A pinboard by
Omolara Ojezele

Lecturer, Federal College of Animal Health and Production Technology


Pesticides residues in a common vegetable and soil samples from South west Nigeria were determined

My research area is in Environmental Chemistry and Pollution Control. Contaminants in fresh food samples, vegetables, canned food, milk and milk products, fruit juices, water samples are determined. The different contaminants are also quantified and the levels are compared with recommended or allowable limits of such contaminants according to WHO/FAO standards. Examples of such contaminants are pesticide residues, heavy metals and some other physicochemical parameters. Also, research works are done on farm settlements where food crops are planted and then transferred to major food markets in South West Nigeria, the farmers are monitored especially when it comes to their pest management methods. Farmers in Nigeria make use of pesticides starting from clearing weeds to just before harvesting their crops, many of them engage in indiscriminate use of such pesticides, they harvest their crops without waiting for the pesticides to wear off, therefore endangering the lives of the consumers. All these practices have been established through the careful observations and questionnaire administered to them. Such food crops from the farms are analysed to check for the presence of these chemicals in them. If they are present, the next question is how much of these chemicals are present?. The pesticide levels are compared with recommended standards. The soil samples upon which the crops are planted are also analysed to evaluate likely transfer of such contaminants from soil to crops. Water samples are also analysed for different contaminants to ascertain their portability. This is done by carrying out investigations on heavy metal levels, physicochemical parameters and other contaminants in such water samples. The outcome of these results are presented to policy makers so as to educate farmers on safe use of pesticides and also to create awareness and enlighten the populace.


Transfer of metals from soil to vegetables and possible health risk assessment.

Abstract: Metal contamination in agricultural soils is of increasing concern due to food safety issues and potential health risks. Accumulation of Heavy and trace metals in vegetables occur by various sources but soil is considered the major one. Consumption of vegetables containing (heavy/trace) metals is one of the main ways in which these elements enter the human body. Once entered, heavy metals are deposited in bone and fat tissues, overlapping noble minerals and cause an array of diseases. The present study aimed to investigate the concentration of different metals in agricultural soil and vegetables grown on those soils and to evaluate the possible health risks to human body through food chain transfer. Contamination levels in soils and vegetables with metals were measured and transfer factors (TF) from soil to vegetables and its health risk were calculated accordingly. Results showed that concentration of Si, Ba, K, Ca, Mg Fe, Sc, V, Cr, Cu, Zn, As, Mn, Co, Ni, Se, Sr, Mo, and Cd in soil is higher than the World Average value and Al, Ti and Pb is lower than the World Average value whereas concentration of toxic elements like As, Co, Cu, Mn, Pb, Se, Ni, V and Zn in vegetable samples are below the World Average value. The intake of toxic metals (Fe, Cu, Mn, Zn Co, Cr, V, Ni, Pb and Cd) from vegetables is not high and within the permissible limit recommended by WHO, Food & Nutritional Board and US EPA. The Hazard Quotient (HQ) for Fe, Cu, Co, Cr, V, Ni, Pb, Mn, Zn and Cd were calculated which showed a decreasing order of Cd>Mn>Zn>Pb>Cu>Fe>Ni>V=Co>Cr. Highest HQ value found for Cd (2.543) which is above the safe value.

Pub.: 07 Sep '13, Pinned: 31 Jul '17

Heavy metal exposure from cooked rice grain ingestion and its potential health risks to humans from total and bioavailable forms analysis.

Abstract: Heavy metal in rice studies has attracted a greater concern worldwide. However, there have been limited studies on marketed rice samples although it represents a vital ingestion portion for a real estimation of human health risk. This study was aimed to determine both total and bioaccessible of trace elements and heavy metals (Cd, Cr, Cu, Co, Al, Zn, As, Pb and Fe) in 22 varieties of cooked rice using an inductively coupled plasma-optical emission spectroscopy. Both total and bioaccessible of trace elements and heavy metals were digested using closed-nitric acid digestion and Rijksinstituut voor Volksgezondheid en Milieu (RIVM) in vitro digestion model, respectively. Human health risks via Health Risk Assessment (HRA) were conducted to understand exposure risks involving adults and children representing Malaysian population. Zinc was the highest while As was the lowest contents for total and in their bioavailable forms. Four clusters were identified: (1) Pb, As, Co, Cd and Cr; (2) Cu and Al; (3) Fe and (4) Zn. For HRA, there was no any risks found from single element exposure. While potential carcinogenic health risks present for both adult and children from single As exposure (Life time Cancer Risk, LCR>1×10(-4)). Total Hazard Quotient values for adult and children were 27.0 and 18.0, respectively while total LCR values for adult and children were 0.0049 and 0.0032, respectively.

Pub.: 31 May '17, Pinned: 31 Jul '17

Feasibility and application of an HPLC/UVD to determine dinotefuran and its shorter wavelength metabolites residues in melon with tandem mass confirmation.

Abstract: A new analytical method was developed for dinotefuran and its metabolites, MNG, UF, and DN, in melon using high-performance liquid chromatography (HPLC) coupled with an ultraviolet detector (UVD). Due to shorter wavelength, lower sensitivity to UV detection, and high water miscibility of some metabolites, QuEChERs acetate-buffered version was modified for extraction and purification. Mobile phases with different ion pairing or ionisation agents were tested in different reverse phase columns, and ammonium bicarbonate buffer was found as the best choice to increase the sensitivity of target analytes to the UV detector. After failure of dispersive SPE clean-up with primary secondary amine, different solid phase extraction cartridges (SPE) were used to check the protecting capability of analytes against matrix interference. Finally, samples were extracted with a simple and rapid method using acetonitrile and salts, and purified through C(18)SPE. The method was validated at two spiking levels (three replicates for each) in the matrix. Good recoveries were observed for all of the analytes and ranged between 70.6% and 93.5%, with relative standard deviations of less than 10%. Calibration curves were linear over the calibration ranges for all the analytes with r(2)≥ 0.998. Limits of detection ranged from 0.02 to 0.05 mg kg(-1), whereas limits of quantitation ranged from 0.06 to 0.16 mg kg(-1) for dinotefuran and its metabolites. The method was successfully applied to real samples, where dinotefuran and UF residues were found in the field-incurred melon samples. Residues were confirmed via LC-tandem mass spectrometry (LC-MS/MS) in positive-ion electrospray ionisation (ESI(+)) mode.

Pub.: 06 Nov '12, Pinned: 31 Jul '17