Direct determination of cadmium in urine by electrothermal atomic absorption spectrometry after in situ electrodeposition

Determination of cadmium in urine by ETAAS suffers from severe interferences deteriorating the precision and accuracy of the analysis. Electrodeposition step prior to ETAAS allows to avoid interferences and makes cadmium determination possible even at ultratrace levels. The proposed procedures involve electrolytic deposition of cadmium from acidified urine on previously electrolytically deposited palladium film on a graphite atomizer tube, followed by removal of residual solution, pyrolysis and atomization. Both electrodeposition processes take place in a drop of the respective solution (palladium nitrate modifier and acidified urine, respectively), when Pt/Ir dosing capillary serves as an anode and the graphite tube represents a cathode. The voltage is held at −3.0 V. Matrix removal is then accomplished by withdrawal of the depleted sample solution from the tube (procedure A) or the same but followed by rinsing of the deposit with 0.2 mol l⁻¹ HNO₃ (procedure B). The accuracy of both procedures was verified by recovery test. Detection limits 0.025 and 0.030 μg Cd/l of urine were achieved for A and B procedures, respectively. Both procedures are time consuming. The measurement cycle represents 5 and 7 min for A and B procedures, respectively.     

The application of electrodeposition on a tungsten wire to furnace atomic absorption spectrometry

This work utilizes electrolytic separation and preconcentration of analyte metals on a thin tungsten wire electrode prior to their determination by furnace atomic absorption spectrometry (AAS). Only a very basic electrolysis system operating at constant applied voltages is needed. Following the deposition step, the wire electrode is inserted into the central region of a miniature CRA 90 furnace and electodeposited metals atomized. Tungsten wire melts in the furnace environment at approximately 2500°C and this restricts the range of metals which can be determined by this technique. So far, elements characterized by relatively low atomization temperatures, such as Cd, Zn, Ag, Pb and Cu, have been studied. Sensitivity improvements ranging from 1.5 to 15-fold over the conventional furnace AAS have been achieved with deposition times between 30 and 300 s. No appreciable background absorption has resulted during the atomization step following depositions from NaCl solutions, confirming very efficient separation. The technique has been successfully applied to the determinations of Pb in blood digest and in seawater. Apart from the analytical applications, the wire deposition approach to furnace atomization offers some more fundamental advantages over systems operated in the conventional manner. It can be used to study the atomization behaviour of elements in metallic form in relation to the atomization of their different compounds. Moreover, by rapidly introducing the wire into the furnace preheated to a constant temperature, very fast atomization is achieved with corresponding improvements in analytical sensitivities. The rapid wire introduction technique also lends itself to studies of the removal of sample vapour from furnaces.     

Extraction atomic absorption determination of traces of phosphorus in tungsten trioxide

Ohne Zusammenfassung

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Dust analysis of anhydrides by ¹H-NMR-spectroscopy

     

Atomic absorption spectrometric determination of trace tellurium after hydride trapping on platinum-coated tungsten coil

In this work, a sensitive and simple method for the determination of tellurium was developed by hyphenation of electrically heated quartz tube atomic absorption spectrometry and tellurium hydride trapping on platinum-coated tungsten coil. With a mixture of Ar and H₂, tellurium hydride was transported to tungsten coil for trapping at 390 °C and releasing at 1200 °C. A limit of detection (LOD, 3σ) of 0.08 ng mL^{− 1} was obtained with 1 min trapping (1.5 mL sampling volume), and enhancement factor was 28 compared to conventional hydride generation atomic absorption spectrometry. The LOD was better or at least comparable to literature levels involving on-line trapping and some other sophisticated instrumental method such as graphite furnace atomic absorption spectrometry (GF-AAS) and inductively coupled plasma mass spectrometry (ICP-MS), and it can be further lowered down to 0.03 ng mL^{− 1} by increasing the trapping time to 4 min. The platinum coating was stable for 300 firings without sensitivity loss. Interference and its alleviation were studied in detail. The proposed method was applied to the determination of tellurium in several geological standard reference materials, and the results were found in good agreement with the certified values.     

The application of electrodeposition techniques to flameless atomic absorption spectrometry : Part I. The determination of cadmium with a tungsten filament

The use of controlled-potential electrolysis-as a separation and preconcentration technique for metal wire flameless atomic absorption analysis has been studied. The metal to be determined is electrolyzed onto a thin tungsten wire, and then atomized by electrical heating of the filament in an inert atmosphere within an absorption cell. A detailed study of the effect of various experimental parameters on the determination of cadmium is presented. The detection limit was found to be 0.1 p.p.b. cadmium, for a 2-min electrolysis period. The absolute detection limit was 4·10^-11 g. The method appears to be well suited for the determination of cadmium in samples with a complex matrix.     

