A study was made on the back mixing or circulation in the continuous phase of a spray type liquid-liquid extraction tower. Concentration profiles of both continuous and dispersed phases were obtained by internal sampling. Mass transfer data are presented for the transfer of acetic acid between water and methyl isobutyl ketone in the 1.5-in. I.D. columns of three different heights. Considerable circulation in the continuous water phase was observed which resulted in the reduction of the driving force for mass transfer. A driving force correction factor, F(m), was obtained from the H.T.U. data using a simplified picture of behaviour at the interface. The height of the tower did not seem to have any effect on F(m). The overall H.T.U. values, obtained from the experimental profiles, were correlated with the flow rates. The end effect due to the agitation and coalescence of the drops at the interface was measured. This end effect was correlated with the overall capacity coefficients and the dispersed phase flow rates. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

Patterns of flavonoid and melanic pigmentation were studied by visual and qualitative chemical means in 20 varieties of cultivated barley. Two new techniques, one manual and one chemical, were developed which made possible the study of the pigments in the separate tissues of the caryopsis. The observation that anthocyanins are localized in the spermoderm and not in pericarp is an example of the usefulness of the techniques. Environmental modifications of pigmentation patterns in varieties and in individual plants are large and biochemical and genetical analyses of patterns are thereby greatly complicated. For example, pelargonidin derivatives were regularly produced in field grown plants but not in greenhouse grown plants. Genes which control pigment production and disappearance during development add to the complexity of pigment patterns. Colors which are visually very similar may be biochemically dissimilar. Leucoanthocyanins occur in aleurone and endosperm but do not occur at any stage in pericarp, spermoderm, or other maternal tissues. In aleurone, which is alkaline, anthocyanins occur as anhydro bases. In aleurone, also, and in certain other tissues, such as the hood veins of the black variety Gatami, anthocyanins may occur as pseudo bases. In young aleurone tissue, anthocyanins are largely free and minor amounts are tissue bound; later in development most are tissue bound. At any stage of development anthocyanins in aleurone are difficult to extract because the nucellar epidermis, alone or with the aleurone envelope, is highly impermeable to most solvents. Biochemical differentiation of anthocyanins, using accepted techniques of extraction and processing, and using paper chromatography, was undertaken for varieties, lines and tissues. Support and extension of earlier genetical study is given. Biochemical phenotypes could be differentiated from basal leaf sheath extracts when visual phenotypes could not be. In varieties such as Black Hulless, anthocyanins from aleurone were largely delphinidin and petunidin derivatives while those from spermoderm were largely derivatives of cyanidin and peonidin. Anthocyanin patterns from different maternal tissues of a single plant were similar but some seasonal variations were recorded. Anthocyanin patterns in varieties, with very different breeding such as Gopal and Black Hulless, even when grown under a variety of environments, were similar and pointed to parallel genetical control of color. Three new anthocyanins with novel characteristics were found in young, but not in mature, caryopses; an outstanding property was their rapid movement on chromatopaper when BAW was the solvent. Whether or not their frequent disappearance was due to inherent instability or was a normal feature of development was uncertain. In some varieties and tissues at least it was established that cyanidin derivatives form first and pelargonidin and/or peonidin derivatives form later. Qualitative associations in development of polyphenols, anthocyanins and melanins were noted. In future, studies of anthocyanins in development would be greatly aided if the experimental barley was grown in constant environments. Detailed characterization of the anthocyanins of barley was made difficult by the complexities of the color patterns and by their instability when commonly accepted processing procedures were used. Most of the anthocyanins of barley were complex and split readily into simpler components. Ninety-three isolates were obtained from basal leaf sheaths and caryopses; some isolates split into as many as 5 components while others did not split. The anthocyanidins of 63 anthocyanin isolates, run against known anthocyanidins, were identified by Rf values obtained in 7 solvents and by spectra; 39 isolates were hydrolyzed for sugar analyses and 25 were hydrolyzed partially for structural elucidation. Many anthocyanins were crystallized and many were rather fully characterized. Many of the anthocyanins of barley are new and had not been reported for other species. New techniques were devised to achieve anthocyanin stability and to enable work with micro amounts of tissue from single hybrid plants. It was shown that evaporation to dryness of extracts in 1% methanolic HC1, a common procedure, is a very serious, but not the single, cause of anthocyanin degradation; certain anthocyanins show a degradative spectral peak ca. 360 mu attributed provisionally to that of chalcones and most show splittings. Clamping and sewing of chromatobands directly to new paper avoided elution and flash evaporation in methanolic HC1. Modification of existing spectral technique also permitted the examination of even very weak anthocyanin bands on paper. Employment of very weak (0.03%) methanolic HCl in procedures was useful. Although the problems of anthocyanin lability were reduced by modifying older procedures and devising new techniques, they were not eliminated. Evidence was obtained finally which showed that anthocyanins are best extracted in neutral methanol as pseudo bases rather than, as is customary, in acidified methanol, as flavylium salts. Not only were techniques devised for anthocyanin stability, they were also devised for handling micro extracts from single plants. Time and materials were conserved in techniques for hydrolysis, concentration, purification and characterization on paper. Complementary equipment for banding and hydrolysis on paper was developed. New solvents for anthocyanidin chromatography greatly aided characterization. Hydrolyses of eluates both from anthocyanins and blank chromatopaper yielded glucose, galactose, xylose and arabinose; a method to remove paper-derived sugar artefacts from chromatographically purified anthocyanins is presented. Additionally, it was found that glycosidic hydrolysis of anthocyanins occurs even on chromatopaper and that the so-called irreversibly adsorbed anthocyanins of many investigators are anthocyanidins. Moreover 'glycosidic' hydrolysis of certain barley anthocyanins, even in crystalline state, to simpler anthocyanins, is the basis of anthocyanin splitting and explains the appearance of the complex chromatoband patterns. Other investigators have also found in other species complex patterns but have assumed them to be in vivo patterns. If biochemical responses to gene action and biogenesis of anthocyanins are to be studied precisely in barley, procedures must avoid artefact production during extraction and processing and yield anthocyanins in their in vivo state. / Land and Food Systems, Faculty of / Graduate

No description available.

