No description available.

Benzotriazoles (BTs) such as 1H-benzotriazole (1H-BT), 5-methyl-1H-benzotriazole (5Me-BT) and 4-methyl-1H-benzotriazole (4Me-BT) have a wide range of industrial applications. BTs are present for example in dishwasher detergents, in automotive antifreeze formulations and aircraft de-icing/anti-icing fluids (ADAF) as corrosion inhibitors. BTs belong to the group of “emerging contaminants” that have got in recent years more and more in the focus of environmental scientists, policy makers and the general public. These compounds are ubiquitous and highly mobile in the aquatic environment. It has been already shown that BTs have negative effects on aquatic organisms. The objective of the present study was among others to monitor 1H-BT, 4Me-BT and 5Me-BT in river- and wastewater. River water samples were taken from five rivers in the Hengstbach/Schwarzbach catchment area, a medium-sized catchment area of about 400 km². River water grab samples were taken during six different sampling. The aim of this monitoring study was to get a seasonal catchment-wide overview on measured concentrations and mass loads of BTs. BTs concentrations were determined in 24-hours influent composite samples taken on different month from three wastewater influents in Germany. In addition, 2-hours composite influent samples collected during one day in April were analyzed to determine the daily periodic emissions of BTs mass flows. Moreover, ADAF used at German airports and three dishwasher detergent tablets commonly used in Germany were analyzed for the presence of BTs to study the distribution pattern of those compounds in different products. An analytical method based on SPE and GC-MS has been developed and optimized for the determination of the presence of the corrosion inhibitors 1H-BT, 4Me-BT and 5Me-BT in environmental samples.

Synthetic fragrances are artificially synthetised organic compounds which are used as fragrant substances in assorted personal care products, perfumes, cosmetics, soaps, detergents, cleansing articles, etc. So-called musk compounds creates significant group of synthetic fragrances which are distinguished by specific fragrance reminiscent of musk. Recently great attention is devoted to musk compounds because they were proved in different units of environment. The aim of diploma thesis was determination of selected linear musk compounds (arocet, aroflorone, linalool 925, lilial, isoamyl salicylate) in real samples of waste water in the influent and effluent from the sewage treatment plant Brno-Modřice. At first optimization of selected method was performed and then this method was used for own determination. Analytes were extracted by solid phase microextraction (SPME) from sample. Method of gas chromatography with mass spectrometry was used for own analysis. The results were used for evaluation of efficiency of removing linear musk compounds from waste water.

Production of renewable fuels is of growing interest due to the ongoing concerns associated with combustion of fossil fuel contributing to global warming. Biomass-derived bio-oil is a potential alternative replacement for conventional fuels. But negative properties such as lower energy density, higher water content and acidity prevent the direct use of bio-oil as a fuel. It is universally agreed that for production of a viable fuel bio-oils must be significantly upgraded. Present upgrading techniques, such as hydrodeoxygenation and esterification consume high amounts of expensive hydrogen or large volumes of alcohols, respectively. Production of low yields continues to be a challenge for hydrodeoxygenation. Therefore, development of more efficient upgrading methods would be desirable. The current research was divided into two parts: in the first part the raw bio-oil was pretreated prior to upgrading to reduce coke formation and catalyst deactivation during upgrading. In the second part pretreated bio-oils were further upgraded by several techniques. The second chapter describes application of an olefination process to raw bio-oil to produce a boiler fuel. In the third chapter, raw bio-oil was pretreated by novel oxidation pretreatment to convert bio-oil aldehydes to carboxylic acids. Aldehydes lead to coke formation and their conversion to carboxylic acids circumvents this issue. Following oxidation pretreatment to raw bio-oil acid anhydride pretreatment was applied to reduce water content which leads to catalyst deactivation during upgrading. The fourth chapter tests esterification of pretreated bio-oil by oxidation to produce boiler fuel with relatively high HHV. The fifth chapter discusses hydrodeoxygenation of oxidized bio-oil produced by oxidation to increase hydrocarbons yield and reduced charring during hydrodeoxygenation. The sixth chapter describes application of catalytic deoxygenation of pretreated bio-oil by oxidation in the presence of pressurized syngas to produce a liquid hydrocarbon mixture. In the seventh chapter we tested direct hydrocracking of pretreated bi-oil by oxidation to produce a liquid hydrocarbon mixture. The end products were analyzed by following the ASTM methods for HHV, water content, viscosity, density, acid value, elemental analysis. Best performing fuels based on high HHV and low acid value were analyzed by FTIR, GC-MS, DHA, 1HNMR and simulated distillation.

