Sol-gel capillary microextraction (CME) is a new direction in solvent-free extraction and preconcentration of trace analytes. CME presents significant interest in environmental, pharmaceutical, petrochemical, biomedical, agricultural, food, flavor, and a host of other important areas. Sol-gel CME utilizes advanced material properties of organic-inorganic hybrid sol-gel polymers to perform efficient extraction and enrichment of target analytes from a variety of matrices. In this dissertation, two novel sol-gel coatings were developed for CME: (a) sol-gel benzyl-terminated dendrimer coating, and (b) sol-gel polytetrahydrofuran (poly-THF) coating. A detailed investigation was conducted to evaluate the performance of the newly developed sol-gel coatings in solvent-free extraction of a wide range of polar and nonpolar analytes. Sol-gel chemistry was used to chemically immobilize dendrimer- and poly-THF-based hybrid organic-inorganic coatings on fused silica capillary inner surface. The sol-gel coatings were created using a coating solution containing a sol-gel active organic component (dendrimer or poly-THF), a sol-gel precursor (methyltrimethoxysilane, MTMOS), a sol-gel catalyst (trifluoroacetic acid, TFA, 5% water) and a deactivating reagent (hexamethyldisilazane, HMDS). Sol-gel reactions were conducted inside a hydrothermally treated fused silica capillary for 60 min. A wall-bonded sol-gel coating was formed via condensation of silanol groups residing on the capillary inner surface with those on the sol-gel network fragments evolving in close vicinity of the capillary walls. Due to the strong chemical bonding with capillary inner walls, these sol-gel coatings showed excellent thermal and solvent stability in CME in hyphenation with gas chromatography (GC).

Bisphenol A used in the production of polycarbonate plastics and epoxy resins is ubiquitous in the environment. The raw material is released to the environment during the manufacturing process and by leaching from consumer products. Recent studies are suggesting that low-dose amounts of Bisphenol A may have adverse health effects on humans. The possibility of removing Bisphenol A from natural water sources or from solvents used to extract the material from consumer products before they enter the market has been studied. The use of model compounds and related substances (4-isopropylphenol, 4-(t-butyl) phenol, and nitrophenols) have been used to study their removal from aqueous solutions using column chromatography and Octolig®, a commercially available material with polyethylenediamine moieties covalently bonded to high-surface area silica gel. The experimental results suggest that 2-nitrophenol and 4-nitrophenol can be successfully removed while 3-nitrophenol, 4-isopropylphenol, and 4-(t-butyl) phenol did not yield a high percent removal. A look at the pKa of the compounds provides an interesting explanation of the results. It is suggested that the compounds with a pKa of approximately 8.3 or higher would require the solution to be at a high pH for anion formation. The resulting pH of the solution would simultaneously deprotonate the ethylenediamine moieties of Octolig® rendering it incapable of removing the anions by ionic interaction.

Two highly polar sol-gel coatings were developed for capillary microextraction (CME). One of the coatings contained cyanopropyl-polydimethylsiloxane (CN-PDMS) and the other low molecular weight polyethylene glycol. These highly polar coatings were immobilized via sol-gel chemistry allowing for direct chemical bonding to the inner surface of fused silica capillaries. These sol-gel coated microextraction capillaries were employed in CME for solvent-free microextraction and preconcentration of trace analytes (polar, moderately polar, and nonpolar) from aqueous matrices. CN-PDMS and short chain PEG extraction phases exhibit both polar and polarizable characteristics. Therefore, both sol-gel CN-PDMS and short chain sol-gel PEG coatings were able to extract analytes of different polarity from aqueous media. Both sol-gel CN-PDMS and sol-gel PEG coatings provided effective extraction of polar analytes such as free fatty acids, alcohols, and phenols without requiring derivatization, pH adjustment or salting out procedures commonly used in SPME experiments with conventional coatings. For each of these coatings, detection limits on the order of nanogram/liter (ng/L) were achieved for both polar and nonpolar analytes extracted simultaneously from aqueous media followed by GC-FID analysis. Both sol-gel CN-PDMS and short chain sol-gel PEG coated microextraction capillaries showed excellent run-to-run and capillary-to-capillary extraction reproducibility (GC peak area RSD < 6% & 5%, respectively) for nonpolar as well as polar analytes. For the sol-gel CN-PDMS coatings, the upper allowable conditioning temperatures were 330 degrees C and 350 degrees C, for the extraction of polar and nonpolar organic analytes, respectively. Similarly, the sol-gel PEG coatings used for the extraction of polar organic analytes survived a conditioning temperature of 340 degrees C. Both sol-gel CN-PDMS and sol-gel PEG coated microextraction capillaries showed no significant changes in the peak areas of the extracted analytes even after being washed with organic solvents (dichloromethane and methanol (1:1), v/v) for 24 hours. The excellent thermal and solvent stabilities can be attributed to the presence of chemical bonds between the sol-gel coatings and the fused silica surface.

M. Tech. Chemistry / Sutherlandia frutescens is a popular indigenous South African medicinal plant which has been identified to re-establish itself on acid rock mine dumps. Medicinal plants such as S. frutescens are harvested from the wild and widely used for primary health care. The primary objective of the study was to determine the effect of soil contamination on the secondary metabolites profile of the plant.

published_or_final_version / Civil and Structural Engineering / Master / Master of Philosophy

No description available.

