MST-Department of Chemistry

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Determination of water transport numbers in cation exchange membranes by an EMF (streaming potential) method
(Kenyatta University, 1987-10) Onindo, Charles Otieno
The use of crown ethers in the von richter reaction
(Kenyatta University, 1988) Langat, Caroline Chelang'at
Kinetics and Mechanisms of Catalysed and Uncatalysed Oxidation of Organic Dyes by Inorganic Species and Indicator Reaction for Determination of Cations
(Kenyatta University, 1998) Ngugi, Sironik Stephen
The rate of oxidation of both the uncatalysed and Vanadium (V) catalysed reaction between indigo carmine (IC) and Chromium (VI) as well as the uncatalysed and Ruthenium (III) catalysed reaction between methylene blue (MB) and cerium (IV) have been studied. Both reactions were performed in sulphuric acid media by monitoring the absorbances of IC and MB at 610 nm and 665 nm respectively at 25°C. The kinetics and the probable mechanisms of these reactions have been elucidated. For the former reaction, the order with respect to IC, H+ and Cr(VI) were 1, 2 and 1.5 respectively and 1 for V(V) in the case of catalyzed reaction while for the latter reaction the partial orders with respect to MB, Ce(IV) and H+ were 2, 1 and 0 respectively and 1 for Ru(III) in the case for the catalysed. The mechanism for the ICCr( VI) reaction involves an initial two electron process which is confirmed by the limiting induction factor of 0.5 from the iodide ion induction reaction. Further the presence of V(V) ion in the reaction mix!ure caused an increase in the rate of the oxidation of IC that was affected by traces of Ru(III) and Mo(VI). The interfering effects of the Ru(III) and Mo(VI) were effectively masked by traces of thiourea and thiocyanate respectively without any appreciable effect on the rate of the uncatalysed reaction. The uncatalyzed and RU(III)-catalyzed reaction between MB and cerium (IV) sulphate in acidic media occurred by means of a chain reaction. The presence of free radicals in the reaction media were established by means of introducing acrylamide which formed a co-polymer with MB whose rate of formation was drastically reduced using 1,4-benzoquinone. In addition a high stoichiometry of MB:Ce(IV) 1:40 was observed for both the catalyzed and uncatalyzed reactions. The presence of Mo(VI), W(VI) and Co(III) ions was found to interfere with the rate of the indicator reaction. The interfering effect of W(VI) and Co(III) were masked by ammonium hydrogen phosphate and sodium fluoride respectively while that of Mo(VI) could be effected by extraction using 2-Methylpropanol followed by ethylacetate prior to oxidation. Further, a fixed time method is described for the determination of V(V) and Ru(III), based on their ability to catalyze the oxidation of IC by Cr(VI) and MB by ceric sulphate respectively and the interference of other cations on their determination studied using synthetic mixtures.
A study of the Reactions of tetrabromopctacarbonyldimolybdenum(II) Complex with 1 ,2-bis(diphcnylphosphino)ethane at Elevated Temperature
(1998) Changamu, Evans O.
The reaction between (Mo(CO)4Br2)2,and 1,2-bis( diphenylphosphino )ethane, (dppe), has been investigated. The results show that at the refluxing temperature of tetralin (about 190 C) (Mo( CO)4Br2h reacts with 1,2-bis( diphenylphosphino )ethane (dppe ),giving disproportionation and decarbonylation products. The decarbonylation products isolated from the reaction mixture wtre a maroon coloured complex of empirical formula Mo( dppe )Br2 and a yellow coloured complex of empirical formula Mo( dppe hBr2. The disproportionation products isolated were a brown coloured Mo(IV) complex, Mo(dppehBq, a yellow coloured Mo(O) complex, Mo(COh(dppeh and a pale flesh complex whose elemental analysis data suggest is Mo(dppe)).CloH12. The UV-VIS and IR spectra of the various complexes isolated have been recorded. The UV-VIS spectroscopy was used to distinguish between the maroon-coloured complex with empircal formula MoBr2(dppe) and the yellow complex MoBr2(dppeh. Electrical conductivity measurements have been done on MoBq( dppe h in nitrobenzene and the results show that it is a 1:1 electrolyte. The possible reaction mechanisms by which these products were formed are suggested.
Assessment of the levels of some toxic and Anti nutritional substances in Kenyan coffee pulp
(Kenyatta University, 2001-01) Kiptoo, Kipkore Jackson
Every year, the Kenyan coffee industry produces over 350,000 tons of clean coffee and similar quantities of associated by-products (coffee pulp and coffee husks). These by-products are often damped into nearby streams causing serious pollution problems. Solution to this problem calls for the evaluation of available alternative uses for the byproducts and safer disposal methods. This work explored the possibility of using Kenyan coffee pulp as animal feed. Levels of some toxic and antinutritional substances in coffee pulp samples collected from fifteen coffee processing factories located in Thika and Kiambu districts were determined. The levels of caffeine, total tannins and potassium were in the range 0.22-0.70, 1.31- 1.56 and 0.9-4.21 %w/w on dry mass basis respectively. Levels of Cu, Zn, Mn and Fe were in the range between 4.90-213.30, 11.23-28.03,3.49-119.29 and 12.53-452.8J..lg/g respectively. Among the pesticides, only chlorothalonil was detected in most samples at appreciable amounts (0.02-1245J..lg/g).After ensiling for a period of four (4) months, the mean percentage losses ranged 30-45.59% for caffeine, 5.56-42.50% for total tannins and 77.28-100% for the pesticide residues. From these figures, it is recognized that ensiling is a significant detoxification method. The distribution of caffeine and tannins seemed to depend on the prevailing environmental conditions. Coffee pulp from well managed farms had higher levels of caffeine while higher levels of tannins were reported in coffee pulp from agro-ecological zones that are more exposed to fungal diseases or insect pests. Coffee pulp from the same agro-ecological zone were close in their K, Zn, Mn and Fe contents, implying that soil characteristics plays an important role in the accumulation of these metals in the pulp. The distribution of copper was rather erratic. Copper sprays as well as spray programmes contribute greatly to the amount of copper in the pulp. The results of this study show that coffee pulp is contaminated with toxic and antinutritional substances. However, the levels of caffeine, tannins and the pesticide residues were reduced significantly upon ensiling, though not completely. The levels of the metals reported in this work are within the levels acceptable to most animals and cannot be considered a major setback in the prospect of converting coffee pulp to animal feed. Although the levels of pesticide residues reported in the fresh pulp are within the levels considered toxic to most animals, ensiling reduced the levels to those below the maximum residues levels (MRL's) in or on animal feeds and feedstuffs as recommended by FAOIWHO (1998). Therefore it appears that coffee pulp can at best be initially used at well-rationed supplemental levels with other forages or feed components as more effective methods of detoxification are explored.
