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 gold in biological materials by electrothermal atomic absorption spectrometry with a molybdenum tube atomizer

Electrothermal atomic absorption spectrometry (ETA-ASS) of gold with a molybdenum tube atomizer has been investigated. A sensitive ETA-AAS method was developed. The gold absorption signal became higher with the heating rate of the tube atomizer and as the ratio of hydrogen in the argon purge gas decreased. The optimal heating rate and the optimal gas flow rate were 5.5 C/msec and Ar 480 ml/min + H(2) 20 ml/min, respectively. The absolute characteristic mass (the mass of element giving 0.0044 abs.) of gold by the atomizer was 1.8 pg and the detection limit was 130 pg/ml (3S/N). These values were > 10 times better than those obtained with graphite atomizers, ICP and ICP-MS. The interferences caused by large amounts of interferents were evaluated. The addition of thiourea served to eliminate severe interferences. The recovery of spiked gold in biological materials was in the range of 101-106%.     

Direct determination of cadmium in biological material using electrothermal atomization atomic absorption spectrometry with a metal tube atomizer and a matrix modifier

A direct determination of cadmium by electrothermal atomization atomic absorption spectrometry with a molybdenum tube atomizer has been investigated. Direct calibration method with cadmium standard solutions and ultrasonic agitation method of a solution including sample powder were used. Sulfur served as a matrix modifier for removal of interferences. Though this direct analytical method for cadmium determination in biological materials had a relatively large standard deviation, the accuracy was similar or superior to those of a sample digestion method and the direct analysis without sulfur. The advantages of this method are its simplicity, low cost, high speed of analysis, and rapid calibration.     

Effect of atomizer surface type on the quantitation of molybdenum and ytterbium by electrothermal atomization atomic absorption spectrometry

The effect of pyrocoated graphite, uncoated graphite, metal-carbide, and metal atomization surfaces on the quantitation of molybdenum and ytterbium by electrothermal atomization atomic absorption spectrometry was investigated. The peak shape was affected by heating rate and the different surfaces gave different shapes. Except for the case of uncoated graphite, the sensitivities and detection limits were similar for all surfaces. In a sodium chloride matrix it is preferable to use uncoated graphite for molybdenum because an ashing stage greater than the boiling point of sodium chloride can be used without loss of molybdenum. Tube lifetime depended on atomization temperature, atomization time and the matrix.     

Preconcentration technique for manganese by adsorption onto a tantalum wire for tungsten tube atomizer electrothermal atomization atomic absorption spectrometry

A multi-pumping flow system for the spectrophotometric determination of nitrite and nitrate is described. The determination of nitrite is based on the Griess-Ilosvay reaction. Nitrate can be determined after its on-line reduction to nitrite using hydrazine sulphate in alkaline medium. Calibration was linear up to 3 mg NO₂ ⁻ L⁻¹ with a limit of detection (3s_b/S) of 0.013 mg NO₂ ⁻ L⁻¹ an injection throughput of 55 injections h⁻¹ and a repeatability (RSD) of 0.5% for the direct determination of nitrite. Two calibration graphs within the ranges 0.039–7 mg NO₃ ⁻ L⁻¹ and 0.026–5 mg NO₂ ⁻ L⁻¹ were run for the determination of nitrate and nitrite under reducing conditions, respectively. A limit of detection of 0.039 mg NO₃ ⁻ L⁻¹ was obtained. An injection throughput of 27 injections h⁻¹ and an RSD lower than 1.5% were achieved. The method was successfully applied to the determination of nitrite and nitrate in water samples. Correspondence: Víctor Cerdà, Department of Chemistry, University of the Balearic Islands, Carretera de Valldemossa Km7.5, 07122 Palma de Mallorca, Spain     

Preconcentration of trace lead by adsorption onto a tantalum wire for electrothermal atomization atomic absorption spectrometry with a tungsten tube atomizer