Using a model system of glycosylated and aglycon standards consisting of rutin and quercetin respectively, and a series of pre-packed solid phase extraction cartridges, including C18 Extra-Clean, DSC-18, DPA-6S, Oasis HLB and Amberlite XAD-2. The experimental findings also showed that use of a commercial hesperinidase preparation, resulted in adequate hydrolysis of the glycosylated standard rutin. Based on these findings, the phenolic compounds and flavonoids from maple sap and syrup were separated using the Amberlite XAD-2 column, where the glycosylated fractions eluted with 60% aqueous methanol solution and the aglycon fractions eluted with a methanol:acetonitrile mixture (1:1, v/v). The recovered glycosylated fractions were subjected to enzymatic hydrolysis using the hesperinidase preparation and the liberated phenolic compounds and flavonoids, as well as the sugar components were analyzed by high-performance liquid chromatography (HPLC).

Comparative high-performance liquid chromatography (HPLC) and gas-liquid chromatography (GC) analyses of selected phenolic and flavonoid standards were developed using a wide range of detectors, including ultraviolet diode-array (UV-DAD) and electrochemical (EC) detectors for HPLC and flame ionization detector (FID) and mass spectrometry (MS) for GC. The results demonstrated that the limits of detection obtained with HPLC-EC analysis were 10 to 500-times higher for phenolic acid standards and 2 to 50-times higher for flavonoid standards than those obtained with the HPLC-UV analysis. HPLC-EC was more sensitive than GC/FID for all investigated standards, especially for vanillin and syringaldehyde. The results indicated that GC/FID/MS analysis of phenolic and flavonoid standards was more efficient than that of HPLC, providing a fast analysis with better resolution and baseline separation of all standards with minimum co-elution. The only co-elution encountered in GC/FID was with coniferol and p-coumaric acids. For HPLC analysis, (-)-epicatechin, caffeic and homovanillic acids were co-eluted at 28.04 min and sinapic and ferulic acids at 34.57 min. Phenolic compounds and flavonoids were extracted from maple sap and maple syrup with ethyl acetate and the recovered compounds were subjected to HPLC and GC analyses. Tentative identification of phenolic compounds and flavonoids in maple sap and maple syrup indicated the presence of protocatechuic acid, hydroxycinnamic acid derivatives, (+)-catechin, (-)-epicatechin, vanillin, coniferol, syringaldehyde, flavanols and dihydroflavonols related compounds. In addition, the identification by GC/MS of protocatechuic acid, vanillin, syringaldehyde, coniferol and p-coumaric acid was made by comparing mass spectrum characteristics of individual peak from total ion chromatogram (TIC) to that of standard compounds. The seasonal variation of selected phenolic compounds and flavonoids present in maple sap and maple syrup was also invest

Perilla L. are significant for multi-pharmacological effect. The aim of this work is to study Perilla L. growth and develop¬ment tendencies, productivity; composition of biologically active compounds and their variations during the vegetation period, and the biological effect of the extracts; to select perspective plants for cultivation in Lithuania and for production of medicinal preparations. The objectives of the Study: To investigate and determine growth dynamics of Perilla L. species and varieties during the vegetation period and to assess the influence of climate conditions on the vegetation rhythmic. To assess the quantity dynamics of Perilla L. species and varieties herbal medicinal raw material and to compare the productivity of Perilla L. species and varieties. To determine the quantity of the essential oil in Perilla L. species and varieties and to identify the chemotypes of the plants. To determine the qualitative composition and variation dynamics of the phenolic acids in Perilla L. species and varieties. To determine the composition and variation dynamics of the flavone complex in Perilla L. species and varieties. To determine the composition and variation dynamics of antho¬cyanidines in Perilla L. species and varieties. To assess the radical scavenging activity of the extracts of Perilla L. species and varieties raw materials. To research the effect of Perilla L. extracts on the oxidative phosphorylation in the rat heart mitochondria. / Perilla L. genties vienmečiai vaistiniai augalai yra augaliniai imunomoduliatoriai, pasižymintys daugeliu farmakologinių poveikių. Darbo tikslas: Ištirti Vidurio Lietuvoje auginamų Perilla L. rūšių ir varietetų augimo ir vystymosi dėsningumus, biologiškai aktyvių junginių sudėtį ir jų įvai¬ravimą vegetacijos metu bei ekstraktų biologinį poveikį; atrinkti perspek¬tyvius augalus auginimui Lietuvoje. Uždaviniai: Ištirti ir nustatyti Perilla L. augimo dinamiką vegetacijos metu ir įvertinti klimatinių veiksnių įtaką augalų vegetacijai. Įvertinti Perilla L. vaistinės augalinės žaliavos kiekio dinamiką vege¬tacijos metu ir palyginti Perilla L. rūšių ir varietetų produk¬tyvumą. Nustatyti Perilla L. rūšių ir varietetų eterinio aliejaus kiekį auga¬luose vegetacijos metu ir identifikuoti augalų chemotipus. Nustatyti Perilla L. rūšių ir varietetų fenolinių rūgščių kokybinę sudėtį ir jų kitimo dėsningumus vegetacijos metu. Nustatyti Perilla L. rūšių ir varietetų flavonų komplekso sudėtį ir kitimo dinamiką vegetacijos metu. Nustatyti Perilla L. rūšių ir varietetų antocianidinų sudėtį bei kitimo dinamiką vegetacijos metu. Įvertinti Perilla L. rūšių ir varietetų žaliavų ekstraktų antiradikalinį aktyvumą. Ištirti Perilla L. rūšių ir varietetų ekstraktų poveikį žiurkės širdies mitochondrijų oksidaciniam fosforilinimui. Tyrimų rezultatai ir poveikiu pasižyminčių junginių identifikavimas atveria perspektyvas ateities tyrimams, kurie reikalingi kuriant preparatus iš perilių augalinių žaliavų.

Thesis (Ph.D)--Mississippi State University. Department of Food Science, Nutrition and Health Promotion. / Title from title screen. Includes bibliographical references.