Determination of Se,Pb, and Sb by atomic fluorescence spectrometry using a new flameless,dielectric barrier discharge atomizer

A flameless atomizer for atomic fluorescence spectrometry (AFS), based on an atmospheric pressure dielectric barrier discharge, has been developed for the atomization of hydride-forming elements, such as Se, Sb and Pb. The atomizer (8 mm o.d, 35 mm length) was operated at a power less than 50 W. The discharge was sustained with argon at the flow rate of 0.85 L min^− 1 after optimization. The characteristics of the atomizer and the effects of different parameters (power, gas flow rate, and KBH₄ concentration) are investigated. The most attractive feature of this atomizer is its low operation temperature (~ 52 °C, detected at the outlet of the atomizer by a thermocouple), allowing both the radiation source and the detector to be placed in close proximity with the atomizer. The analytical performance of the atomizer has been evaluated, and detection limits for Se, Sb and Pb obtained with the present technique were 0.08, 0.11 and 0.27 μg L^− 1, respectively. The accuracy of the system was verified by the determination of Se, Sb and Pb in reference material of spinage GBW 10015. The concentrations of Se, Sb, and Pb determined by the present technique agreed well with the reference values (Se: 92 ± 24 mg kg^− 1, Sb: 43 ± 14 mg kg^− 1, Pb: 11.1 ± 0.9 mg kg^− 1). This detector is very promising for field elements detection with portable AFS.     

A simple,low cost,multielement atomic absorption spectrometer with a tungsten coil atomizer

An inexpensive, multielement atomic absorption spectrometer utilizing a tungsten coil atomizer has been developed. The novel optical arrangement employs three 60° beam combiners to blend the spectral output from four light sources such as electrodeless discharge lamps, or hollow cathode lamps, and then direct that output over an atomizer. This instrument uses an inexpensive tungsten coil atomizer that is extracted from a standard 150 W projector bulb. The temperature of the coil is computer-controlled by changing the voltage across the coil. A low voltage is first used to dry the sample then a higher voltage is used to atomize the sample. Simultaneous detection of the analyte absorption signals is accomplished using a charge-coupled device. The elements of interest in this study were Cd, Pb, and Cu. Near-line background correction was used to correct for nonspecific analyte absorption.     

ET-AAS determination of traces of As, Sb and Sn in pure gold after matrix separation with hydrazine

Summary The possibilities of ET-AAS using the graphite furnace or the tungsten coil atomizer were compared by the trace As, Sb and Sn determination in the chloride-containing solution resulting after gold reduction with hydrazine. It was found that the tungsten coil atomizer tolerates higher concentrations of chloride ions than the conventional graphite furnace.     

Electrothermal atomization from metallic surfaces: Part 1. Design and Performance of a tungsten-tube atomizert

A tungsten-tube atomizer has been developed and tested for a number of elements. The atomizer can be accommodated in the support of a commercial Varian carbon rod atomizer (CRA-63 or CRA-90) and operated as an alternative to the graphite tubes and cups. Characteristic concentrations, detection limits, optimum atomization temperatures, reproducibility and profiles of calibration curves obtained for Ag, Al, Ba, Cd, Co, Cu, Mg, Mn, Ni, Pb and V are similar to those obtained with the graphite-tube atomizer. The main advantage of this atomizer is its simple construction, low cost, long lifetime and excellent analytical performance, particularly for elements forming refractory carbides.     

Electrothermal Atomization Atomic Absorption Spectrometry with Platinum Tube Atomizer in Air

Abstract

An electrothermal atomization method of atomic absorption spectrometry using a platinum tube atomizer in air is described. The atomizer consists of 0.025 mm-walled platinum tube and two supports. The remarkable merit of the platinum atomizer is the stability in air, when heated. This paper describes the improved performance for volatile elements like alkalimetals. Detection limits and characteristic mass are calculated for 7 elements and compared with literature values. The platinum atomizer can be used with a simple, effective and relatively low-cost atomic absorption spectrometer for routine in situ analysis.     

