Evaluation of tungsten coil electrothermal vaporization-Ar/H2 flame atomic fluorescence spectrometry for determination of eight traditional hydride-forming elements and cadmium without chemical vapor generation

A tungsten coil electrothermal vaporizer (W-coil ETV) was coupled to an Ar/H(2) flame atomic fluorescence spectrometer for the determination of eight traditional hydride-forming elements (i.e., As, Bi, Ge, Pb, Sb, Se, Sn, and Te) as well as cadmium without chemical vapor generation. A small sample volume, typically 20muL, was manually pipetted onto the W-coil and followed by a fixed electric heating program. During the vaporization step, analyte was vaporized off the coil surface and swept into the quartz tube atomizer of AFS for further atomization and excitation of atomic fluorescence by a flow of Ar/H(2) gas, which was ignited to produce the Ar/H(2) flame. The tungsten coil electrothermal vaporizer and Ar/H(2) flame formed a tandem atomizer to produce reliable atomic fluorescence signals. Under the optimal instrumental conditions, limits of detection (LODs) were found to be better than those by flame atomic absorption spectrometry (FAAS) or inductively coupled plasma optical emission spectrometry (ICP-OES) for all the nine elements investigated. The absolute LODs are better or equivalent to those by hydride generation atomic fluorescence spectrometry (HG-AFS). Possible scattering interferences were studied and preliminary application of the proposed method was also reported.     

Comparison of the helium/oxygen/acetylene and air/acetylene flames as atom sources for continuum-source atomic fluorescence spectrometry

The helium/oxygen/acetylene flame is compared to the more widely used air/acetylene flame for its utility as an atom cell for atomic fluorescence spectrometry. Nearly identical experimental arrangements were used for both flames in order to make the comparison valid. With a continuum source used for excitation, fluorescence detection limits in the helium/oxygen/acetylene flame were between 13 and 60 times better (lower) than those determined for the same eight elements in the air/acetylene flame. The improved detection limits are attributable mainly to the higher temperature, increased thermal conductivity and lower quenching in the helium flame. Fluorescence background spectra were obtained for both flames over the wavelength range 185–650 nm, and showed the helium flame to have slightly smaller background fluctuations, but a much larger background because of the more favorable fluorescence conditions in the flame.     

Construction and performance of a time-multiplex multiple-slit flame atomic fluorescence spectrometer for multi-element analysis

The design and performance characteristics of a new multi-element flame atomic fluorescence spectrometer are presented. Radiation from four hollow-cathode tubes is directed onto an unsheathed air—hydrogen flame. The resulting atomic fluorescence is viewed by a special monochromator with a separate exit slit for each element. The light exiting from all slits is directed to a single photomultiplier tube. The fluorescence signals from different elements are distinguished by a time multiplex approach. Single-element detection limits for ten elements and multi-element detection limits for four elements are presented. The degradation of detection limits by flame background emission noise and effect of flame composition on performance are discussed. Better than 1% precision is obtained for moderate analyte concentrations.     

Comparison of atomic fluorescence power efficiencies for the helium-oxygen-acetylene and air-acetylene flames

Power efficiencies for five elements have been measured for the helium-oxygen-acetylene and air-acetylene flames. The increased power efficiencies found in this study for the helium-diluted flame, coupled with its enhanced atom-formation capabilities, suggest that lower atomic fluorescence detection limits should exist. However, in a comparison study with an air-acetylene flame using identical experimental conditions, a decreased atomic fluorescence signal-to-noise ratio was found for most elements in the helium-diluted flame. This decrease is ascribed to greater background emission noise in the hotter helium-diluted flame and decreased nebulization efficiency caused by the low density of the helium-containing nebulizer gas. A comparison of flame emission detection limits for the two flames confirms the increased sensitivity of the hotter helium-oxygen-acetylene flame, despite its lower nebulization efficiency.     

Studies in atomic fluorescence spectrometry: Part II. Interference effects in the determination of tin with various premixed flames

The interference effects are reported for 27 elements, 6 acids and 4 organic liquids on the atomic fluorescence determination of tin with argon-hydrogen, argon-oxygen-hydrogen and argon-separated air-acetylene flames. The addition of1000 p.p.m. iron (III) eliminates most interferences from the elements but not from the acids. The basic trends in the interference effects in the argon-hydrogen flame for the atomic absorption and atomic fluorescence determinations of tin are similar. The detection limit, for an 18.2-s time constant, in the argon-oxygen-hydrogen and argon-hydrogen flames is 0.006 p.p.m. and in the air-acetylene flame it is 0.05 p.p.m. These detection limits are significantly better than previously reported limits. Analytical curves in all three flames studied are linear between the detection limits and 250 p.p.m.     

