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The simple geometry and multiple applications of a rotating drum, such as mixing, segregation, drying, and coating in chemical, mining, chemical, metallurgy, civil, food processing, and waste management industries, have made it a focus of studies on the behaviour of granular particles. Studying that behaviour experimentally is very expensive and simulations require very high computational power. But with the advent of greater and cheaper computational power, it has become economical to use simulations. The dynamic properties and behaviours of particles in a drum and their mixing and segregation have been the main fields of study. Those studies have dealt with problems related to drums rotating horizontally. However, very few studies have analysed particle behavior in an inclined rotating drum (IRD), although those drums have long been used in waste management and process industries. Therefore, in this study, a comprehensive focus was given to particle behavior in an IRD and its applications. This study took an overview and brief look at various aspects of particle behavior in the IRD, because to the author’s knowledge, no study of this scale has focused on that type of drum. The discrete element method (DEM) was used to study particle behavior in the IRD. Because research related to that behaviour is at a very early stage, the DEM simulations required experimental validation. Therefore, an experimental setup was designed and fabricated, and its results were used to validate the DEM results with the help of Altair’s EDEM simulation software. In this study, the DEM model was implemented on the EDEM platform. Initially, a system using only one particle type was used to validate the DEM results with the experimental results, and after that, a two-particle system was used for segregation. The particles were spherical. The experimental and simulation results had similar patterns, which validated the DEM simulation results, thus justifying the use of DEM to study the particles in an IRD system. The DEM is a contact-based model, where particle behavior broadly depends on the velocity of the particles. Hence, dynamic properties such as velocity, contact forces, torque, and coordination number of the particles in a rotating drum with the inclined axis of rotation play a major role in understanding particle behavior.

Complex samples of natural origin, such as, tobacco leaf extracts and coffee bean extracts, comprise a vast number and variety of compounds. The characterisation of such complex samples can be arduous and time consuming. Multidimensional analytical techniques have the potential to provide detailed and informative characterisation data, especially if these techniques exploit separation selectivity and detection selectivity. This thesis explores multidimensional approaches for the analysis of complex samples using High Performance Liquid Chromatography (HPLC) and selective detection. Uni-dimensional HPLC (1DHPLC) multi-detection and multiplexed detection through the use of Active Flow Technology (AFT) columns were used to characterise tobacco leaf extracts to determine key chemical entities by systematically reducing the data complexity of the sample whilst obtaining a greater degree of molecule-specific information. Even though substantial chemical data was obtained, there were limitations; in particular the separation performance of 1DHPLC. This lead to studies directed towards two-dimensional HPLC (2DHPLC), where separation selectivity could be exploited by optimising stationary phase and mobile phase combinations; tailored to the characteristics of the sample. In this work, various combinations of stationary and mobile phases were explored to determine the optimal 2DHPLC selectivity conditions for the separation and analysis of tobacco leaf extracts. However, the performance of 2DHPLC is compromised by the interface between each dimension, namely the compatibility of the solvents and the volume of fluid required in the transfer from the first to the second dimension. This incompatibility often results in loss of separation performance. A preliminary investigation was therefore undertaken to assess the performance of AFT columns in 2DHPLC. The outcomes from this work showed that efficiency and sensitivity could both be improved with the use of AFT columns, however, the results were highly dependent on the construction of the HPLC system.

