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.     

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.     

Multiple microflame quartz tube atomizer — further development towards the ideal hydride atomizer for atomic absorption spectrometry

The development of an improved type of hydride atomizer for atomic absorption spectrometry — multiple microflame quartz tube atomizer (MMQTA) — is presented. The main feature of this atomizer is recurrent analyte atomization proceeding over its whole optical tube length, which is achieved by production of H-radicals at multiple points within the tube by oxygen microflames burning in the hydrogen-containing atmosphere. The MMQTA design optimization leading to a complete filling of the observation volume with H-radicals is described. The influence of individual atomization parameters is discussed. Optimum H-radical producing oxygen intake into the MMQTA was found to correspond to a H₂:O₂ stoichiometric (3:1) ratio. The performance of the individual MMQTA tube designs is evaluated and compared to a typical externally heated quartz tube atomizer (EHQTA) — the linearity of calibration graphs for As, Se and Sb is significantly improved in all MMQTA tubes, without compromising the sensitivity, simplicity, low cost and easy operation. In fact, the free atom reactions within the tube causing calibration curvature are avoided up to an analyte concentration of at least 200 ng ml⁻¹ for Se and Sb and 100 ng ml⁻¹ for As. Tolerance limits of 0.7, 1.4, 0.2 and 0.2 μg ml⁻¹ are achieved for the atomization interferences of As on Se, Se on As, Sb on Se and Se on Sb, respectively, which is an improvement by 1–2 orders of magnitude in comparison to the conventional EHQTA with the same hydride generation system.     

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.     

Precision and Accuracy Studies of Impaction-Electrothermal Atomization Atomic Spectrometry

Abstract

The precision of aqueous solutions of cadmium, copper, and manganese introduced as an aerosol by an pneumatic nebulizer and electrothermal vaporizer to an impaction-electrothermal atomization atomic absorption spectrometeric system was in the range of 1–3% which was similar to that obtained by manual introduction of similar concentrations of aqueous solutions of cadmium, copper, and manganese to the electrothermal atomizer and atomic absorption spectrometry. The precision of a laboratory air sample was 7.6–9.9%. Accuracy was assessed by comparison to conventional methods of sampling air by collection on a filter followed by digestion of the filter and analysis by flame atomic absorption spectrometry The levels were found to be 59–69% compared to the conventional method.     

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.     

Gas-phase atomization in analytical atomic spectrometry

Summary The most important problems of analytical atomic spectrometry are introduction of the sample into the atomizer and atomization of the sample. To solve these problems gas-phase atomization is suggested. This consists of preliminary isolation of the elements to be determined in the form of gaseous (volatile) compounds with subsequent gas-chromatographic separation. Separated compounds are fed into the atomizer individually in a stream of inert gas. This technique is the basis of development of dispersionless modes of atomic emission, atomic fluorescence and atomic absorption multielement analysis using non-selective detection.

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Gasphasen-Atomisierung in der analytischen Atomspektrometrie

     

The determination of germanium by atomic absorption spectrometry with a graphite tube atomizer

A carbon filament atom reservoir and a graphite tube atomizer are compared as methods for the determination of germanium by atomic absorption spectrometry. It is shown that the filament technique is not applicable, probably because of loss of the sample as a volatile oxide species which results in inefficient atomization. The design of a small graphite tube atomizer is described; with this, a limit of detection for germanium of 3·10^-10 g was found. For a 20-μl sample, this corresponds to a concentration of 0.015 p.p.m. The interfering effect of 13 anions and cations is studied.     

Shadow spectral imaging of absorbing layers in a transversely heated graphite atomizer: Part 1. Analyte atoms

The technique of shadow spectral imaging was used to investigate dynamics of formation and dissipation of Ag, In, Ga, Bi, Mn, Cu and Tl atomic layers in a transversely heated graphite tube atomizer (THGA) with and without integrated platform under gas-stop and gas-flow conditions. It is shown that non-uniform heating of the tube walls and platform surface in the radial cross section is the main reason for analyte transfer from atomizer bottom to less heated sides of the tube and platform before atomization temperature is reached. This transfer in the atomizer transverse cross section can be an additional factor that reduces matrix interferences in the THGA. In all the investigated cases, the atomic absorbing layers are not spatially uniform. Absorbance gradients grow up to 0.2 mm^− 1 even in the case of chemically inert silver atomization. Inverse atomization of In, Bi, Ga and Tl when atoms first appear in the atomizer's upper part was detected in THGA with platform. The effect of the internal gas flow on the spatial structure of analyte atoms is less pronounced in the transversely heated atomizer as compared to the end-heated furnaces.     

