[Zurück]

W. Nischkauer:
"Development of advanced methods for the determination of Platinum Group Elements in plant material";
Betreuer/in(nen): A. Limbeck, M.-A. Néouze; Institut für Chemische Technologien und Analytik, 2011; Abschlussprüfung: 18.11.2011.

Platinum, Palladium and Rhodium are members of the Platinum group Elements (short PGEs); these elements are used in large quantities as catalysts in the chemical industry as well as in automobile catalysts. The latter reduce the emission of noxious gases like carbonmonoxide, nitrogen oxides and non-combusted fuel and have been widely applied both in passenger cars and in freight vehicles since the mid-1980ies. The catalytically active PGEs are finely dispersed on a ceramic material; due to thermal stress, mechanical shock and high gas-flow rates abrasion of the carrier material and the PGEs takes place. The resulting particles are co-emitted with the vehicle´s exhaust gases and are deposited along roadsides. Due to environmental conditions (rain, wind) and their incorporation in biomass, they can gain additional mobility. Knowledge about PGE´s toxicity and/or carcinogenic behaviour is still scarce; as long as the actual infliction of PGEs on living species is not totally understood and their respective potential to enter the food chain is unknown, monitoring of these elements is required. The analysis of PGEs in environmental samples is a rather challenging task, as several factors hamper their correct determination. Firstly, the natural background-concentration of these elements is very low. Even soils collected along heavily frequented highways contain PGEs in concentrations of only some μg per kg. Secondly, many analytical methods are interfered by elements or compounds inherent to environmental surroundings like crustal elements, other trace metals and organic material. These interfering agents are found to be several orders of magnitude higher in concentration than the PGEs. It is obvious that the removal of these interferences respectively the correction of their negative effects is considered a major task in trace metal analysis.
In this Diploma Thesis two methods for the assessment of PGEs in plant material are presented; the instruments used throughout the process are well introduced to analytical laboratories therefore it should be easy to actually implement the methods in routine analysis. The work is structured in three main parts, the first (chapter 1) providing general information about the technological use of PGEs and the faith of these elements in the environment. Analytical methods commonly applied for the assessment of PGEs are compared.
In the second part (chapter 2), a novel approach in sample pre-treatment using a modified solid phase extraction method is introduced which allows the enrichment of palladium from aqueous solutions. Due to this enrichment, it was possible to quantify comparatively low concentrations of Palladium in digested plant material using ET-AAS; the spatial distribution of this analyte in various parts of the plants could therefore be determined and a significant difference in Pd- content between leaves, stem and roots was discovered. In order to enable the analysis of plants that show restricted growth (low sample mass), direct sampling of PGE containing plant material using electro thermal vaporisation ICP-OES is presented in the third part (chapter 3). The major advantage of this direct sampling approach lies in the reduction of time consuming sample pre-treatment steps and the avoidance of potentially dangerous chemicals. Furthermore, the inevitable dilution of the target analytes after sample digestion is eliminated since no dissolution of the samples is required. The results are compared with the results of a conventional ICP-OES analysis using digested plant material and are found to be in good accordance if correct quantification is applied.