A preconcentration method of lead in waters by adsorption on a tantalum wire was developed for electrothermal atomization atomic absorption spectrometry with a tungsten tube atomizer. After the preconcentration, the tantalum wire was directly inserted into the tungsten tube atomizer. In the preconcentration (adsorption) process for lead, the optimal immersing time was 90 s and the best pH was 4. Under the optimal conditions, the detection limit for lead by the tantalum wire preconcentration method was 6.0 pg mL^− 1 (3S/N) and the relative standard deviation was 6.1%. The influences of large amounts of concomitants on the preconcentration of lead were evaluated. Even though 10³ to 10⁴-fold excess of matrix elements existed in aqueous solution, the lead absorption signal was not significantly affected by the matrix elements. The method with preconcentration on a tantalum wire was applied to the determination of lead in river waters and proved to be sensitive, simple, and convenient. Because this preconcentration method can be utilized in the in-situ treatment of trace lead in environmental water samples, it was unnecessary to carry the water samples to the analytical work place. The present technique was shown to be useful for the determination of lead in environmental water samples at 0.1−1 μg L^− 1.     

Direct determination of molybdenum in mineral waters by atomic absorption spectrometry with electrothermal atomization

A new method for the direct determination of molybdenum by ETA-AAS in mineral waters without prior separation or concentration is proposed. With careful control of the graphite furnace conditions selective volatilization of the salt matrix is successfully attained. The possible spectroscopic interference due to common metals as well as the reproducibility, precision and repeatability of the method has been studied and the molybdenum content of 21 mineral waters measured.     

Transverse heated filter atomizer for electrothermal atomic absorption spectrometry

The filter furnace atomization concept was applied for the transverse heated atomizer. A graphite filter with graphite fiber reeled onto it was inserted into the tube of the standard transverse heated graphite atomizer (THGA) in the place of the platform. Automatic plugging of the sampling hole was applied during the atomization stage. The performance of the filter atomizer (THFA), compared with the THGA, was tested for the determination of Ag, As, Au, Bi, Cd, Cu, Ga, In, Mn, Pb, Sb, Se and Tl. The analytical performances of the THFA displayed some advantages in comparison with the THGA. The sampling volume varied in the range of 5–90 μl, while drying time for any volume was less than half of that used for the THGA. Owing to the reduced diameter of the analytical zone (2 mm) along the filter axis, a sensitivity improvement was observed for all elements, 1.3–2.8-fold without plugging and 4.3–4.8-fold for Bi, Cd, Pb and Tl with plugging of the dosing hole. An increased peak width (by two to five times for the elements tested) limited the determination of less-volatile metals. The intensity of light decreased by 20–30% in comparison with the THGA. Taking into account the sensitivity, sampling volume, light loss and signal width, the calculated gain in relative detection limit is substantial (about 2.5–7 times) only for volatile elements when the plugging is applied. The pyrolysis temperatures for Ag, As, Au, Cd, Cu and Se in the THFA without addition of modifier were by 200–600°C higher than in the THGA using Pd/Mg modifier. The lifetime of THFA tubes was similar to that of THGA tubes.     

Plasma afterglow atomization in electrothermal atomic absorption spectrometry

Potentialities of an Ar/H₂ microwave induced plasma afterglow at 8.2 mbar as an atomization source in electrothermal atomic absorption spectrometry have been examined. More specifically the atomization efficiency, as shown from appearance temperatures, and the reaction mechanisms of the atomization of the oxides and chlorides of alkaline earth and transition metals have been investigated and compared with conventional electrothermal atomization. For all the investigated metal chlorides and alkaline earth oxides, a considerable decrease in appearance temperature (some 500 K), is observed in the plasma afterglow. Such enhanced atomization is believed to be linked to reactions with H atoms. No plasma enhancement, however, is measured for the atomization of the transition metal oxides. All metal oxides are effectively reduced to free metal in the solid state by the Ar/H₂ afterglow, and as a consequence the supply rate is governed by the metal sublimation for these compounds. For metal chlorides, however, strong evidence is found for the atomization process to proceed via gas phase reactions.     

Atomic absorption spectrometry of tellurium with electrothermal atomization in a molybdenum microtube

Hydrogen, added to argon purge gas, is necessary to protect the molybdenum microtube atomizer from oxidation, but it increases the atomization temperature and decreases the maximum absorbance of tellurium. A mixture of thiourea and copper removes the interfering effects of diverse elements and counteracts the effect of hydrogen. Tellurium (20–200 ppm) in copper can be determined after extraction as a chloride complex.     

