Titrimetrische Bestimmung von Zink mit Äthylendiamintetraessigsäure in Gegenwart von Palladium(II)

Zusammenfassung Komplexometrische Methoden zur Bestimmung von Zink in Gegenwart von Palladium(II) wurden ausgearbeitet. Dabei wird Palladium(II) mit Kaliumcyanid getarnt und der Zinkgehalt entweder bei p_H 5,8 oder nach Demaskierung mit Chloralhydrat bei p_H 10 mit ÄDTA gegen Methylthymolblau titriert. Diese Zinkbestimmung läßt sich auch in Anwesenheit einer Mischung von Palladium(II), Kupfer(II), Nickel und Kobalt(II) durchführen.

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Summary Complexometric methods have been developed for determining zinc in the presence of palladium(II). In these procedures, Pa(II) is masked with potassium cyanide and the zinc content is titrated either at p_H 5.8 or after demasking with chloralhydrate is titrated with EDTA at p_H 10 in the presence of methylthymol blue. This zinc determination may also be conducted in the presence of a mixture of palladium(II), copper(II), nickel(II),and cobalt(II).

     

Charge-transfer chromatographic study of the interaction of anticancer drugs with acetyl-β-cyclodextrin

The interaction between 23 anticancer drugs and acetyl-β-cyclodextrin (acetyl-β-CD) was studied by reversed-phase charge-transfer thin-layer chromatography and the relative strength of interaction was calculated. Acetyl-β-CD formed inclusion complexes with 16 compounds, the complex always being more hydrophilic than the uncomplexed drug. The inclusion forming capacity of drugs differed considerably according to their chemical structure. The significant linear correlation between the hydrophobicity and specific hydrophobic surface area of anticancer drugs indicated that they can be considered as a homologous series of compounds, however, their chemical structures are highly different.     

Estimation of radon and thoron caused dose at exraction and processing sites of mineral sand mining area in Vietnam (HA TINH province)

Mineral sands are mined in several countries to supply to the titanium and zircon producing industries. Coastal black mineral sands usually contain, besides ilmenite (FeTiO₃) and rutile (TiO₂), radioactive minerals such as zircon (ZrSiO₄) and monazite (RePO₄). Radon and thoron activity concentration originated from natural radioactive contents of the black mineral sand was monitored at the extraction and processing for black minerals in the coastal areas of Ha Tinh Province, one of the around 40 coastal mineral sand deposits in Vietnam. The survey was carried out with the Raduet chambers made by Radosys Ltd—Hungary. The obtained results for 25 investigated points show that the measured values are not high in the residential houses and in case of the sand extraction site as well. At the titanium processing plant the measured values were higher than outside the facility (Radon: 18–55 Bq/m³ with average of 34 Bq/³ and Thoron 33–118 Bq/m³ with average of 58 Bq/m³) but still comparable to the average concentration of the world published by UNSCEAR. The typical outdoor levels of radon and thoron gas are each of the order of 10 Bq/m³. Although the radon concentrations were low in the zircon and titanium processing plants, the thoron concentrations in the houses for separating rutile and zircon were very high. At zircon processing factory, the thoron concentration could reach 2,931 Bq/m³ and the estimated annual effective dose would be 21.4 mSv/a. Intervention has to be taken in order to reduce the thoron level in this factory since the level of thoron and its progenies corresponding to an annual occupational effective dose is beyond the action level of 6 mSv/a.     

Coulometric redox titrations of hydrazine,phenylhydrazine and isoniazid with electrogenerated lead(IV) acetate and manganese(III) acetate in acetic acid

Summary The conditions fox coulometric determination of small quantities of hydrazine, phenylhydrazine and isoniazid in glacial acetic acid with electrogenerated manganese(III) acetate and lead(IV) acetate were investigated. With the direct coulometric method at room temperature, good results were obtained in the determination of hydrazine and isoniazid with lead(IV) acetate and in the determination of phenylhydrazine with manganese(III) acetate. Hydrazine and isoniazid can also be determined by the coulometric back-titration method if the oxidation with manganese(III) acetate is performed at elevated temperature.

