This project has focused on the applicability of using superheated water as an alternative eluent for use in reversed phase high performance liquid chromatography (RP-HPLC). A system based on instrumentation from gas chromatography (GC), HPLC, and supercritical fluid chromatography (SFC) was utilised with some success. Of particular importance was the stability of the column stationary phases commonly employed in RP-HPLC. The most popular phases based on alkyl bonded silica proved unsuitable due to excessive dissolution of the base silica at high temperatures. Nevertheless, two other phases—one a poly(styrene-divinylbenzene) material and the other a porous graphitic carbon—proved stable to temperatures as high as 240°C. At such temperatures compound stability was good, except for a notable case with nitrobenzene. The mechanism of elution remained reversed phase mode throughout, with polar solutes being eluted before non-polar ones.

An in-house developed method is presented for the purity analysis of nitrogen (N2) built-in purifier (BIPTM)) gas for the trace contaminant gases carbon dioxide (CO2), oxygen (O2)) and carbon monoxide (CO), using gas chromatography with a pulsed discharge helium ionisation detector (GC-PDHID). Nitrogen BIPTM gas is used as a “matrix” gas or diluent gas for the gravimetric preparation of binary reference materials of CO, CO2), sulphur dioxide (SO2)) and nitric oxide (NO) at the CSIR NML gas metrology laboratory. Purity analysis of nitrogen BIPTM is required to decrease the measurement uncertainty of the calculated gravimetric concentrations of the gaseous reference materials produced. The aim of the research was to find a method where amounts <0.25 x 10-6 mol•mol-1 of CO2), O2) and CO could be simultaneously analysed in high purity nitrogen within a short time, with minimum cost and on a routine basis. Gas mixtures of trace amounts of CO2), O2) and CO in N2) were separated and quantified using a parallel dual capillary column configuration with temperature and pressure programming and a pulsed discharge helium ionisation detector (PDHID). The detection limits were 9 x 10-9 mol•mol-1 for CO2), 7 x 10-9 mol•mol-1 for O2) and 37 x 10-9 mol•mol-1 for CO with repeatability precision of 1% for carbon dioxide, 1% for oxygen and 10% for carbon monoxide for a 0.2 x 10-6 mol•mol-1 standard. The detection limits obtained were lower than those reported previously by other investigators for similar methods and the validation for the method as set out in this investigation seems to be the first for trace amounts of CO2), O2) and CO in nitrogen. The method was validated by comparison of the CO2) and CO results with results obtained using a flame ionisation detector and methanisation. The technique of sequence reversal was used to improve the peak shape of CO but there was no improvement on the results obtained with temperature and pressure programming. Although no helium purging was used to reduce atmospheric contamination, it was shown that the main source of contamination from the air was through the sampling system which was reduced to a level of ± 20 x 10-9 mol•mol-1 oxygen simply by using a higher sample flow rate. It was also found that even when large amounts of CO2) were adsorbed onto the molecular sieve column, this made no difference to the column performance at trace levels. The method has also been validated for the analysis of nitrogen in high purity oxygen and may also be used to analyse carbon dioxide and carbon monoxide in oxygen as well. / Dissertation (MSc (Chemistry))--University of Pretoria, 2008. / Chemistry / unrestricted

No description available.

There has been substantial market demand for a portable Gas Chromatography (GC) system. Throughout the years, much progress has been made on fabricating a micro system that works as well as a benchtop system. Unfortunately, even though many substrates, channel types, channel widths, temperature control systems, and interface solutions have been attempted, existing versions of the micro-GC still fall short of the ideal. This thesis presents the design, fabrication, and testing of a silicon based micro-GC column that presents a solution for interfacing and heating of the chip. A polyimide resin is used to create a durable high temperature low thermal mass interface with the chip, while a silk screen method is demonstrated for easy printing of heaters. Chromatogram results are shown in both Temperature Program and Thermal Gradient runs.

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Call number: LD2668 .T4 1961 S53

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Yeung Wing Cheung. / Bibliography : leaf 91 / Thesis (M.Phil.)--Chinese University of Hong Kong, 1982

by Lung Man Tung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1991. / Includes bibliographical references. / ACKNOWLEDGMENT --- p.i / ABSTRACT --- p.ii / Chapter CHAPTER 1 --- GENERAL INTRODUCTION --- p.1 / Chapter 1.1 --- Stationary phases and detectors --- p.2 / Chapter 1.2 --- Internal standardization --- p.5 / Chapter 1.3 --- Common pre-treatment technique --- p.6 / Chapter 1.4 --- Pre-treatment techniques --- p.9 / Chapter 1.5 --- Objectives of this work for the determination of styrene --- p.11 / Chapter CHAPTER 2 --- EXPERIMENTAL --- p.13 / Chapter 2.1 --- Instrumentation --- p.13 / Chapter 2.2 --- Reagents and solutions --- p.16 / Chapter 2.3 --- Preparation of stock solutions --- p.18 / Chapter 2.4 --- Sample preparation --- p.19 / Chapter 2.5 --- Extraction method for food samples --- p.20 / Chapter 2.6 --- Procedure for the analytical finish --- p.22 / Chapter 2.7 --- Assessment of the food matrix effect on the recovery of styrene --- p.23 / Chapter 2.8 --- Confirmatory Procedures --- p.23 / Chapter 2.9 --- Treatment of data --- p.24 / Chapter CHAPTER 3 --- DEVELOPMENT OF METHOD --- p.26 / Chapter 3.1 --- Development of GC method --- p.26 / Chapter 3.2 --- Development of the extraction method --- p.29 / Chapter CHAPTER 4 --- DETERMINATION OF RESIDUAL STYRENE IN POLYSTYRENE POLYMER --- p.50 / Chapter 4.1 --- The proposed method --- p.50 / Chapter 4.2 --- Identification of polymer and one cup for the ice-cream cone --- p.51 / Chapter 4.3 --- Determination of residual styrene monomer in polystyrene container and cup --- p.52 / Chapter CHAPTER 5 --- DETERMINATION OF STYRENE MONOMER MIGRATED INTO FOODSTUFFS --- p.58 / Chapter 5.1 --- Methodolgy and scope --- p.58 / Chapter 5.2 --- Determination of styrene migrated into ice-cream --- p.59 / Chapter 5.3 --- Determination of styrene migrated into Yakult and Yogo --- p.60 / Chapter 5.4 --- Determination of styrene migrated into foodstuff kept at elevated temperature in polystyrene containers --- p.60 / Chapter 5.5 --- Conclusion --- p.74 / REFERENCES --- p.76 / APPENDIX --- p.80