Application of atmospheric pressure dielectric barrier discharge plasma for the determination of Se,Sb and Sn with atomic absorption spectrometry

The atomization of hydride-forming elements, Se, Sb and Sn, has been studied with an atmospheric pressure dielectric barrier discharge atomizer. The elements were first converted to hydride through the reaction with NaBH₄. Then the hydride were atomized in the atomizer and detected by atomic absorption spectrometry. The effects of operational parameters such as power, gas flow rate and concentrations of HCl and NaBH₄ were investigated. Compared with other hydride atomization methods, the proposed atomizer shows the following features: (1) small size, which is preferable for the miniaturization of the total analytical system; (2) low temperature, which would be helpful for further improvement in the compactness of the total analytical system; (3) low power consumption, which is also necessary for the development of analytical instrumentation for in situ detection of environmentally important elements. The analytical performance of the atomizer has also been investigated. The detection limits of Sb, Se and Sn obtained with the present method were 13.0, 0.6 and 10.6 μg l^− 1. This detector is a very promising technique for hydride detection.     

Electrothermal atomization from metallic surfaces: Part 3. Some new developments in design and performance of a tungsten-tube atomizer

A new design of a work-head for a tungsten-tube atomizer as well as voltage- and temperature-feedback circuits added to the power supply of a Varian model CRA-63 atomizer are described. The importance of rapid, temperature-controlled heating of the atomizer is shown. The effect of heating rate (0.5–20 K ms^-1) on the analytical signal of many elements is investigated; experimental atomization and residence times and peak absorbance values are evaluated. The analytical performance of the tungsten-tube atomizer is tested for elements of different volatilities.     

便携式钨丝电热原子吸收光谱仪测定水样中铜、铬、铅和镉

以钨丝原子化器和小型化CCD检测器为主要部件,组装了便携式钨丝电热原子吸收光谱分析仪,优化了载气(Ar/H2) 流速、空心阴极灯位置、原子化器高度、灰化和原子化电流等主要仪器条件.最佳载气(Ar/H2)流速(mL/min)为600 /300(Cd),800/200(Cu, Pb, Cr);灰化电流为2.9～3.2 A;原子化电流为8.5 A;CCD的积分时间为50 ms.并在优化的仪器条件下准确测定了环境水样中的铜(Cu)、铬(Cr)、铅(Pb)和镉(Cd),进样10 μL时,其检出限分别为2、5、9和0.5 μg/L.此便携式原子吸收光谱仪在环境水样痕量元素分析中可望有良好的应用前景.     

Comparative Study of the Effect of Sample Matrix on the Atomic Absorption of High-Volatile Elements in Two-Step and Conventional Atomizers

The space–time dynamics of absorbing atomic layers of cadmium and lead and molecular layers of zinc chloride in a commercially produced transverse-heated graphite atomizer and a newly developed two-step atomizer was studied. It was shown that the limiting temperature of cadmium pyrolysis in the two-step atomizer without the use of modifiers may be as high as 1000°C, whereas in the commercial analyzer is it not higher than 300°C. Levels of nonselective absorption due to sodium chloride were compared. It was found that, for a two-step atomizer, the maximum allowable mass of sodium chloride for which the background at lead and cadmium lines can be adequately compensated is 17–30 times higher than that for the commercial atomizer. The atomization of cadmium in the presence of sodium chloride was studied using time, space, and spectral resolution. It was shown that the effect of the chloride matrix in the two-step atomizer is suppressed because of sample fractionation and distillation in the course of its evaporation and condensation.     

Temperature distribution in a tungsten electrothermal atomizer

Temperature distribution in the tube surface of a tungsten electrothermal atomizer (WETA-82) has been studied both theoretically and experimentally; also, the temperature distribution in the gas inside the atomizer has been studied theoretically. A theoretical model of the temperature distribution in the tube surface and in the gas inside the atomizer is proposed. It is considered that thermal radiation to the surroundings and beat conduction towards the water-cooled electrode supports are the only paths for heat loss, and electrical resistive heating and conduction from adjacent nodes are the only sources of heat gain. The time rate of change in temperature of the atomizer is expressed in the form of a differential equation. A finite-difference form of the differential equation is used in a computer program to calculate the temperature at each time step. Optical pyrometry was used to determine the surface temperature of the tube atomizer. The model predicts that an increase in the heating rate of the tube atomizer will slightly decrease the temperature gradient over the tube circumference; however, unambiguous observation of this decrease could not be made in the sequentially measured temperature difference between two selected point using optical pyrometry. Variation in the hydrogen content of the hydrogen-argon mixture purge gas did not have a significant effect on the temperature gradient of the tungsten tube surface. The results of this study have indicated possible improvements in the atomizer design with a view to making the temperature distribution over the circumference of the tube atomizer more uniform.     