The determination of stability constants of cadmium complexes with selected ligands and modelling the likely speciation of cadmium in lake Bogoria, Kenya
(2003) Njomo, Njagi
This thesis is a report of a speciation study of the complexes formed by cadmium with selected ligands found to be dominant in an inland salt lake, Lake Bogoria. Water from Lake Bogoria was analysed using standard analytical techniques to obtain the stoichiometric concentrations of the major ions. Differential pulse anodic stripping voltammetry (DPASV) and hanging drop amalgam voltammetry (HDA V) were then used to measure oxidation peak potential shifts of cadmium in presence of the inorganic ligands carbonate, bicarbonate, chloride, fluoride and hydroxide. The peak potential shifts were then used to calculate the stability constants of cadmium complexes at the ionic strength of the lake using DeFord-Hume graphical method. The determined stability constants were then used to model the speciation of the lake using Incenzy method. Three carbonato species CdC03°, Cd(C03)22- and Cd(C03)34- were identified in both the KN03 aqueous and lake water media using data from DP ASV while only two species, "CdC03 ° and Cd(C03)l- were identified with data from HDA V. With DP ASV data, four bicarbonato complexes, CdHCO/, Cd(HC03)20 , Cd(HC03)3- and Cd(HC03)/- were shown to exist in both the KN03 aqueous and lake water media while three bicarbonato species; CdHCO/, Cd(HC03)20 Cd(HC03)3- were obtained using data from HDA V. DPASV data showed existence of six hydroxo complexes, CdOW, Cd(OH)2°, Cd(OH)3-, Cd(OH)/-, Cd(OH)s3- and Cd(OH)64- in the lake water medium and four complexes vi , . CdOW, Cd(OH)2° , Cd(OH)3- and Cd(OH)/-in the KN03 aqueous medium. With HDAV, five complexes were identified. These were; Cd(OH)+, Cd(OH)20 , Cd(OH)J, Cd(OH)/- and Cd(OH)s3-. Five chloro species were found to exist in the KN03 aqueous medium using data from both the DPASV and HDAV. These were cacr, CdCho, CdCl,", CdCI/- and CdCls2-. Three fluoro complexes CdF+, CdF20 and CdF3- were found using data from both techniques. The study has shown that the stabilities, relative proportions and distribution of the various species vary quite significantly with the composition of the matrix mixture.
Oil plants as sources for production of fatty acid methyl asters (biodiesel ) in Kenya.
(2011-05-09) Wagutu, Agatha W.
The increased environmental awareness, the world's petroleum supply constraints and high petroleum fuel prices have spurred efforts in many countries to search for suitable alternatives to diesel fuels. Diesel fuels derived from triglycerides (vegetable oils or animal fats) present a promising alternative. In this study, oils extracted from: four plants, Jatropha curcas L., Croton megalocarpus Hutch., Calodendruin capense (L.f.) Thunb. (cape chestnut) and Cocos nucifera L. (coconut) were transesterified in mc:llanol using sodium hydroxide catalyst. Methyl esters obtained were characterized by (,C-MS and further tested for fuel properties relative to convectional diesel fuels (autos iotive diesel and kerosene). Methyl esters of commercial oils; sunflower and soybean were also prepared and tested for fuel properties for comparison. The results showed hexadecanoate and octadecanoate were common fatty acids esters identified in the four analyzed methyl esters. Total unsaturation was highest for Croton ester with 86.6% and lowest for coconut ester, 2.8%. The esters viscosities at 40 °C were in the range of 4.16-4.63 , mm2/s except coconut ester whose viscosity (2.71 mm 2/S) was close to that of kerosene, 2.35 mm2/s. All esters were found to be less volatile than diesel fuels. The flash points of the esters were much higher (>100 °C) than referenced diesel fuels. Jatropha, sunflower and soybean esters passed the ASTM Standard D6751 for flash point, 130 °C minimum. All the esters however, were within the European Standard EN-14214 for biodiesel of above 101 °C. The densities of the esters were 2-4% higher than that of automotive diesel and 10-12% more than that of kerosene. The heating values of the esters were 12% lower than diesel fuels on average. The esters of Jatropha curcas and croton megalocu7pus were further blended with automotive diesel in ranges of 5-70% on volume to volume ratio. Blend of 20% biodiesel in 80% diesel demonstrated the most ideal properties with viscosity, density same as that of diesel, distillation temperature in the range f5% relative to diesel fuel and heating value 3-13% higher than the pure ester fuels. Al the esters were further tested in a multi-wick stove following standard water boiling test (WBT) and their performance in terms of time to boil, heat transfer efficiency, power output and specific fuel consumption. The esters burnt with odorless and non-pungent smell unlike kerosene fuel taking 50-100% more time while consuming 67-89%, by weight, more fuel than kerosene to boil a liter of water. Heat transfer efficiency for esters was 4-l3% lower than for kerosene during boiling phase while specific consumption for the esters was 16-33% higher than kerosene. Ideally it was found that methyl esters (biodiesel) of non-coconut origin showed fuel properties very close to automotive diesel while blended or neat and thus could be used in diesel appliances without any modifications. Cocoamt ester on the other hand showed properties very close to kerosene and gave stove performance characteristics almost similar to kerosene, making it most favorable as biokcrosene.