Slurry sampling electrothermal atomic absorption spectrometric determination of copper in herbal medicine samples with a molybdenum tube atomizer

An ultrasonic slurry sampling electrothermal atomic absorption spectrometric method with a molybdenum tube atomizer has been developed for the determination of copper in herbal medicine samples. Glycerol solution (10%) was used as the slurry medium. The optimum pyrolysis temperature was 760 °C. The detection limit was 72 fg (3×S/N ratio). Matrix element interference was investigated and it was found that glycerol as a chemical modifier eliminated the interference. The amounts of copper in herbal medicines determined by the method proposed are in good accordance with those measured in dissolved acid-digested samples. The method enables rapid calibration, and simple and rapid analysis of copper in herbal medicine samples at low cost.     

Determination of lead and cadmium in urine by electrothermal atomization atomic absorption spectrometry

The applicability of a DETATA sorbent to the preconcentration of lead and cadmium followed by the determination of these elements in urine using atomic absorption spectrometry with electrothermal atomization was demonstrated. After preconcentration by a factor of 10, the limits of detection were 0.01 and 0.2 μg/L for cadmium and lead, respectively. The accuracy of the results was supported by the analysis of Seronorm Trace Elements Urine (Batch no. 101021).     

Matrix modification by Cu(NO3)2 for the determination of gold by electrothermal atomic absorption spectrometry with a molybdenum tube atomizer

Matrix modification by copper nitrate in electrothermal atomic absorption Spectrometry (ETAAS) of gold with a molybdenum tube atomizer has been investigated. The addition of copper nitrate served to eliminate the interferences from 10⁴–10⁵-fold concentrations of foreign elements at the 890 °C pyrolysis temperature. The absolute characteristic mass (giving 0.0044 absorbance) of gold in the presence of copper nitrate with the Mo atomizer was 0.26 pg and the detection limit was 38 pg/ml. These values were several times better than those obtained with graphite atomizers. The recovery of spiked gold in biological materials was in the range 96–106%. A sensitive and accurate ETAAS method was developed for complex matrix samples.     

Determination of thallium by electrothermal atomic absorption spectrometry with a metal atomizer

Summary Electrothermal atomization of thallium in a molybdenum microtube atomizer is described. The addition of a low flow rate of hydrogen to argon purge gas resulted in higher peak absorption. In the presence of thiourea the addition of hydrogen did not alter the peak absorption value in pure argon, although the peak temperature shifted to lower region. A high heating rate of the atomizer was recommended for higher peak absorption and improvement of interferences from concomitants. The interferences by concomitants at 50 ng level were modified with thiourea. Modification with thiourea was effective even for interferences from 500 ng of cadmium, zinc or copper, while it was insufficient for 500 ng of calcium, magnesium, chromium, bismuth or lead. Provided the atomization of thallium was carried out at high heating rate and on addition of thiourea as a matrix modifier, the interference from chloride (500 ng) was modified. The absolute sensitivity (0.0044 abs) for thallium was 1.2 pg.

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Thalliumbestitmmung durch AAS mit elektrothermischer Atomisierung in einem metallischen Atomizer

Zusammenfassung Zur AAS-Bestimmung von Thallium wird eine Molybdän-Mikroröhre als Atomizer empfohlen. Zusatz von geringeren Wasserstoffmengen zum Argongas ergab eine höhere Absorption. In Gegenwart von Thioharnstoff erfolgte durch Wasserstoff-Zugabe keine Änderung des Absorptionswertes in reinem Argon, obwohl die Peaktemperatur in einen niederen Bereich verschoben wurde. Für höhere Absorption und zur Verminderung von Störungen durch Begleitelemente wurden höhere Erhitzungsgeschwindigkeiten empfohlen. Störungen durch Begleitelemente im Bereich von 50 ng konnten mit Thioharnstoff verringert werden. Die Zugabe von Thioharnstoff erwies sich ebenfalls als wirksam für 500 ng Cadmium, Zink oder Kupfer, während sie für dieselben Mengen an Calcium, Magnesium, Chrom, Bismut oder Blei ungenügend war. Mit hoher Erhitzungsgeschwindigkeit und Thioharnstoffzusatz konnte eine Störung durch Chlorid im Bereich von 500 ng reduziert werden. Die absolute Empfindlichkeit für Thallium (0,0044 abs) betrug 1,2 pg.

