Papers by Dereje Yenealem
Black cumin (Nigella sativa), and Coriander (Coriandrum sativum L.) are common culinary spices th... more Black cumin (Nigella sativa), and Coriander (Coriandrum sativum L.) are common culinary spices that are used singly or combined in the diet of many populations of Ethiopia and there is a long-held belief of their health-enhancing properties. The present study was designed to investigate the antioxidant properties, phenolic and flavonoid contents of aqueous methanolic extracts from Nigella sativa and Coriandrum sativum L. seed samples. The contents of polyphenols and flavonoids were evaluated by colorimetric method and antioxidant activity was determined based on the ability to scavenge free radicals by using DPPH assay. An aqueous methanol extract of Coriandrum sativum L. resulted in the highest phenolic content from West Dembia (1.799 ± 0.0011 mg GAE/g), followed by Nigella sativa from East and West Dembia (1.737 ± 0.0014 & 1.734 ± 0.0013 mg gallic acid equivalent per gram (mg GAE/g) respectively) and Coriandrum sativum L. from West Dembia (1.678 ± 0.0018 mg GAE/g) measured by the ...
Research Square (Research Square), Apr 10, 2024
The study aimed to detect the level of a atoxin contamination and risk assessment of a atoxins. A... more The study aimed to detect the level of a atoxin contamination and risk assessment of a atoxins. A total of eighteen roasted peanut samples were collected and analyses in different area of Gondar City. The a atoxin was extracted from peanut with (Acetonitrile: Methanol: Water (15: 25: 60) and the analyses were performed using High-Performance Liquid Chromatography detector method. From the result, A good linearity of standard calibration was found for AFB1, AFB2, AFG1 and AFG2 at a range of 0.2-50 ppb. Regression coe cient (R 2) values were >0.996. The average recoveries for spiked sample were ranged from 81.83 to 108.16% and Limit of detection and quanti cation ranged from (0.138-0.6 ppb), (0.46-2.0 ppb), respectively. The determined a atoxin contamination levels in roasted peanut samples ranged from 2.
Research Square (Research Square), Apr 17, 2024
In this study, cabbage samples were meticulously gathered from various locations in the northern ... more In this study, cabbage samples were meticulously gathered from various locations in the northern Gondar (Debark and Dabat) and central Gondar zone (Amba-Giorgis, Arada, and Azezo) regions during June 2020. The purpose was to assess the presence and levels of heavy metals including Copper (Cu), Zinc (Zn), Chromium (Cr), Manganese (Mn), Lead (Pb), and Cadmium (Cd) within the sampled cabbages. To determine the concentrations of these metals, advanced analytical techniques involving atomic absorption spectrophotometry following optimizing by wet digestion process were employed The obtained results revealed metal concentrations within the cabbage samples ranging from 0.103 ± 0.004 to 0.
Simultaneous electrochemical determination of l-cysteine and l-cysteine disulfide at carbon ionic liquid electrode
Amino Acids, 2014
A linear sweep voltammetric method is used for direct simultaneous determination of L-cysteine an... more A linear sweep voltammetric method is used for direct simultaneous determination of L-cysteine and L-cysteine disulfide (cystine) based on carbon ionic liquid electrode. With carbon ionic liquid electrode as a high performance electrode, two oxidation peaks for L-cysteine (0.62 V) and L-cysteine disulfide (1.3 V) were observed with a significant separation of about 680 mV (vs. Ag/AgCl) in phosphate buffer solution (pH 6.0). The linear ranges were obtained as 1.0-450 and 5.0-700 μM and detection limits were estimated to be 0.298 and 4.258 μM for L-cysteine and L-cysteine disulfide, respectively. This composite electrode was applied for simultaneous determination of L-cysteine and L-cysteine disulfide in two real samples, artificial urine and nutrient broth. Satisfactory results were obtained which clearly indicate the applicability of the proposed electrode for simultaneous determination of these compounds in complex matrices.