Phytochemical and antimicrobial studied of teclea noblis Del.used in traditional medicine in Kenya
(2011-05-09) Onyancha, Evans M.
Historically, plants have provided a good source of antimicrobial agents. Plant based antimicrobials represent a vast untapped source of medicine with an enormous therapeutic potential. They are effective in treatment of diseases while simultaneously mitigating many of the side effects that are often associated wills synthetic antimicrobials. The isolated bioactive compounds can be used in future His an antimicrobial or as blueprint or starting point for the manufacture of antimicrobial. The present research concentrated on the Kenyan plant, Teclea nohilis Del. Collected from Siroch in Kerio Valley basin. The powdered dry leaves of Teclea nohilis were successively extracted in hexane, dichloromethane, ethyl acetate and methanol. The resulting crude extracts were tested for lethality test 6y use of brine shrimp (Anemia salina) as well as antimicrobial test. The Hexane crude extract had 235, DCM 165, EtClAc 557 and McOH 268 ug/ml LD50 values. The hexane and dichloromethane crude extracts, showed mild activity for both lethality test and antimicrobial test (9 mm for Staphylococcus aureus and 8 mm for Streptococcus pnuemoniae). The hexane and dichloromethane extracts were subjected to fractionation where seven compounds were isolated and purified by use of chromatographic techniques; vacuum liquid chromatgraphy (VLC), column chromatography (CC) and thin layer chromatography (TLC) that were extensively used. The isolated compounds were kokusaginine (1), 4,8-dimethoxy-7-(3-methylbut-2enyloxy)furo[2,3-b]quinoliue (1I), skimmianine (III), dictaniine (IV), b-sitosterol (V), lupeol (VI), and flindersiamine (VII). The compounds showed antibacterial activity ranging from mild to moderate activity (from 7-11 mm). These activities are relatively high mainly to gram positive bacteria as compared to the activity exhibited by the crude hexane and diclimnetliane extracts. Though the trend exhibited in the crude extracts is maintained by the isolated compounds-gram negative being more susceptible to the extracts. The compounds isolated can be used as templates for the formulation of antibacterial drugs in future given the current trend in drug resistance.
Phytochemical and anti-microbial investigation of ochna holtzii gilg. from the Kenyan Costal region
(2011-07-26) Awadh, Mohamed Mbarak
Plants are used widely in traditional health systems to treat a variety of diseases. This research was specifically directed to investigate a coastal plant Ochna holtzii Gilg., a medicinal plant mainly found in the coastal region of Kenya. The communities in the region use various parts of the plant (stem and root bark) to treat different health problems. Common uses include treatment of high fever, headache and coughs, and relieving persistent backaches especially in the old age. It is also used extensively as a mixture with other plant extracts in treating microbial infections. Crude solvent (hexane, DCM, ethyl acetate and methanol) extracts of O. holtzii were subjected to antimicrobial bioassays against two Gram-positive bacteria: Staphylococcus aureus and Bacillus subtilis, two Gram-negative bacteria: Salmonella typhi and Pseudomonas aeruginosa and a yeast Candida albicans. The methanol extracts of the root bark (2 mg/disc) showed the highest activity against B. subtilis and S. aureus with zones of inhibition of 20 and 14 mm, respectively. The zones of inhibition for the stem bark against the same bacteria were 14 and 12 mm, respectively. Ethyl acetate extracts of both the root and the stem bark (2 mg/disc) showed moderate activities against the same bacteria with zones of inhibition of 11 and 9 mm, respectively. Hexane and DCM extracts showed no activity. The minimum inhibitory concentrations (MICs) of the root bark methanol extract was 250 and 500 ug/ml against B. subtilis and S. aureus, while that of the stem bark was 500 and 1000 ug/ml, respectively. Isolation and purification of the bioactive constituents of the plant were made using standard chromatographic techniques: VLC, TLC, CC, prepTLC, Sephadex LH-20. Eight compounds were isolated in relatively pure forms from ethyl acetate extracts of root and stem barks. The structures of the compounds were elucidated using standard spectroscopic techniques: UV, IR, 1 D and 2D NMR and comparison with known spectral data. All compounds except one were found to be rearranged biflavonoids, of which three [afzelone D methylether (MM/HRE/03), dehydrolophirone C (MM/HSE/04) and the dephenyl lophirone C (MM/HSE/06)] have not been reported previously, while the other four [lophirone A (MM/HRE/01), afzelone D (MM/HSEV/02), lophirone K (MM/HSE/05) and calodenin B (MM/HRE/07)] are known compounds. The eighth compound was 5-methyl-3,5-resorcinol (MM/HSE/08). Three of the compounds: lophirone A, afzelone D methylether and calodenin B were isolated from the root bark. Two compounds (lophirone A and calodenin B) were bioassayed against S. aureus and P. aeruginosa where lophirone A showed significant activity with zone of inhibition 15 and 11 mm, respectively. Calodenin B was less active against the same bacteria, with zones of inhibition of 11 and 13 mm, respectively. Further extensive research work needs be done on the isolation and identification of other constituents of the plant to establish the full range of bioactive constituents in O. holtzii.
