Preconcentration of trace elements by partial dissolution of the matrix—multielement preconcentration from manganese

Trace elements such as Ag, Au, Bi, Cd, Co, Cu, Fe, Ga, In, Ni, Pb, Pd and Tl, can be preconcentrated with recoveries of better than 95% from high-purity manganese if the sample is coated with a thin layer of mercury before its dissolution in HCl to a small residue. For determination of the trace elements, the residue is completely dissolved in aqua regia. After separation of the mercury by reductive precipitation, Bi, Cd, Co, Cu, Fe, Ga, In, Ni, Pb, and Tl are determined by flame a.a.s. ('injection method'). Ag, Au and Pd are determined in the mercury-containing solution. The relative standard deviation was usually about 5%; Cu, Fe and Pb were proved to be inhomogeneously distributed in the sample (electrolytically produced manganese), and so the standard deviations were considerably greater. The detection limits for the different elements were between 0.6 and 0.004 ppm, depending on the sensitivity of their a.a.s. determination. The theoretical basis of this preconcentration method and its applicability to multielement analysis of different high-purity metals are discussed.     

The far infra-red spectra of the isomorphous nitrates of calcium,strontium, barium and lead

The far infra-red spectra of the isomorphous nitrates of calcium, strontium, barium and lead were observed in the frequency range 25 to 200 cm⁻¹. The spectra are similar and have seven absorptions in this range. These absorptions are assigned to modes involving translations of the metal ions and translations and librations of the nitrate ions. Estimates are made of the inter-ionic forces, effective ionic charges and of the damping constants.     

On-line trace preconcentration / matrix separation by high-performance flow atomic spectrometry (HPF-FLAME AAS)

Summary In HPF-atomic spectrometry a high-performance flow / hydraulic high-pressure nebulization (HPF / HHPN) system is used for sample introduction and aerosol generation. By employment of techniques common in HPLC or ion chromatography, on-line trace element preconcentration / matrix separation and atomic spectrometric trace determinations can be carried out. Preconcentration of trace elements in samples of drinking water allows determinations within the lower g/L region by using flame AAS. On-line trace element preconcentration / matrix separation from aluminium leads to detection limits of approx. 0.1 to 1 g/g within less than 3 min of total analysis time. Dependent on concentration and the element involved, the relative standard deviation amounts to approx. 2 to 4% (2.5 to 25 g/g traces/aluminium).Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthday     

Simultaneous multielement AAS with carbon furnace atomization for the analysis of biological samples

Summary A continuum source AAS spectrometer coupled with a graphite furnace atomizer was employed for the determination of trace elements in biological materials (enzymes, blood serum). With proper furnace conditions, accurate multielement determinations can be made simultaneously.

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Simultane Multielement-AAS mit Graphitofen-Atomisierung zur Analyse biologischer Proben

Zusammenfassung Eine Kontinuum-Lichtquelle in Verbindung mit einem Graphitofen-Atomiser wurde zur Bestimmung von Spurenelementen in biologischen Materialien (Enzyme, Blutserum) eingesetzt. Die erreichte Genauigkeit ist mit der bei der Isotopenverdünnungs-MS erzielbaren vergleichbar. Matrixeffekte können reduziert werden.

     

Hydraulic high-pressure nebulization sample introduction for direct analysis or on-line matrix separation and trace preconcentration in flame AAS

Summary Only by replacement of the pneumatic nebulization by the new hydraulic high-pressure nebulization (HHPN) in flame AAS 2 to 10 times higher power of detection (depending on the element) can be achieved for the direct trace determination in a saturated tungstate solution. HHP-nebulization leads in general to higher sensitivity and additionally to lower matrix interferences. The HHPN-sample introduction system offers also facilities for a quick on-line matrix separation/trace preconcentration. Detection limits of 0.1 to 1 g/g were achieved for a tungsten matrix (depending on the element).     

Spectrophotometric and AAS determination of trace amounts of cobalt after preconcentration by using alpha-benzilmonoxime-microcrystalline naphthalene.

