Development of green sample preparation methods for the analysis of organic substances in aqueous matrices with gas chromatography mass spectrometry

The demand for green analytical methods is increasing. Microextraction methods pose the green alternative to large-scale extractions in research as well as in standard methods. The world's most used and well-accepted microextraction technique, solid-phase microextraction (SPME), is solvent-free, miniaturized, simple to handle, and automatable. The drawbacks of SPME, such as the poor mechanical resilience and small phase volume, were rectified by its further development SPME arrow. For water analysis using gas chromatography mass spectrometry (GC-MS), the choice of the extraction method is a critical step in terms of analytical performance and greenness. Nevertheless, the standardization of microextraction methods is still lacking. Therefore, this thesis investigates the applicability of SPME and SPME arrow for GC-MS water analysis in the fields of industrial process surveillance for the analysis of fatty acids and fatty acid methyl esters and non-targeted wastewater monitoring. Moreover, several challenges such as the combination of microextraction and derivatization, fiber cleaning, and extraction of analytes with different polarities are addressed. The optimization of the critical extraction parameters, such as time, temperature, and pH, by design of experiments significantly increased the gained response in all the applications and is discussed in detail to minimize the effort for future use and development of the methods. A chemical-thermal fiber cleaning procedure was developed, which substantially reduced the carry-over effect. The method detection limits obtained in this study ranged from low ng L-1 to low μg L-1, which is lower than achieved by several research studies. With SPME headspace operation, no pre-treatment was necessary, even though the samples possess complex matrices. Additional reduction of sample matrix-based analysis interferences for target analysis was implemented by selective tandem mass spectrometry. A non-target approach using GC time-of-flight mass spectrometry with parallel electron ionization (EI) and chemical ionization (CI) was tested in combination with a prototype hydrophilic-lipophilic balanced (HLB) SPME with special focus laid on the identification of substances using the complementary dataset from EI and CI. The approach extracted and analyzed analytes with very different polarities resulting in the expectation that the HLB could become the new use-one-for-all material in SPME. For the investigated research fields, SPME and SPME arrow performed well, consequently their future implementation in standard methods is supported by the obtained results.


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