Browsing by Author "Kilulya, Kessy"
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Item Controlling the release of wood extractives into water bodies by selecting suitable eucalyptus species(2012-12) Kilulya, Kessy; Msagati, Titus A. M.; Mamba, Bhekie B.; Ngila, Jane C.; Bush, TamaraPulping industries are increasing worldwide as a result of the increase in the demand for pulp for cellulose derivatives and paper manufacturing. Due to the activities involved in pulping processes, different chemicals from raw materials (wood) and bleaching agents are released in pulp-mill effluent streams discharged into the environment and find their way into water bodies. Large quantities of water and chemicals used in pulping result in large amounts of wastewater with high concentrations of extractives such as unsaturated fatty acids, which are known to be toxic, and plant sterols which affect the development, growth and reproduction of aquatic organisms. This study was aimed at assessing the composition of extractives in two eucalyptus species used for pulp production in South Africa, in order to identify the suitable species with regard to extractive content. Samples from two eucalyptus plant species (Eucalyptus grandis and Eucalyptus dunnii) were collected from three sites and analysed for extractives by first extracting with water, followed by Soxhlet extraction using acetone. Compounds were identified and quantified using gas chromatography-mass spectrometry (GC-MS). Major classes of extractives identified were fatty acids (mainly hexadecanoic acid, 9,12-octadecadienoic, 9-octadecenoic and octadecanoic acids) and sterols (mainly β-sitosterol and stigmastanol). E. dunnii was found to contain higher amounts of the compounds compared to those found in E. grandis in all sampled sites. Principal component analysis (PCA) was performed and explained 92.9% of the total variation using three principal components. It was revealed that the percentage of fatty acids, which has a negative influence on both principal components 2 and 3, was responsible for the difference between the species. E. grandis, which was found to contain low amounts of extractives, was therefore found suitable for pulping with regard to minimal water usage and environment pollution.Item Effect of site, species and tree size on the quantitative variation of lipophilic extractives in Eucalyptus woods used for pulping in South Africa(2014-04) Kilulya, Kessy; Msagati, Titus A. M.; Mamba, Bhekie B.; Ngila, Jane C.; Bush, TamaraLipophilic wood extractives have serious negative impacts on both pulping process and quality of produced pulp. This study aimed at identifying suitable wood materials for pulping with respect to their lipophilic extractives contents. The effect of site, species and tree sizes on the amount of lipophilic extractives was evaluated. The lipophilic extractives from selected Eucalyptus species used for pulping in South Africa were quantified using gas chromatography–mass spectrometry. It was revealed by the use of analysis of covariance (ANCOVA) that the quantitative variation of lipophilic extractives in Eucalyptus woods is significantly affected by respective sites and tree species. Principal component analysis (PCA) revealed the correlation of the amount of lipophilic extractives in wood materials with tree species/clones and site soil composition. Thus, high amounts of lipophilic extractives were found in Eucalyptus trees grown at sites with a high composition of clay soil and organic matter. Whereas, Eucalyptus dunnii was found to contain a higher amount of lipophilic extractives than Eucalyptus grandis in all the sampled sites, implying an increased risk of pitch formation during the pulping process.Item Evaluation of the influence of lipophilic extractive residues on dissolving pulp quality parameters by partial least squares method of chemometrics(2014-12) Kilulya, Kessy; Mamba, Bhekie B.; Ngila, Jane C.; Bush, Tamara; Msagati, Titus A. M.Dissolving pulp samples collected from the various pulping stages of the acid-bisulphite process were analysed for the lipophilic extractive residues as well as their effects and influence on the quality parameters of dissolving pulp were evaluated. The results obtained using the partial least squares (PLS) regression model showed that sterols, fatty alcohol, saturated and unsaturated fatty acids significantly influenced/affected the viscosity, Kappa number and carbohydrates in the pulp. The PLS model clearly separated the analysed pulp in terms of the species of the raw materials and pulping stages. Furthermore, it was observed that lipophilic extractives are negatively correlated to the yield of α-cellulose. Sterols, fatty acids and alcohols negatively influenced glucose in pulp, while xylose was found to be positively correlated to these components. Generally, the components of lipophilic extractives that have a major influence on the quality parameters were found to be sterols and saturated fatty acids.Item Extraction Procedures and GCxGC-TOFMS Determination of Fatty Acids (FAs) in Cyanobacteria Cultures and the Effect of Growth Media Iron Concentration Variation on Cellular FAs Composition(2015-03) Kilulya, Kessy; Mamba Bhekie B.; Msagati, TitusCyanobacteria are a diverse group of photosynthetic organisms found mostly in freshwater bodies [1]. Cyanobacteria, apart from producing different useful metabolites for different applications such as pharmaceuticals, production of fine chemicals, biofertilizers and animal feed [2-5], they are known to produce lipophilic extractives such as fatty acids which are somewhat toxic to aquatic organisms, especisally unsaturated fatty acids. They are known to affect fish in freshwater bodies by interfering with the gill basolateral membrane ion-extrusion mechanisms leading to the death of fish [1,6]. Thus, the toxicity properties of fatty acids released by cyanobacteria in freshwater bodies to other aquatic organisms have increased the need to characterise the composition of fatty acids in cyanobacteria. Currently the production of biodiesel has increased the importance of lipids and hence the extraction techniques from different sources [7]. Moreover, fatty acids have been identified as essential components of the diet of humans and animals [8]. This fact has highly contributed to the interest of different researchers on the effective techniques to obtain fatty acids from cyanobacteria. Polyunsaturated fatty acids such as 9,12-Octadecadienoic acid (C18:2) and γ-6,9,12-octadecatrienoic acid (γ-C18:3) are known for their human health importance [1,9]. Furthermore, the analysis of long chain fatty acids has been so significant for biological and medical investigations [7]. The most prominent analytical instrument for fatty acids analysis is gas chromatography-mass spectrometry (GC-MS) [10]. However, due to the separation problem of fatty acids with similar chemical structures such as fatty acids with a chain of 18 carbon atoms, a more advanced gas chromatographic technique (GCxGC-TOFMS) has been employed in fatty acids and lipids analysis. GCxGC-TOFMS is a powerful analytical technique for the qualitative and quantitative determination of lipid composition. Fatty acids are currently best determined by GCxGC-TOFMS after derivatization to fatty acids methyl esters (FAMEs). The use of deconvolution algorithm of ChromaTOF software of GCxGC-TOFMS enables the separation of mass spectra and identification of FAMEs which some have a tendency of coeluting and bearing similar mass spectra due to their similar chemical structures. Extraction of fatty acids and lipids from the solid samples has generally been achieved by using volatile organic solvents under different extraction techniques reported in the literature. However, due to the nature of algae biomass, and the fact that they contain unusual lipid classes and fatty acids which differ from the ones in higher animals and plants [7], it is important to investigate a suitable extraction method for lipids and fatty acids from algae biomass. Among the techniques which are reported to be suitable, ultrasonic solid liquid extraction techniques has been found to be more effective as well as time effective [11]. Lipids and fatty acids in particular can be effectively extracted using polar organic solvents which are able to extract a larger range of organic compounds from biomass samples mostly at an elevated temperature [12].Item Imidazolium-Based Ionic Liquids as Solvents for Analysis of Lipophilic Extractives from Biomass(2015-05) Kilulya, Kessy; Mamba, Bhekie B.; Msagati, Titus A. M.Ionic liquids are organic salts made of cations and anions of which most of them are liquids at room temperature [1-3]. This is generally a newly emerging class of compounds which so far has been discovered to have numerous applications in chemistry [2] due to their attractive features such as negligible vapour pressure, high thermal stability, biodegradability, ability to solvate compounds of different polarity and miscibility with aqueous and organic solvents [4], [5]. Different classes of ionic liquids have been synthesised so far, such as, imidazolium, ammonium, pyridinium, isoquinolinium, sulfonium, phosphonium, pyrrolidium and others [6]. Since their discovery ionic liquids have raised a considerable excitement among researchers due to their ability to combine with different reagents in number of applications. The other aspect of ionic liquids is their ability to be recycled which minimizes the cost of usage as well as making them environmentally friendly. Ionic liquids so far have been used as solvents in different areas including for catalysis, synthesis and purification [6]. They have high ability of dissolving biopolymers such as cellulose and other biomass due to their ability to interact with biopolymer matrix forming hydrogen bonding [7] (Scheme 1).Item Ionic Liquid-Based Extraction of Fatty Acids from Blue-Green Algal Cells Enhanced by Direct Transesterification and Determination Using GC x GC-TOFMS(2014-02) Kilulya, Kessy; Msagati, Titus A. M.; Mamba, Bhekie B.Blue-green algae commonly referred to as cyanobacteria are known to grow in freshwater bodies when they are provided with suitable growth conditions such as nutrients, temperature and light. Algae biomass is known to contain a large amount of lipids, such as saturated and unsaturated fatty acids. In this study, fatty acids from algal cells were extracted using a newly developed extraction protocol using ionic liquid enhanced by direct transesterification at an elevated temperature. The identification and quantification of fatty acids was performed using gas