Thesis (M.Sc.(Chemistry))--University of Pretoria, 2000. / Includes abstract in English and Afrikaans. Includes bibliographical references. Also available online.

Thesis (MTech. degree in Chemistry)--Tshwane University of Technology, 2008. / This work is aimed at experimental verification of the theory about the advantages of the two-step sample vapour release in a fast-heated ballast furnace. The term “ballast” was introduced earlier in electrothermal atomic absorption spectrometry, as an alternative to a platform to describe a compact body of refractive material loosely located on the bottom of a tube furnace atomiser. The thermal behaviour of the ballast furnace is similar to that of the platform, but without restriction created by the platform area. Compared with the flat or concave platform, a compact ballast of similar mass to the platform should have less impact on gas temperature because of the smaller surface area. The theoretical predictions concerning atomisation efficiency in the fast-heated ballast furnace were examined by the determination of metals in organic and inorganic matrices using a Quantum Z.ETA atomic absorption spectrometer. The instrument provided fast heating of the tube atomizer, 10 K ms-1. It is shown that in the employed ballast furnace the vapour released into the gas phase occurs after interim condensation on the ballast. For the samples of tetraethyllead, base oil and aqueous solutions of various metals, analytical signals are observed after stabilisation of tube temperature, independent of volatility of the analyte and level of temperature setting. For those samples, a high gas phase temperature provides complete recovery of the analyte without involvement of chemical modifiers and the reduction of spectral interferences from chloride matrices.

published_or_final_version / Chemistry / Master / Master of Philosophy

Thesis -- Departmental honors in Chemistry. / Bibliography: ℓ. 26-28.

Thesis (M. Phil.)--University of Hong Kong, 1998. / Includes bibliographical references.

by Lai Yuen Kwan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references (leaves 41-45). / Abstract --- p.i / Acknowledgement --- p.ii / Contents --- p.iii / List of Figures --- p.vi / List of Tables --- p.vii / Chapter 1. --- INTRODUCTION / Chapter 1.1 --- Air Pollution in Hong Kong --- p.1 / Chapter 1.2 --- Lead in Air and its Harmful Effects on Human --- p.3 / Chapter 1.3 --- Sampling of Air Particulates --- p.6 / Chapter 1.3.1 --- Principles of filter sampling --- p.6 / Chapter 1.3.2 --- Filter media for air sampling --- p.7 / Chapter 1.4 --- Sample Treatment --- p.9 / Chapter 1.4.1 --- Acid digestion - standard method for analysis of metals --- p.9 / Chapter 1.4.2 --- Slurry sampling - direct method for analysis of metals --- p.9 / Chapter 1.4.3 --- Literature survey on slurry sampling --- p.10 / Chapter 1.4.4 --- Comparison between acid digestion and slurry sampling methods --- p.10 / Chapter 1.5 --- Instrumental Analysis --- p.11 / Chapter 1.5.1 --- Graphite furnace atomic absorption spectrometry --- p.11 / Chapter 1.5.2 --- Background correction by the Zeeman effect --- p.12 / Chapter 2. --- EXPERIMENTAL / Chapter 2.1 --- Apparatus --- p.14 / Chapter 2.2 --- Reagents --- p.14 / Chapter 2.3 --- Procedure --- p.15 / Chapter 2.3.1 --- Selection of sample introduction technique --- p.15 / Chapter 2.3.2 --- Recovery study of lead in standard reference material (SRM) in 1-decanol --- p.16 / Chapter 2.3.3 --- Study of suspension behavior of solvents with SRM --- p.16 / Chapter 2.3.4 --- Recovery study of lead in SRM in ethylene glycol --- p.17 / Chapter 2.3.5 --- Determination of lead in SRM by the developed method --- p.17 / Chapter 2.3.6 --- Determination of lead in SRM by the acid digestion method --- p.18 / Chapter 2.3.7 --- Application of the developed method on the analysis of real sample --- p.18 / Chapter 3. --- RESULTS AND DISCUSSION / Chapter 3.1 --- Choice of Solvents for Suspension of Air Particulates --- p.20 / Chapter 3.2 --- Sample Introduction Technique --- p.20 / Chapter 3.3 --- Recovery Study of lead in SRM in 1-Decanol --- p.22 / Chapter 3.3.1 --- Drying stage of the temperature program for analysis --- p.23 / Chapter 3.3.2 --- Effect of 1-decanol on the absorbance signal of the analyte --- p.24 / Chapter 3.3.3 --- Sample injection volume --- p.25 / Chapter 3.3.4 --- Design of temperature program for analysis --- p.25 / Chapter 3.4 --- Study of Suspension Behavior of Solvents --- p.27 / Chapter 3.5 --- Recovery Study of lead in SRM in Ethylene Glycol --- p.32 / Chapter 3.6 --- Evaluation of the Developed Method --- p.33 / Chapter 3.6.1 --- Determination of lead in SRM --- p.33 / Chapter 3.6.2 --- Application of non-linear standard addition method --- p.35 / Chapter 3.6.3 --- precision and accuracy of the developed method --- p.36 / Chapter 3.7 --- Recovery Study with the Acid Digestion Method --- p.36 / Chapter 3.8 --- Analysis of Real Sample by the Developed Method --- p.37 / Chapter 3.8.1 --- Principles of TEOM® on mass measurement --- p.37 / Chapter 3.8.2 --- Selection of filter media for air sampling --- p.37 / Chapter 3.8.3 --- Study of dislodging efficiency of air particulates from Teflon filter --- p.38 / Chapter 3.8.4 --- Comparison with the acid digestion method --- p.39 / Chapter 4. --- CONCLUSION --- p.40 / Chapter 5. --- REFERENCES --- p.41 / Chapter 6. --- APPENDIX --- p.46