Evaluation of Total Phenolic, Flavonoid Contents and Antioxidant Activities of Seed Extracted from Coriander (Coriandrum Sativum L) and Black cumin (Nigella Sativa) Spices
Black cumin (Nigella sativa), and Coriander (Coriandrum sativum L.) are common culinary spices th... more Black cumin (Nigella sativa), and Coriander (Coriandrum sativum L.) are common culinary spices that are used singly or combined in the diet of many populations of Ethiopia and there is a long-held belief of their health-enhancing properties. The present study was designed to investigate the antioxidant properties, phenolic and flavonoid contents of aqueous methanolic extracts from Nigella sativa and Coriandrum sativum L. seed samples. The contents of polyphenols and flavonoids were evaluated by colorimetric method and antioxidant activity was determined based on the ability to scavenge free radicals by using DPPH assay. An aqueous methanol extract of Coriandrum sativum L. resulted in the highest phenolic content from West Dembia (1.799 ± 0.0011 mg GAE/g), followed by Nigella sativa from East and West Dembia (1.737 ± 0.0014 & 1.734 ± 0.0013 mg gallic acid equivalent per gram (mg GAE/g) respectively) and Coriandrum sativum L. from West Dembia (1.678 ± 0.0018 mg GAE/g) measured by the ...
Square Wave Voltammetric Determination of Paracetamol in Drugs and Human Urine Samples, 2019
A method based on square wave voltammetry (SWV) on activated glassy carbon electrode (AGCE) was i... more A method based on square wave voltammetry (SWV) on activated glassy carbon electrode (AGCE) was investigated for the determination of Paracetamol (N-acetyl-p-aminophenol) (APAP) from drugs and human urine samples. The AGCE was prepared by applying a potential of 1750 mV, sensitivity of 100 µA/V, on bare glassy carbon electrode (GCE), dipped in 0.1 M phosphate buffer solution (PBS) at pH 7.0, for 200 s. It was found that AGCE efficiently electro catalyzed the oxidation of APAP than bare GCE. Cyclic voltammetric study showed that AGCE decreases the over potential of APAP by 131 mVs compared to bare glassy carbon electrode. The optimal SWV operational conditions of the proposed method were: step potential; 8 mV, accumulation potential 250 mV, accumulation time 30 s and square wave amplitude; 70 mV and square wave frequency; 30 Hz using a phosphate buffer solution at pH 7.0. The method was linear in the range 0.4 100 μM paracetamol with detection limit of 0.0134 μM. The proposed method was applied for APAP determination in commercial tablets and also in human urine with 99% accuracy and interferents like uric acid, copper sulphate, pyridine, acetic acid and glucose also investigated. Only uric acid showed a great interfering effect for the detection of paracetamol.
Simultaneous Electrochemical Determination of Paracetamol and Caffeine using Activated Glassy Carbon Electrode
Black cumin (Nigella sativa), and Coriander (Coriandrum sativum L.) are common culinary spices th... more Black cumin (Nigella sativa), and Coriander (Coriandrum sativum L.) are common culinary spices that are used singly or combined in the diet of many populations of Ethiopia and there is a long-held belief of their health-enhancing properties. The present study was designed to investigate the antioxidant properties, phenolic and flavonoid contents of aqueous methanolic extracts from Nigella sativa and Coriandrum sativum L. seed samples. The contents of polyphenols and flavonoids were evaluated by colorimetric method and antioxidant activity was determined based on the ability to scavenge free radicals by using DPPH assay. An aqueous methanol extract of Coriandrum sativum L. resulted in the highest phenolic content from West Dembia (1.799 ± 0.0011 mg GAE/g), followed by Nigella sativa from East and West Dembia (1.737 ± 0.0014 & 1.734 ± 0.0013 mg gallic acid equivalent per gram (mg GAE/g) respectively) and Coriandrum sativum L. from West Dembia (1.678 ± 0.0018 mg GAE/g) measured by the ...