Comprehensive multidimensional separations are today dominated by systems that are fundamentally limited to highly asymmetrical online separations sacrificing separation space, or to lengthy, time consuming offline separations. With the exception of pulse-modulated methods in gas chromatography, separations have thus been limited to two dimensions. In liquid chromatography, the highest efficiencies in terms of separation power are achieved through asymmetric comprehensive online two-dimensional separations where the capacity to separate analytes within a given time is severely restricted by the need to avoid under-sampling of the first dimension and by the subsequent limitation of peak capacity within the second dimension. These limitations have been overcome in this thesis by employing multi-dimensional detection whereby both the retention times and frequencies of analyte pulses are recorded. Within a given separation dimension, analyte pulses were related to their linear velocities. Time dependent frequency analyses combined with knowledge of the physical dimensions of that separation dimension allowed the determination of both the times at which analytes entered that separation dimension and their retention times within that dimension. By this means, it is possible to reconstruct a virtual comprehensive multidimensional separation. This approach has been called Comprehensive Online Multidimensional Frequency Transform Separations (COMForTS). Analyte pulses can be introduced either as physical pulses resulting from alternately switched valves or as virtual pulses produced from the combination of signals from multiple in-separation detectors. The principle of operation being the same in both cases, a semi-empirical computer model of a physically pulsed system was developed and its feasibility positively demonstrated in simulations of high-efficiency separations in two dimensions. In that model, time-dependent frequency spectra were obtained by short time Fourier transforms. Performance characteristics with respect to harmonics, overtones, pulse width, peak width and peak frequencies were identified. Separations of higher dimensionality were also shown to be possible. Following this theoretical groundwork, a basic prototypical COMForTS instrument together with custom control software and signals processing system was designed and constructed based upon a less physically demanding on-column multipoint detector array. Practical online two-dimensional separations were performed in which varied and controlled degrees of peak wrap-around and physical overlap were generated, replicating the effects of first-dimension under sampling. It was simultaneously shown that while a conventional online two-dimensional separation failed, COMForTS was able to fully, and correctly, resolve all analytes. Improvements in peak production rates of between 26-and 41-fold were observed and quantitative results were obtained. Minimal interferences were observed when time-dependent frequency transforms were cross-correlated. Significant future improvements to both the efficacy and speed of signals processing were also identified. COMForTS also places no restriction on the analysis time (or peak capacity) of second, or higher separation dimensions. Total analysis times increase only additively with dimensionality whilst increases in peak production rates are multiplicative - possibly approaching three orders of magnitude in three-dimensional separations. Most significantly, COMForTS demonstrated an exceptionally high confidence in the purity of peaks, bypassing limitations imposed by current statistical peak overlap theory by applying conditional logic to the separation of analyte information. COMForTS is limited in that it provides separation information rather than a physical separation and that, in its most efficient form, detection is limited to non-destructive, arrayed, in-separation methods. Nonetheless, the method exhibits great potential for applications that demand complex separations with rapid turnaround, such as in process control, comparative metabolomics, fingerprinting of natural products and rapid screening of complex samples. It is envisaged that these applications of the method would leverage emerging high-efficiency micro-and nanoscale separations technologies facilitating close to time-of-sampling analytical results.

This research program investigates the behaviour of analytical scale modified silica monoliths in reversed phase HPLC. Each silica monolith was purchased commercially and modified in-situ using a silane reaction. Column efficiency, measured using the 2nd moment method, for each column was between 33,261- 105,162 N/m for all modified columns. Stationary phase stability was tested through the entire study using a standard test mix of substituted aromatics. For each modified monolithic surface, where column solvent consumption exceeded 2,000 column volumes, no stationary phase or monolithic bed displayed degradation. The modified silica monoliths were characterised chromatographically through tests that investigated the efficiency, selectivity, adsorption isotherm behaviour, and six common characteristic parameters within the Tanaka test that are often used to compare novel or developed stationary phases of commercial quality. Other techniques, such as, SEM and elemental analysis were used to characterise the modified monolithic bed integrity and also the surface coverage of different sections of the monolithic bed, which required the destruction of the column. The modified monoliths repeatability of stability test results ensured the commercial quaility was not compromised or influenced by a degrading stationary phase column and that the destructive techniques could correlate to the chromatographic findings. This thesis proved to develop and characterise the behaviour of novel modified monoliths (cyano and phenyl selectivities), and to illustrate that a single silica monolith had the potential to be coated more than once (involving a silica surface regeneration process to remove the previous coating) with the third coating, for example, displaying only small variances in chromatographic behaviour compared to the first modification process. The findings of this work has shown that the limited selectivity in commercial monoliths (bare silica, C8 and C18) no longer poses any impediment, as the separation scientist can utilise the speed of silica monoliths and bond a moiety tailored to the separation problem through a time and cost effective in-situ modification method while maintaining or improving the initial commercial quality of the column.