No description available.

A sodium fusion-Ion chromatographic method for determination of fluorine, chlorine, bromine, and iodine in organic compounds is described. Seventeen organic halogen compounds and eleven mixtures were decomposed by Na fumes at 280-290°C for one hour or longer. The absorbing solutions were injected for ion chromatographic analysis using electrochemical and conductometric detectors. The arrangement of the apparatus includes the placement of the electrochemical and conductometric detectors. This method provides a mechanism providing for complete analysis for all four halogens in one ion chromatographic sample injection. Reproducibility is excellent and liquid sample handling is mentioned.

Several chromatographic and spectroscopic techniques were applied to Suwanne River reference fulvic acids (FA) and their permethylated derivatives. Retention mechanisms, structural characteristics, and thermal stabilities of FA and its derivatives and fractions were evaluated.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Pesticide residue analysis is very important both in agriculture and environmental protection. The effectiveness of the analytical method depends very much on the extraction and preconcentration of the analytes prior to the actual analysis, as these analytes occur in trace concentrations that may be lower than the detection limit of the instrument. Various methods of extraction and pre-concentration have been introduced in an effort to decrease costs and other negative environmental impacts without compromising efficiency. One such method is single-drop micro-extraction (SDME), whose benefits cannot be overemphasised. This method has been recently introduced in the pool of pre-concentration methods for pesticide and other organic residues. In this study, the SDME method has been developed using chloroform as a solvent for preconcentration of a ten-component mixture of triazine (TP619) herbicides, followed by analysis by gas chromatography and flame ionisation detector (ppm level detection) and mass spectrometry for detection at sub-ppb level. The developed method uses the simple introduction of an air bubble to the micro-litre droplet of the organic solvent used for extraction of the triazines. This air-bubble showed the increase in the extraction efficiency of the method by about 30% relative to the optimised extraction without the air bubble. The air bubble works very well with addition of the salt (10% NaCl) to the solution being extracted, with further extraction enhancements being observed. Traditionally, the solution being extracted is stirred to achieve good mass transfer. However, the present method does not require stirring as stirring makes the system unstable resulting in reduced precision. The optimum conditions for the newly developed method, named bubble-in-drop single-drop micro-extraction (BID-SDME) were found to be as follows: 1 μL chloroform, 0.5 μL air bubble, 10% NaCl and static equilibration for 20 minutes, while the sample volume is 1 mL. This method showed linearity in the region of 1 ppm to 0.05 ppb (about six orders of magnitude) as long as the instrumental settings were optimised for increased sensitivity. The RSD values observed in this method were better than those recorded in literature, being <10%. Some instrumental manipulations are necessary to realise the full potential of the instrument. Various settings were explored on the GC-MS to optimise its performance below the ppb level. It was observed that the configuration that gave the best sensitivity and the lowest limits of detection was the high-pressure and split-less injection mode. This improved the detection limits of the instrument by 2 orders of magnitude (from 1 ppb to below 0.05 ppb). The GC-MS performance was further improved by the use of selected ion monitoring (SIM) mode of analysis. This technique reduced the interferences from the co-extracted compounds that can compromise the precision and accuracy of the analytical method especially at low concentration applicable in trace analysis. The new BID-SDME method was applied to various samples (dam water, synthetic hard water, dam sediment, humic and sandy soil samples) giving unsurpassed efficiencies with very low RSD values. In these systems, NaCl addition (10% w/v) not only increased extraction efficiency but also had a matrix-normalising effect as the RSD values were reduced and the matrix effects somewhat diminished. The application of this method to orange juice required the addition of only 5% NaCl (not 10% like the other samples). The results obtained with the extraction of orange juice were better than those recorded in literature. The normalising effect was further observed as the RSD values with addition of the NaCl were reduced the RSD from 11.7 (salt-free solution) to 5.56 (5% NaCl). These application experiments were carried out at the 0.2 ppb level using spiked samples. The method was compared against the other extraction techniques used in trace analysis (especially SPME) and it performed better overall giving lower RSD values and much improved detection limits. The calculated detection limits for the ten triazines used in the mixture were in the region of parts per trillion (0.9-14 ppt) with RSD values of < 10% with the use of internal standard. / Prof. D.B.G. Williams Mr. R. Meyer

Call number: LD2668 .T4 1950 S663 / Master of Science

The three factors of the resolution (Rs)equation(see Equation 1.1)were explored in this thesis. During the course of the research project, an important aim was to explore separation processes that would lead to an increase in productivity without sacrificing Rs. To that end, an increase in the retention factor (k)to enhance Rs was deemed detrimental to the cycle time, hence the production rate, particularly when preparative separations are involved. Consequently the primary objectives were to (i)prepare more efficient columns and (ii)investigate new strategies in manipulating selectivity. The significance of the work contained in this thesis is highlighted in 27th International Symposium on High Performance Liquid Phase Separations and Related Techniques (HPLC 2003)held in Nice, France between 15-19 June, 2003. Many of the papers presented significantly compared to chapters contained in this research / Doctor of Philosophy (PhD)