Prediction of reaction mechanism and absolute rate constant using computer algorithm: the bromate ion in acidic media reaction
(2011-08-03) Kiruri, Wairimu Lucy
This study examined the methods used by the Kenya Tourist Board in marketing adventure tourism in the Mount Kenya region. The study used descriptive survey design in which data was collected using both open and close-ended questionnaires and interviews. The questionnaire was administered to 120 tourists selected using stratified random sampling in order to capture their socio-demographic profiles. Questionnaires were also administered to 13 camp sites and 20 tour operators to obtain information on the methods of marketing of adventure tourism in the study area. An interview schedule was used to obtain information from the senior management of the Kenya Tourist Board. The data was analyzed using descriptive and inferential statistics. The research findings indicate that the study area has a lot of potential for adventure tourism. A significant majority of the tourists (91.2%) interviewed stated that the region has potential for adventure tourism. The Null hypothesis that there is no significant difference between the number of visitors attracted to the study area by its potential for hard adventure tourism activities and those attracted by its soft adventure tourism activities was rejected and the alternative hypothesis was accepted. It was also revealed that the Kenya Tourist Board did not play a major role in the marketing of adventure tourism in the area. The study found out that majority of tourists (83%) obtained information about adventure tourism in the region from tour operators, travel agents and campsite owners. The Null hypothesis that there is no significant difference between the frequency of visits by tourists obtaining information from Kenya Tourist Board and those with alternative sources of information was rejected and the alternative one accepted. The Chi-square test established that there was no difference between the methods of marketing used by the Kenya Tourist Board and those of other marketing organizations. Student's t test revealed that there was a significant relationship between the level of education of tourists and their frequency of visit in the area. This study recommends that the Kenya Tourist Board should find ways of raising adequate funds for marketing the region. It should also improve its website to include accurate and relevant information on adventure tourism in order to gain competitive edge over its rivals. Furthermore, there is need for further research on tourists' preferences regarding the type of activities at camp sites and their attitudes towards adventure tourism facilities and services offered.
The Water Hyacinth Eichhornia Crassipies (mart) Solms as a Biosorbent for Cadmium (II) and Lead (II) Removal: Kinetic and Equilibrium Studies
(2011-08-08) Murithi, Leonard Genson; Onindo, Charles O.; Muthakia, G. K.
Presence of heavy metals in aquatic systems has become a serious problem. As a result there has been great attention given to new technologies for the removal of heavy metals from contaminated waters. Biosorption is one such emerging technology that utilizes naturally occurring biomass or waste materials to sequester heavy metals from industrial wastewater. Currently, water hyacinth, Eichhornia crassipes, is of low economic value and is available abundantly in some of Kenya's inland water systems. The aim of the present study was to assess the suitability of Eichhornia crassipes root biomass as a biosorbent for heavy metals from aqueous system. The adsorption of lead (II) and cadmium (II) ions by the water hyacinth Eichhornia crassipes roots has been studied. The abilities of Eichhornia crassipes roots to remove lead (II) and cadmium (II) ions from aqueous solutions were compared. Batch adsorption studies were carried out to examine the influence of various parameters such as the initial pH, contact time. adsorbent dose, initial metal ion concentration, temperature and agitation speed on the metal ion uptake. Uptake of lead (II) and cadmium (II) ions on the Eichhornia crassipes roots showed a pHdependent profile. The maximum metal uptake values were 163.90 mg/g and 104.16 mg/g for lead (II) and cadmium (II) ions respectively. Both Langmuir and Freundlich models fitted the experimental sorption equilibrium data, with Langmuir providing the best fit (R2 > 0.99). The biosorption kinetics was determined by fitting first-orderLagergren and Pseudo- second- order models to the experimental data. It was found that the data was better described by the pseudo- second- order model (R2 > 0.99) than the first- order- Lagergren. FTIR analysis suggested the possibility of the participation of carboxyl groups in metal uptake. Calcium and Magnesium nitrate salts were found to affect considerably the metal ion biosorption. A comparison of the maximum sorption capacity of several untreated biomaterial based residues showed that Eichhornia crassipes roots are suitable candidates for use as biosorbents in the removal of heavy metal ions from aqueous solutions.