High attrition rates in Science, Technology, Engineering, and Mathematics (STEM) fields are major challenges in undergraduate education. Many students enrolled in STEM fields end up switching their majors to non-STEM fields or leave college without earning any academic qualification. Due to these reasons, the United States is facing a critical shortage of future talented STEM personnel in the domestic workforce. Therefore, graduating a sufficient number of talented students in STEM fields has come to national attention. It is important to examine strategies for improving STEM-major retention and undergraduate education in STEM disciplines. The main purpose of this study was to investigate methods to improve students’ social and peer-mentoring interactions within the undergraduate chemistry program at Mississippi State University to improve student learning and their attachment to chemistry and the STEM major. In Chapter II, a study performed to examine peer-mentoring interaction patterns that occur between laboratory partners in the General Chemistry I laboratories is discussed. In this study, five different laboratory partnership types were created. In the development of some partnership types, Math ACT score and lecture section were used as metrics for matching lab partners to create supportive peer-mentoring interactions. Also, students were encouraged to participate in external study groups during the semester. This research study determines whether valued peer-mentoring interactions in the laboratory could support students to be more successful in their chemistry coursework and to have improved social interactions. In Chapter III, a peer review writing assignment that mimics the publication process is presented. This writing assignment supports students to improve their writing skills by reviewing peer write-ups and practicing critical analysis of their work. This assignment is introduced to upper-level undergraduate students to improve their scientific literacy skills in order to prepare them for future scientific communication. In Chapters IV and V, two new laboratory experiments that are connected to real-life scenarios are presented. These laboratory experiments are designed to improve student interest in laboratory learning and to enhance their learning in chromatography techniques and hands-on experience with the GC-MS instrument.

Sound research and effective teaching are both essential to the progress of science. This thesis encompasses two studies to address the two needs: a multi-scale soil study designed to validate a novel soil biological characterization method; and a pilot pedagogical study designed to test the efficacy of authentic science inquiry into gas chromatography. The soil study relies on a comparison of six soils taken from the Bahamas and Michigan. The novel method, using soil-derived VOCs analyzed via gas chromatography-mass spectrometry (GC-MS), proved effective for resolving soils, as hypothesized, and may prove useful for analyzing soil biology rapidly and non-destructively in future studies. The pilot pedagogical study compares traditional recipe-style instruction with authentic science inquiry in an undergraduate chemistry laboratory class. Pre- and post-assessments of students’ conceptual understanding, retention of terms, and attitude revealed the hypothesized superior efficacy of authentic science inquiry over traditional recipe-style instruction.

No description available.

Much attention has been recently devoted to sensorially active substances affecting beer quality in the Czech Republic and worldwide. Among them, the heterocyclic and sulphur containing compounds play an important role, some of them with high sensorial activity even in extremely low concentrations. Trace amounts of these compounds, which can be frequently found in foods, participate in formation of their aroma and this effect can be generally evaluated as favorable However, in malt or beer it is true only to a limited extent and the presence of heterocyclic and sulphur containing compounds are in this respect assessed rather unfavorably. The aim of the present study was to provide a survey about of problems in the field of sulphur containing compounds in barley, malt and beer, to describe metabolic paths leading to their formation and to verify experimentally possibilities of their determination using modern analytical methods. Sulphur-containing amino acids are a natural part of barley, malt and beer and are precursors of the origin of volatile sulphur substances. The most frequently occurring sulphur amino acids, metionine, cysteine and homocysteine, were selected for analytical monitoring. The method of gas chromatography was used to determine sulphur-containing amino acids in barley, malt and beer. Prior to the analysis, sulphur-containing amino acids were derived and volatile N(O,S)-ethoxycarbonyl propyl esters were formed; they were subsequently analyzed using the gas chromatography with mass detector (GC/ MSD) and the gas chromatography with flame photo detector (GC/ FPD). Direct analysis of sulphur volatile substances is possible only rarely as they are found in the analyzed matrices (malt, beer) only in very low concentrations ( g/kg,l - ng/kg,l). Before the analysis, the analytes must be extracted from the matrix and concentrated. The modern analytical methods SPME (Solid Phase Micro Extraction), SPDE (Solid Phase Dynamic Extraction) and TDAS (Thermal Desorption Autosampler) were experimentally compared for the extraction and subsequent concentration of sulphur volatile substances. The method of gas chromatography with flame photo detector was used to determine sulphur volatile substances. Following volatile sulphur substances were monitored: dimethyl sulphide, dimethyl disulphide, dimethyl trisulphide, carbon disulphide, ethyl sulphide, diethyl disulphide, methionol, 3-methylthiophen, ethyl thioacetate, 2-methyl-1-buthanthiol. Only metionine was detected in significant amounts in the barley samples analyzed. Not only content but also dependence on a variety and locality were studied. Further, changes in methionine, cysteine and PDMS content during malting were followed. Results proved a significant decline in these substances content depending on the kilning temperature. Three types of fibers were tested for the analyses of the selected volatile sulphur substances in beer in the SPME method. PEG - a fiber with stationary phase Carbowax, PDMS - a fiber with stationary phase polydimethylsiloxan and a combined fiber CAR/PDMS - Carboxen and polydimethylsiloxan. Carbon disulphide, methionol, dimethyl sulphide, 3-methylthiophen and diethyl disulphide were detected with this method. Content of the other analyzed volatile sulphur substances was below the limit of detection. Further was tested usage the SPDE and TDAS methods. Both methods appear to be the suitable for the determination of volatile sulphur substances in beer.

No description available.

No description available.