Line selection and interference correction for the analysis of tungsten alloy by inductively coupled plasma atomic emission spectrometry

A method for the analysis of tungsten alloy to determine selected elements using inductively coupled plasma atomic emission spectroscopy is described, with emphasis on line selection and spectral interference. The spectral interference coefficients were calculated for the spectral lines of selected major and trace elements. These values were used to select analytical lines and to calibrate concentrtions of the analytes. The detection limits of the elements for this method were determined and compared with those obtained by flame atomic absorption spectrometry and direct current carbon are emission spectrometry. The results indicated that the detection limits for all of the elements determined by the proposed method are significantly better than those obtained by other techniques. In this study, the analytical reliability of the proposed method was estimated by comparison of the analytical data for the two types of tungsten alloys produced by the Korean Tungsten Company with those obtained by the matrix matching method and the results indicated that the accuracy of multi-element analysis is satisfactory.     

Atomiser, source, inductively coupled plasmas, in atomic fluorescence spectrometry (ASIA). Some recent work

The dual-plasma atomic fluorescence/atomic emission spectrometer (ASIA spectrometer) is described and the detection limits for several elements in both the fluorescence and the emission mode are presented and compared directly. The detection limits for the non-refractory elements are, in general, better in fluorescence than emission While for the refractory elements the converse is true, but all are in the ng ml⁻¹ range. Growth curves for a refractory and a non-refractory element are presented and evaluated.     

Multielement atomic absorption analysis using Hadamard transform spectroscopy with a new computation and superposition procedure

The application of Hadamard transform spectroscopy (HTS) to analytical atomic spectroscopy has been investigated. A theoretical examination of the signal to noise ratio indicates that HTS offers a slight multiplex advantage over single slit scanning of the spectrum for the measurement of intense lines, as in atomic absorption, but is disadvantageous for measuring small signals in atomic emission and fluorescence. Using a simple HT spectrometer Mg and Pb were determined simultaneously by flame atomic absorption spectrometry. Sensitivities similar to those of conventional systems were obtained but, owing to instrumental imperfections and a short data collection time, detection limits were worse. Optimum system performance was obtained when the mask interval width was equal to the width of the image of the spectrometer entrance slit. Greater spectral detail was revealed by superposition of a set of computed spectra in which the starting point of each spectrum was displaced from the others by a distance less than the interval width of the Hadamard mask. This approach gave improved spectra without increased instrumental complexity.     

Laser excited atomic fluorescence of some transition elements in the nitrons oxide-acetylene flame

A pulsed, tunable dye laser, pumped with a nitrogen laser is used to excite the atomic fluorescence of Sc, V, Hf, Nb, Os, Zr, W, Rh and Ru. Except in the case of Rh, the nitrous oxide-acetylene flame has been used. The results obtained for Zr and W are due to scattering of the laser radiation from unvaporized particles in the flame. Since, for most elements, several fluorescence lines of comparable intensity have been observed after the primary excitation process, the usefulness of observing non-resonance fluorescence is stressed, particularly with regard to the possibility of minimizing spectral interferences. The experimental results demonstrate that the limits of detection obtained with the dye laser source are comparable or better than the best atomic absorption limits only when the same primary absorption line used for the atomic absorption measurements can be used for exciting the fluorescence.     

Atomic absorption spectrometry and other instrumental methods for quantitative measurements of arsenic

Progress in instrumental methods for quantification of arsenic during the past decade is reviewed. Particular emphasis is placed on atomic absorption spectrometry, where major progress has been made in flame methods in conjunction with hydride generation procedures and in electrothermal methods with the graphite furnace. Specific materials in which arsenic is quantified by atomic absorption techniques are also listed. Progress in the application of neutron activation—γ-spectrometry, emission spectrometry, electrometric methods, x-ray procedures and atomic fluorescence spectrometry is also reviewed. The limits of detection and time requirements of all the techniques are compared.     

Anregung von Spektren durch niederenergetischen Elektronenstoβ mit Anwendung als Lichtquelle für Spektralanalyse

Detection limits of atomic absorption spectroscopy (AAS) and atomic fluorescence spectroscopy (AFS) have been improved by the use of a King furnace. In atomic emission spectroscopy, however, the King furnace was hitherto used only in connection with thermal or RF excitation.The object of this work was to combine the advantages of the King furnace and the advantages of excitation by electron impact for AES. A light source based on a work by Ritschl in 1932 was built. The device consists of a King furnace for sample evaporation. Excitation of atoms is achieved by separate production and acceleration of electrons.The spectrochemical application of this excitation method was tested with Cd, Mg, Hg and B. Detection limits were measured and compared with those attained by other methods. Detection limits are better than those of comparable AES methods using thermal light sources. They compete favourably with those of AAS and AFS using a graphite crucible. The detection limit of Cd, for example, is 3·10^?13 g.The source was applied to determine traces in spectral graphite and to study the transport of material between the electrodes in high-voltage spark.     

Gas-Phase Sample Introduction Techniques in Plasma Atomic Emission Spectrometry

Clearly, the introduction of sample materials in the gas phase is an ideal technique for analytical atomic spectroscopy, i.e., atomic absorption, atomic emission and atomic fluorescence spectrometry.     