Atomic absorption determination of traces of elements in ammonium perrhenate of high purity

Summary Methods for the determination of traces of As, Bi, Ca, Cd, Co, Cu, Cr, Fe, In, K, Mg, Mn, Mo, Na, Ni, Pb, Se, Si, Sb, Sn, Te, Tl, V and Zn in ammonium perrhenate of 99.99% –99.999% purity grade are proposed. Na, K, Ca, Mg and Si are determined directly in the aqueous sample solution, while the remaining elements, except Mo, are determined after preliminary extractive separation of their dithiocarbamate complexes at two different pH-values (8-9 and 5–6). Mo is separated from the matrix by extraction with -benzoinoxime. The analaysis is carried out by FAAS or ETAAS, depending on the concentration of the corresponding trace elements. The recovery factor is checked for impurity amounts of 1 g/ml and 0.2 g/ml, respectively.

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AAS-Bestimmung von Elementspuren in hochreinem Ammoniumperrhenat

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Dedicated to Prof. Dr. G. Tölg on the occasion of his 60th birthday     

The application of electrodeposition techniques to flameless atomic absorption spectrometry. Part III. The determination of cadmium in urine.

Cadmium in urine can be determined by a simple flameless atomic absorption technique, in which the metal is electrolyzed onto a thin platinum wire, followed by electrical heating of the wire. The technique is compared with the well-established flame procedure, involving extraction with APDC into MIBK. The data obtained by the two techniques are in good agreement. Large individual variations occur in the urinary concentration of cadmium for workers suspected of cadmium exposure. The group mean values for these workers lie in the range 4–5 p.p.b.; mean values for unexposed control groups are around 1 p.p.b. On a group basis, the results indicate a significantly higher urinary excretion of cadmium for the workers than for the control groups.     

Atomic absorption spectrometry of cadmium after solvent extraction with zinc dibenzyldithiocarbamate

The AAS determination of cadmium extracted as dibenzyldithiocarbamate in methyl isobutyl ketone was investigated. Cadmium was quantitatively removed from the aqueous phase at pH 5 ± 0.5 with a single extraction by shaking for 2 min. The sensitivity of the method was found to be 6 ppm (1% absorption). The precision expressed as coefficient of variation was 1.5% at the 40-ppM level. Interference from foreign cations and anions was examined.     

Atomic absorption spectrometry of vanadium with a tungsten electrothermal atomizer

A detailed study of the atomic absorption characteristics of vanadium with a tungsten micro-tube atomizer is presented. The absolute sensitivities (1% absorption) were 2 × lO^-10 and 4 × 10^-11 g of vanadium for ammonium vanadate and the vanadium N-benzoyl-N-phenylhydroxylamine complex, respectively. Diverse elements and acids have pronounced depressive effects, but vanadium may be determined in rocks after selective extraction of the above complex into chloroform.     

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.     

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.     

Electrothermal atomic absorption spectrometric determination of cadmium in environmental samples with niobium wire preconcentration method

A preconcentration method by adsorption of cadmium on a niobium wire was developed for the environmental waters, followed by electrothermal atomic absorption spectrometry with a tungsten tube atomizer. After the preconcentration, the niobium wire was directly inserted into the tungsten tube atomizer. In the preconcentration (adsorption) process of cadmium, the optimal immersing time was 60?s. The effects of large amounts of concomitants on the preconcentration of cadmium were evaluated. When 10³–10⁴ fold excess of matrix elements existed in aqueous solution at pH 4 and 9, the cadmium response was profoundly affected by the matrix elements. However, the cadmium absorption signal was not significantly influenced at pH 7. Therefore, pH 7 was selected for the application into the real environmental samples. Under the optimal conditions, the detection limit (3S/N) for cadmium by the niobium wire preconcentration method was 7.0?pg?mL^?1 and the relative standard deviation was 6.8%. The method with preconcentration on a niobium wire was applied to the determination of cadmium in water and proved to be sensitive, simple and convenient. Because this preconcentration method can be utilized in the in situ treatment of trace cadmium in environmental water samples, it was unnecessary to carry the water samples to the analytical work place. The technique was shown to be useful for the determination of cadmium in environmental water samples at 0.1–1?µg?L^?1 levels.     

Atomic absorption spectrometry of traces of tri- and hexavalent chromium

Summary Atomic absorption spectrometry combined with extraction is described for the determination of tri- and hexavalent chromium. The chromium diethyldithiocarbamate chelate was used for chromium (VI), whereas hydroxyquinolate or thenoyltrifluoroacetonate chelate for chromium(III). The method is rapid and precise.