     

Kinetics of indium atomization from different atomizer surfaces in electrothermal atomic absorption spectrometry (ETAAS)

The kinetic parameters of indium atomization in electrothermal atomic absorption spectrometry (ETAAS) have been determined by a newly proposed method. Effect of the atomizer surface and the palladium modifier on the kinetics of indium atomization has been investigated. The mechanisms of indium atomization seem to be identical for the pyrolytically coated graphite and the uncoated graphite tubes, i.e. the rate-limiting step for the atomization changes from a first order kinetics at lower temperatures into a nearly 1/3 order kinetics at higher temperatures, which may suggest that the analyte moves from a dispersed state to agglomates with increasing temperature. However, for the zirconium coated graphite tube, the atomization of indium is controlled by a single mechanism with the kinetic order of near 2/3 and the activation energy of 186 ± 13 kJ/mol. Relatively weak indium—zirconium carbide interactions and the release of indium from the sphere of molten indium metal on the zirconium coated surface are suggested. In the presence of palladium, a simple mechanism, i.e. the release of indium from the solid solution of the In and the Pd on the pyrolytically coated graphite surface, is proposed to account for the observed first order kinetics and the activation energy of 421 ± 27 kJ/mol.     

电热原子吸收光谱法中原子形成过程的探讨

本文提出了测定电热原子吸收光谱法中原子形成过程动学参数的新方法, 并用此法测定了铜、铁、铝、钴和钼等原子形成过和的动力学级数和原子化能。结果表明这些元素的原子形成均为零动力学。通过比较原子化能的实验值与有关过程的焓变探讨了这些元素的原子化过程 。     

Mechanism of yttrium atom formation in electrothermal atomization from metallic and metal-carbide surfaces of a heated graphite atomizer in atomic absorption spectrometry

Mechanism of Y atom formation from pyrocoated graphite, tantalum and tungsten metal surfaces of a graphite tube atomizer has been studied and a mechanism for the formation for Y atoms is proposed for the first time. The following is the mechanism of yttrium atom formation regardless of whether the atomizing surface is pyrolytic graphite, tantalum or tungsten metal.

     

Determination of manganese in herbal medicine samples by slurry-sampling electrothermal atomic absorption spectrometry with a metal tube atomizer

An ultrasonic slurry-sampling electrothermal atomic absorption spectrometry with a molybdenum tube atomizer has been developed for the determination of manganese in herbal medicine samples. Ten percent glycerol solution was used as the slurry medium. The optimum pyrolysis temperature was 400 degrees C. The detection limit was 69 fg (3xS/N). Matrix element interference was checked and it was found that glycerol as a chemical modifier eliminated the interference. The amounts of manganese in herbal medicines determined by the proposed method are in good accordance with those measured in dissolved acid-digested samples. The method enables rapid calibration, and simple and rapid analysis of manganese in herbal medicine samples at low cost.     

Direct determination of cadmium in calcium drug samples using electrothermal atomic absorption spectrometry with a metal tube atomizer and thiourea as a matrix modifier

A laboratory constructed molybdenum tube atomizer was used for direct determination of trace cadmium in drug samples by the electrothermal atomic absorption spectrometric (ETAAS) method. An ultrasonic agitation method for a solution including the sample powder was used. A calibration curve was constructed with a cadmium standard solution including matrix. To eliminate interference from other matrix elements, a chemical modifier thiourea, was used. The detection limit were 17 pg ml(-1) (3 S/N), and the RSD of the direct analysis was 5-17%. The results for cadmium in the four drug samples analysed by the direct ETAAS method matched well with those obtained with nitric acid digested samples. The recovery of added cadmium was 103-106%. An accurate method is elaborated for the determination of cadmium in drug samples by direct ETAAS techniques. The merits of this method are rapid calibration, simplicity, fast analysis, and low cost.