Please read the abstract in the section 00front of this document / Dissertation (MSc (Water Utilization))--University of Pretoria, 2006. / Chemical Engineering / unrestricted

The concept of flow injection (PIA), introduced as a simple and convenient principle, has established itself as a well defined analytical technique. With achievement and improvement of FIA as a general analytical laboratory technique, on-site monitoring and process analysis becomes a reality. It introduces a great improvement in the objectivity of the analysis, accuracy of the analytical information and greatly enhances the rate of the analytical process. The aim of this research was to determine the content of selected substances of biological importance from food industry (chloride, zinc, a-amylase), and also from the pharmaceutical industry (paracetamol). The importance of adopting FIA systems for these purposes is to increase the objectivity and the speed of their determination, and also to give the possibility of on-line assay. Because only reliable methods can be automated, it was necessary to choose between the methods available for the assay of chloride, zinc, a-amylase and paracetamol. The next step was to optimize the FIA system, and after it to evaluate the FIA/spectrophotometric systems. The results obtained for all substances proved a high reliability. The sample rate was high. Practically no sample interaction was recorded. These characteristics obtained for the proposed methods made them suitable to be used on-line in food and pharmaceutical industry, respectively. / Dissertation (MSc (Chemistry))--University of Pretoria, 2007. / Chemistry / unrestricted

The synthesis of bromochloromethane (BCM) in a batch reactor, using phase transfer catalysis, was investigated. During the synthetic procedure, sodium bromide (100.0g, 0.97mol) along with an excess amount of dichloromethane (265.0g, 3.12 mol) was charged to a reactor containing benzyl triethylammonium chloride (13 mmol), dissolved in 50 ml of water. The bench scale reactions were all carried out in a Parr 4520 bench top pressure reactor coupled to a Parr 4841 temperature controller. The method produced a 50.0 percent yield of the product BCM after a reaction time of 12 to 13 hours. The main objective for this investigation was to optimize the abovementioned reaction with respect to yield and reactor throughput. Quantitative analysis of BCM was performed on a Focus Gas Chromatograph, fitted with a flame ionization detector, and a BP20 column (30m × 0,32mm ID × 0,25 mm). Delta software, version 5.0, was applied for data collection and processing. The injector and detector port were set at 250°C and 280°C, respectively. The oven temperature was set and held at 40°C for a period of 2 minutes, then gradually increased at a rate of 10°C/min to 130°C, with the final hold time set for 1 minute. An analytical method for the quantitative analysis of BCM was developed, optimized and validated. Validation of the analytical method commenced over a period of three days, and focussed the following validation parameters: Accuracy, precision, and ruggedness. Statistical evaluation of the results obtained for precision showed that the error between individual injections is less than 2 percent for each component. However, ANOVA analysis showed a significant difference between the mean response factors obtained in the three day period (p-value < 0.05). Thus we could conclude that the response factors had to be determined on each day before quantitatively analyzing samples. The accuracy of the analytical method was assessed by using the percent recovery method. Results obtained showed that a mean percent recovery of 100.18 percent was obtained for BCM, with the absolute bias = 0.0004, and the percent bias = 0.18 percent. Hence the 95 confidence intervals for the percent recovery and percent bias are given by: (Lz, Uz) = (100.56 percent percent 102.15 percent), 13 (LPB, UPB) = (0.56 percent, 2.15 percent), respectively. Since the 95 percent confidence interval for the percent recovery contains 100, or equivalently, the 95 percent confidence interval for percent bias contains 0, the assay method is considered accurate and validated for BCM. In the same manner the accuracy and percent recovery for DCM and DBM was evaluated. The method was found to be accurate and validated for DBM, however, slightly biased in determining the recovered amount of DCM. With the analytical method validated, the batch production process could be evaluated. A total of six process variables, namely reaction time, water amount, temperature, volume of the two phases, stirring rate, and catalyst concentration, were selected for the study. The effects of the individual variables were determined in the classical manner, by varying only the one of interest while keeping all others constant. The experimental data generated was fit to a quadratic response surface model. The profile plots that were obtained from this model allowed a visual representation of the effect of the six variables. The experimental results obtained showed that the reaction follows pseudo zero-order kinetics and that the rate of the reaction is directly proportional to the concentration of the catalyst. The reaction obeys the Arrhenius equation, and the relatively high activation energy of 87kJ.mol -1 signifies that the rate constant is strongly dependent on the temperature of the reaction. The results also showed that the formation of BCM is favoured by an increase in the reaction temperature, catalyst concentration, and a high organic: aqueous phase ratio. Thus the synthesis of BCM using phase transfer catalyst could be optimised, to obtain a 100 percent yield BCM, by increasing both the reaction temperature to 105°C, and the concentration of the phase transfer catalyst -benzyl triethylammonium chloride - to 5.36 mol percent. The reaction time was also reduced to 6 hours.