Application of Microflame Atomizer to Gas Chromatography-Atomic Absorption Spectrometry

One of the successful methods for the determination of organometallic compounds is the combination of Gas Chromatography-Atomic Absorption Spectrometry (GC-AAS). The atomizer of AAS was connected with the column of GC by a transfer tube. Three types of the atomizer were reported as flame burner,electrothermal quartz tube and graphite furnace. A large amount of gas or electric energy was required to produce a high temperature for the atomization of analytes, A microflame atomizer of GC-AAS was developed in this paper to circumvent above problems. The volume of the atomizer is one-fifth of the normal flame burner, and a hydrogen gas was used as the carrier gas (35ml/min) and the fuel gas for the atomization of analytes.     

Tungsten coil devices in atomic spectrometry: absorption, fluorescence, and emission.

In this work, tungsten coil (W-Coil) devices are used as atomizers for electrothermal atomization atomic absorption spectrometry (ETAAS), electrothermal atomization laser excited atomic fluorescence spectrometry (ETA-LEAFS), and electrothermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES). For most cases in ETAAS and ETA-LEAFS, limits of detection (LODs) using the W-Coil are within a factor of ten of those observed with commercial graphite furnace systems. LOD for Cd by W-Coil AAS is 10 pg, while LODs for As, Se, Cr, Sb and Pb by W-Coil LEAFS are 950, 320, 1400, 330, and 160 fg, respectively. The compact W-Coil device makes it an ideal atomizer for portable atomic spectrometry instrumentation, especially when coupled with a miniature charge coupled device spectrometer. Alternatively, the atomizer can be used as an inexpensive, modular add-on to an existing commercial ICP-AES system; and the thermal separation of Pb with interference elements Al, Mn, and Fe is demonstrated.     

Vaporization of atoms and molecules during heating of cadmium,lead and zinc salts in a carbon tube atomizer

Vaporization characteristics of atoms and molecules produced during heating of aqueous solutions of Cd, Pb and Zn salts in the carbon tube atomizer are described. Sulfates, nitrates and fluorides are decomposed completely to free atoms without losses. When concentrated halide solutions are employed, gaseous metal chlorides, bromides and iodides are removed partly from the atomizer in the initial atomization phase, and the atomic absorption response is decreased. This loss can be suppressed effectively by adding nitric or sulfuric acid to the halide solutions.     

Electrothermal atomization from metallic surfaces: Part 2. Atom formation Processes in the tungsten-tube atomizer

A modified carbon rod atomizer (Varian M-63) is used to study the mechanism of atom formation of Al, Ba, Co, Pb, Ni and V in a tungsten-tube atomizer by a combined thermodynamic—kinetic approach. The atomizer is made from two profiled tungsten strips held in two copper supporting electrodes and forming a cylindrical cavity (5 mm long, 4 mm i.d.). Appearance temperatures and atomization energies are compared with those obtained for a graphite-tube atomizer. The major pathways leading to gaseous atoms are thermal dissociation of the metal oxide (or hydroxide) and reduction of the metal oxide followed by the atomization of free metal, depending on the protecting atmosphere (argon or argon—hydrogen mixture) and analyte.     