Evaluating farmers knowledge in pesticide handling and determining pesticides levels in maize after various processing methods and different storage conditions
(2011-08-09) Njoroge, Samuel
Post-harvest pesticides applied to consumable foodstuffs usually pose a serious but silent threat to human and livestock health. Some pesticides accumulate slowly in various strata of the ecosystem causing irreparable damage to the environment and wildlife. In Kenya huge quantities of these pesticides are used to preserve maize grains during storage. The amount of pesticide residues consumed through maize grains and its products depend on ambient storage conditions of grains, the nature of the active compound of particular pesticide and the processing technique of the grains before consuming. The purpose of this study was to investigate the effects of ambient storage conditions on the concentrations of pesticide residues in post-harvest maize grains and to evaluate the extent to which the consumer is exposed to these pesticides. The research involved a field survey that assessed the knowledge, attitudes and practices of the community regarding the safe use of pesticides (occupational exposure). The study also analyzed the residual concentrations of pesticides in stored maize grains and some of its processed products (milling fractions) such as white flour and whole meal flour. Gas chromatographic method using flame ionization detector (FID) was used for quantization of pesticide residues of two organophosphates (malathion, piriminiphosmethyl) and one synthetic pyrethroid (permethrin) in maize grains and its milling fractions. Three parameters were measured: level of pesticides in two maize milling fractions (whole meal and white flour) and level of pesticide residue that remained on maize grains after various cleaning processes (hulling, waterwash, detergent wash), extent of health risks associated with consuming maize grains and flour treated with pesticides (dietary exposures) and persistence of pesticide residues in maize grains stored under simulated storage conditions (temperature, light and relative humidity). The maize grains samples for the simulated storage were initially treated with 0.3mgkg -I permethrin, 3.9mgkg -1, pirimiphosmethyl and 3.92mgkg-1 malathion prior to storage and portions analysed at regular intervals for the pesticide residues. Data was analysed by SPSS and Genstat version 6.1 computer software. Field survey information indicated that more than 95% of farmers in Chilchila do not practice safety precautions during pesticide formulation and application. After six months of simulated storage, at ambient temperatures averaging 22 c and 55% RH the level of the initial residues that persisted on the maize grains was 63.3% permethrin, 64% pirimiphosmethyl and 56% malathion. The rates of dissipation of the pesticide from the maize grains decreased with storage time and followed a biphasic pattern for all storage conditions. Applying first order reaction kinetics, the following halflifes were obtained at the ambient storage conditions of the study area: maize grains treated with permethrin had 130 days; maize grains treated with pirimiphosmethyl had 77 days and the maize grains treated with malathion had 30 days. This trend was repeated for all the other storage conditions, giving a persistence order of permethrin followed by pirimiphosmethyl then malathion. Mean residue concentrations in whole meal were 1.7 mgkgl, 1.3mgkg-1 and 0.16mgkg-1 for pirimiphosmethyl, malathion and permethrin respectively. All these residue levels were above the ADI level for each pesticide. Results for white flour indicated mean residue levels of 0.54mgkg -1, for pinmiphosmethyl, 0.53 mgkg-1, for malathion and 0.06 mgkg -1 for permethrin, while hazard index analysis for maize grains, whole meal and white flour gave values greater than one for malathion and pirimiphosmethyl. The hazard index analysis was less than one for permethrin. These two observations meant that, the organophosphate pesticides (malathion and pirimiphosmethyl) occurred at levels risky to human consumption in all food products analysed while the pyrethroid pesticide (permethrin) occurred at a safe level for human consumption.
Study of reactions of molybdenum (ii) and tungsten (ii) halocarbonyls with nitrogen bases.
(2011-08-10) Nyawade, Adhiambo Eunice
The study focused on the possible oxidation of various nitrogen bases by molybdenum(II) and tungsten(II) halocarbonyls, formation of zerovalent aminecarbonyl metal complexes and mode of coordination of nicotine to molybdenum and tungsten. Aminecarbonyls of the type M(CO)3L3 (M=Mo, W; L= CH3NH2, CH3CH2)2NH), M(CO)4TMEDA and M(CO)5nicotine were prepared by a reaction of the halocarbonyls [M(CO)4X2]2 (M=Mo, W; X=Br or Cl) with selected nitrogen bases. The crystal structure of Mo(CO)4TMEDA and W(CO)5nicotine well obtained by X-ray diffraction confirming the structures of the compounds Nicotine coordinated to the metal through the imine nitrogen, as shown seen in the crystal structure, to form M(CO)5(nicotine) (M=Mo, W). The amine carbonyl compounds were isolated by filtration while the organic by-products, were isolated from the filtrate by column chromatography. The nitrogen bases were oxidized by the halocarbonyls to imines which may have been hydrolyzed by water to an amine and an aldehyde or a ketone. This was shown by the presence of IR bands in the region of 1740cm-I in the infrared spectra of all the oily by-products from reaction of M(CO)4X2 (M=Mo, W; X=Br or Cl) with N,N-methylamine. The ethyleiiamine was hydrolysed to methanal and methylamine. The presence of a new IR band at 1651.9cm-1 in the IR spectrum of the oily by-product from reaction of nicotine with the tetrahalocarbonyls suggested that nicotine was oxidized by the tetrahaIooctacarbonyImetaI(11) M(CO)4X2 (M=Mo, W; X=Br or Cl). 11I NMR, "C NMR, infrared spectroscopy, melting point and elemental analysis were used to characterize the products. The halides were determined gravimetrically as the silver halides, AgX (X=Br or Cl) while molybdenum and tungsten were determined by weighing as the oxides M03 (M=Mo, W). The results confirmed that the reactions of the halocarbonyls [M(CO)4X2]2 (M=Mo, W; X=Br or CI) with the nitrogen bases studied takes place via a redox mechanism. All preparative work was done in an atmosphere which was dry and oxygen-free
Analysis of chemical composition of cowpea floral volatiles and nectar
(2011-08-23) Ager, Consolata Atieno