Atomic absorption spectrometry of germanium with a tungsten electrothermal atomizer

The electrothermal atomization of germanium in a metal micro-tube atomizer is described. Tungsten is preferable to other metals for the atomizer. Hydrogen lowers the atomization temperature of germanium, and improves the sensitivity for germanium significantly when the optimum flow rates are applied. There are pronounced interferences from diverse elements and acids on the atomization of germanium. A procedure which involves carbon tetrachloride extraction of germanium tetrachloride and back-extraction of germanium into water avoids many of the interferences and is recommended for rock samples.     

Different platform and tube geometries and atomization temperatures in graphite furnace atomic absorption spectrometry: Cadmium determination in whole blood as a case study

In the present work the performance of different platform and tube geometries and atomization temperatures in graphite furnace atomic absorption spectrometry was investigated, using the determination of Cd in whole blood as an example. Grooved, integrated and fork platforms as well as atomization temperatures between 1200 °C and 2200 °C were investigated in a longitudinally heated graphite atomizer and compared with the performance of a transversely heated furnace. In the longitudinally heated furnace the increase of the atomization temperature in the studied range resulted in an increase of matrix effects for all platform geometries. The integrated platform exhibited slightly lower sensitivity and increased multiplicative interferences in comparison to the other two platform designs. Interference-free Cd determination was possible with all types of platforms and 1200 °C as the atomization temperature as well as with grooved and fork platforms at 1700 °C. On the other hand, lower atomization temperatures resulted in poorer limits of detection, due to the longer integration time needed. No matrix effect was observed at any atomization temperature using the transversely heated atomizer; in addition, limits of detection were better than those observed with the longitudinally heated atomizer. Best values were around 0.02 μg L^− 1 with the latter atomizer compared to values around 0.02 μg L^− 1 with the former one.     

The Determination of Trace Transition Elements in Biological Tissues Using Flameless Atom Reservoir Atomic Absorption

Abstract

The development of an analytical technique generally applicable to the determination of Ag, Cd, Co, Cu, Fe, Mn, Ni, Pb, V, and Zn in all biological tissues is described. All of these elements may readily be determined in tissue samples of less than 0.5 g using flameless atom reservoir atomic absorption with a Perkin-Elmer heated graphite atomizer. Some of the operational characteristics of this atomizer system are discussed. The utility of the method is illustrated by analyses of selected marine biota and of NBS standard orchard leaves.     

Electrothermal atomic-absorption spectrometry of arsenic and its application to environmental samples

Electrothermal atomization of arsenic with a metal micro-tube atomizer has been studied. Thiourea and thionalide were found to give effective atomization of arsenic. A method involving extraction of the thionalide complex for determining traces of arsenic in water and soil is described.     

Electrostatic Accumulation Furnace for Electrothermal Atomic Spectrometry (E. A. F. E. A. S.)

Abstract

A new technique is described for rapid elemental analysis of atmospheric particulates. The basic principle is direct deposition of atmospheric particulate matter in a furnace for electrothermal atomization and analysis by atomic absorption spectrometry. A prototype instrument has been tested by analyzing the lead content in the laboratory atmosphere.     

Dynamics of the Spatial Distribution of Atomic and Molecular Absorbing Layers in the Electrothermal Vaporization and Electrostatic Precipitation of an Analyte in an Atomizer

An experimental device was described for atomic absorption analysis with the electrothermal vaporization of the initial sample followed by the condensation of vaporization products and the electrostatic precipitation of the resulting aerosol in the secondary atomizer. Working conditions ensuring the maximum transfer of the sample to the atomizer were determined. The dynamics of the spatial distribution of the absorbing atomic and molecular layers was studied for atomization in a graphite furnace after the direct sample injection and electrostatic precipitation. The contribution of some physicochemical processes to the formation of the structure of cadmium atomic layers was assessed for different methods of sample injection into the atomizer. It was shown that an additional vaporization–condensation step significantly decreases the level of nonselective absorption and smoothes its gradients.     