Chromatography is a powerful separation technique that was initially developed for the isolation of natural components in a highly purified form from complex mixtures. However, early applications of chromatography that were preparative in nature were quickly surpassed by analytical separations as the need for qualitative and quantitative information about components present in simple and complex mixtures became the primary objective. HPLC is the commonly used analytical separation technique for the determination of components in complex mixtures as it offers high sensitivity and also high selectivity. In general, HPLC is carried out in a single dimension using one primary retention mechanism dictated largely by the stationary phase. Although modern HPLC column technology has made available stationary phases with improved efficiency, particularly for the separations of complex mixtures, there are limits to its use. In reality there is only so much space available for components in a given sample to be separated into individual peaks, which is limited by the peak width and determined by the efficiency of the column. This is highly dependent upon the number of theoretical plates (N) available for the separation and therefore the peak capacity. Multidimensional HPLC is a technique that is gaining appreciable support at the analytical level due to the vastly expanded separation space that allows for increased resolution of components in complex samples. The introduction of a second dimension, which offers a change in selectivity to that of the first dimension, is a means of increasing the total peak capacity of the separation process and therefore expanding the separation space. Two-dimensional HPLC is an effective separation technique for the analysis of complex mixtures if the sample’s complexity can be reduced as the separation mechanism of the first dimension may be tailored towards the sample’s multidimensionality and/or its physical characteristics such as size, polarity, charge and shape. Reducing the complexity can be as simple as ensuring co-elution of the key components in the first dimension, but then utilising the second dimension to resolve those components co-eluting in the first dimension. Here the first dimension can be considered essentially as a ‘clean-up’ step in order to isolate the required targets in the second dimension. This essentially reduces the required peak capacity of the first dimension and the separation space in the second dimension more than compensates for this reduction as the second dimension is required to separate a lower number of components. Preparative HPLC has only seen resurgence in the last few decades with traditional methods such as distillation, centrifugal extraction and crystallisation unsuitable for the problems encountered by the various industries. The stringent regulations of governing bodies for the approval of highly purified products to be released into a highly competitive market dictate largely the advancement of chromatographic methods for preparative separations. Chapter 1 is a general introduction with a brief history of chromatography presented. The theory and practice of two-dimensional chromatographic separations and preparative chromatographic separations are also discussed. Sample dimensionality and its importance to the determination of orthogonality of separation steps are also considered. Chapter 2 details the chemicals and equipment used to perform the experiments outlined throughout the thesis. Specific general methods are also included here for reference. Chapter 3 describes a model framework for the development of a two-dimensional liquid chromatographic system and was reliant on low molecular weight oligostyrenes as they are complex, are indefinitely stable and easily characterised. The ultra high resolution separation of diastereomers of low molecular weight oligostyrenes on carbon adsorption stationary phases are also discussed. Chapter 4 examines the practical aspects in the optimisation of targeted isolations in two-dimensional HPLC with emphasis on analytical scale analysis. The emphasis in this chapter was on the isolation of “a‟ target analyte from “a‟ complex mixture, where effectively ‘a’ represents a generic sample, complex in nature. Chapter 4 also examines the practical aspects in the optimisation of targeted isolations in two-dimensional HPLC with emphasis on analytical scale analysis. However this chapter focuses on maximising the recovery of the target component at analytical scale analysis. Chapter 5 investigates the practical aspects in the optimisation of preparative scale two-dimensional isolations by the establishment of a continuous batch-wise 2D purification process, with the intent to preparative scale-up. In this chapter the experimental variables that effect the production of a target component are introduced and the influences they have on the separation are discussed. Chapter 5 also investigates the use of the system introduced at the preparative level however high sample loads are now used to determine the effect of the recovery in both the first and second dimensions; the purity of the collected product; and finally the product recovery yield, effective production rate and the practical production rate. Chapter 6 focuses on improving the quality of the isolation process by increasing the peak capacity of the second dimension firstly, followed by an increase in the peak capacity in both the first and second dimensions. This improved the resolution and therefore reduced the number of components transferred to the second dimension. This had the benefit of decreasing the performance demand of the second dimension column. Chapter 7 summarises all of the findings contained throughout this thesis.