chromatography coupled to a time-of-flight mass spectrometer (GC × GC-TOFMS). The extracted fatty acids were dominated by those with carbon chain of C16 and C18; [i.e. 7-hexadecenoic acid (C16:1) and hexadecanoic acid (C16:0) for C16, whereas C18 includes γ-linolenic acid (γ-C18:3); linoleic acid (C18:2); linolenic acid (C18:3); 6,9,12,15-octadecatetraenoic acid (C18:4); oleic acid (C18:1) and octadecanoic acid (C18:0)]. The obtained fatty acid composition was then compared with that obtained by organic solvent extraction using a mixture of chloroform and methanol. Statistical evaluation was performed using one-way ANOVA and found that there was no statistically significant difference (P = 0.908) between the two extraction methods, a finding which indicates the usefulness of ionic liquid as a solvent to replace volatile organic solvent to minimize environmental pollution.Item Preparation of SPE hybrid mesoporous silica sorbents for the analysis and removal of organic pollutants in water(2014-09) Maiga, D. T.; Msagati, Titus A. M.; Kilulya, Kessy; Mamba, Bhekie B.Polycyclic aromatic hydrocarbons (PAHs) are organic pollutants that threaten the health of humans and the environment. PAHs are found naturally in the environment but they can also be man-made. PAHs are produced when products like coal, oil, gas, and garbage are burned in an incomplete burning process. PAH’s can be introduced into water bodies in several ways including industrial, domestic and commercial effluents, sewage, agricultural runoff and wastes. Monitoring of PAH’s in water is of great importance because of their mutagenic and carcinogenic properties. The aim of this study was to develop the hybrid mesoporous silica sorbents for the analysis and removal of organic pollutants (OPs) in water especially PAH’s. The determination of PAHs was performed using gas chromatography coupled to time of flight mass spectrometry (GCxGC-TOFMS). The hybrid materials were successfully synthesized using silica gel as a source of silica followed by modification with organic compounds. However the performance of the materials was evaluated using GCxGC-TOFMS for the determination of recovery PAH’s concentrations. At optimum conditions sorbent materials were able to remove 95.9±12.21% of the PAHs in spiked water samples at a laboratory scale.Item A Quantitative Near Infrared Spectroscopy Model for the Assay of Efavirenz in Tablets(2013-12) Mgoyela, Geovin; Sempombe, Joseph; Kilulya, Kessy; Chambuso, Mhina; Mugoyela, Veronica; Kaale, Eliangiringa A. K. K.Near-infrared-spectroscopy combined with multivariate data analysis represents the most recent and efficient technology in analytical chemistry. The objective of this study was to utilize near infrared spectroscopy as an adapted technology for the quantitative assay of efavirenz. The study developed and validated a quantitative model for estimating the amount of efavirenz in efavirenz uncoated tablets. The quantification was based on the partial least squares algorithm and constructed by cross-validation. A UV spectrophotometric procedure was used as the reference method. Different pre-processing methods were employed in the development of calibration models. The best calibration model was that using partial least squares as the regression algorithm in association with Multiplicative Scattering Correction as the spectrum pre-processing method. The model estimators were: coefficient of determination (R²) 0.9815, standard error of cross validation 2.0346 and a factor of 5. The chosen model correlated well with the prediction results in accordance with the Mahalabinos distance limits. The developed NIR method allows the estimation of the amount of efavirenz in tablets without sample preparation thus proving to be a simple, fast and suitable method for the quantitative assay of efavirenz in uncoated tablets. Hence, NIR coupled with chemometric methods can be used for on-line, in-line or at-line monitoring of the manufacturing process and are helpful in achieving the goals of Process Analytical Technology.Item Study of the Fate of Lipophilic Wood Extractives During Acid Sulphite Pulping Process by Ultrasonic Solid-Liquid Extraction and Gas Chromatography Mass Spectrometry(2012-06) Kilulya, Kessy; Msagati, Titus A. M.; Mamba, Bhekie B.; Ngila, Jane C.; Bush, TamaraLipophilic extractives in dissolving pulp are still a big concern for pulp industries due to their detrimental effect on the quality of pulp. Since lipophilic extractives remaining in pulp are trapped in low-accessible fiber structures, effective extraction methods need to be established for studying their fate in the process. A simple, ultrasonic, solid liquid extraction established in this study was found to be more effective in capturing extractive residues in all “elemental chlorine-free” bleaching stages. Its efficiency was dependent on the extraction temperature, time, and solvent composition. A linearly correlated removal pattern of sterols and unsaturated fatty acids by the bleaching sequence was observed. It was further found that the bleaching combination did not fully remove lipophilic extractives. This study suggests an opportunity to explore ultrasonication-based extraction as an effective extraction procedure prior to gas chromatography mass spectrometry analysis for monitoring extractives in pulp.