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Zusammenfassung Die Bedingungen für die coulometrische Bestimmung kleiner Mengen Hydrazin, Phenylhydrazin und Isoniazid mit elektrolytisch erzeugtem Mangan(III)-Acetat und Blei(IV)-Acetat in Eisessig wurden untersucht. Bei Zimmertemperatur wurden gute Resultate durch direkte coulometrische Titration des Hydrazins und Isoniazids mit Blei(IV)-Acetat und bei Titration des Phenylhydrazins mit Mangan(III)-Acetat erhalten. Durch coulometrische Rücktitration können bei höheren Temperaturen Hydrazin und Isoniazid mit Mangan(III)-Acetat erfolgreich bestimmt werden.

     

Electrochemical generation of manganese(III) and behaviour of the generated oxidant in acetic acid in the presence of perchlorate ions

Summary Research was carried out to determine conditions for the anodic generation of manganese(III) with high current efficiency in solutions of sodium perchlorate in acetic acid, and to examine the behaviour of the oxidant thus generated. The effects of water and acetic anhydride on current efficiency in the generation of the oxidant was also examined. The formal redox potential of the Mn(III)/ Mn(II) system is decreased with increasing concentrations of sodium acetate in the solution. The effect of sodium perchlorate and perchloric acid concentrations is the reverse. Procedures for coulometric titrations of a number of substances with the generated oxidant were developed, end point being detected using biamperometric and potentiometric methods. Perchloric acid accelerates the oxidation of certain substances with manganese(III) in acetic acid and increases the sensitivity of end-point detection using the potentiometric method.

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Elektrochemische Erzeugung von Mangan(III) und das Verhalten dieses Oxydationsmittels in Essigsäure bei Gegenwart von Perchlorat

Zusammenfassung Die Bedingungen der anodischen Erzeugung von Mangan(III) mit hoher Stromausbeute in Essigsäure, nach Zugabe von Natriumperchlorat wurden untersucht; das elektrochemische Verhalten des so dargestellten Oxydationsmittels wurde ebenfalls untersucht. Der Einfluß von Wasser und Essigsäureanhydrid auf die prozentuelle Stromausbeute des erwähnten Oxydationsmittels wurde verfolgt. Das Formalredoxpotential des Systems Mn(III)/ Mn(II) sinkt bei Erhöhung der Konzentration an Natriumacetat in der Lösung. Perchlorsäure wie auch Natriumperchlorat üben eine entgegengesetzte Wirkung aus und führen zur Steigerung des Formalredoxpotentials bei Erhöhung ihrer Konzentration. Verfahren zur coulometrischen Titration verschiedener Substanzen mittels biamperometrischer oder potentiometrischer Erfassung des Titrationsendpunktes wurden ausgearbeitet. In Gegenwart von Perchlorsäure wächst die Geschwindigkeit der Oxydation einiger Substanzen in Essigsäure in Gegenwart von Mn(III) und auch die Empfindlichkeit der Endpunktbestimmung verbessert sich.

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Presented at the 9th International Symposium on Microchemical Techniques, Amsterdam, August 28–September 2, 1983.     

Inclusion complexing by water-soluble β-cyclodextrin polymers

Cross-linked -cyclodextrin with a molecular weight of less than 10000 has good solubility in water, and it is a better inclusion complexing agent than the parent -cyclodextrin. By including lipophilic guest molecules into the apolar cyclodextrin cavity, their apparent lipophilicity is reduced because the outer surface of the molecular wrapping (the crosslinked -CD) is highly hydrophilic. The relative stability of the inclusion complexes can be rapidly determined by reversed-phase thin-layer chromatography. The reversed-phase TLC behaviour of 25 triphenylmethane derivatives and analogues were studied in the presence of -cyclodextrin polymers containing neutral and carboxyl groups. Increasing the molecular weight results in an increased complex-forming capacity. The carboxyl group modifies the accessibility of the CD cavity which in turn results in increased or decreased complex stability, depending on the guest molecule. The presence of organic solvents diminishes the stability of the CD complexes.