Phenyl type stationary phases have the ability to undergo π-π interactions with aromatic compounds and have the potential to take advantage of this particular sample dimension in 2DHPLC. This thesis examined a series of phenyl type sta¬tionary phases that were synthesised and packed in-house, containing systematic changes in the length of the chain binding the aromatic ring to the silica sup¬port (between 0 and 4 carbon atoms). The stationary phase was characterised and tested to determine retention characteristics with both linear and non-linear chromatographic measurements. The linear measurements involved a selectivity study with homologues of lin¬ear polycyclic aromatic hydrocarbons and n-alkylbenzenes to determine the aro¬matic and methylene selectivities, respectively. It was found that there were distinctly different trends in aromatic selectivity occurring on these phases that was dependent on an even or odd number of carbon atoms in the spacer chain. For short chain lengths the even phases were more aromatic selective though for longer chain lengths the odd phases were more selective. Ab initio calculations performed on these ligands show a change in the ring orientation between even and odd chain lengths that can explain the different trends in selectivity. The changes in methylene selectivity were relatively minor. Selectivity changes were also measured for a series of propyl phenyl (3 carbon spacer chain) stationary phases with different ligand densities. It was found that aromatic selectivity increased with ligand density and methylene selectivity plateaued near a ligand density of 2.0 µmol m−2 . Adsorption isotherm measurements, by frontal analysis with independent steps, of the different chain lengths with small substituted aromatics found that there were different retention processes occurring on the even and odd phases and this affected the saturation capacity. It was found that the degree of heterogeneity on these surfaces was weak and that small degrees of lateral adsorbate-adsorbate interactions occurred that are related to π stacking. To gain quantitative information from a two-dimensional separation methods need to be employed that can identify the location of each peak. A peak picking algorithm was utilised that identifes peaks in each one-dimensional cut using derivatives, followed by comparing peak overlap and peak maximum profiles. When the peaks are located it is relatively simple to perform statistical analysis to quantitate/compare 2DHPLC separations. The propyl and butyl phenyl chain lengths (i.e. 3 and 4 spacer carbons, re¬spectively) were tested in a two-dimensional separation with caf´e espresso coffee, a complex sample matrix, to determine if there was a difference in a real separa¬tion. The performance of the two separations were quantifed using an algorithm programed in-house to identify two-dimensional peaks and then performed a ge¬ometric approach to factor analysis and calculated the normalised mean radius in the separation quadrants. Subtle differences in the separations were observed when examining and comparing the individual quadrants, however the analysis of the entire separation showed very little difference.

Reactive intermediates in the oxidative processes are among the major sources of primary catalysts that initiate oxidation in vivo and in vitro; a process that is one of the major causes of food quality deterioration and generation of chronic diseases. Antioxidants, both natural and synthetic, have been widely used at legal limits in food, medical and personal care industries. However, recently, the use of synthetic antioxidants has been severely restricted because of the evidence that suggests they may be harmful to human health. As such, the importance of screening naturally occurring alternatives, which are presumably safe, effective as dietary supplements or as processing aids, is increasing. Natural products are well known for their molecular biodiversity and are of great interest as potential source for novel antioxidant molecules. Due to the chemical complexity of natural products, determining their antioxidant content can be a formidable task, but at the same time likely to be worthwhile task. This thesis investigates the hyphenation of one- and multi-dimensional chromatography towards to profiling antioxidant content in natural products.

