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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Production Systems and Processing Effect on Phytochemicals in Citrus Fruits and Their Analytical and Isolation Methods

Uckoo, Ram 1980- 14 March 2013 (has links)
The emerging scientific evidences on the role of food components in prevention of several chronic diseases are the momentum for shifting from a traditional focus on production to enhancement of nutritional quality. To further understand the role of these phytochemicals this dissertation describes the development of rapid analytical and isolation methods, and the effect of production systems and processing techniques on the levels of phytochemicals in citrus fruits. In the first study, a simultaneous high performance liquid chromatography (HPLC) method for the rapid analysis of amines and organic acids was developed. The simultaneous extraction and analysis of samples provides an economical method for analyzing a large number of samples. In the second study, rapid separation method of potent health beneficial phytochemicals such as polymethoxyflavones from citrus peels using flash chromatography was developed. Using the developed method, five polymethoxyflavones were separated and isolated with high purity in gram level quantity. In the third study, the levels of phytochemicals in organically and conventionally grown lemons and their storage at market simulated conditions were determined. Results suggest that organically produced citrus fruits have higher content of organic acids and flavonoids than conventionally produced. The fourth and fifth study determined the influence of household processing (blending, juicing, hand squeezing techniques) and emerging processing (high pressure processing [HPP], thermal processing) on the phytochemicals content of ‘Rio Red’ grapefruits. Fruits processed by blending had significantly higher levels of flavonoids, furocoumarins and limonin compared to juicing and hand squeezing, while HPP enabled in extending the shelf life of the processed juice without any adverse effects. Therefore, consuming grapefruit juice processed by blending may provide higher levels of health beneficial phytochemicals. The sixth study describes a rapid flash chromatography method for isolation of PMFs and furocoumarins from citrus industrial by products such as peel oil. In the seventh study the developed method was applied to isolate 10 different phytochemicals from an unexplored citrus species, Miaray mandarin (Citrus miaray TAN.). Among them, the 5,7,8,3',4' pentamethoxyflavone was isolated for the first time from the genus Citrus.
72

Detection of inositol phosphates with HPLC-ICP-AES : Method development

Wintergerst, Mieke January 2013 (has links)
Inositol phosphates (IPs) represent a major part of the organic phosphorus found in the environment, which makes their identification and quantification very important. The goal of this project was to explore the possibility of quantification of IPs with inductively coupled plasma - atomic emission spectrometry (ICP - AES). This paper deals with the creation of an in-house IP standard and the considerations for the successful linking of high performance liquid chromatography (HPLC) with ICP - AES. Experiments with different nebulizers, mobile phases, standard solutions and model substance were performed. The proposed optimal conditions for the ICP experiments are: the use of a modified Lichte nebulizer, mobile phase without methanol and the use of standards matched to the mobile phase. Adenosine monophosphate (AMP) was found to be a good model substance and showed that the band broadening from HPLC to ICP – AES was approximately a factor of 2. Limits of detection for AMP were 5 µM for HPLC and 20 µM for ICP – AES. The optimal way to create an in-house standard was using the potassium salt of IP6 and treating it for 90 minutes at a temperature of 120 ºC with 3.2 M acetic acid.
73

Development of HPLC-FID Coupling Using Water as the Eluent

Zhang, Rui January 2010 (has links)
The characterization of all components of pharmaceutical preparations, especially in the analysis of impurities present at levels higher than 0.05% of the main component, is a challenge in the pharmaceutical industry because no single detector can detect all impurities present. All commercial detection methods suffer from certain disadvantages. Universal sensitive detection with a wide dynamic range is strongly demanded. This results in an increasing interest in the development of universal sensitive detection methods for the pharmaceutical industry, which was the goal of this project. In this project, universal detection of analytes by HPLC-FID coupling was explored. Due to the large volume of the vapours of the mobile phase in HPLC, flame-based detection systems are prone to flame instability. To overcome this problem, a series of improvements were evaluated: 1) a fraction of the total volume of the effluent was delivered to the flame of the FID in a split mode; 2) a tubular oven was used before the FID to preheat the effluent and remove a large fraction of the mobile phase before the detector; 3) oxygen gas and a modified FID with an elongated burner were used to improve the performance of the FID. Finally, optimization of the FID design and parameters was performed by running a series of tests in flow injection mode using simplex optimization method.
74

Polycyclic aromatic hydrocarbons in the sediments of the coastal areas along the southwestern Taiwan.

