Browsing by Author "Tan G. H."

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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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    Headspace solid phase microextraction (HS-SPME) coupled to gas chromatography-mass spectrometry (GC/MS) for the analysis of multi-class 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.