Electrothermal atomic absorption spectrometry of elements after electrochemical deposition on graphite electrodes

The application of electrochemical deposition on graphite rods for separation and preconcentration prior to electrothermal atomic absorption spectrometry (a.a.s.) is examined. The metals to be determined are electrolyzed onto a graphite rod which is tehn transferred to a cup atomizer for a.a.s. Although only some of the element present in the solution is deposited on the surface of the graphite rod, favorable preconcentration rates are obtained. The method was tested on the determination of cadmium in aqueous solution. The precision is satisfactory for concentrations down to 5 × 10^?8 g l^?1 cadmium, and the detection limit is 4 × 10^?9 g l^?1.     

Laser ablation for aerosol deposition graphite furnace atomic absorption spectrometry

A commercially available pulse laser was used with a graphite furnace (GF) atomic absorption (AA) spectrometer for the trace analysis of metals in solid samples.Laser ablated solid material was deposited onto the inner surface of the GF. The optimum deposition temperature was 300 K. The deposited aerosol was atomized in a conventional GF heating regime.The analytical results in the deposition technique for Cd, Zn, Pb, Ag, Mn, Fe and Ni contained in different target materials were compared with results obtained with another laser ablation GF technique, which is characterized by the transport of the ablated material into a constant temperature GF with immediate atomization of the aerosol particles. The deposition technique improved the sensitivity and precision for the low volatile elements Cd, Zn and Pb. In contrast, the aerosol injection technique is preferable for the determination of elements that require more energy for atomization. Working with tube temperatures of up to 2800 K the authors obtained higher absorbance values (peak height) for Mn, Fe and Ni using the injection technique. The use of multiple deposition of laser ablated material inside the GF to achieve improved detection limits and higher precision for one atomization seems promising only for selected matrices.     

Determination of palladium and platinum by electrothermal atomic absorption spectrometry after deposition on a graphite tube

The inner wall of a pyrolytically coated graphite tube served as the surface for adsorptive accumulation and/or for electrodeposition of palladium and platinum. A flow system for this preconcentration was constructed. For the electrodeposition a three-electrode arrangement was used. The flow rate for deposition, the medium and deposition potentials were optimized. After the deposition step, the graphite tube was placed into the graphite furnace and an atomization programme was applied. The procedure was applied for the determination of Pd and Pt in airborne particulates.     

On-line electrochemical preconcentration of manganese for graphite furnace atomic absorption spectrometry using a flow-through electrochemical cell

A flow system incorporating a 2-electrode electrochemical microcell with a working electrode made from crushed reticulated vitreous carbon and a graphite furnace AAS instrument was used for the preconcentration and determination of trace amounts of Mn. The sample, rinsing and elution solutions were pneumatically transported through the system. Mn²⁺ ions can be quantitatively deposited both anodically and cathodically at a voltage of +1.5 to + 3 V and –2.5 to –4V, respectively applied to the cell. Samples of 0.1 to 1 ml volume were analyzed within 5–10 min. The limits of detection and determination were 8.7 and 29 pg, respectively. The reproducibility was 1.5 to 5%. The electrochemical behaviour of Mn in the flow system was studied by using a 3-electrode flow-through cell coupled on-line to a flame AAS instrument.On leave from Department of Analytical Chemistry, Slovak Technical University, CS-812 37 Bratislava, Czechoslovakia     

Electrothermal atomic absorption spectrometry determination of molybdenum in whole blood

A method for the determination of molybdenum in whole blood by atomic absorption spectrometry with electrothermal atomization was developed and evaluated. Erbium (25 μg) was chosen from several potential chemical modifiers (Sm, Lu, Ho, Eu and Pd+Mg) as the most appropriate for the sensitive and reliable determination of molybdenum in such sample. The process used was direct dilution of the sample in a ratio 1:2 with a 0.1% (v/v) Triton X-100 solution. The injection of 20 μl of a solution of 15% (w/v) hydrogen peroxide and running the temperature program after 5 firings greatly reduced the effect of build-up of carbonaceous residues within the atomizer. The limit of detection and working ranges, respectively, were 0.6 and 2.0–100.0 μg l⁻¹, and the characteristic mass was 7.2 pg. The relative standard deviation varied from 0.8 to 1.5% for within and between batch determinations, respectively. The determination of molybdenum in Seronorm™ Trace Elements in Whole Blood with known added amounts of the analyte was performed to asses the accuracy. The optimized procedure has been applied to the determination of molybdenum in whole blood specimens of 20 subjects taken before and 10–12 h after receiving an over-supply of 1 mg of molybdenum. The molybdenum concentrations (±S.D.) were 10.9±0.4 μg Mo l⁻¹ (range 9.9–11.6 μg Mo l⁻¹) and 15.4±0.4 μg Mo l⁻¹ (range 13.1–16.9 μg Mo l⁻¹) for the individuals before and after the administration of molybdenum.     

