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Cheung Chung Hong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 126-137). / Abstracts in English and Chinese. / ABSTRACT (English version) --- p.iii / ABSTRACT (Chinese version) --- p.vi / ACKNOWLEDGMENTS --- p.viii / TABLE OF CONTENTS --- p.ix / LIST OF FIGURES --- p.xiii / LIST OF TABLES --- p.xvii / Chapter CHAPTER ONE: --- INTRODUCTION --- p.1 / Chapter 1.1 --- Molecular Structure Determination --- p.1 / Chapter 1.2 --- Methods for Structure Determination --- p.1 / Chapter 1.2.1 --- Infrared (IR) Spectroscopy --- p.1 / Chapter 1.2.2 --- Electron Microscopy (EM) --- p.2 / Chapter 1.2.3 --- X-ray Diffraction (XRD) --- p.2 / Chapter 1.2.4 --- Nuclear Magnetic Resonance (NMR) Spectroscopy --- p.3 / Chapter 1.3 --- Solid State NMR Spectroscopy 一 Chemical Shielding Tensor --- p.4 / Chapter 1.4 --- Scope of This Thesis --- p.6 / Chapter CHAPTER TWO: --- PRINCIPLE AND THEORY --- p.7 / Chapter 2.1 --- Introduction --- p.7 / Chapter 2.2 --- Chemical Shielding Tensor (CST) --- p.7 / Chapter 2.2.1 --- Basis of Nuclear Magnetic Resonance --- p.7 / Chapter 2.2.2 --- Theoretical Description of CST --- p.8 / Chapter 2.3 --- CST Calculation --- p.11 / Chapter 2.3.1 --- Ramsey's Theory --- p.11 / Chapter 2.3.2 --- Gauge-including Atomic Orbitals (GIAO) Method --- p.13 / Chapter 2.4 --- Density Functional Theory (DFT) --- p.14 / Chapter 2.4.1 --- KS Theorem --- p.14 / Chapter 2.4.2 --- B3LYP - Hybrid DFT Functional --- p.16 / Chapter 2.5 --- Molecular Mechanic (MM) --- p.16 / Chapter 2.5.1 --- Basis Principle 一 Ball and Spring Model --- p.16 / Chapter 2.5.2 --- MM+ --- p.18 / Chapter 2.5.2.1 --- Bond Stretching --- p.18 / Chapter 2.5.2.2 --- Bond Bending --- p.19 / Chapter 2.5.2.3 --- Torsional Motion --- p.19 / Chapter 2.5.2.4 --- van der Waals Interaction --- p.19 / Chapter 2.5.2.5 --- Electrostatic Interaction --- p.20 / Chapter 2.5.2.6 --- Stretching-bending Interaction --- p.21 / Chapter 2.6 --- Isodesmic Reaction --- p.21 / Chapter CHAPTER THREE: --- METHODOLOGY AND EVALUATION --- p.23 / Chapter 3.1 --- Introduction --- p.23 / Chapter 3.2 --- Computational Method --- p.24 / Chapter 3.2.1 --- Evaluation of Different NMR Computation Level --- p.24 / Chapter 3.2.2 --- Computational Error 一 Round Off Error --- p.32 / Chapter 3.3 --- Local Structure Determination and Evaluation --- p.34 / Chapter 3.3.1 --- Methodology --- p.34 / Chapter 3.3.2 --- Definition of Local Structure --- p.37 / Chapter 3.3.3 --- Models used in Local Structure Determination --- p.37 / Chapter 3.3.3.1 --- Model without CST Modification (Mod-1) --- p.38 / Chapter 3.3.3.2 --- Models with CST Modification --- p.39 / Chapter 3.3.3.2.1 --- Model Using Correction Factors (Mod-2) --- p.39 / Chapter 3.3.3.2.2 --- Model Using Linear Equation (Mod-3) --- p.40 / Chapter 3.3.4 --- Evaluation - Me2P(S)C(OH)R1R2 --- p.41 / Chapter 3.4 --- Determination of Possible Conformation in Powder and Evaluation --- p.53 / Chapter 3.4.1 --- Introduction --- p.53 / Chapter 3.4.2 --- Methodology --- p.54 / Chapter 3.4.2.1 --- Preparation of Calibration Curve --- p.54 / Chapter 3.4.2.2 --- Determination of Possible Conformation Contributing to the Observed CST --- p.57 / Chapter 3.4.3 --- Evaluation --- p.59 / Chapter 3.5 --- Discussion --- p.72 / Chapter 3.5.1 --- Factors Affecting CST --- p.72 / Chapter 3.5.1.1 --- Inter-molecular Interaction --- p.72 / Chapter 3.5.1.1.1 --- O-H----S --- p.73 / Chapter 3.5.1.1.2 --- C-H----S --- p.78 / Chapter 3.5.1.1.3 --- van der Waals Forces --- p.80 / Chapter 3.5.1.2 --- Conformation --- p.81 / Chapter 3.5.2 --- Effect of Experimental Error on the Calculated Structure --- p.82 / Chapter 3.6 --- Summary --- p.84 / Chapter CHAPTER FOUR: --- APPLICATIONS --- p.86 / Chapter 4.1 --- Introduction --- p.86 / Chapter 4.2 --- Tetramethyldiphoshine Disulfide (TMPS) --- p.86 / Chapter 4.2.1 --- Local Structure --- p.87 / Chapter 4.2.2 --- Conformation --- p.92 / Chapter 4.3 --- "Carbon Compounds : 1,3,5-Trimethoxybenzene (1,3,5-TMB) and 1,4-Dimethoxybenzene (1,4-DMB)" --- p.97 / Chapter 4.3.1 --- Local Structure --- p.98 / Chapter 4.3.2 --- Conformation --- p.103 / Chapter 4.4 --- Conclusion --- p.110 / Chapter CHAPTER FIVE: --- CONCLUSIONS --- p.111 / APPENDIX --- p.114 / REFERENCES --- p.126

A direct injection nebulizer (DIN) was constructed in our laboratory and was evaluated as an interface between a liquid chromatography column and an inductively coupled plasma-atomic emission spectrometer (ICP-AES). Optimum operating conditions, detection limits and reproducibility of the DIN closely matched literature data for a somewhat different commercial device. In addition, when using the DIN for sample introduction, the ICP detection exhibited uniform response towards phosphorous compounds of different volatilities. / Department of Chemistry

Devido à importância da agricultura para a economia do Brasil e para a dieta da população brasileira, um esforço contínuo tem sido feito para preservar a qualidade dos alimentos. Um dos mais importantes critérios de qualidade é a concentração correta dos pesticidas ou a não detecção destes nos alimentos. O objetivo deste trabalho é estudar o efeito matriz na analise de resíduos de pesticidas por cromatografia à gás em manga, a contaminação de mangas compradas na cidade de São Paulo por pesticidas e a otimização de um método multiresíduo neste tipo de matriz. O método empregado foi o utilizado pelo Governo Holandês adaptado de Lucke (1975), e constou da extração com acetona e partição em uma mistura diclorometano:hexano 1:1. O extrato foi concentrado e injetado em cromatógrafo à gás com detector de captura de elétrons e detector fotométrico de chama. Foram analisados 23 princípios ativos diferentes entre herbicidas, inseticidas, fungicidas e acaricidas; a metodologia empregada permitiu um limite de quantificação que variou de 0,01 mg/Kg a 0,30 mg/Kg. A recuperação de amostras fortificadas variou de 70 a 120%. Os resultados mostraram que a matriz apresenta uma grande influência na determinação dos princípios ativos Procloraz, Difenoconazol, Fosmete, Azoxistrobina e sulfato Endosulfam; o único princípio ativo encontrado nas amostras compradas no varejo foi o fungicida Procloraz com valores permitidos pela Legislação Brasileira. / Due to the importance of Agriculture for the economy of Brazil and for the diet of Brazilian population, a continuous effort is being made to preserve its high quality characteristics. One of the most important quality criteria is the right concentration or better not detectable pesticide residues. This work had the objective to study the matrix enhancement effect in gas chromatographic analysis of pesticide residue in mango fruit; the contamination of mango fruit by pesticide bought in Sao Paulo city and the optimization of the multiresidue method in this matrix. The employed method in the analysis was adapted from Lucke (1975), used by Netherlands Government; extraction