Evaluation and application of internal standardization in atomic absorption spectrometry with electrothermal atomization

A new dual-channel system developed for use in atomic absorption spectrometry is used to assess the internal standard technique for electrothermal atomization. Cobalt was found to be a suitable internal standard for iron determinations, and is used for determination of 7—330 ng Fe ml^-1 in water samples. With use of the internal standard technique, fluctuations caused by atomizer variables are reduced and interferences from many cations are also decreased.     

Determination of Rhodium in Biological Materials by Electrothermal Atomic Absorption Spectrometry with a Tungsten Tube Atomizer

Abstract

Electrothermal atomic absorption spectrometry (ETAAS) of rhodium with a tungsten tube atomizer has been investigated under optimum conditions (atomization temperature; 2230 C, purge gas; Ar 480 ml min^?1 + H₂ 20 ml min^?1, and pyrolysis temperature; 590 C). The absolute characteristic mass (the mass of element giving 0.0044 abs.) of rhodium by the atomizer was 86.5 pg and the detection limit was 16.5 ng ml^?1 (3S/N). The interferences caused by large amounts of interferents were evaluated. Al, Ca, Cu, Fe, K, Mg, Na, Pb and Zn severely interfered in the AA signal of rhodium. Ammonium phosphate, ascorbic acid, palladium nitrate, copper nitrate, lanthanum nitrate, thiocyanate and thiourea, well known as matrix modifiers were tested to eliminate the severe interferences. However, by the addition of these compounds, the rhodium signal was not recovered. The standard addition method was adapted for the determination of rhodium in biological materials. The recovery of spiked-rhodium in biological materials was in the range of 97.4 to 107%.     

On-line coupling of electrochemical preconcentration in tungsten coil electrothermal atomic absorption spectrometry for determination of lead in natural waters

A flow injection system was coupled to a tungsten coil electrothermal atomizer (150 W) for on-line separation and preconcentration of lead based on its electrochemical reduction on the atomizer surface. The electrochemical cell is built up inside the furnace by using a Pt flow-through anode and the atomizer itself as the flow-through cathode. The manifold and the tungsten coil power supply were controlled by a computer running a program written in Visual Basic, which was utilized in synchronism with the original software of the atomic absorption spectrometer. The flow-through anode (50 mm long, 0.7 mm i.d.) was inserted in tip of the autosampler arm by replacing the last section of the PTFE sample delivering tube. The tungsten coil atomizer and the counter electrode were easily connected to a d.c. power supply. An enrichment factor of 25 was obtained for lead after a 120-s electrodeposition for a sample flowing at 1.0 ml min⁻¹. The method detection limit was 0.2 μg l⁻¹ Pb and the R.S.D.<5% (n=10 for 5 μg l⁻¹ Pb). Up to 2% m/v NaCl or KCl and 5% m/v CaCl₂ or MgCl₂ did not interfere on the separation and atomization of 5 μg l⁻¹ Pb.     

Surface testing of a tungsten atomizer

This paper deals with the structure and surface changes of a tungsten atomizer. Atomizers made by Metallwerk Plansee for the Czech equipment WETA 90 were studied. Their effect on the height and shape of the peaks of absorption signals was investigated in dependence on number of atomization firings. The influence of various sample matrices on material changes and the evaporation of tungsten during the atomization cycle were also studied. A relationship was found between sensitivity changes and surface quality in dependence on the number of firings carried out. Good stability of sensitivity is guaranteed if the right thermal conditioning process of the atomizer is used. The influence of 4 mol dm⁻¹ HNO₃, HCl, H₂SO₄ and HC1O₄ and 5% H₂O₂ on the corrosion of the atomizer surface was investigated, and significant corrosion was observed only for H₂SO₄ and H₂O₂. The concentration of free tungsten atoms was measured from the absorbance at the tungsten 255.1 nm line (bandpass 0.1 nm) and was significantly registered over 3000°C. No influence of the concentration of hydrogen in the argon protective atmosphere on this parameter was observed.