Browsing by Author "Gichumbi, J.M."

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Determination of precursors of acrylamide formation in roasted maize
(Advances in Phytochemistry, Textile and Renewable Energy Research for Industrial Growth – Nzila et al. (Eds), 2022-04) Koske, M.C.; Kiprop, A.; Ongoma, O.; Kariuki, P.; Kagwanja, S.M.; Gichumbi, J.M.
Acrylamide, an organic compound with the formula CH2=CHCONH2, is a contaminant generated through high-temperature cooking processes as a result of Maillard reactions catalyzed by the presence of reducing sugars and free amino acids in starchy food compounds. Acrylamide and its major metabolite, glycidamide, have been considered probable human carcinogens. In this study, we report on the acrylamide content in roasted maize from some Kenyan markets. Raw maize was purchased from local markets and roasted under laboratory conditions. They were crushed and extracted using water and hexane in a ratio of 2:1. The extract was derivatized with potassium bromate and potassium bromide and further subjected to liquid–liquid extraction using ethyl acetate-hexane (4:1, v/v). The final bromoprop-2-enamide (BPA) analyte was analyzed using gas chromatography–flame ionization detector. Acrylamide was not detected in any of the samples (at limit of detection of 20 µg/kg), which was consistent with reports from other countries.
Phthalate Levels in Wastewater Treatment Plants of Lake Victoria Basin
(Science and Education Publishing, 2021) Onchiri, R.; Ongulu, R.; Orata, F.; Getenga, Z.M.; Gichumbi, J.M.; Ogora, E.N.
Phthalates are examples of EDCs, which have been used as plasticizers for longtime worldwide. However, their occurrence in these environments causes adverse effects such as congenital anomalies, endocrine disruption and chronic toxicity. Wastewater is the source of these phthalates in the environment. The main aim of this study was to determine the levels of dimethyl phthalate (DMP), benzyl butyl phthalate (BBP) and bis (2-ethylhexyl) phthalate (BEHP) in wastewater sampled from wastewater treatment plants (WWTPs) of Nyalenda, Homabay and Kisii, in Kenya during wet and dry seasons. Thermos Scientific Dionex UltiMateTM 3000 HPLC system was used to analyze the residue levels at 0.004 and 0.005 mg/L limits of quantification during wet and dry seasons, respectively. Most sites sampled had detectable levels of DMP, BBP and BEHP. Higher concentrations were detected during wet season compared to dry season. At Nyalenda treatment plant, DMP was detected at 0.99 ± 0.0005 mg/L and 0.79 ± 0.0005 mg/L at the inlet sampling point during the wet and dry seasons, respectively. The concentrations detected were high at the inlet and lowest at the outlet sampling points. The residue levels obtained showed significant differences at 5% confidence limits with Zcalculated for DMP at Nyalenda, Homabay and Kisii WWTPs obtained as 0.2650, 0.2183 and 0.1983, respectively. These Z-score values (Zcalculated) were less than the critical value (Zcritical = 1.96). Similar observations were observed with BBP and BEHP.
Structural properties of high density polyethylene matrix composites reinforced with open air and furnace rice husks ash
(Journal of Chemical Engineering and Materials Science, 2021-12) Jonathan, M.K.; Osamong, G.A.; Butembu, S.; Kamweru, P.K.; Gichumbi, J.M.; Ndiritu, F.G.
In this work, rice husks ash (RHA) was introduced to pure and recycled high density polyethylene (HDPE) matrix, at varying ration (0-50%) to formulate rice husks ash High density polyethylene (RHAHDPE) composite. RHA was obtained by burning fresh rice husks either by open-air burning (oRHA) or furnace calcination at 700°C (fRHA). The composite samples were made by melt-mixing the HDPE in an oven at a temperature of 150°C and adding different percentages of RHA in presence of maleic anhydride compatibilizer. Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) were carried out to determine the structural properties of the samples, and both suggest occurrence of composting chemical changes. For all RHA-HDPE samples, a broad band was noted between 970-070cm-1 . This was highly contributed by the RHA and associated to Si-O-Si stretching modes. Other peaks are associated with Si-O-C interaction and O-Si-O bending vibrations in the samples. Scanning electron Microscopy (SEM) micrographs for HDPE indicated a smooth and uniform surface with a number of voids. On addition of RHA, the particles filled these voids making the sample surface rough. This roughness is seen to increase with increased percentage of RHA. The studies conclude that the cheaply obtained oRHA is as good as the fRHA in making RHA-HDPE composite.
Synthesis and Insecticidal activities of some selected hydroxytriazenes
(2012-10) Ombaka, O. *; Gichumbi, J.M.
Eight hydroxytriazenes were synthesized and then subjected to spot tests. The composition of these hydroxytriazenes was analyzed using elemental analysis and their physical characteristics like melting point, crystal shape and colour were studied into details. The synthesized compounds were screened for their insecticidal activities against one day old male Drosophila melanogaster Meig (vinegar flies or fruit flies). Out of all the eight compounds screened, 3-hydroxy-3-m-tolyl-1-m-nitrophenyltriazene, 3- hydroxy-3-m-tolyl-1-p-methoxyphenyltriazene, 3-hydroxy-3-n-propyl-1-o-chlorophenyltriazene were the most active having LC50 values of 2.898, 3.898 and 1.812 ppm respectively. The least active compound is 3-hydroxy-3-m-tolyl-1-phenyltriazene having the value of 16.850 ppm. Heptachlor, a commercial product, had LC50 value of 1.570 ppm.
Synthesis and insecticidal activities of some selected hydroxytriazenes
(2011-10) Ombaka, O*; Gichumbi, J.M.
Eight hydroxytriazenes were synthesized and then subjected to spot tests. The composition of these hydroxytriazenes was analyzed using elemental analysis and their physical characteristics like melting point, crystal shape and colour were studied into details. The synthesized compounds were screened for their insecticidal activities against one day old male Drosophila melanogaster Meig (vinegar flies or fruit flies). Out of all the eight compounds screened, 3-hydroxy-3-m-tolyl-1-m-nitrophenyltriazene, 3- hydroxy-3-m-tolyl-1-p-methoxyphenyltriazene, 3-hydroxy-3-n-propyl-1-o-chlorophenyltriazene were the most active having LC50 values of 2.898, 3.898 and 1.812 ppm respectively. The least active compound is 3-hydroxy-3-m-tolyl-1-phenyltriazene having the value of 16.850 ppm. Heptachlor, a commercial product, had LC50 value of 1.570 ppm.