Cowpea is one of the 14 species of grain legumes. It rewards insects by producing nectar and it advertises to the pollinators by producing floral volatiles. The volatiles act as cues that guide insect pollinators in terms of pollen and nectar. Floral volatile quality also influences the efficiency of pollination. Genetic manipulations involving selection of varieties with high quality floral volatiles and nectar can therefore increase pollination efficiency and hence cowpea yields. It is believed that efficiency of insect pollination in several food crops is dependent on the quality of floral volatiles. Several molecules, including allozyme, codominant and isozyme DNA molecular markers (AFLP, RAPD and SSR) among others are useful in the selection of disease resistant and high yielding food crop cultivars in breeding programmes. Floral volatiles and nectar profiles can therefore act as molecular markers in compea breeding programmes. This project involved the collection, analysis and characterization of cowpea floral nectar and volatile composition. The flowers bloomed for one day and nectar was secreted between 6.00 and 10.00 am East African time. The flower sizes in the six selected cultivars were measured, nectar withdrawn using microlitre syringe and its characteristics (volume and sugar composition) examined. The sugar composition of the nectar was analyzed using HPLC, LC-MS and co-injection with authentic standards. Hydro-distillation and static headspace trapping with adsorbents (activated charcoal, reversephase, CIa bonded silica and porapak Q) was done in the six selected cultivars and volatiles concentrated using gentle stream of NZ while cooling under ice. GC was used to analyze the composition of floral volatiles and GC-MS for identification of the components. Co-injection with authentic standards was used to confirm identity of the components. Nectar volume varied as a function of time. A correlation between nectar production and time was observed. There were significant quantitative differences in the volumes of nectar produced in the different cowpea cultivars. The highest volume collected (18 m) was from cultivar 219, with a mean of 7.99 ± 0.78 Eil and the lowest recorded value (0.2m) was from SP46 with a mean of 3.65 f 0.5911.1. The cultivars showed similar trends in the rate of reduction in the volumes of nectar produced with time. Sucrose (0.104 f 0.099 mg), glucose (0.0224 ± 0.006 mg), and fructose (0.0225 ± 0.012 mg) occured frequently in the nectars. Lactose (0.003 ± 0.001 mg), raffinose (0.004± 0.002 mg), and mannose (0.006 ± 0.004 mg) were present in trace amounts. The biggest flower size recorded (47 mm) was from cultivar 219 with a mean of 42.62 ± 0.65 mm while the smallest size (10 mm) was from SP46, with a mean of 17.13 ± 0.65 mm. The nectar volume is directly proportional to the flower size. The total number of trapped volatile compounds ranged from 43-109 for headspace trapping and hydrodistillation.Porapak Q trapped the largest number of compounds.Quantitative and qualitative differences in volatile composition of various cultivars were noted. Aliphatic compounds were the most abundant followed by benzenoids, monoterpenes, sesquiterpenes, norisoprenoids and other compounds. The most common cowpea floral volatiles were toluene, 1-hexanol, benzaldehyde, acetophenone, limonene, 1-octen-3-ol, artemisia alcohol and nerolidol. Palmitic acid was the most abundant component of steam distillates. Due to the high protein content, grain legumes should help in reducing protein deficiency cases in developing countries. Improved legume yields should be encouraged to address protein deficiency in children. There is need to intensify production of cowpea by developing more efficient and well adapted varieties with good pest and disease resistance through biotechnology
Determination of thiocyanate among smokers and non-smokers using urine as a biological indicator and other contributing factors of cyanide exposure
(2011-08-23) Nyachoti, Syprose Kemunto; Njue, W. M.; Jane Murungi; Wanjau, R. N.
The low levels of thiocyanate (SCN) normally present in body fluids increase with chronic exposure to cyanide. Cyanide (CN-) is a fast-acting, potentially deadly chemical which prevents or inhibits cellular respiration and inactivation of cytochrome oxidase killing the cell. Humans are exposed to cyanide from dietary, industrial, environmental and other sources. Tobacco smoking is an important source of cyanide exposure. After absorption, cyanides are readily distributed in the body through the blood and are converted to thiocyanate by sulphur transferase enzyme. Thiocyanates are removed from the body through urine. Thus, the determination of urine SCN is a necessary study in establishing the extent of cyanide overload. This study was therefore set to evaluate the concentration of thiocyanate in urine of smokers (n = 128) and non-smokers (n = 123) aged between 20-70 yrs as a biomarker of cyanide exposure. The sampling covered Kahawa Wendani, Kahawa Sukari, Githurai, Ruiru, Kiwanja and Kenyatta University in Nairobi and Thika, Kenya. Information on factors that influence the accumulation of cyanide was assessed using a questionnaire. The UV-visible spectrometer was used to determine the concentration of the thiocyanate using the picrate paper method, developed by Bradbury et al. The mean thiocyanate measured in the urine of smokers was 3.89 ± 0.17 mg/L and that of non-smokers was 1.99 ± 0.12 mg/L. The mean SCN levels in smokers were significantly higher than those of non-smokers (P<0.05; df = 230). Factors that were found to have significant influence were diet particularly cassava and sorghum which gave values of 4.16±0.33 mg/L and 3.75±0.27 mg/L respectively. Utilization of cassava in Kenya is limited to a few places, however, cassava and its products have been reported to be highly used in western (Busia) and coastal regions of the country. The duration and number of cigarettes per day were found to have a statistically significant influence. Fifteen samples purposively sampled were analysed using Lundquist method mainly for comparison purposes. For the samples analysed by these methods, a regression line gave very good agreement (r2 = 0.9942). This information can be used to sensitize the public on the effects of cigarette smoke. The results of this study can also be used by the government to formulate policies and strategies to reduce cyanide exposure thereby addressing some of the health issues affecting people in Kenya
Synthesis, characterization and electrochemical studies of heterobimetallic complexes of schiff base ligands containing vanadium (II) or nickel (II) and molybdenum (II) centers
(2011-08-23) Situma, S. M.; Muthakia, G. K.; Kagwanja, S. M.