Electrothermal atomic absorption spectrometry of silicon vaporized from different surfaces

The dependence of silicon absorbance on inert gas flow rate, ashing temperature and the amount injected was studied for uncoated, pyrolytically coated and tantalum carbide-coated graphite tubes. The reasons for the anomalous curvature of the calibration graphs and other unusual phenomena are discussed. Most sensitive results for silicon were obtained by isothermal atomization from a tantalum-treated tube and platform.     

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.     

Slurry sampling for graphite furnace atomic absorption spectrometry

Summary Slurry preparations are an effective way to introduce solids into the graphite furnace. Ultrasonic agitation keeps samples mixed prior to analysis. Several aspects of the ultrasonic slurry sampling approach are discussed including contamination concerns, analyte partitioning, and the effect of particle size. In addition, sample preparation strategies for slurry preparations of non-powdered materials are reviewed. The suitability of this method for assessing homogeneity is demonstrated.     

Electrothermal atomic absorption spectrometry in the study of metal ion speciation

The literature on the use of electrothermal atomic absorption spectrometry (ETAAS) in the determination of metals in speciation studies of different samples is comprehensively reviewed. The methods of extraction, preconcentration, etc. in connection with speciation studies have been highlighted. The ETAAS programmes and other details of the developed methodologies are discussed. On critical examination it becomes obvious that chromium is the metal which has been analysed by most workers. Study of other metals falls in the following order: Pb, Sn, Cu, As, Al, Cd, Zn, Fe, Ni and Se. It is clearly evident that the major work on metal ion speciation has been carried out in natural water, followed by biological materials. There are also many reports on the speciation analysis of soil and sediment. Only a few papers have been published on metal speciation in airborne particulates. The analytical details of the developed methodologies have been examined in terms of limit of detection, precision and accuracy. Received: 27 December 1995 / Revised: 20 May 1996 / Accepted: 26 May 1996     

Electrothermal atomic absorption spectrometry in the study of metal ion speciation

The literature on the use of electrothermal atomic absorption spectrometry (ETAAS) in the determination of metals in speciation studies of different samples is comprehensively reviewed. The methods of extraction, preconcentration, etc. in connection with speciation studies have been highlighted. The ETAAS programmes and other details of the developed methodologies are discussed. On critical examination it becomes obvious that chromium is the metal which has been analysed by most workers. Study of other metals falls in the following order: Pb, Sn, Cu, As, Al, Cd, Zn, Fe, Ni and Se. It is clearly evident that the major work on metal ion speciation has been carried out in natural water, followed by biological materials. There are also many reports on the speciation analysis of soil and sediment. Only a few papers have been published on metal speciation in airborne particulates. The analytical details of the developed methodologies have been examined in terms of limit of detection, precision and accuracy. Received: 27 December 1995 / Revised: 20 May 1996 / Accepted: 26 May 1996     

Electrothermal atomic absorption spectrometry with two-step probe atomization and primary absorption signal feedback

A method is proposed to reduce the relative detection limits for elements in an atomic absorption spectrometer with a graphite furnace and two-step probe atomization, based on using feedback between the absorption impulse of primary sample atomization and probe fixation in the position for vapor fractionation. Deposition of sample fractions on the probe, which interferes with measuring the analytical signal, is reduced. The relative limits of the direct detection of Pb, Cd, and Tl in NaCl and K₂SO₄ are lowered by more than one order of magnitude in comparison to the atomization of such salts under the conditions of a temperature-stabilized furnace with a platform. The detection limits are 10^?7 to 10^?8 wt %. The relative standard deviation of the analytical signals does not exceed 5%, which is appropriate for the measurement of concentration.     

Preconcentration of palladium in a flow-through electrochemical cell for determination by graphite furnace atomic absorption spectrometry

An electrochemical preconcentration at a controlled potential on the electrode in a flow-through mode followed by graphite furnace atomic absorption spectrometric (GFAAS) detection is proposed for determination of trace amounts of palladium. After electrolysis the polarization of the electrodes was changed and deposited metal was dissolved electrochemically in the presence of an appropriate stripping reagent. Conditions for the electrodeposition, such as pH of the solutions, a deposition potential, dissolution potential and a composition of stripping solution were optimised. The graphite electrode (GE) and glassy carbon electrode (GCE) were tested for the palladium reduction process. The detection limit of 0.05 ng ml⁻¹ Pd (1 pg) was obtained after palladium preconcentration on the GCE and dissolution with 0.2 mol l⁻¹ thiourea in 0.1 mol l⁻¹ HCl followed by GFAAS detection. The method was applied for the determination of palladium in spiked tap water and road dust samples.     