BMC chemistry, Nov 5, 2022
y up and mature. Extracted honey is a gelatinous liquid foodstuff containing a number of nutritio... more y up and mature. Extracted honey is a gelatinous liquid foodstuff containing a number of nutritiously important complementary elements [4-8] such as carbohydrates, maltose, sucrose, fructose, glucose, traces metals, organic and inorganic substances and water [9, 10]. High concentrations of these trace toxic elements in honey may result minimized quality set by regular control of food [11-14]. In ancient time the golden yellow liquid honey processed for its medicinal properties [15]. The heavy metals found in the environment can deposit at the hairy bodies of bees hive, flower, herb and water [16]. The toxic metals in the human body, causing the side effects, so honey quality specific elemental content becomes the important issue for human nutrition and safety [17, 18]. High accumulation of toxic heavy metals in plants is hazardous for the food chain and may result in damages to human and animals heaths [19]. Contaminated water and agricultural BMC Chemistry
Assessments of physico-chemical parameters, nutrient load and trace metal levels in spring and river water using multivariate statistical methods, South Gondar Zone, Ethiopia
Physico-chemical and selected heavy metals were investigated. Seven water samples were collected.... more Physico-chemical and selected heavy metals were investigated. Seven water samples were collected. The results of water quality parameters ranged pH, EC, TSS, turbidity, TDS, total alkalinity, DO, temperature, Salinity, Chlorides, NH3, PO4 − 3, SO4 − 2, NO3 − 2, NO2− 0.015 to 0.139 mg/L, Cr, Mn, Fe, Ni, Pb and Cd. Most of the results are comparable with WHO standards, in contrast some of are above permissible limits. Evaluated data through multivariate statistical techniques Principal correlation analysis (PCA), Cluster analysis and correlation matrix were performed. The sampling points extracted three clusters for nutrient water quality which suggested similar pollution sources. The water sample was polluted due to the anthropogenic effects of Mekan Eyesus Town while in the spring water high concentrations of Cl−, NH3 and PO4 − 3 were recorded. These might be natural sources of pollution. Most of the physicochemical parameters and the nutrients showed significant relationships excep...
The extensive use of pesticides considered as a global threat to the ecological integrity of aqua... more The extensive use of pesticides considered as a global threat to the ecological integrity of aquatic ecosystems. Most developing countries including Ethiopia are burdened with these toxic and persistent pesticides due to their wider used for agricultural pest and malaria control. The present study was aimed to investigate the concentration of Organochlorine pesticides water, sediment and fish samples in Lakes Tana and Hayqe. Eight samples of each water and sediment and five fish samples were collected. A laboratory based cross sectional study was conducted from Dec 2020 to March 2021 in Lakes Tana and Hayqe. A more sensitive method for the determination of 18 Organochlorine pesticides in water, sediments, and fish samples were adopted using QuEChERS and the analyses were done using GC-MS. Water samples were processed using a liquid–liquid extraction technique and gas chromatograph equipped with mass spectroscopy (GC-MS). Dispersive-solid-phase extraction (d-SPE) was used for fish an...
BMC Chemistry
Nowadays, there are more than fourteen major state and private owned textile industries and garme... more Nowadays, there are more than fourteen major state and private owned textile industries and garment factories in Ethiopia. However, these textile effluents are directly discharged without treatment to the surrounding environment, as a result, the pollutants bring serious problem to the surrounding community including health such as skin diseases, asthma, abortion, carcinogenic effect, biodiversity loss and mutagenic effect on the. The main objective of this study is characterization and treatment of the textile effluent using aluminum electrodes in the electrocoagulation process. EC experimental setups were designed and different parameters were optimized. Electrocoagulation treatment process eliminates physicochemical quality indicators such as pH, electrical conductivity (EC); turbidity, biological oxygen demand (BOD), ammonia; nitrate, nitrite, total nitrogen (TN) and phosphate were determined using standard procedures. From the result, the maximum removal efficiency of phosphate...
Honey is a natural, sugary and sticky liquid that is produced from the nectars of flowers. This s... more Honey is a natural, sugary and sticky liquid that is produced from the nectars of flowers. This study aimed to analyze the concentration of some selected heavy Metals (Zn, Cu, Mn, Cd, Pb, and Cr) in honey samples. 1g of honey sample was digested by a hot plate using 9ml of HNO3 and 3ml of H2O2. The concentrations of the heavy metals in the digested were detected using a flame atomic absorption spectrometer. The results of this study found that the concentrations of the heavy metals in the honey samples were ranged from 1.97 to 2.04 µg/g for Zn, 1.93µg/g to 2µg/g for Cu, 0.83 to 1.01 µg/g for Mn, 0.25 to 0.45 µg/g for Cr, (0.025–0.031 µg/g for Cd. However, Pb was not detected in all honey samples. Hence, the levels of heavy metals found were below the permitted levels set by the World Health Organization.The contamination levels of the heavy metals are also found to be below the detection levels. The results of this study helped us to know that the acceptable amounts of heavy metals ...
