检测方法的研究进展进行了综述,内容包括原子吸收/原子荧光光谱法,荧光光度法,X-射线荧光光谱法,中子活化分析,电感耦合等离子体原子发射光谱法、电感耦合等离子体质谱法以及其干扰效应、进样技术和分析应用.引用文献127篇.     

Matrix interference in laser atomic absorption spectrometry

The combination of graphite furnace atomic absorption spectrometry and ruby laser evaporation of solid samples is described. The influence of the matrix composition on analytical results is shown in the determination of Ag, Al, Cd, Ga, Mn and Pb. In the presence of halides a depression of the absorbance values of Al and Ga was observed. The formation of diatomic molecules and the dissociation of these in the laser plasma and in the hot graphite furnace are discussed.     

Atomic fluorescence spectrometry with laser excitation

A laser atomic fluorescence spectrometry for the detection of trace concentrations of the elements is described. The detection limits for Pb, Fe, Na, Pt, Ir, Eu, Cu, Ag, Co and Mn in aqueous solutions obtained at present are the best ones for the rapid spectral analytical methods. The analytical potentials of the laser spectrometer are exemplified by the analysis of real samples of different chemical composition.     

Capacitive Discharge Graphite Furnace Laser-Excited Atomic Fluorescence of Thallium

For the first time, an anisotropic graphite furnace heated by capacitive discharge was used for laser-excited atomic fluorescence spectrometry. A detection limit of 5 fg for thallium was obtained with a laser repetition rate of 500 Hz and a peak integration time of 80 ms. The use of a capacitive discharge furnace allows for a shorter integration time, which in turn should allow for integration of less background noise, and improved detection limits. Theoretically, the magnitude of the shot noise should be proportional to the square root of the integration time, and inversely proportional to the square root of the laser repetition rate. Experimental data illustrated the effect of laser repetition rate, but were inconclusive with respect to integration time. The linear dynamic range of the calibration curve was six orders of magnitude, which was comparable to that normally obtained for laser-excited atomic fluorescence in modern commercial graphite furnaces. Thallium was accurately determined in NIST biological samples at levels one to two orders of magnitude below the detection limit of electrothermal atomic absorption spectrometry, with an analytical precision between 8 and 20%. The interference effects of calcium, sodium chloride, and potassium chloride on the thallium signal were investigated and shown to be similar to both laser-excited atomic fluorescence in a conventional furnace and capacitive discharge furnace atomic absorption results reported in the literature.     

Analytical Potentials and Features of Atomic Emission Analysis Using Electron-Impact Excitation of Atoms in Helium under Atmospheric Pressure

A device is described for the atomic emission analysis of vaporous samples using electron-impact excitation in helium under atmospheric pressure. The device consists of a cathode atomizer with a test sample applied onto it and the anode located at 1–3 mm from the cathode. The electrons emitted by the cathode upon heating are accelerated by applying a constant voltage to the electrodes. The mechanism for the formation of a non-self-sustained gas discharge between the cathode and anode is considered and the properties of the discharge are compared to those of the known discharges used in atomic emission spectrometry. The influence of atomization temperature and helium pressure on the analytical and background signals was studied. It is shown that, under certain conditions, the analytical signal increases with helium pressure. The relative detection limits attained for a number of elements are from tenths to dozens of nanogram per liter; this is two or three orders of magnitude lower than those in inductively coupled plasma atomic emission spectrometry and of the same order of magnitude as detection limits in inductively coupled plasma mass spectrometry.     

Bridging the gaps in analytical atomic absorption spectrometry

The techniques of analytical, valence electron, atomic spectrometry (absorption, fluorescence and emission), by themselves, are mainly for the determination of the amount of an element in a sample which has been prepared as a . For a large fraction of trace element analysis such an approach is satisfactory. However, there are some other very important requirements in trace element analysis not now adequately being addressed by analytical atomic spectrometry. A selection of these, familiar to the present writer, will be covered in this presentation. Some interesting initiatives to “bridge the gaps” are now being made. The topics to be discussed are; elemental speciation, direct analysis of solids, elemental and natural isotope analysis using plasma sources, micro analysis by laser probe and vapour generation approaches to improved detection limits. This is not intended to be an exhaustive review of these subject areas but will present material of interest together with recently published key papers. Greatest emphasis is given to the very important topic of speciation.     

Status and future prospects for use of the graphite furnace for elemental trace analysis of liquids and solids

Summary An overview of the versatility and use of the graphite furnace for elemental trace analysis of liquids and solids using spectrochemical detection is presented. The analytical performance of conventional graphite furnace atomic absorption spectrometry is compared to other popular state of the art spectrochemical techniques with respect to detection power, precision, sample compatibility and throughput. Some applications of the graphite furnace to practical problem solving in trace analysis are highlighted, including its use with atomic absorption, coherent forward scattering, laser excited atomic fluorescence, laser enhanced ionization and coupled methodologies. Prospects for future use and evaluation are given.     

Comparison of electrothermal atomization diode laser Zeeman- and wavelength-modulated atomic absorption and coherent forward scattering spectrometry

Atomic absorption and coherent forward scattering spectrometry by using a near-infrared diode laser with and without Zeeman and wavelength modulation were carried out with graphite furnace electrothermal atomization. Analytical curves and limits of detection were compared. The magnetic field was modulated with 50 Hz, and the wavelength of the diode laser with 10 kHz. Coherent forward scattering was measured with crossed and slightly uncrossed polarizers. The results show that the detection limits of atomic absorption spectrometry are roughly the same as those of coherent forward scattering spectrometry with crossed polarizers. According to the theory with bright flicker noise limited laser sources the detection limits and linear ranges obtained with coherent forward scattering spectrometry with slightly uncrossed polarizers are significantly better than those obtained with crossed polarizers and with atomic absorption spectrometry. This is due to the fact that employing approaches of polarization spectroscopy reduce laser intensity fluctuations to their signal carried fractions.     