Measurement of Cr(III)/Cr(VI) species by wavelength modulation diode laser flame atomic absorption spectrometry

High-performance flow atomic spectrometry of Cr(III) and Cr(VI) species by high-performance liquid chromatography (HPLC) separation, hydraulic high-pressure nebulization (HHPN) for sample introduction and wavelength modulation-laser atomic absorption spectrometry (WM-LAAS) with diode lasers in an analytical flame is reported. 3σ detection limits of 0.5 and 1 ng ml⁻¹ have been obtained for Cr(VI) in deionized and drinking water, respectively. Due to relatively high blank levels, the corresponding detection limits of Cr(III) are higher than for Cr(VI), i.e. 1.6 ng ml⁻¹ in deionized water and 5 ng ml⁻¹ in drinking water.     

A demountable boosted-output spectral lamp for atomic absorption and fluorescence measurements

A demountable boosted-output spectral lamp is described that permits easy exchange of the cathode, which is in the form of a disc pressed from the appropriate powder or machined from rod. The new lamp overcomes to a large extent the major disadvantage of the conventional boosted hollow-cathode lamp, namely the interaction of the sputtering and boosting discharges. In flame atomic absorption spectrometry it yields calibration curves more nearly linear than those obtained with commercial hollow-cathode lamps. In non-dispersive flame atomic fluorescence it permits the attainment of detection limits rather better than those obtained with other high-intensity light sources.     

Measurement of relative atomic transition probabilities using flame atomic absorption spectroscopy

A simple and straightforward technique has been developed to measure relative atomic transition probabilities (A_ji) using flame atomic absorption spectroscopy (FAAS). A_ji values for Cu, Ag, Mn and Mo are calculated from absorption measurements in an air—acetylene flame using both line emission (AAL) and continuum excitation (AAC) sources. For Mn and Mo, large discrepancies for A_ji are found between AAL and AAC, which may be attributed to hyperfine structure (hfs). For continuum source measurements the absorbance is independent of the absorption line profile thus eliminating the problems associated with hfs. Therefore, AAC provides a more accurate method for relative A_ji measurements, with determinations of better than 10% relative standard deviation for all elements.     

Comparative studies on the fluorescence behaviour of some mono- and diaminopyridines

The fluorescence characteristics of 2-, 3- and 4-aminopyridine, 2,3-, 3,4- and 2,6-diaminopyridine, and 2-amino-6-picoline were investigated in various solvents and at different pH values. 4-Aminopyridine exhibits negligible fluorescence probably because of (n, π^*) transitions. All other compounds are strong fluorophores, which is mainly due to the (π, π^*) nature of the lowest excited state. Practical data for the fluorimetric determination of small amounts of these molecules are reported, i.e. excitation and emission maxima, relative fluorescence intensities, optimum pH, limits of linearity, detection limits, and ultraviolet absorption maxima; 0—0 bands, and variation of excitation and emission wavelengths and of fluorescence intensities with pH are also reported. Even nanogram amounts can be identified and determined.     

微波辅助消解-原子荧光法测定玻璃中的镉砷铅

光学玻璃中的各种元素对玻璃的光学性能有不同的影响。如加入镉可以提高玻璃折射率;砷的引入能增加玻璃的透光度,含铅玻璃具有低成本、高折射性等优点。但是镉、砷、铅均为有毒元素,玻璃加工和处理过程以及毒废弃物的处理都可能引起水、土壤、大气的污染并给人体带来一定的危害     

食品中无机盐检测方法研究进展

介绍了食品中无机盐前处理和检测技术研究进展,主要阐述了包括火焰原子吸收光谱法、石墨炉原子吸收光谱法、电感耦合等离子体原子发射光谱法、原子荧光光谱法、X射线荧光光谱法及联用等技术在近年来的应用,并对以后的发展方向进行了展望。     

Mechanical feed burner with total consumption for flame photometry and atomic absorption spectroscopy

A mechanical feed burner has been developed for use in flame photometry and atomic absorption spectroscopy. The optimum flame conditions for cinisaion and absorption are very different. These conditions are also modified when organic instead of aqueous solvents are used. When different organic solvents are used, the interference is eliminated with atomic absorption but not emission. Flame profiles of a.tomic absorption and emission signals indicate that the processes are independent; the best signal for each is obtained at different parts of the flame. With emission, it appears that line spectra and background emission originate from the same process e.g. chemiluminescence     

Combination of flow-injection techniques with atomic spectrometry in agricultural and environmental analysis

Combinations of flow-injection techniques with flame atomic absorption spectrometry (a.a.s.) and inductively-coupled plasma/atomic emission spectrometry (i.c.p./a.e.s.) are reviewed in the general context of agricultural and environmental analysis. The flow-injection systems are valuable for sample introduction; appropriate dispersion control allows the analysis of solutions containing as much as 40% (w/v) urea or phosphate in fertilizers. A study on the determination of cadmium in soil extracts by on-line ion-exchange preconcentration and flame a.a.s. detection is described. The interpolative standard-addition method with i.c.p./a.e.s. detection is outlined. Improvements in the determinations of selenium in environmental samples by hydride-generation a.a.s. and of mercury by cold-vapour a.a.s. are reported.