In recent times polynuclear complexes have generated a lot of interest in the minds of chemists because of their many applications, they have found use as catalysts. in molecular electronics and are also of biological importance. The work reported in this thesis involved synthesis, characterization and electrochemical studies of heterobimetallic complexes of vanadium and nickel metal ions incorporated in schiff base ligands. The schiff base ligands were synthesized by condensation of either 2,5- or 2,4-dimethylbenzaldehyde and salicylaldehyde with various á-)-diamines (I molar equivalents), giving both "para" and "meta" (with respect to the oxygen atom of the central co-ordination site) ligands, respectively. Individual schiff base ligands were reacted with Vanadyl sulphate in ethanol (1 molar equivalents) to yield mainly red/or green monometallic complexes. The red/or green complexes were further reacted with [MO(NO)L*Cl2 (L*=hydrotris(3,5-dimethylpyrazolyl)borate} to yield wine red bimetallic complexes. The complexes were characterized using physical techniques and found to be paramagnetic. The electrochemical studies showed that there is a small cathodic shift of reduction potentials of molybdenum redox center in the presence of the Vanadyl ion. The lengthening of the polymethylene carbon of the ligand did not have a detectable effect on the reduction potentials. The nickel schiff base complexes were synthesized in a similar manner to their vanadium analogues by reacting schiff bases with nickel(II) chloride hexahydrate to form mainly red/or brown monometallics. The monometallics were further reacted with [Mo(NO)L*CI2 to yield blue or wine red bimetallic complexes. The nickel complexes CV although reversible, gave voltammogrammes with peaks that were in some cases not well resolved. They appeared as a merger of Mo(NO);+ and that of Nit+ reduction potentials. Differential pulses voltammetry timescale gave similar results to those of CV except that the peaks were well resolved. The electrochemical studies showed that there was minimal interaction between the two metal centres. The reduction potentials were also found to be solvent dependent as the metal centres reduced at slightly more cathodic potentials in McCN than the corresponding DCM potentials by 20 - 50 mV. In conclusion we were able to synthesize and characterize the heterobimetallic complexes of vanadium (ii) or nickel (ii) and Mo(NO)L*Cl2 using the Schiff bases as the ligand, and determined their electrochemical behavior
The speciation of copper(II) ions in dilute solution in the presence of selected amino acid contaminants
(2011-08-23) Wekesa, Isaac Masika; Onindo, Charles O.; Gerald Muthakia
The stability constants of a number of copper complexes were determined using pHmetric titrations to investigate the effect of complexes, if any, on solubilization of copper. Potentiometric studies were conducted on copper (1I) ions with some selected organic contaminants. The organic contaminants selected are present in the effluents of coffee processing industry. These comprise of amino acids, which include alanine, serine, glycine, lysine, proline and valine. The pH-metric titrations were carried at 25 ± 0.5 °C and ionic strength, I = 0.1 M KN03. Copper and amino acids complexes were investigated to find their possible role in copper solubilization. The molspin pH metric data obtained was further used by SUPERQUAD program to calculate stability constants for the complexes formed. SPECIES program was used to find the most probable models. From the results, it was established that valine, lysine and glycine formed mostly single ligand complexes at pH 6 - 8.5 with log b > 7.9 implying that they are important in holding copper in solution. However, for the mixed ligand complexes investigated; Copper-Valine-Glycine-Hydroxide, Copper-Valine-Glycine and Copper-Glycine-Lysine systems were formed significantly at pH greater than physiological pH range implying that they may not have significant role in the ionic equilibria associated with their transport
Determination of Selected Essential Elements in Traditional Vegetables, Medicinal Plants, Fruits and Conventionally grown Vegetables in Koibatek, Kenya
(2011-08-23) Cherop, Bernard Kipkemboi
There is growing awareness about tile efficacy of' essential elements in the maintainance of' good health and prevention of diseases. Zinc plays a vital role in wound healing. immune system, reproductive system and nervous system. Zinc wades off oxygen free radicals and also aid in metabolism of carbohydrates by assisting insulin to function. Chromium lowers blood sugar and also works with insulin in metabolization of sugar, while copper is required for conversion of body's Fe into haemoglobin. Copper lowers low density lipoprotein (LDI.) cholesterol, raises high density lipoprotein (I-IDL) cholesterol and prevent oxidation of low density lipoprotein (LDL) cholesterol. Iron is necessary for production of' haemoglobin, immune functioning and drug detoxification. Manganese aids in maintenance of blood glucose level, synthesis of interferon, energy production and bone growth. In this study Zn, Cu, Mn, l e and Cr in selected traditional vegetables, fruits, medicinal plants and conventionally grown vegetables growing/found in Koibatek district (Kenya) were determined using atomic absorption .spectroscopy (AAS) and energy dispersive X- ray fluorescence (EDXRF). This study analysed the elemental contents of a total 312 randomly collected plant samples. In this study Zn, Fe, Cu, Mn and Cr were detected in all the samples, and thb results indicated that traditional vegetables and medicinal plants had high levels of these elements compared to conventionally grown vegetables. However, traditional vegetables had the highest levels of tilt specified essential elements of all the plant samples analysed. Amaranthus hyridicus had the Highest levels or Zn (77.62±33.09 mg/kg), while Gynandropsis gynandra was the best source of' Fe (1 108.00 ± 410.28 mg/kg). Utica mussaica had highest levels of Cr (28.28 ±18.08 mg/kt,) while Gullinsoga paruiflora was the best source of Cu (14.47 ± 6.97 rng/kg). essential elements leached into tire surrounding cooking water when traditional vegetables were boiled and the loss was significant in some samples. 'there were positive and negative correlations between certain metal pair interactions for instance in vegetables there was a high degree of positive correlation in Mn-Cr interaction (r = 0.87). The research findings will help the people of Koibatek district to achieve food security, manage micronutrient deficiencies and to generate income through utilization or sale of traditional vegetables, fruits and medicinal plants from wider sources
