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    Removal of arsenic from aqueous solution by synthetic hematite
    (Journal of Chemical Society of Nigeria, 2011) Adekola, F. A.; Abdus-Salam, N.; Abdulrauf, L. B.
    A sample of hematite has been prepared and characterized by determination of some physico-chemical parameters such as X- ray Diffraction analysis, specific gravity and point of zero charge measurement. The potential of synthesized hematite for the sorption of arsenic(III) aqueous solution was also investigated, and the sorption data were found to be fitted with Langmuir adsorption isotherm (type 2) as well as Freundlich and Temkin isotherms with corresponding correlation coefficient (R) of 0.96, 0.94 and 0.94 respectively. The adsorption capacity calculated from the Freundlich and Langmuir isotherms were 0.35 and 0.60 respectively. The sorption kinetics was also investigated and the equilibrium time determined to be 320mins. The kinetics was found to follow pseudo – first order kinetics. Desorption study was also carried out with concentrated HNO3 (1M), and was found to be effective for the stripping of 86% of pre – sorbed arsenic from the adsorbent after the first use
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    Headspace Solid Phase Microextraction (HS-SPME) coupled to Gas Chromatography-Mass Spectrometry (GC/MS) for the Analysis of MultiClass Pesticides
    (Ilorin Journal of Science, 2014) Abdulra'uf, L. B.; Ibrahim, H. B.; Tan, G. H.
    The development of a method based on headspace solid phase microextraction (HS-SPME) technique, for the simultaneous determination of 7 multiclass and multiresidue pesticides (fenobucarb, diazinon, chlorothalonil, thiobencarb,chlorpyrifos,endosulfan I and endosulfan II) in two species of apple, using gas chromatographymass spectrometry is discussed. The different parameters affecting the SPME technique were evaluated. The extraction capacity of three fiber coatings; polydimethylsiloxane (100µm PDMS), polyacrylate (65µm PA), and polydimethylsiloxane-divinylbenzene (85µm PDMS-DVB), were studied and compared. Validation of the method using two apple species spiked with standard solution yield better linear range, accuracy, precision, detection and quantification limits. The linearity was between 5 to 500 µg.kg–1 with good correlation coefficients (R) greater than 0.989. The average recoveries for all pesticides investigated were between 89– 100% in green apple and 94–103% in red apple with RSD ranging from 0.67–3.32% and 1.00 - 2.69 % respectively. The LOQs were between 6.71 and 14.56 µg.kg–1 and LODs ranged from 2.23 to 11.11 µg.kg-1.
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    Applications of Experimental Design to the Optimization of Microextraction Sample Preparation Parameters for the Analysis of Pesticide Residues in Fruits and Vegetables
    (J AOAC International, 2015) Abdulrauf, L. B.; Sirhan, A. Y.; Tan, G. H.
    Sample preparation has been identified as the most important step in analytical chemistry and has been tagged as the bottleneck of analytical methodology. The current trend is aimed at developing cost-effective, miniaturized, simplified, and environmentally friendly sample preparation techniques. The fundamentals and applications of multivariate statistical techniques for the optimization of microextraction sample preparation and chromatographic analysis of pesticide residues are described in this review. The use of PlacketBurman, Doehlert matrix, and Box-Behnken designs are discussed. As observed in this review, a number of analytical chemists have combined chemometrics and microextraction techniques, which has helped to streamline sample preparation and improve sample throughput.
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    Chemometric approach to the optimization of HS SPME/GC-MS for the determination of multiclass pesticide residues in fruits and vegetables
    (Elsevier, 2015) Abdulra’uf, L. B.; Tan G. H.
    An HS-SPME method was developed using multivariate experimental designs, which was conducted in two stages. The significance of each factor was estimated using the Plackett–Burman (P–B) design, for the identification of significant factors, followed by the optimization of the significant factors using central composite design (CCD). The multivariate experiment involved the use of MinitabÒ statistical software for the generation of a 27–4 P–B design and CCD matrices. The method performance evaluated with internal standard calibration method produced good analytical figures of merit with linearity ranging from 1 to 500 lg/kg with correlation coefficient greater than 0.99, LOD and LOQ were found between 0.35 and 8.33 lg/kg and 1.15 and 27.76 lg/kg respectively. The average recovery was between 73% and 118% with relative standard deviation (RSD = 1.5–14%) for all the investigated pesticides. The multivariate method helps to reduce optimization time and improve analytical throughput.
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    Effect of Copper-Based Fungicide on Chemical Composition of Cocoa Seeds
    (2025) Lawal, A. R.; Olayinka, B. U.; Olahan, G. S.; Omorinoye, O. A.; Abdulsalam, H. A.; Abdulra’uf, L. B.
    Production of cocoa seeds, one of Nigeria’s major non-oil foreign exchange earners as well as a major raw material for the beverage industry, is greatly hindered by diseases caused by various species of the genus Phytophthora. To avert this, copper-based fungicides are sprayed on the leaves of cocoa trees to control or prevent the survival of this organism by the farmers without paying attention to the effects of this chemical on the proximate composition of cocoa seeds. This study therefore investigated the effects of a copper-based fungicide (Ridomil Gold Copper) on the quality of the cocoa seeds by spraying cocoa trees, including the pods, with 50.00 g/L of copper-based fungicide. The results obtained showed that cocoa seeds from the control trees showed significantly higher contents of fiber (4.51%), protein (15.1%), and fat (36.1%) when compared to the respective values of 3.45, 3.95, and 7.59% obtained for the cocoa seeds harvested from the fungicide-treated cocoa trees. All other proximate compositions did not show any statistical difference, except for carbohydrate and calorific values, which were significantly higher in cocoa seeds from fungicide treated cocoa trees. Seeds from fungicide-treated trees showed significantly higher potassium, phosphorus, and magnesium contents but lower zinc and copper contents. However, phytochemicals such as phenols, alkaloids, flavonoids, and tannins were significantly lower in content in the seeds of fungicide-treated cocoa trees. The contents of glycosides and antioxidants in the cocoa seeds were statistically similar for both the control and treatment, except for ascorbic acid, which showed a significantly lower value (4.8 mg/100 ml) in cocoa seeds from fungicide-treated cocoa trees, compared with the value recorded for the control in this study (13.33%). The foregoing results showed that the use of copper-based fungicides for the control of black pod disease in cocoa adversely affected the quality of cocoa seeds from the treated trees.