with acetone and partition in a dichlorometane:hexane (1:1), and Gas Chromatographic determination with ECD and FPD. We studied about 23 active substances among herbicides, fungicides, insecticides and acaricides, the developed method allowed a quantification limit ranging from 0,01 mg/Kg to 0,30 mg/Kg. The recoveries of fortified samples ranged from 70 to 120%. The results showed that the matrix had a effect in the determination of the pesticides: prochoraz,difenoconazol, Fosmete, Azoxistrobina and Endosulfam Sulfate. It was found that the mango fruit were contaminated only by Procloraz; according to the Brazilian legislation, this pesticide can be present in mango.

Devido à importância da agricultura para a economia do Brasil e para a dieta da população brasileira, um esforço contínuo tem sido feito para preservar a qualidade dos alimentos. Um dos mais importantes critérios de qualidade é a concentração correta dos pesticidas ou a não detecção destes nos alimentos. O objetivo deste trabalho é estudar o efeito matriz na analise de resíduos de pesticidas por cromatografia à gás em manga, a contaminação de mangas compradas na cidade de São Paulo por pesticidas e a otimização de um método multiresíduo neste tipo de matriz. O método empregado foi o utilizado pelo Governo Holandês adaptado de Lucke (1975), e constou da extração com acetona e partição em uma mistura diclorometano:hexano 1:1. O extrato foi concentrado e injetado em cromatógrafo à gás com detector de captura de elétrons e detector fotométrico de chama. Foram analisados 23 princípios ativos diferentes entre herbicidas, inseticidas, fungicidas e acaricidas; a metodologia empregada permitiu um limite de quantificação que variou de 0,01 mg/Kg a 0,30 mg/Kg. A recuperação de amostras fortificadas variou de 70 a 120%. Os resultados mostraram que a matriz apresenta uma grande influência na determinação dos princípios ativos Procloraz, Difenoconazol, Fosmete, Azoxistrobina e sulfato Endosulfam; o único princípio ativo encontrado nas amostras compradas no varejo foi o fungicida Procloraz com valores permitidos pela Legislação Brasileira. / Due to the importance of Agriculture for the economy of Brazil and for the diet of Brazilian population, a continuous effort is being made to preserve its high quality characteristics. One of the most important quality criteria is the right concentration or better not detectable pesticide residues. This work had the objective to study the matrix enhancement effect in gas chromatographic analysis of pesticide residue in mango fruit; the contamination of mango fruit by pesticide bought in Sao Paulo city and the optimization of the multiresidue method in this matrix. The employed method in the analysis was adapted from Lucke (1975), used by Netherlands Government; extraction with acetone and partition in a dichlorometane:hexane (1:1), and Gas Chromatographic determination with ECD and FPD. We studied about 23 active substances among herbicides, fungicides, insecticides and acaricides, the developed method allowed a quantification limit ranging from 0,01 mg/Kg to 0,30 mg/Kg. The recoveries of fortified samples ranged from 70 to 120%. The results showed that the matrix had a effect in the determination of the pesticides: prochoraz,difenoconazol, Fosmete, Azoxistrobina and Endosulfam Sulfate. It was found that the mango fruit were contaminated only by Procloraz; according to the Brazilian legislation, this pesticide can be present in mango.