Simultaneous Electrochemical Determination of Paracetamol and Caffeine using Activated Glassy Carbon Electrode
Herein, we report simultaneous electrochemical determination of Paracetamol (PAR) and Caffeine (C... more Herein, we report simultaneous electrochemical determination of Paracetamol (PAR) and Caffeine (CAF) at activated glassy carbon electrode (aGCE) using cyclic voltammetry (CV) and square wave voltammetry (SWV). Comparison was made for cyclic voltammetric response of PAR and CAF at bare glassy carbon electrode (bGCE) and aGCE in 0.1 M phosphate buffer solution (PBS) of pH 7.0. The experimental result showed that the redox process of PAR was both diffusion and adsorption controlled, whereas the oxidation reaction of CAF is diffusion controlled at aGCE. The aGCE showed a linear response to PAR in the concentration range of 10-180 μM when the concentration of CAF was kept constant (25 µM). Similarly, the linear range for CAF was from 10 -95 μM at a constant concentration of 10 μM PAR. The detection limit (LOD) of PAR and CAF was found to be 2.55 μM, 2.36 μM (3σ/m), respectively. The validity of the demonstrated method was checked by using commercial tablet which contain different amount ...
Determination of Caffeine in Commercially Available Coffee, Tea and Coca-Cola by using UV-Visible Spectrometer
The study was done to determine caffeine content of coffee, tea and coca-cola samples that are av... more The study was done to determine caffeine content of coffee, tea and coca-cola samples that are available at local market of Ethiopia. Caffeine is a naturally occurring alkaloid which is a pharmacologically active substance. The most important sources of caffeine are coffee, tea leaves, cocoa beans and cola nuts. The isolation of caffeine was done by liquid-liquid extraction method, using important extracting solvents such as dichloromethane (DCM), chloroform and distilled water at a range of 220 nm – 340nm wave lengths. Quantitative estimation of caffeine concentration in the samples was performed by a simple and fast standard UV spectrometric (181884-01-0076) method. Caffeine concentration was observed in coca-cola samples (2.101ppm) while in coffee samples (4.66ppm). The concentration of caffeine in coca-cola was the lowest. The levels of caffeine in all samples are well below the maximum allowable limits set by the food regulatory bodies.
Differential Pulse in the metric Determination of Paracetamol Using Activated Glassy Carbon Electrode- Ethiopia
Journal of Electrical & Electronic Systems, 2021
Abstract: The electrochemical property of paracetamol was investigated at a glassy carbon electro... more Abstract: The electrochemical property of paracetamol was investigated at a glassy carbon electrode and activated glassy carbon electrode. Differential pulse voltammetry and cyclic voltammetry were used as diagnostic techniques in the determination of paracetamol. The activated glassy carbon electrode exhibited excellent electro-catalytic behaviour for the oxidation of PAR as evidenced by the enhancement of the oxidation peak current and the shift in the oxidation peak potential to less positive values by (13mv) in comparison with a bare GCE. In the present work the activated glassy carbon electrode was prepared by activating 200 s in a time base technique at a potential of 1750 mV. The electrode process of paracetamol was studied and some the experimental parameters which affect the response paracetamol, such as pH, effect of PAR concentration and scan rate on AGC electrode. The analysis of cyclic voltammogram gave fundamental electrochemical parameters including the electroactive surface coverage, the electron transfer coefficient and the heterogeneous rate constant (ks). The variation of scan rate study shows that the system undergoes adsorption controlled process. The equation of the calibration curve was found to be: Ip=0.429C + 6.43, R2=0.993. The LOD and LOQ for the developed method were determined to be 8×10-8 mol L-1 and 2.6×10-7mol L-1 respectively. Phosphate buffer pH 7.0 was selected for analytical purpose.
American Journal of Physical Chemistry, 2021
Abstract: The electrochemical property of paracetamol was investigated at a glassy carbon electro... more Abstract: The electrochemical property of paracetamol was investigated at a glassy carbon electrode and activated glassy
carbon electrode. Differential pulse voltammetry and cyclic voltammetry were used as diagnostic techniques in the
determination of paracetamol. The activated glassy carbon electrode exhibited excellent electro-catalytic behaviour for the
oxidation of PAR as evidenced by the enhancement of the oxidation peak current and the shift in the oxidation peak potential
to less positive values by (13mv) in comparison with a bare GCE. In the present work the activated glassy carbon electrode
was prepared by activating 200 s in a time base technique at a potential of 1750 mV. The electrode process of paracetamol was
studied and some the experimental parameters which affect the response paracetamol, such as pH, effect of PAR concentration
and scan rate on AGC electrode. The analysis of cyclic voltammogram gave fundamental electrochemical parameters including
the electroactive surface coverage, the electron transfer coefficient and the heterogeneous rate constant (ks). The variation of
scan rate study shows that the system undergoes adsorption controlled process. The equation of the calibration curve was found
to be: Ip=0.429C + 6.43, R2=0.993. The LOD and LOQ for the developed method were determined to be 8×10-8 mol L-1 and
2.6×10-7mol L-1 respectively. Phosphate buffer pH 7.0 was selected for analytical purpose.