Thesis (MTech. degree in Chemistry)--Tshwane University of Technology, 2010.

published_or_final_version / abstract / toc / Chemistry / Master / Master of Philosophy

High-pressure homogenization using a new flat valve homogenizer in combination with enzymatic digestion with a crude protease was investigated as a means of releasing Se compounds from zoological and botanical matrices prior to slurry introduction GF-AAS. Timed trials with four zoological certified reference materials (CRMs), three botanical reference materials (RMs), and a food crop indicated that Se release was quantitative after homogenization or became quantitative within 1 h of digestion at 60°C. / The same technique was employed on five animal feed samples. / A new model of homogenizer equipped with ceramic homogenizing valve was evaluated in terms of analyte metal contamination levels within the final sample dispersion. / Five animal feed samples and four wood pulp samples, were investigated for their content of Cu, Fe and Mn using high-pressure homogenization as the sample preparation technique prior to GF-AAS. Dispersions of dried animal feeds were sub-sampled reliably after 7 days of storage at 4°C. Trials on pulp samples indicated that pulps could be sub-sampled reliably after 1 day of storage. (Abstract shortened by UMI.)

The scope of these studies was two-fold: to evaluate high pressure homogenized slurries as a rapid means of screening wood pulps for their Cu, Mn and Fe content and to evaluate the high pressure homogenization in combination with chelating agents or enzymatic digestion for the liberation/extraction of metal ions from this matrix. / Cu, Mn and Fe were determined successfully in pulp samples using high-pressure homogenization prior to slurry introduction-GF-AAS. The analysis time of the method from sample acquisition to determination was of the order of a few minutes per sample. / Different cellulose swelling/dissolution agents were evaluated for the generation of quasi-stable pulp suspensions, rich in cellulose. High-pressure homogenization alone or in combination with chelating agents or enzymatic digestion was also investigated as a means of quantitatively releasing these metal ions into the liquid phases. / A new model of homogenizer equipped with ceramic homogenizing valve with a few modifications was evaluated in terms of metal contamination levels within the final sample dispersion. (Abstract shortened by UMI.)