Atomic absorption spectrophotometric determination of gold with preconcentration by Donnan dialysis

Donnan dialysis enrichment with tubular cation-exchange membrane was used as a preconcentration method prior to determination of gold by flame atomic absorption spectrometry (FAAS). The value of enrichment factor can be controlled for a particular application through adjustment of the membrane tuning length, dialysis time, carrier flow rate, composition of the receiver solution and by addition of complexing ligand to the receiver or the sample solution. For 10 min dialysis enrichment factor above 3 can be achieved. The detection limit (signal-to-noise ratio = 3) of 35 ng/ml was obtained. RSD at 0.2 mug/ml level was 4.7% (n = 6). The results of dialysis of noble metals mixtures are demonstrated.     

The influence of the local surrounding on the hyperfine interactions in Zr(Fe1−x Ni x )2 compounds

Mössbauer spectroscopy and the TDPAC method have been used to study Zr(Fe_1–x Ni _x )₂ compounds forx0.30. The hyperfine magnetic field at the Fe sites and the quadrupole splitting as functions of nickel concentration were analysed by use of⁵⁷Fe Mössbauer spectroscopy. Values of the internal magnetic field on¹⁸¹Ta nuclei have been found by means of the TDPAC method.     

The determination of environmental and industrial exposure to heavy metals based on the quantitative isolation of metallothionein from human fluids, with application of covalent affinity chromatography with thiol-disulphide interchange gel as a solid-phase extraction support

The aim of this study was to present a new analytical method for the quantitative determination of metallothionein (MT) proteins in human body fluids and tissues, in order to determine the level of environmental and industrial exposure to heavy metals. For MT isolation, covalent affinity chromatography with thiol-disulphide inter-change (CAC-TDI) was applied. Fundamentals of indirect determination of the contents of metallothionein proteins were worked out through estimation of the quantities of metals bound with metallothionein protein and adsorbed on covalent affinity chromatography gel as on solid-phase extraction support during separating process. The (CAC-TDI) gel, specially prepared, was used as a solid phase extraction support (SPE) for preconcentration of Hg-thionein (Hg-Th), Cd-thionein (Cd-Th), Zn-thionein (Zn-Th) and Cu-thionein (Cu-Th) proteins and Hg, Cd, Zn and Cu bonded with MTs from water, human fluids such as: urine, human plasma, breast milk and tissues homogenates.     

On two methods of determining the ellipses and ellipsoids of positioning accuracy of robot manipulators

Summary When analysing the problem of the positioning accuracy of robot manipulators it is important to know how far random deviations of the hand may be from the desired position if the joint positioning errors possess a normal distribution. Two methods of determining the ellipses and ellipsoids of probability concentration are compared. The first of them is based on the standard procedure of the probability calculus. The second approximate method consists in finding at first the polygon or polyhedron of the positioning accuracy, and then in finding the ellipse or ellipsoid with principal axes and second order moments coinciding with those of the polygon or polyhedron, respectively. Examples of application demonstrate that these two methods give very close results.

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Zwei Methoden zur Bestimmung der Ellipsen und Ellipsoide der Positioniergenauigkeit von Handhabungsrobotern

Übersicht Bei der Untersuchung der Positioniergenauigkeit von Handhabungsrobotern ist es wichtig, die Größe zufälliger Abweichungen des Greifers von der erstrebten Position zu kennen, wenn die Lagefehler der Verbindungen eine Normalverteilung besitzen. Es werden zwei Methoden zur Bestimmung der Ellipsen bzw. Ellipsoide der Wahrscheinlichkeitsdichte verglichen. Die erste beruht auf dem Standardverfahren der Wahrscheinlichkeitsrechnung. Die zweite Näherungsmethode besteht darin, daß zunächst das Polygon bzw. Polyeder der Positioniergenauigkeit bestimmt wird und danach die Ellipse bzw. das Ellipsoid mit den Hauptachsen und Momenten zweiter Ordnung wie das Polygon oder Polyeder. Beispiele zeigen, daß beide Methoden zu sehr ähnlichen Ergebnissen führen.