Development of electrothermal atomic absorption spectrometry in 2005–2016

The review covers publications of 2005–2016 on achievements in the development of electrothermal atomic absorption spectrometry (ETAAS). The main directions in the authors’ opinion are revealed, i.e., (1) improvements of the method and equipment and (2) studies of thermochemical processes in a graphite furnace. In the first group, the authors consider high- and low-resolution continuum source atomic absorption spectrometry, diode laser atomic absorption spectrometry, new designs of electrothermal atomizers, and new devices for ETAAS. Studies of mechanisms of element atomization, formation of analytical signals, and action of chemical modifiers belong to the second group.     

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.     

Comparison of atomic absorption,mass and X-ray spectrometry techniques using dissolution-based and solid sampling methods for the determination of silver in polymeric samples

In this work, the capabilities and limitations of solid sampling techniques – laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS), wavelength dispersive X-ray fluorescence spectrometry (WD-XRFS) and solid sampling electrothermal atomic absorption spectrometry (SS-ETAAS) – for the determination of silver in polymers have been evaluated and compared to those of acid digestion and subsequent Ag determination using pneumatic nebulization ICPMS (PN-ICPMS) or flame AAS (FAAS).     

Organic ion imaging of biological tissue with secondary ion mass spectrometry and matrix-assisted laser desorption/ionization

Organic secondary ion mass spectrometry (SIMS) and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry can be used to produce molecular images of samples. This is achieved through ionization from a clearly identified point on a flat sample, and performing a raster of the sample by moving the point of ionization over the sample surface. The unique analytical capabilities of mass spectrometry for mapping a variety of biological samples at the tissue level are discussed. SIMS provides information on the spatial distribution of the elements and low molecular mass compounds as well as molecular structures on these compounds, while MALDI yields spatial information about higher molecular mass compounds, including their distributions in tissues at very low levels, as well as information on the molecular structures of these compounds. Application of these methods to analytical problems requires appropriate instrumentation, sample preparation methodology, and a data presentation usually in a three-coordinate plot where x and y are physical dimensions of the sample and z is the signal amplitude. The use of imaging mass spectrometry is illustrated with several biological systems.     

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.     

电热原子吸收分析中的固体进样技术

本文综述了电热原子吸收分析中固体进样技术的进展,详细讨论了固体直接进样和悬浮体进样和样品制备方法、进样工具、校正曲线、基体改进技术、分析性能及其最新应用。     

Determination of gold and palladium in rocks and ores by atomic absorption spectrometry using two-stage probe atomization

The efficiency of two-stage probe atomization for the determination of gold and palladium in geological samples by electrothermal atomic absorption spectrometry is studied. The effects of temperature–time program and the position of the probe in an atomizer on the fractionation of sample components and the magnitude of the analytical signal are studied. It is demonstrated that gold and palladium can be quantitatively determined by atomic absorption spectrometry in rocks and ores, using a two-stage probe atomization with the limits of detection for gold and palladium 0.01 and 0.04 g/t, respectively.     

The influence of laser-particle interaction in laser induced breakdown spectroscopy and laser ablation inductively coupled plasma spectrometry

Particles produced by previous laser shots may have significant influence on the analytical signal in laser-induced breakdown spectroscopy (LIBS) and laser ablation inductively coupled plasma (LA-ICP) spectrometry if they remain close to the position of laser sampling. The effects of these particles on the laser-induced breakdown event are demonstrated in several ways. LIBS-experiments were conducted in an ablation cell at atmospheric conditions in argon or air applying a dual-pulse arrangement with orthogonal pre-pulse, i.e., plasma breakdown in a gas generated by a focussed laser beam parallel and close to the sample surface followed by a delayed crossing laser pulse in orthogonal direction which actually ablates material from the sample and produces the LIBS plasma. The optical emission of the LIBS plasma as well as the absorption of the pre-pulse laser was measured. In the presence of particles in the focus of the pre-pulse laser, the plasma breakdown is affected and more energy of the pre-pulse laser is absorbed than without particles. As a result, the analyte line emission from the LIBS plasma of the second laser is enhanced. It is assumed that the enhancement is not only due to an increase of mass ablated by the second laser but also to better atomization and excitation conditions favored by a reduced gas density in the pre-pulse plasma. Higher laser pulse frequencies increase the probability of particle-laser interaction and, therefore, reduce the shot-to-shot line intensity variation as compared to lower particle loadings in the cell. Additional experiments using an aerosol chamber were performed to further quantify the laser absorption by the plasma in dependence on time both with and without the presence of particles. The overall implication of laser-particle interactions for LIBS and LA-ICP-MS/OES are discussed.     

Capillary Electrophoresis Coupled On-Line with Inductively Coupled Plasma Atomic Emission Spectrometry for Elemental Speciation

Capillary electrophoresis (CE) has become a powerful analytical technique for the separation of a variety of analytes ranging from small inorganic ions to large biomolecules such as proteins and nucleic acids. A selective and sensitive detector for CE has been one of the most important and challenging prerequisites for the growth of CE. On-column UV-Vis detectors are commonly used to determine the analytes separated by CE. However, these detectors are often not very selective. Other detection techniques such as mass spectrometry, laser induced fluorescence, amperometry, and inductively coupled plasma spectrometry have been investigated to provide a more sensitive and selective detection for the target analytes. However, relatively few studies have been published on the use of inductively coupled plasma atomic emission spectrometry (ICP-AES) as a means of detection in CE separation.