The formed cobalt-a-benzilmonoxime complex was adsorbed onto microcrystalline naphthalene. Then it was determined by zero and first derivative spectrophotometry and by atomic absorption spectrophotometry (AAS) after dissolving into chloroform and methylisobutylketone (MIBK), respectively. Under optimum conditions, cobalt in the range of 1.0 - 20.0, 0.4 - 30.0 and 2.5 - 50.0 microg could be determined by spectrophotometry, first derivative spectrophotometry and AAS method, respectively. By the method, a preconcentration factor equal to approximately 30 for cobalt was obtained. The effect of diverse ions on the determination of 5.0 microg cobalt was also studied. The method was successfully applied to some pharmaceuticals and synthetic alloy samples.     

Semipermeable ion-exchange membranes as a preconcentration matrix for trace analysis by electrochemical and neutron-activation techniques

Ion-exchange membranes were used in conjunction with neutron-activation analysis and anodic stripping voltammetry for the determination of certain trace metal ions. The various parameters which govern the applicability, limitations and sensitivity of the methods were investigated. A new membrane "barrier" electrode assembly was introduced and found to be useful for the anodic stripping determination of trace metal ions in the presence of surface active materials.     

Reagent-loaded and unloaded polyurethane foam as preconcentration matrix in neutron activation analysis

Loaded and unloaded polyurethane foams were examined as a preconcentration matrix in combination with neutron activation analysis. The structure of the foamed polymer is not damaged by short irradiation periods. However the foam skeleton degraded after irradiations for one hour or longer in a neutron flux of 3·10¹³ n ·cm⁻²·s⁻¹. The presence of tin as a major impurity in the polyether-type foam has been detected. This may affect the sensitivity of determination of the relatively short lived isotopes of the elements collected on the foam. On the other hand the polyester-type foam was found to contain only very low amounts of tin. Antimony, indium, gold and mercury collected on the foams were determined with reasonable accuracy.     

Substoichiometric precipitation of silicon as barium fluorosilicate

Distillation and substoichimetric precipitation for silicon have been developed for the determination of trace amounts of silicon. It is based on substoichiometric precipitation as barium fluorosilicate and the distillation of silicon tetrafluoride. The separation has been applied for the determination of silicon in gallium arsenide and NBS steel as standard reference material.     

Rhodizonate as reagent for barium,strontium, and calcium

Summary The specificity and sensitivity of the spot tests for barium and strontium is improved by treating the brownish red rhodizonate fleck with a solution of dimethylamine hydrochloride. Calcium may be identified by the separation of characteristic crystals after adding a solution of rhodizonic and benzoic acids. A simple scheme of separation has been developed, which makes use of these confirmatory tests.

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Zusammenfassung Die Spezifität und Empfindlichkeit der Tüpfelproben für Barium und Strontium wird durch Behandlung des mit Natriumrhodizonat erhaltenen Tüpfelfleckes mit Dimethylaminhydrochlorid verbessert. Calcium kann durch die Abscheidung von charakteristischen Kristallen nachgewiesen werden, die nach Zugabe einer Lösung von Rhodizonsäure und Benzoesäure erhalten werden. Ein einfacher Trennungsgang wurde ausgearbeitet, der die nutzbringende Verwendung dieser Nachweisproben möglich macht.

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Résumé La spécificité et la sensibilité de la recherche du baryum et du strontium par essais à la touche sont améliorées en traitant la tache rouge brunâtre de rhodizonate par une solution de chlorhydrate de diméthylamine. Le calcium peut être identifié par la séparation de cristaux caractéristiques après addition d'une solution d'acides rhodizonique et benzoïque. On a mis au point un schéma simple de séparation dans lequel on fait usage de ces tests de confirmation.

     

Micellar ultrafiltration preconcentration of strontium by anionic micellar solution

Th anionic micellar system of the sodium dodecylsulphate (SDS) with di-2-ethylhexylphosphoric acid (D2EHPA) chelating ligand reagent in acctate buffer solutions was studied. The influence of the concentration and the composition of the micellar system for strontium preconcentration was determined. Different pH values of solutions as well as different concentration ratios of the ligand to the surfactant were used.     

Monohydrates of strontium and barium hydroxide

The monohydrates of strontium and barium hydroxide have been prepared by decomposition, under vacuum, of the corresponding octahydrates. X-ray powder data for both compounds are reported, together with that for anhydrous strontium hydroxide; the latter is included in order to clarify an apparent anomaly in the literature.