The separation work in this thesis focuses on adsorption of riboflavin (RB) or Maillard browning colorants from lactose process stream using porous adsorbent materials. The aim was to look at the suitability of using adsorbent resin to decolorise lactose solutions and how it performs compared to activated carbon (AC), which is more commonly used in lactose purification process. The work presents an approach to other separation problems. Adsorbent resin FPX66 was selected and tested to remove RB from whey permeate model solution of 8.5 mg/L (± 1 mg/L) RB in water or in 15% lactose. The RB was adsorbed in stirred and agitated batch vessel at 30 to 60 °C and CAR (mass of resin/mass of RB) ranged from 0.28 to 0.89 g/mg. Adsorption in glass chromatography columns of different packed bed dimensions was undertaken by batch mode (recirculation of feed), continuous mode (feed passes once through column), and at different flow rates. Riboflavin content was estimated using a modified HPLC method or spectrophotometry. Lactose content was monitored using refractometry or a HPLC lactose anomers analysis method. Adsorption data from 21 experiments yielded an equation, which allows predicting the equilibrium RB concentration in the resin and adsorption efficiency from a known CAR. Kinetic and diffusion analysis measured the pseudo-first-order rate constant (k1), pseudo-second-order rate constant (k2), continuous run rate constant (kc), film diffusivity (Df), intra-particle diffusivity (Dp) and full uptake curve diffusivity (D). Results showed that most of the adsorptions in stirred and agitated vessels were predicted better by a pseudo-second-order model while those in the columns fitted better to a slower pseudo-first-order model. Slower adsorption in the columns was attributed to the limitation of resin movement in a packed bed. The faster adsorptions were ahead during the initial stages but most of all experiments reached similar equilibrium stages. Factors that promote higher adsorption and diffusion rates the most were higher CAR, greater resin movement, shorter bed height and higher flow rates. In almost all cases, film diffusivity was the rate-limiting step in the adsorption processes. Film diffusivity in continuous adsorption was greater than in the batch adsorption due to the higher driving force typical of continuous adsorption. For future work, optimisation problem can be set up for selecting between continuous and batch column modes. Regeneration case study showed that resin adsorbed with RB could be regenerated using 20% ethanol solution in downward column flow. Single-pass mode gave far higher regeneration efficiency than batch. Further, polynomial equations allow prediction of the volume of regenerant needed to achieve a certain degree of desorption at flow rates ranging from 9 to 38 mL/min. The resin and AC both performed similarly in decolorising lactose process streams that contain RB such as decalcified whey permeate, but the AC could decolorise streams containing Maillard browning colorants, such as mother liquor, better than the resin. This was attributed to the higher porosity of AC, which suggests its higher adsorption capacity. The systematic and theoretical based approaches used in this study can be used for testing the feasibility of adsorbent media in various applications, not limited to decolorisation of lactose solutions.

HPLC has been used and can quickly determine several ions simultaneously. The method of determination described for transition metals [Cr(III), Fe(III), Ni(II), Co(II), Cu(II), Zn(II), Cd(II), Mn(II)] and [Ca(II), Pb(II)] using HPLC with UV-VIS detection is better than the PAR complexation method commonly used. The effects of both eluent pH and detector wavelength were investigated. Results from using different pHs and wavelengths, optional analytical conditions for the separation of [Ni(II), Co(II), Cu(II)], [Cr(III), Fe(III), Ca(II), Ni(II), Cu(II)], and [Ca(II), Zn(II), Pb(II)] in one injection, respectively, are described. The influence of adding different concentrations of Na_2EDTA solvent to the sample is shown. Detection limits, linear range, and the comparisons between this study and a post-column PAR method are given.

The effectiveness of micellar-enhanced ultrafiltration (MEUF) and ligand-modified micellar-enhanced ultrafiltration (LM-MEUF) techniques for removal of heavy metal ions and/or organic pollutants from aqueous streams are studied. In MEUF metal ions bind to the surface of negatively charged micelles of an anionic surfactant while organic solutes dissolve inside the micelles. In LM-MEUF a surfactant and a ligand are added to a solution containing ions of like charge. The ligand complexes with the target ion of interest and incorporates inside the micelles. In both processes the mixture is passed through an ultrafiltration membrane with pore sizes small enough to reject the micelles and their associated ions or solubilized organics. In Chapter 1 the technical feasibility of LM-MEUF process for selective removal of copper from an aqueous solution using a commercial ligand in a cationic surfactant is investigated. The effect of pH, and the concentrations of copper, calcium, surfactant, and the ligand on the efficiency of copper removal are reported. A novel surfactant/ligand regeneration scheme is also introduced in this Chapter. Chapter 2 evaluates the economic feasibility of LM-MEUF based on the experimental results in Chapter 1. This Chapter includes a sensitivity analysis for several operating scenarios to determine the most favorable operating conditions. A comparative cost estimate is performed to assess the economic viability of LM-MEUF copper extraction process compared to the conventional copper extraction process. In Chapter 3 the advantages of addition of small concentrations of nonionic surfactant to an anionic surfactant in MEUF system is discussed. The resulting anionic-nonionic mixture exhibits negative deviation from ideality of mixing which results in a larger fraction of the surfactant being present in micellar form. The contribution of concentration polarization and membrane charge to solute rejection is also studied; comparison of experimental solute rejections to those predicted by equilibrium models support the presence of these mechanisms.