Direct atomic absorption determination of mercury in drinking water and urine using a two-step electrothermal atomizer

A new method was developed for the direct electrothermal atomic absorption determination of mercury in drinking water and urine using double vaporization in a two-step atomizer with a purged vaporizer. In this method, a sample is placed in the vaporizer of a two-step atomizer, dried, and vaporized. The sample vapor is transferred to an unheated atomizer cell with a flow of argon and trapped by the inner surface of cell walls. This procedure can be performed repeatedly to preconcentrate mercury in the atomizer cell. Next, a portion of the sample transferred to the inner surface of the atomizer cell is revaporized and atomized by heating the atomizer cell of the two-step atomizer with a purged vaporizer, and the atomic absorption of mercury is measured. It was found that the degree of mercury transfer and trapping is as high as 100% at sufficiently high temperatures of primary vaporization, regardless of the material of the inner surface of the atomizer cell. The detection limits for mercury were 0.24 or 0.024 µg/L for drinking water at a sample volume of 100 µL using a single sample transfer or the procedure repeated ten times, respectively, and 2.0 µg/L for urine at a sample volume of 20 µL and a single sample transfer. The accuracy of the results was confirmed by the analysis of certified mercury samples and samples with known additives.Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 1, 2005, pp. 45–51.Original Russian Text Copyright © 2005 by Vilpan, Grinshtein, Akatov, Gucer.     

A method for reduction of matrix interferences in a commercial electrothermal atomizer for atomic absorption spectroscopy

A CRA-63 atomizer has been modified by replacement of the conventional center supports with 2-pronged supports that hold the atomizer tube at both ends. This arrangement allows current to flow only across the atomizer ends. The center is heated by conduction. Large initial temperature differences (750–900 K) between the sample-containing center and the ends eliminates or decreases the interferences on Pb normally observed with this atomizer. Six chloride and one sulfate matrices were studied.Longer atomizers and higher power produced the largest temperature differences and, therefore, the best lead recoveries. At a given length, recovery eventually plateaued while the signal for lead in the absence of matrices decreased when heating power was further increased. It was concluded that further improvements would require longer tubes and a combination of end and center heating.The importance of considering interferent/analyte ratios in interpreting recovery data was examined for the interference of MgCl₂ on lead.     

原子荧光光度计在砷测定过程中出现的一例故障及故障排除方法

介绍了原子荧光光度计中原子化器温度降低在砷测定过程的故障现象、故障诊断及故障排除方法。阐述了由于测定原理不同,原子化器温度降低对砷、硒、汞检测影响的差异。     

Electrothermal atomization with a metal micro-tube in atomic absorption spectrometry

The processes of atom formation and dissipation in a molybdenum micro-tube atomizer have been studied to obtain information on the reaction involved. Vapor temperature was found to be close to atomizer surface temperature. Appearance temperatures and activation energies were obtained for Al, Co, Cu, Mn, Pb, Sb, Se, Sn and Te in argon and argon-hydrogen atmospheres. The atom formation processes are divided into two groups : the reduction of the metal oxide followed by the atomization of free metal, and thermal dissociation of the metal oxide. Hydrogen significantly changes atom formation processes for some metals compared to those in pure argon. The dissipation process of atoms from the micro-tube atomizer appears to be purely gas-phase diffusional.     

Einsatz der flammenlosen Atom-Absorption (Graphitrohrküvette) zur Bestimmung von Kupferspuren in Stahl und anderen Metall-Legierungen nach Extraktion

The determination of small and smallest amounts of copper in steel and other metal alloys by atomic absorption spectroscopy was investigated. It has been found, that the interferences caused by accompanying elements in the determination in aqueous solution with the flame can be completely removed by extracting the copper with Pb-DDTC in chloroform and determining this extract with the heated graphite atomizer. Moreover, it was recognised, that working with the heated graphite atomizer in organic solutions shows great advantages compared with the flame, because any solvent may be used. The methods of continuous variation by Job and the molar ratio by Yoe and Jones for the determination of the complex stoichiometry were transferred to the system Cu-DDTC by working with the heated graphite atomizer.     

Atomic Absorption Spectrometry with Thin-Wall Tungsten Tube Atomizer in the Presence of Ammonium Thiocyanate

Abstract

A sensitive atomic absorption spectrometry with a thin-wall tungsten tube atomizer is described. By addition of thiocyanate, sensitivities and detection limits were improved over that of a conventional atomizer for several elements.