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

No description available.

High-energy ion beam based proton induced x-ray (PIXE) is an ideal analytical tool suitable for simultaneous quantification of trace elements with high accuracy. The quantification of trace elements in solids using PIXE has been well established for over two decades. The main objective of this study is to extend this capability to solids with an inhomogeneous internal structure. In this study, pure GAC and PAC samples were soaked in known concentration of arsenic (As) solution and the trace amount of As uptake was determined during these exposures using PIXE, neutron activation analysis (NAA) and atomic absorption spectroscopy (AAS). There is a good agreement between the values and adsorption mechanisms derived from the NAA and pelletised PIXE measurements and some AAS measurements. Micro-PIXE was used to understand the discrepancies in the As adsorption on the pore and flat surfaces of GAC samples. / Master of Science (Hons) (Physics)

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 361-380).

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.)

Three direct interfaces for coupling high performance liquid chromatography (HPLC) with atomic absorption spectrometry (AAS) were developed and optimized for the determination of ionic organolead, organoselenium and organoarsenic compounds. The first all-quartz interface consisted of a thermospray nebulizer and a flame microatomizer in which ionic alkyllead analytes (R$ sb{ rm n}$Pb$ sp{ rm (4-n)+};$ R = CH$ sb3,$ C$ sb2$H$ sb5)$ were atomized by a methanol (from HPLC eluent)-oxygen kinetic flame, and channeled in a quartz tube (atom keeper) mounted into the AAS optical beam. Alternately, the classical electrothermal atomization technique for organolead species (quartz furnace under hydrogen atmosphere) was coupled with a post-column derivatization-volatilization apparatus based on the ethylation of ionic alkylleads by sodium tetraethylborate. The limits of detection provided by these two approaches were 1.0-3.4 ng and 0.10-0.15 ng, respectively. Arsonium ((CH$ sb3) sb3$RAs$ sp+;$ R = CH$ sb3,$ CH$ sb2$CH$ sb2$OH, CH$ sb2$COOH) and selenonium ((CH$ sb3) sb2$RSe$ sp+;$ R = CH$ sb3,$ CH$ sb2$CH$ sb2$OH) species were quantified using a novel HPLC-AAS approach based on a direct coupling of three processes: thermospray nebulization, thermochemical hydride generation using hydrogen gas, and diffuse flame atomization. Direct evidences for the thermochemical hydride generation process was obtained by injecting (CH$ sb3) sb3$SeI and SeO$ sb2$ into the interface and capturing the gaseous end products in liquid chemical traps specific for SeH$ sb2$ and Se(IV). Both analytes were derivatized to SeH$ sb2$ only in the presence of hydrogen in the interface. Reverse- and normal-phase high pressure liquid chromatographic methods were also developed and adapted for the HPLC-AAS analyses of alkyllead, arsonium and selenonium compounds in real samples. The limit of detection of the arsonium and selenonium cations were 7.6-13.3 ng and 31.0-43.9 ng, respectively.

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.)

Several biologically important arsenic compounds including methylarsonate, trimethylarsine oxide, tetramethylarsonium ion, arsenobetaine and arsenocholine were prepared, in good yields, from sodium arsenite, or dimethylarsinic acid. These organoarsenic compounds together with arsenite, arsenate and dimethylarsinic acid were used as standards for the development of analytical methods for determining the levels of individual arsenic compounds (arsenic speciation) present in natural matrices. / Arsenobetaine, arsenocholine and tetramethylarsonium ion were separated by high performance liquid chromatography (HPLC) with on-line detection by thermochemical hydride generation (THG)-AAS. The analytes were eluted from the cyanopropyl bonded phase HPLC column with a 1% acetic acid methanolic mobile phase which also contained diethyl ether triethylamine, and trimethylsulfonium iodide or picrylsulfonic acid. A surface response methodology and a univariate optimization procedure were used to determine the optimum concentration of solvent modifiers in the methanolic mobile phase. Limits of detection in the range 4-5 ng (as As) were obtained for the arsonium analytes under optimum chromatographic conditions. / A simple phenol extraction procedure was developed to isolate arsonium analytes from edible marine tissues (lobster tail muscle, peeled and deveined shrimp, and cod fillet), cod liver oil and human urine. The crude extracts were separated on the cyanopropyl column using a methanolic mobile phase and detected on-line by THG-AAS. Recoveries from tissues or from urine which had been spiked at 0.1-3.4 $ mu$g of As cation/g of fresh weight were 80% or greater for each of five sample types. / An improved HPLC-AAS interface which was compatible with either aqueous or organic mobile phases was also developed. The interface provided approximately equivalent responses to different arsenic oxidation states which resulted in low to subnanogram chromatographic limits of detection for arsenic oxyanions and arsonium cations in an aqueous or methanolic mobile phase. Nascent As anions and As cations were conveniently coextracted from aqueous solution or from fish muscle by phenol extraction and quantified in the same chromatographic run. This method has been applied to a standard reference sample of dogfish muscle (DORM-1), a marine reference sediment sample (PACS-1) and to sediment porewaters (SAG-15) from the Saguenay Fjord.