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Zusammenfassung Es wurden die Monohydrate von Strontium und Bariumhydroxid im Vakuum aus den entsprechenden Octahydraten hergestellt. Röntgenographische Daten für beide Verbindungen sowie für wasserfreies Strontiumhydroxid wurden gegeben; für Letzteres, um gewisse Anom alien in der Literatur zu klären.

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Résumé Préparation des hydroxydes de strontium et de baryum monohydratés par décomposition dans le vide des octohydrates correspondants. Etude par rayons X de ces composés ainsi que de l'hydroxyde de strontium anhydre, dans le but, pour ce dernier, d'élucider certaines anomalies de la littérature.

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The authors wish to thank Mr. A. Miller for taking the X-ray powder photographs.     

Bicarbonate complexes of barium and strontium

Dissociation constants and free energies of formation for the BaHCO₃⁺ and SrHCO₃⁺ complexes were determined in the BaCl₂H₂CO₃ and SrCl₂H₂CO₃ systems, respectively. These values are as follows: K_BaHCO3⁺ = (3·03 ± 0·17) × 10⁻², ΔF_BaHCO3⁺° = −276·39 ± 0·04 kcal/mole, and K_SrHCO3⁺ = (5·70 ± 0·54) × 10⁻², ΔF_SrHCO3⁺° = −275·21 ± 0·06 kcal/mole.     

Systematic investigations of the multi-element preconcentration from copper by precipitation of the matrix as copper(I) oxide and copper(I) thiocyanate

Two methods for multi-element preconcentration from copper by reductive matrix precipitation are presented. In systematic investigations on the coprecipitation behaviour of Ag, Al, Au, Bi, Cd, Co, Cr, Fe, Ga, In, Mn, Mo, NJ, Pb, Sb, Se, Sn, Te and Zn during precipitation of the copper matrix as Cu₂O or CuSCN, the separation parameters were optimized. By combination with a hexamethyleneammonium hexamethylenedithiocarbamate collector precipitation, a concentration of 8 elements (Cu₂O precipitation) or 13 elements (CuSCN precipitation) in a small volume was achieved. The limits of detection of the procedures are, depending on the element, 0.1–5 μg g^?1 for flame atomic absorption spectrometry (AAS) and 0.01–0.1 μg g^?1 for graphite furnace AAS. The relative standard deviations are about 3%. The analytical performance of the procedures is compared with that of an electrolytic copper separation.     

Radiochemical microdetermination of Manganese, strontium and barium by ion-exchange

A rapid radiochemical ion-exchange method has been developed for the quantitative separation of microamounts of Mn, Sr and Ba in the presence of other elements with atomic numbers below 84. The method proposed, combined with neutron-activation analysis, has been successfully applied to the simultaneous determination of Mn, Sr and Ba in plant and animal tissues. The method is simple and accurate.     

Oxidative degradation of ethers promoted by strontium and barium tetraphenylimidodiphosphinates

The novel M[(OPPh2)2N]2.nTHF (M = Sr (2), Ba (3)) complexes were prepared and characterized. Upon exposure to atmospheric oxygen, 2 and 3 were transformed to the dinuclear species Sr2-[(OPPh2)2N]4.2C3H6O3 (4) and Ba(2)[(OPPh2)2N]4.2C4H8O3 (5), respectively. Compounds 4 and 5 contain coordinated carboxylic acids obtained from the oxidative degradation of DME and THF, respectively, which were used as solvents for crystallization.     

Characterization of strontium and barium manganates by abrasive stripping voltammetry

Abrasive stripping voltammetry is applied in order to characterize barium and strontium manganates-(V) and -(VI) in solid state phases. Voltammetric reduction peak potential values of KBaMnO₄, Ba₃(MnO₄)₂, Ba₃(MnO₄)_{2− x} (BO₃) _x (x=0.031(1)), Ba₅(MnO₄)₃OH, Ba₅(MnO₄)₃Cl, Sr₅(MnO₄)₃OH and BaMnO₄ are shown to be proportional to the corresponding average Mn-O distances, which were determined from X-ray powder diffractometric data through Rietveld refinement analyses. Received: 25 November 1997 / Accepted: 28 January 1998