Browsing by Author "Tan, G. H."

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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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    Determination of pesticide residues in beans using QuEChERS technique coupled to gas chromatography-mass spectrometry: Multivariate optimization of CEN and AOAC methods
    (Elsevier, 2025) Abdulra’uf, L. B.; Junaid, A. M.; Lawal, A. R.; Ibrahim, H. B.; Tan, G. H.
    The use of pesticides has led to environmental pollution and posed a global health risk, since they remain as residues on foods. Beans one of the most widely cultivated crop in Africa, and susceptible to attack by insects both on field and during storage, leading to the application of pesticides to control pests’ infestation. However, misuse of these chemicals by farmers on beans has resulted in the rejection of beans exported to European countries, due to the presence of pesticide residues at concentrations higher than the maximum residues levels (MRLs). In this study, the effectiveness of the Association Official Analytical Chemists (AOAC) Official Method and the European Committee of Standardization (CEN) Standard Method, were determined using multivariate approach for the analysis of organochlorine pesticide residues in 6 varieties of beans samples. The significance of factors (mass of sample, volume of acetonitrile, mass of magnesium sulphate, sample pH, centrifugation time and speed) affecting the efficiency of extraction was estimated using Plackett-Burman design, while central composite design was used to optimize the significant factors. The following optimum factors were subsequently used for method validation, recovery tests, and real sample analysis: 4 g of sample sludge (1:1 v/v), 10 mL of acetonitrile, 4.45 g of MgSO4, and 5 min of centrifugation at 5000 rpm. The figure of merit of analytical methodology estimated using matrix-matched internal standard calibration method gave linearity ranging from 0.25 to 500 μg/kg, with correlation coefficient (R2) greater than 0.99, the recovery ranged from 75.55 to 110.41 (RSD = 0.70–16.65), with LOD and LOQ of 0.23–1.77 μg/kg and 0.76–5.88 μg/kg, respectively.
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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.