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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.
Herrn Prof. Dr. G. Tölg zum 60. Geburtstag gewidmet 相似文献
Herrn Prof. Dr. G. Tölg zum 60. Geburtstag gewidmet 相似文献
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Irmgard Pfitzer 《Fresenius' Journal of Analytical Chemistry》1957,156(2):128
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A. Heinsius und F. Campbell 《Fresenius' Journal of Analytical Chemistry》1872,11(1):351-353
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Hanns Malissa 《Fresenius' Journal of Analytical Chemistry》1966,222(2):100-119
Zusammenfassung Bei der Automation in der analytischen Chemie sind zwei wichtige Faktoren zu beachten: 1. rein organisatorische und 2. automatische Analysenabläufe. Die verschiedenen Arten der Automation können nach folgenden Gesichtspunkten geordnet werden: 1. offene Systeme; 2. geschlossene Systeme; 3. selbstanpassende Systeme; 4. Computersysteme. Wirtschaftlich besonders wichtig ist die Automation zur Erreichung analytisch erfaßbarer Daten. Beispiele werden angeführt.
Summary Automation in analytical chemistry requires consideration of two important factors: 1. pure organization, and 2. automatic courses of analyses. The different kinds of automation may be arranged in the following way: 1. open-loop systems; 2. closed-loop systems; 3. self-adaptive systems; 4. computer systems. With regard to economy automation is especially important on order to get analytically obtainable data. Examples are presented.相似文献
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