     

Flotation—spectrophotometric determination of osmium with thiocyanate and methylene blue

A sensitive flotation—spectrophotometric method, based on the ion associate formed by the anionic thiocyanate complex of osmium with the basic dye methylene blue (MB) is described. The ion associate precipitates when the aqueous solution is shaken with toluene, and the separated and washed compound is dissolved in acetone. The molar absorptivity is 2.2 × 10⁵ l mol^-1 cm^-1 at 655 nm. Beer's law is obeyed. The molar ratio of Os:SCN:MB in the separated and washed ion associate is 1:6:3. Ruthenium reacts similarly. The method is applied to the determination of traces of osmium in crucible platinum after separation of osmium by distillation as tetroxide.     

Untersuchung der Absorption der bei der Verbrennung phosphororganischer Verbindungen entstehenden P-Oxide mittels32P-markierter Verbindungen

Zusammenfassung Bei der Pyrolyse phosphor-organischer Verbindungen in Sauerstoffatmosphäre bilden sich P-Oxide, die die C,H-Bestimmung stören. Deren Verhalten im Verbrennungsrohr und ihre Absorption an geeigneten Kontakten wurden untersucht. Durch den Einsatz³²P- markierter Ausgangsverbindungen und Aktivitätsmessung des³²P sowohl durch die Wandung des Verbrennungsrohres als auch im zerkleinerten Füllungsmaterial war die laufende Bestimmung der durch die Kontaktschicht absorbierten Phosphormenge möglich. 30 verschiedene Absorptionsmittel wurden geprüft. Der Einfluß der Strömungsgeschwindigkeit des Trägergases, der Temperatur der Kontaktschicht, der Art der Verbrennung sowie der Anordnung des Verbrennungsrohres wurde untersucht. Die Absorptionsleistung der Kontakte ist stark von der Gasgeschwindigkeit abhängig.

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Investigation of absorption of the phosphorus oxides arising in the combustion of organophosphorus compounds by means of³²P-labelled substances

Summary In the pyrolysis of organophosphorus compounds in an oxygen atmosphere P oxides are formed which interfere with determination of carbon and hydrogen. Their behaviour in the combustion tube and their absorption on suitable contacts were investigated. By the use of³²P-labelled starting compounds and measuring the activity of³²P both through the wall of the combustion tube and in the comminuted filling material, continuous determination of the amount of phosphorus absorbed through the contact layer was possible. Thirty different absorption media were tested. The influence of the flow rate of the carrier gas, the temperature of the contact layer, the nature of combustion as well as the arrangement of the combustion tube was examined. The absorption efficiency of the contacts is highly dependent on the speed of the gas.

     

Über einige neue Bispirane

We have obtained four new bispirane systems in which both spiroatoms are vicinal atoms in cyclopropane or cyclobutane rings and in which the heterocyclic component has the basic structure of 1,4-dioxep-2-ene. We have shown that from two possibilities (bispiran, propellan) the general reaction leads only to a bispiran system. To the bispiran2 exhibiting the highest hyperchromism we ascribed the bispirocoplanar conformation (Fig. 1).

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Mit 3 Abbildungen     

Radiation reduction of Cr, Mo and W isopolymetalates in aqueous system

The radiation-chemical processes in aqueous solutions of dichromates, isopolymolybdates and isopolytungstates have been studied. The radiation reduction of Cr(VI) to Cr(III), Mo(VI) to Mo(V) and W(VI) to W(V) takes place. Molybdenum and tungsten blues are the products of the last two processes in acid solutions. The yields of reduction decrease significantly with the increase of pH. The mechanisms of the processes have been discussed. The photochemical reduction of Mo(VI) and W(VI) for the production of corresponding 5-valent states have been used to the study of their electron scavenging efficiencies. It has been shown that these efficiencies decrease in the order: Mo(V)>W(V)>Cr(VI)>Mo(VI)>W(VI).     

Separation of four platinum metals by anion-exchange in hydrobromic acid medium

Distribution coefficients of Pt, Ir, Pd and Rh in the systems Dowex 1 [Br^?]?HBr plus 0.0035M bromine and Dowex 1 [Br^?]?HBr plus 2% N₂H₄·HCl, were determined with the aid of radioactive tracers by batch equilibration for the resins of nominal cross-linking 2, 4 and 8, respectively. Column experiments showed that Dowex 1X4 should be used for separations because of the favourable dynamics of the column process. Elution conditions for the quantitative separation of both trace and milligram amounts of Ir?Pt, Rh?Pt, Pd?Pt and Ir?Pd?Pt mixtures are given. Some data on the effect of temperature upon the quality of separation are also presented.