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KÜÇÜK, MELİKE

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KÜÇÜK

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    Publication
    Dummy molecularly imprinted polymer-based solid-phase extraction method for the determination of some phthalate monoesters in urine by gas chromatography-mass spectrometry analysis
    (Elsevier, 2023-11-24) Küçük, Melike; Osman, Bilgen; Özer, Elif Tumay; KÜÇÜK, MELİKE; OSMAN, BİLGEN; TÜMAY ÖZER, ELİF; Fen Edebiyat Fakültesi; Kimya Bölümü; 0000-0001-8406-149X; V-1616-2019; JCP-4547-2023; JME-2199-2023
    A dummy molecularly imprinted polymer-based solid-phase extraction (SPE) sorbent was used for the selective extraction of some phthalate monoesters, monoethyl phthalate (MEP), monobutyl phthalate (MnBP) and mono-(2-ethylhexyl) phthalate (MEHP) in urine prior to gas-chromatography-mass spectrometry (GC-MS) analysis. Diethyl phthalate (DEP), a phthalate ester, was successfully used as a dummy template to prepare selective sorbent for MEP, MnBP, and MEHP extraction. DEP-imprinted poly(ethylene glycol dimethacrylate N-meth-acryloyl-L-tryptophan methyl ester) (DPEMT) microbeads were synthesized by suspension polymerization and characterized by Fourier Transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and Brunauer Emmet Teller (BET) analysis. The critical parameters (i.e., pH, sorbent amount, ionic strength, sample volume, elution solvent) affecting the extraction performance of the DPEMT-SPE sorbent were optimized. Under optimum conditions, good linearities were obtained in the concentration range of 4 to 60 ng/mL with deter-mination coefficients (R2) of greater than 0.9959. The developed SPE method provided low limits of detection (LOD) of 0.05-1.20 ng/mL and limits of quantification (LOQ) of 0.18-4.01 ng/mL with relative standard de-viations (RSDs) of less than 8.95 % for intra-and inter-day analyses. The proposed SPE method was used to analyze phthalate monoesters in spiked urine samples, and recoveries of 97.45-109.26 % were obtained. DPEMT-SPE sorbent was reused for 15 times without any losses of performance. Consequently, a highly selective and sensitive SPE method based on a dummy molecularly imprinted polymer combined with GC-MS was suc-cessfully developed to monitor human phthalate exposure via urine samples.
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    Adsorptive removal of 4-hydroxybenzoic acid via cross-linked polymeric microbeads: Analysis of isothermal, kinetic and thermodynamic parameters
    (Taylor & Francis Inc, 2023-05-26) Özer, Elif Tumay; Osman, Bilgen; KÜÇÜK, MELİKE; OSMAN, BİLGEN; TÜMAY ÖZER, ELİF; Fen Edebiyat Fakültesi; Kimya Bölümü; 0000-0001-8406-149X; JCP-4547-2023
    In this study, the performance of cross-linked microbeads prepared through suspension polymerization was investigated for removal of 4-hydroxybenzoic acid (4-HBA) from aqueous solution. Adsorption studies were conducted at different pHs (2.0-8.0), temperatures (282-308 K) and initial 4-HBA concentrations (1-500 mg/L). The maximum 4-HBA adsorption was 49.05 +/- 2.89 mg/g at pH 2.0 (282 K). The adsorption data obeyed to the Langmuir isotherm model. The modified Ritchie second-order and the pseudo second-order kinetic model fitted the adsorption data. The 4-HBA adsorption capacity did not significantly change after 10 consecutive usages. Gibbs free energy changes of the adsorption were calculated as -24.372, -28.431 and -29.093 kJ/mol for 282, 298 and 308 K, respectively. The microbeads were also used for the removal of 4-HBA from spiked river water samples. The removal efficiencies of 43.2% to 68.8% and RSDs of 0.49% to 4.78% demonstrated the usability of the microbeads in application.