Analysis of lead zinc and copper levels of roadside soil and plants across Thika-Nairobi highway, Kenya
(2011-08-23) Magothe, Jackson Mathenge; Wanjau, R. N.; Paul K. Tarus
The importance of studying highway pollution has increased dramatically in recent years due to the rapid growth in the transportation sector which has resulted in environmental degradation. Increase of registered motor vehicles has been on the rise with 70 % being petrol driven while 30 % having diesel propelled engines. In the year 2000, the number of registered vehicles increased by 20,262. But due to improvement in economic growth and reforms in transportation sector that facilitated the reinforcement of traffic rules and regulations by Kenya government on January 2004, a major influx of motor vehicles on Kenyan roads increased by 42,634 which rose further by 85,324 in the year 2007. This rapid increase in transportation services is now a major source of heavy metals pollution, particularly along the busy urban highways. The exposure of man to these heavy metals has caused great concern due to their effect on human health. Therefore, there is need to continue monitoring the heavy metal inputs and levels in the environment. This study was undertaken to determine the levels of Pb, Zn and Cu in the soil and plants across the Thika-Nairobi highway, which is one of the busiest road connecting Nairobi City and other provinces. The samples were collected from five different sites situated along the highway and their levels determined by X-Ray Fluorescence (XRF) technique. The soil and plants samples were investigated as a function of traffic density on the highway, distance from highway, and depth in soil profile. The results showed significant difference (P<0.05) for Pb, Zn and Cu to increase with increase in traffic volume. There was gradual decrease in soil metal levels with increase in distance (5-80 M) from the highway. The mean average levels of Pb distribution on the top soil (up to 10 cm below surface) in the five sampling sites along the Thika-Nairobi highway ranged from 83.2 to 208.1 µg/g during the dry season and 52.5 to 151.8 µg/g during the wet season. Similarly, Zn values ranged from 94.4 to 267.2 pg/g for the dry season and 57.5 to 212.6 µg/g during the wet season. In addition, Cu recorded between 10.4 to 25.3 µg/g during the dry season and 5.6 to 14.7 µg/g during the wet season. The study also showed higher accumulation of Pb, Zn and Cu in the soil depth, 0-10 cm than in the soil depths 10-20 and 20-30 cm. The mean Pb levels on 0-10 cm ranged from 14.5 to 343.5 pg/g and rapidly decreased with depth from ND to 167.6 µg/g at 20-30 cm while Zn registered 21.5 to 376.9 µg/g (0-10 cm) and ND to 194.3 µg/g (20-30 cm) in addition to Cu recording ND to 56.8 µg/g (0-10 cm) and ND to 19.2 µg/g (20-30 cm) across the highway during dry and wet seasons. The levels of Pb, Zn and Cu in pasture grass (Typha elephantina) were higher than in napier grass (Pennisetum purpureum). This indicated that pasture grass posed greater hazard potential than napier grass since it is widely spread along the highway and is oftenly harvested by farmers to make hay to feed animals. The study findings would enable planning and decision making by the concerned stakeholders in resource management geared towards attainment of vision 2030 and thus making Kenyan highways pollution free and therefore creating a habitable ecosystem for all
Sorption of copper (II) ions from acqueous solutions by regenerated spent bleaching earth
(2011-08-23) Enos, Wamalwa Wambu
Copper pollution of water systems has increased greatly in the recent years in many parts of the world because of increased industrial demand for copper, its heavy use in agrochemicals and inefficiency of conventional water filtration techniques. The present study was designed to investigate the efficacy of Spent Bleaching Earth (SBE) as a low cost adsorbent for the removal of copper from aqueous solutions. The SBE, a clay waste generated by edible oil refineries, was washed in excess methyl-ethyl ketone and subjected to heat and/or acid treatments at various conditions. The resultant regenerated spent bleaching earth (RSBE) was then used in a series of experiments to assess its ability to sorb Cu (II) ions from aqueous solutions. The time of contact, adsorbate concentration, adsorbent dosage and the effects of change in adsorbate pH were studied among other parameters. The study showed that copper (II) ions could be removed from aqueous solutions by adsorptive method using RSBE. Methyl-ethyl ketone residual oil extraction followed by heat treatment of the material at 350-370 °C was most effective SBE regeneration procedure for copper adsorption. The materials obtained in this way were characterized by high Cation Exchange Capacity (CEC) of up to 6000 mg/g of Na ions equivalents. They had Point of Zero Net Charge (PZNC) at pH 5.5. The pH, sorbent dosage and initial adsorbate concentrations were key parameters affecting adsorption characteristics of Cu (II) ions onto RSBE. Over 94% Cu (II) removal was recorded at pH 5.5 using 272 mg/l of initial Cu (II) concentration at 0.1 mass (grams) to volume (milliliters) of adsorbent dosage. Based on analysis of changes in solution pH during the adsorption process, it was suggested that that hydrolysis species were more favorably adsorbed onto the RSBE soil particles. The highest distribution coefficient, KD, of 590.76 was recorded for 370 °C regenerated materials and the standard Gibbs free energy (G0) (which ranged from -11.9611 kJmol-1 to5.8042) indicated that the adsorption process was spontaneous and mainly based on physical ion-exchange type interactions between the metal ions and cations at the RSBE surfaces. Analysis of the adsorption kinetics indicated that Cu (11) adsorption on RSBE is a rapid phenomenon reaching its initial equilibrium in less than six hours. The sorption process fitted Lagergren pseudo-second order mechanism in the initial stages although the MorisWeber intra-particle diffusion mechanism was more favored at prolonged periods of equilibration. The adsorption data was better described by the Langmuir isotherm than the Freundlich Isotherm was. And desorption experiments illustrated that pH adjustments were more effective in recovery of sorbed copper ions from RSBE than competitive cationic desorbing agents. Over 80% removal of sorbed copper was realized showing that the sorbed metal can substantially be recovered from the materials before their final disposal

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