Advances in ultrasonic slurry graphite furnace atomic absorption spectrometry

Summary Ultrasonic slurry graphite furnace atomic absorption spectrometry is a useful technique for automated direct analysis of solids. The effectiveness of ultrasonic agitation for mixing samples is demonstrated. This analytical approach is evaluated to identify sources of imprecision. Strategies for optimizing slurry preparations are discussed, focusing on particle size, density, analyte partitioning, and sampling limitations. Finally, a teflon bead method is presented for grinding biological and botanical samples. An optimized general approach for ultrasonic slurry sampling is presented.Presented at the 5th International Colloquium on Solid Sampling with Atomic Spectroscopy, May 18–20, 1992; Geel, Belgium. Papers edited by R. F. M. Herber, Amsterdam.     

Determination of heavy metals by electrothermal atomic absorption spectrometry after electrodeposition on a graphite probe

Traces of heavy metals were separated and preconcentrated electrochemically at a controlled potential on the graphite ridge probe. After the electrolysis, the electrode-probe was inserted in the graphite furnace for atomization of metal deposit by an automatic system. Conditions for the electrodeposition, such as pH of solutions, the deposition potential and concentration of electrolyte, were optimized. Detection limits improved with increased time of electrodeposition and were 16 ng l⁻¹ Cu, 1.0 ng l⁻¹ Cd, 6.0 ng l⁻¹ Pb, 64 ng l⁻¹ Ni, 14 ng l⁻¹ Cr (III) and 17 ng l⁻¹ Cr (VI) for a 10-min deposition. This method was applied for the determination of copper, cadmium, lead, nickel and of chromium species in seawater.     

Determination of trace elements in Antarctic krill samples by inductively coupled atomic emission and graphite furnace atomic absorption spectrometry

Analytical methods were developed for the determination of trace elements in Antarctic krill samples applying inductively coupled plasma atomic emission spectrometry (ICP-AES) and graphite furnace atomic absorption spectrometry (GF-AAS). Cu, Fe, Mn and Zn were determined by ICP-AES, while Cd and Pb by GF-AAS technique. Two microwave assisted digestion procedures were elaborated for the preparation of 0.5-g krill samples using open and closed vessel systems. The efficiency of the digestion processes was checked by measurements of the total organic carbon content of the solutions obtained. The deviations of the analytical data from the certified values and the relative standard deviations of the concentration measurements were lower for all six elements investigated applying the closed vessel digestion system.     

Latest innovations in graphite furnace atomic absorption spectrometry technique

An overview of the latest innovations in the graphite furnace atomic absorption spectrometry technique is described. The use of the transverse heated graphite atomizer technology with its huge advantages, the possibilities of running powdered solids through the slurry technique, and the future possibility of using flow injection on-line with the graphite furnace are mentioned.     

Electrothermal atomization atomic absorption spectrometry of cadmium with a platinum tube atomizer

The determination of cadmium by electrothermal atomization atomic absorption spectrometry with a platinum tube atomizer in the presence of air has been investigated. The detection limit of cadmium was 0.09 pg (9 pg/ml for a 10-mul volume). The relative standard deviation of the measurement was 2.9%. For 2.5 pg of cadmium, Cu, Pb, Zn, Al, Ca, Fe, K, Mg and Na (10(4)-10(5)-fold) did not interfere with the absorption signal. The method has been applied to the determination of cadmium in some biological materials. The average analytical value found for the standards lay within the limits of the certified values. The remarkable merits of the platinum atomizer are its stability in air and long life-time (able to withstand more than 1000 heating cycles in air).     

Determination of indium by graphite furnace atomic absorption spectrometry after coprecipitation with chitosan.

A sensitive and simple method for the determination of trace amounts of indium in water samples by graphite furnace atomic absorption spectrometry (GFAAS) after coprecipitation with chitosan was investigated. Indium was quantitatively preconcentrated from water samples by coprecipitation with chitosan at pH 7.0-9.0. The coprecipitant was easily dissolved with acetic acid, and indium in the resulting solution was determined by GFAAS. The addition of lanthanum as a chemical modifier was more effective for the atomic absorbance of indium. The detection limit (S/N > or = 3) for indium was 0.04 microg dm(-3), and the relative standard deviations (n = 5) were 3.5-4.5% at 1.0 microg/100 cm3. The results obtained in this study indicate that the proposed method can be successfully applied to the determination of trace indium in water samples.