ACTA CHEMICA IASI
Simultaneous voltammetric determination of paracetamol (PA) and ascorbic acid (AA) at activated g... more Simultaneous voltammetric determination of paracetamol (PA) and ascorbic acid (AA) at activated glassy carbon electrode (aGCE) using cyclic voltammetry (CV) and square wave voltammetry (SWV) was studied. The electrochemical responses of PA and AA were compared at bare (bGCE) and aGCE. The aGCE displayed excellent electrochemical catalytic activities and decreased the over-potential for simultaneous determination of PA and AA. It was found that the redox process at aGCE for both PA and AA is adsorption-controlled process. The linear range, limit of quantification (LOQ) and detection limit (LOD) of PA were found to be 10 to 100 µM; 0.517 µM and 0.155 µM, respectively. Similarly, the linear range, LOQ and LOD of AA were found to be 0.4 to 0.95 mM, 6.32 µM and 1.89 µM, respectively. The validity of the proposed method was checked by using commercial drug which contain different amount of PA and AA and satisfactory percent recoveries were obtained.
American Journal of Physical Chemistry, 2021
The electrochemical property of paracetamol was investigated at a glassy carbon electrode and act... more The electrochemical property of paracetamol was investigated at a glassy carbon electrode and activated glassy carbon electrode. Differential pulse voltammetry and cyclic voltammetry were used as diagnostic techniques in the determination of paracetamol. The activated glassy carbon electrode exhibited excellent electro-catalytic behaviour for the oxidation of PAR as evidenced by the enhancement of the oxidation peak current and the shift in the oxidation peak potential to less positive values by (13mv) in comparison with a bare GCE. In the present work the activated glassy carbon electrode was prepared by activating 200 s in a time base technique at a potential of 1750 mV. The electrode process of paracetamol was studied and some the experimental parameters which affect the response paracetamol, such as pH, effect of PAR concentration and scan rate on AGC electrode. The analysis of cyclic voltammogram gave fundamental electrochemical parameters including the electroactive surface coverage, the electron transfer coefficient and the heterogeneous rate constant (k s). The variation of scan rate study shows that the system undergoes adsorption controlled process. The equation of the calibration curve was found to be: I p =0.429C + 6.43, R 2 =0.993. The LOD and LOQ for the developed method were determined to be 8×10-8 mol L-1 and 2.6×10-7 mol L-1 respectively. Phosphate buffer pH 7.0 was selected for analytical purpose.
SIMULTANEOUS VOLTAMMETRIC DETERMINATION OF p-AMINOPHENOL AND PARACETAMOL USING ACTIVATED GLASSY CARBON ELECTRODE: CYCLIC VOLTAMMETRY AND DIFFERENTIAL PULSE VOLTAMMETRY STUDY
ACTA CHEMICA IASI
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Papers by Dereje Yenealem
carbon electrode. Differential pulse voltammetry and cyclic voltammetry were used as diagnostic techniques in the
determination of paracetamol. The activated glassy carbon electrode exhibited excellent electro-catalytic behaviour for the
oxidation of PAR as evidenced by the enhancement of the oxidation peak current and the shift in the oxidation peak potential
to less positive values by (13mv) in comparison with a bare GCE. In the present work the activated glassy carbon electrode
was prepared by activating 200 s in a time base technique at a potential of 1750 mV. The electrode process of paracetamol was
studied and some the experimental parameters which affect the response paracetamol, such as pH, effect of PAR concentration
and scan rate on AGC electrode. The analysis of cyclic voltammogram gave fundamental electrochemical parameters including
the electroactive surface coverage, the electron transfer coefficient and the heterogeneous rate constant (ks). The variation of
scan rate study shows that the system undergoes adsorption controlled process. The equation of the calibration curve was found
to be: Ip=0.429C + 6.43, R2=0.993. The LOD and LOQ for the developed method were determined to be 8×10-8 mol L-1 and
2.6×10-7mol L-1 respectively. Phosphate buffer pH 7.0 was selected for analytical purpose.