Wang, Chih-ying 05 August 2005 (has links)
The objective of this study is to quantify the polycyclic aromatic hydrocarbons (PAHs) of the sediments along the coast of south-western Taiwan and to investigate possible sources. The south-western coastal area is full of heavy industries. There are tens of industrial parks along with export processing zone, steel-making plant, oil refinery, shipbuilding plant, Hsin-ta pelagic fishing port, Hsin-ta thermal power plant and Kaohsiung international port. It is reasonable that the wastewater went into rivers or pipes and eventually enters coast area. Concentrations of total polycyclic aromatic hydrocarbons (PAHs) in the sediments of south-western Taiwan were between 197.3~2498.9 (ng/g ¡Vdw) with the average of 912.0 (ng/g ¡V dw). Among all stations sampled in this study, A3, located at the waterway of Kaohsiung, has the highest value. The wastewater ejected by ships might be the major factor. The second highest value we got is from C2, which located at the area farer from shoreline than A3. Total organic carbon (TOC) versus median particle size has linear relationship, however, total organic carbon (TOC) versus concentrations of polycyclic aromatic hydrocarbons (PAHs) showed no linear relationship. This is probably due to the wide sampling area of this study and sources of polycyclic aromatic hydrocarbons (PAHs) were not the same. Principal component analysis shows three principal components were extracted and up to 78.79% of total variance can be explained. As indicated on rotated loadings, the three major components were characterized by 4-6 rings PAH compounds, 3-4 rings PAH compounds and 2-5 rings PAHs compounds, respectively. Results of Hierachical cluster analysis also show three major groups (Group 1, 2 and 3) can be geographically related. In addition, according to isomer ratios of PAH compounds, pollution sources of each group can be specified. Group 1, stations located northern bound, has mainly pyrogenic pollution sources, while Group2, stations located at central area of this study, has pyrogenic/petrogenic sources. For Group 3, stations located southern bound, was mainly polluted by petroleum. In regards to the sediment quality guidelines, ERL and ERM, there are one third of stations exceed ERL regarding to Acp and Phe, but only station A3 exceeds ERL regarding to F1 and Pyr.
75

none

Chang, Lan-fang 18 July 2007 (has links)
none
76

none

Chiou, Chwel-Shenq 12 July 2000 (has links)
none
77

none

Liu, Chen-ling 20 January 2009 (has links)
none
78

In-vitro-Untersuchungen zur Pharmakokinetik von Haloperidol in menschlichem postmortem Gewerbe mit einer neuen Methode der direkten Quantifizierung durch Hochdruckflüssigkeitschromatographie /

Schultz, Andreas. January 2002 (has links)
Würzburg, Universität, Thesis (doctoral), 2001.
79

Development of HPLC-FID Coupling Using Water as the Eluent

Zhang, Rui January 2010 (has links)
The characterization of all components of pharmaceutical preparations, especially in the analysis of impurities present at levels higher than 0.05% of the main component, is a challenge in the pharmaceutical industry because no single detector can detect all impurities present. All commercial detection methods suffer from certain disadvantages. Universal sensitive detection with a wide dynamic range is strongly demanded. This results in an increasing interest in the development of universal sensitive detection methods for the pharmaceutical industry, which was the goal of this project. In this project, universal detection of analytes by HPLC-FID coupling was explored. Due to the large volume of the vapours of the mobile phase in HPLC, flame-based detection systems are prone to flame instability. To overcome this problem, a series of improvements were evaluated: 1) a fraction of the total volume of the effluent was delivered to the flame of the FID in a split mode; 2) a tubular oven was used before the FID to preheat the effluent and remove a large fraction of the mobile phase before the detector; 3) oxygen gas and a modified FID with an elongated burner were used to improve the performance of the FID. Finally, optimization of the FID design and parameters was performed by running a series of tests in flow injection mode using simplex optimization method.
80

Adsorption isotherm parameter estimation in nonlinear liquid chromatography /

Forssén, Patrik, January 2005 (has links)
Diss. (sammanfattning) Uppsala : Uppsala universitet, 2005. / Härtill 6 uppsatser.

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