Die entwicklung edelmetallselektiver extraktionsmittel und ihre anwendbarkeit in der analytischen chemie

Summary The classical fire assay technique is still the most important procedure for the isolation and determination of precious metals. However, the lead collection system is basically suitable for extracting gold and silver, less for platinum, palladium and the rare precious metals. Extensive corrections are required to achieve accurate results. Many attempts are published to improve the situation by applying alternate collectors, additional chemical separations and instrumental determinative methods, such as atomic absorption and plasma emission spectrometry.Promising methods could be employed if certain separating media (solvent extractants, ion-exchange resins) are provided which extract precious metals selectively and reversibly. In such a case the final calibration step can be carried out with standard solutions of definite composition.The designing of ler made extractants has to consider the complex nature of the solution chemistry of precious metals. Hence, the relationship between metal properties and solvent extraction and ion exchange is briefly surveyed. The outlook with respect to the authors' research activities is focussed on the synthesis, characterization and application of new organic liquid and solid extractants (modified polystyrene and silica gel). These materials are based on chelating formazans and ion-exchanging tetrazolium salts. The selectivity, efficiency and mechanism of metal extraction and re-extraction are reviewed with respect to the effects of substituents attached to the metal binding groups, the influence of organic solvents and the nature of various supports (silica gel, polystyrene). Certain analytical applications are presented, e.g. the determination of silver, gold, platinum and palladium by means of formazan extraction, sorption on to tetrazolium-resins and DCP-emission spectrometry. The methods offer the advantages of selectivity and simplicity.

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Herrn Prof. Dr. G. Tölg zum 60. Geburtstag gewidmet