M.S.

Rapid advances in computer technology over the last few years and their integration into analytical instruments have led to tremendous increases in data collection rates. The need for tools to assist analytical chemists, and especially spectroscopists, in their task of interpreting such vast quantities of data is immediate. This work focuses on the development of an algorithm based on an alternative to the Fourier transform, the Hartley transform, for the qualitative and quantitative analysis of multi-component mixtures using Excitation Emission Matrices. The algorithm involves the reverse search of a compressed reference spectral library for the identification of possible components of the mixture and the method of Non-Negative Least Squares for the quantification of the components. A number of techniques for pre-processing of three dimensional fluorescence spectra along with several spectral encoding methods for the compression of the spectra were investigated. Both simulated and real data collected with a fluorescence spectrophotometer were used in this study. The algorithm proved capable of analyzing mixtures of five components with relative concentrations ratio of about 100:1 and significant spectral overlap. At the same time a compression ratio of about 10:1 for the spectra in the reference library was achieved. Finally, a library of three dimensional fluorescence spectra of some aromatic and poly-aromatic hydrocarbons was developed to be used with the algorithm. Such a library, along with the algorithm, provides a tool for the quick and simple qualitative and quantitative determination of mixtures of aromatic and poly-aromatic hydrocarbons. / Ph. D.

Surface Acoustic Wave delay lines have been used as probes for chemical analysis. The interaction between matter adjacent to the SAW device surface and the propagating Raleigh wave caused measurable changes in the amplitude, phase and resonant frequency of the wave. The effectiveness of various electronic detection schemes was evaluated along with the response of the device to changes in pressure and temperature. A lithium niobate SAW device was used as a detector for gas chromatography. Frequency shifts of a SAW oscillator provided the highest sensitivity to compounds eluting from the G.C. column. Sensitivity and specificity of the detector to polar and non-polar organic compounds was greatly enhanced by thin chemical coatings applied to the detector surface. Submicrogram quantities of material were easily detected. Linearity and dynamic range of the detection system was poor. Numerous refinements remain to be made which could significantly improve performance. Thermomechanical analysis of thin polymer films were accomplished using a 32 MHz quartz delay line. Very large wave amplitude shifts were observed as the polymer reached its glass transition temperature. Tg measurements were performed on samples clamped to the surface and cast on the surface. Agreement with low frequency dynamic mechanical measurements was good for the clamped specimens, indicating the absence of wave coupling. Specimens cast on the surface experienced large Tg shifts and therefore were coupled to the surface wave. More subtle transitions were also detected. A crystalline transition around room temperature in a TEFLON film clamped to the SAW device provided an easily observed shift in SAW amplitude. Explanations of this behavior have been proposed. The SAW device also provided an ideal vehicle for examining the behavior of thin photoresist films on the surface. Information on solvent evaporation processes and photo-induced crosslinking rate was obtained. The attractive features of the device for polymer thermomechanical analysis include low cost, ruggedness, high sensitivity and ease of use. / Ph. D.

Woven textile fabrics were designed and constructed from hydrophilic and hydrophobic spun yarns to give planar substrates containing amphiphilic microchannels with defined orientations and locations. Polypropylene fibers were spun to give hydrophobic yarns, and the hydrophilic yarns were spun from a poly(ethylene terephthalate) copolyester. Water wicking rates into the fabrics were measured by video microscopy and longitudinal wicking tests from single drops and from reservoirs. Intra-yarn microchannels in the hydrophilic polyester yarns were shown to selectively transport aqueous fluids, with the flow path governed by the placement of the hydrophilic yarns in the fabric. Simultaneous wicking of an aqueous and hydrocarbon fluid into the hydrophilic and hydrophobic microchannels of an amphiphilic fabric was successfully demonstrated. The high degree of interfacial contact and micron-scale diffusion lengths of such co-flowing immiscible fluid streams inside amphiphilic fabrics suggest potential applications as highly scalable and affordable microcontactors for industrial liquid-liquid extractions. The efficiency of liquid-liquid extractions carried out with the amphiphilic fabrics was evaluated. Solvent extraction efficiencies were shown to reach up to ~98%.