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Zusammenfassung Extraktion und darauffolgende Messung der Atomarabsorption wurden zur Bestimmung von drei- und sechswertigem Chrom verwendet. Die Chelatverbindung mit Diäthyldithiocarbamat wurde für Chrom(VI), der Chelatkomplex mit Hydroxychinolin oder Thenoyltrifluoraceton für Chrom(III) verwendet. Das Verfahren ist rasch und genau.

     

Matrix modification for the direct determination of cadmium in urine by electrothermal atomic absorption spectrometry

Matrix modification with ammonium nitrate, ammonium dihydrogen-phosphate and Triton X-100 proved suitable. Optimization of the graphite furnace parameters allowed cadmium to be quantified at 800°C. The response was 0.1 μgl^-1 for 1% absorption, and the relative standard deviation for consecutive determinations of a urine containing 1.5 μg Cd l^-1 was 4%. Urinary cadmium levels of 0.4–1.8 μg l^-1 were found in five occupationally unexposed persons.     

Atomic absorption determination of nicotine in tobacco

A new method for the determination of nicotine alkaloid has been developed. This method is based on the quantitative precipitation of the alkaloid with metals such as Cu²⁺, Pb²⁺, Zn²⁺ and Hg²⁺. Then either the equivalent or residual metal is determined.The proposed method was successfully applied to the determination of nicotine in various types of tobaccos.     

Direct determination of cadmium in urine using graphite furnace atomic absorption spectrometry with Zeeman-effect background correction

A procedure is described for the direct determination of cadmium in human urine using graphite furnace atomic absorption spectrometry with Zeeman-effect background correction. Except for a straightforward 1 + 1 V/V dilution of samples with 1.5% nitric acid, no matrix modifier or sample pre-treatment was necessary, thus reducing the risk of contamination. The concentration of cadmium in urine was evaluated directly from a calibration graph prepared using a metal-spiked human urine pool. In this way the time-consuming method of standard additions was avoided, permitting an increased sample throughput (120-150 samples per day; 90 s per analysis) with minimal attention of the analyst. In routine use, the precision (both within day and day to day) and limit of detection were of the order of less than 10% and 0.05 micrograms l-1 of Cd, respectively. The method is suitable for the biological monitoring of cadmium in the general population or in occupationally exposed persons.     

超声辅助萃取-钨丝电热原子吸收光谱法测定痕量镉

镉对人体和动植物而言是一种非必需的元素,当其含量超过一定浓度就会产生毒性.由于镉在生物体内的半衰期长达1年之久,一旦进入生物体就不易排出.因此,测定食物样品中的镉对保证人类和动物的健康有重要的意义[1].     

Atomic absorption spectrometric determination of trace amounts of copper and zinc after simultaneous solid-phase extraction and preconcentration onto modified natrolite zeolite.

This work assesses the use of modified natural natrolite zeolite as an adsorptive material for the separation and preconcentration of trace amounts of ions. In this work we investigated the potential of modified natural natrolite zeolite for the simultaneous separation and preconcentration of trace amounts of copper and zinc ions. We have developed a simple, rapid, selective, sensitive and economical method for the simultaneous separation and preconcentration of trace amounts of copper and zinc in an aqueous medium using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) as an analytical reagent. The sorption was quantitative in the pH range 7.5 - 9.5, whereas quantitative desorption occurred instantaneously with 5.0 mL of 2 mol L(-1) nitric acid. Linearity was maintained between 0.05 - 6.0 microg mL(-1) for copper and 0.02 - 1.5 microg mL(-1) for zinc in the final solution. Ten replicate determinations of 1.0 microg mL(-1) copper and 0.5 microg mL(-1) zinc in a mixture gave mean absorbances of 0.1687 and 0.2788 with relative standard deviations of +/-1.2% and +/-1.3%, respectively. The detection limits were 0.03 ng mL(-1) for Cu(II) and 0.006 ng mL(-1) for Zn(II) in the original solution (3 sigma(bl)/m). Different parameters, such as the effect of the pH, flow rate, breakthrough volume and interference of a large number of anions and cations, were studied and the proposed method was used for the determination of these metal ions in water as well as standard samples (e.g. Nippon Keikinzoku Kogyo (NKK) CRM, No. 916 and No. 920 aluminum alloy, National Institute for Environment Studies (NIES) No. 1 pepperbush and NIES No. 2 pond sediment). The determination of these metal ions in standard samples showed that the proposed method has good accuracy (recovery > 97%).