Doctor's Theses (authored and supervised):

S. Hossein-Zadegan:
"Accurate Trace Metal Analysis in Environmental Samples using Functionalized Sorbent Particles for Analyte Extraction and Pre-concentration prior to ICP-OES Measurement";
Supervisor, Reviewer: A. Limbeck, S. Hann, C. Streli; Institut für Chemische Technologien und Analytik, 2017; oral examination: 2017-11-22.

English abstract:
Trace metal analysis has been noticed since the hazards of their exposure to human body was realized. Several methods of analysis such atomic absorption spectrometry (AAS), atomic emission/fluorescence spectrometry (AES/AFS), inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectrometry (ICP-OES), neutron activation analysis (NAA), X-ray fluorescence (XRF), and anodic striping voltammetry (ASV) have been applied over years. Although the sort of sample and the level of target metal concentration is the confining factor to select the analysis method, ICP-MS and ICP-OES techniques are the methods of choice because these techniques enable sensitive multi-elemental analysis with high accuracy and precision.
Owing to low concentration levels of target analytes in environmental or biological sample digests (usually in the range of ng L-1 or g L-1) a pre-concentration step is required prior to measurement. Furthermore, the presence of major sample constituents (sometimes in the range of g L-1) demands isolation of the analytes from matrix components to reduce potential interferences in ICP-MS/OES analysis. In literature, several well-established techniques are reported for enrichment and/or isolation of target analytes. Among all applied methods like cloud point extraction (CPE), liquid-liquid extraction (LLE) and solid phase extraction (SPE) the latter one has been commonly used due to the ease of application, selectivity and high recovery. In solid phase extraction, the analyte-containing sample solution is passed through a column packed with a sorbent material. The analytes are trapped by the sorbent and thereby separated from sample matrix which does not interact with the sorbent. After a washing step, the retained elements are desorbed by elution with appropriate solvents. Nevertheless, this routine method suffers some deficiencies such as incomplete analyte elution, or the use of solvents not or only partially compatible with ICP analysis. Moreover, time effort and possibility of column contamination have to be considered. To solve these problems, an improved method for analyte enrichment has been developed recently at the Institute of Chemical Technologies and Analytics, which is named dispersed particle extraction (DPE). This method is based on the concept of solid phase extraction but it benefits from the use of fresh sorbent particles instead of packed columns, which results in faster reaction time, less chemical consumption and higher reproducibility.
In the present thesis, the idea is to further improve the extraction process and enhance accuracy and sensitivity of analyte measurement using ICP-OES. To achieve these goals, two kinds of adsorbent particles including magnetic nanoparticles and natural bioparticles were prepared. Furthermore, alternative sample introduction strategies were developed, including Electro-Thermal-Vaporization for measurement of organic bioparticles and flow-injection combined with a magnetic trap for analysis of Co-nanoparticles.

Trace element analysis, dispersed particle extratction, ICP-OES

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