Due to the inadequate schooling system and the underpreparedness of learners in South African High Schools, Higher Education Institutions are faced with learners who do not meet the minimum criteria for acceptance into mainstream science programmes. In an attempt to increase access into the institution and meet the demands of more science and technology graduates, the Department of Chemistry at the historically disadvantaged ML Sultan Technikon introduced the Augmented programme for the National Diploma: Analytical Chemistry in 1994. This study provides a report on the profile of the students registered from 1994 to 1996, their graduation rate and a correlation of their points calculated for matric symbols with their graduation rate as well as their performance in Analytical Chemistry, the major subject of their diploma. Interviews are used to determine the perceptions of the lecturers regarding the structure of and teaching in the Augmented programme. / Chemistry / M.Sc. (Chemical Education)

Dissertation submitted in partial compliance with the requirements of the Masters Degree in Technology: Chemistry, in the Faculty of Applied Sciences at the Durban University of Technology, 2008. / In this work, a holistic approach to validate analytical methods was assessed by virtue of Monte Carlo simulations. This approach involves a statement of the methodsâ s scope (i.e. analytes, matrices and concentration levels) and requisites (internal or external); selection of the methodâ s (fit-for-purpose) features; pre-validation and validation of the intermediate accuracy and its assessment by means of Monte Carlo simulations. Validation of the other methodâ s features and a validity statement in terms of a â fit-for-purposeâ decision making, harmonized validation-control-uncertainty statistics and short-term routine work with the aim of proposing virtually â ready-to-useâ methods. The protocol could be transferred to other methods. The main aim is to harmonize the work to be done by research teams and routine laboratories assuming that different aims, strategies and practical viewpoints exist. As a result, the recommended protocol should be seen as a starting point. It is necessary to propose definitive (harmonized) protocols that must be established by international normalisation/accreditation entities. The Quality Assurance (Method verification and Internal Quality Control, IQC) limits, as well as sample uncertainty were estimated consistently with the validated accuracy statistics i.e. E U (E) and RSDi + U (RSDi). Two case studies were used to assess Monte Carlo simulation as a tool for method validation in analytical laboratories, the first involves an indirect polarographic method for determining nitrate in waste water and the second involves a direct determination of heavy metals in sea water by differential pulse anodic stripping voltammetry, as an example of the application of the protocol. In this sense the uncertainty obtained could be used for decision making purposes as it is very tempting to use uncertainty as a commercial argument and in this work it has been shown that the smaller the uncertainty, the better the measurement of the instrument or the laboratoryâ s reputation.

A chromium plating line used by a local company was monitored to identify any potential waste minimisation opportunities. Plating of the workpiece surface is carried out by immersing the workpiece in seven process (treatment) solutions including nickel and chromium plating baths. Between each process step the workpieces are rinsed. The chromium plating process was evaluated using the results of a waste minimisation audit. This involved gathering data on the composition, flow rates and costs of the inputs of the process. Two types of data were collected namely new and existing data. The new data included chemical monitoring (concentration levels of Ni, Cr, Na, S, B, P, Si, Fe, Cu, Zn, Pb as well as conductivity, TDS, SS and pH measurements) and water usage data. The existing data included raw materials, utility inputs, composition of process solutions and product outputs. The data were analysed using three established waste minimisation techniques. The Water Economy Assessment (a form of Monitoring and Targeting) results were determined using an empirically derived model. The Water Balance and True Cost of Waste results were obtained through more detailed calculations using the results of the chemical analysis. The results from the audit showed that the water usage on the chromium plating line has the highest waste minimisation potential. The True Cost of Waste analysis showed there is no significant chemical wastage in the effluent stream. The potential savings of the effluent stream was negligible (approximately R10 for 238 days). Drag-out calculations were also performed and showed that the drag-out volumes were in good agreement with the typical volumes found in the metal finishing industry. Intervention using simple lowcost and no-cost waste minimisation opportunities were recommended as a first step before contemplating further focus areas for technical or feasibility studies. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.