Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 8Citation - Scopus: 10Trypsin-Immobilized Silica: a Novel Adsorbent for V(iv) and V(v) Removal From Water(Water Environment Federation, 2018) Erdem Yayayürük, Aslı; Shahwan, Talal; Şanlı Mohamed, Gülşah; Eroğlu, Ahmet EminIn the present study, trypsin-immobilized silica was employed for the removal of V(IV) and V(V) ions from water. The synthesized sorbent was first characterized and then investigated for the removal of V(IV) and V(V) under various experimental conditions. The adsorption performance of the sorbent was tested as a function of pli, sorbent amount, initial vanadium concentration, contact time, and temperature. The sorption process was then investigated, both from a kinetic perspective and also in terms of isotherm models. The Langmuir adsorption isotherm was the best model to describe the sorption process. Sorption thermodynamics were spontaneous and exothermic. The proposed method was successfully applied to real samples for the removal of V(IV)and V(V) with sufficient accuracy and precision.Article Citation - WoS: 55Citation - Scopus: 60Development of Molecularly Imprinted Polymers (mips) as a Solid Phase Extraction (spe) Sorbent for the Determination of Ibuprofen in Water(Royal Society of Chemistry, 2017) Ölçer, Yekta Arya; Demirkurt, Merve; Demir, Mustafa Muammer; Eroğlu, Ahmet EminIbuprofen is a well-known endocrine disrupter. In this study, highly selective molecularly imprinted polymers (MIPs) with different morphologies were synthesized via precipitation and bulk polymerization of methacrylic acid (MAA) and trimethylolpropane trimethacrylate (TRIM) in the presence of ibuprofen as a template. Non-imprinted polymers (NIPs) were also synthesized via the same procedure in the absence of ibuprofen. Spherical and monolithic MIPs were obtained using different experimental conditions, and the spherical MIP was shown to have better sorption towards ibuprofen. The optimum sample pH, sorbent amount, sample volume, and sorption time were determined to be 8.0, 25.0 mg, 10.0 mL, and 30.0 min, respectively. A methanol water mixture (MeOH:H2O, 80:20, pH 3.0) was employed as an eluent with >97% (±0.8, n = 3) desorption. The MIP demonstrated high selectivity towards ibuprofen in the presence of naproxen and ketoprofen. The validity of the proposed method was checked via spike recovery tests using drinking and tap water samples. The method worked efficiently for both water types, resulting in the recoveries of 97.2% (±0.3, n = 3) and 97.7% (±0.2, n = 3).Article Citation - WoS: 20Citation - Scopus: 24Preparation and Characterization of Sodium Dodecyl Sulfate Doped Polypyrrole Solid Phase Micro Extraction Fiber and Its Application To Endocrine Disruptor Pesticide Analysis(Elsevier Ltd., 2013) Korba, Korcan; Pelit, Levent; Okçu Pelit, Füsun; Özdokur, K. Volkan; Ertaş, Hasan; Eroğlu, Ahmet Emin; Ertaş, Fatma NilA robust in house solid-phase micro extraction (SPME) surface has been developed for the headspace (HS)-SPME determination of endocrine disruptor pesticides, namely, Chlorpyrifos, Penconazole, Procymidone, Bromopropylate and Lambda-Cyhalothrin in wine sample by using sodium dodecylsulfate doped polypyrrole SPME fiber. Pyrrole monomer was electrochemically polymerized on a stainless steel wire in laboratory conditions in virtue of diminishing the cost and enhancing the analyte retention on its surface to exert better selectivity and hence the developed polymerized surface could offer to analyst to exploit it as a fiber in headspace SPME analysis. The parameters, mainly, adsorption temperature and time, desorption temperature, stirring rate and salt amount were optimized to be as 70°C and 45min, 200°C, 600rpm and 10gL-1, respectively. Limit of detection was estimated in the range of 0.073-1.659ngmL-1 for the pesticides studied. The developed method was applied in to red wine sample with acceptable recovery values (92-107%) which were obtained for these selected pesticides.Article Citation - WoS: 24Citation - Scopus: 26Composition of Carotenoids in Scenedesmus Protuberans: Application of Chromatographic and Spectroscopic Methods(Springer Verlag, 2015) Erdoğan, Ayşegül; Çağır, Ali; Conk Dalay, Meltem; Eroğlu, Ahmet EminThis study aimed to identify and determine the carotenoids from green microalga, Scenedesmus protuberans using analytical techniques. Identification of carotenoids was realized by comparing their absorption and mass spectral data with those of reference standards available and reported values. Chromatographic data were then combined with the spectroscopic information. The separation of carotenoids was achieved by C30 column and high-performance liquid chromatography-diode array detection was used for their determination. In the present work, the carotenoid content of S. protuberans was found to be 1.45 mg/g of violaxanthin, 2.47 mg/g of all-trans-lutein, 0.15 mg/g of all-trans-α-carotene, 0.55 mg/g of all-trans-β-carotene, and 0.20 mg/g of 9 or 9′-cis-β-carotene. Due to lack of their standards, the amount of all-trans-loroxanthin and cis-isomers of other carotenoids could not be quantified. In order to validate the method, Certified Reference Material (BCR 485-Mixed vegetables) was used. In conclusion, this study can serve as a reference for the analysis of carotenoids in other microalgae.Article Citation - WoS: 18Citation - Scopus: 22Fucoxanthin Content of Cylindrotheca Closterium and Its Oxidative Stress Mediated Enhancement(Central Fisheries Research Inst, 2016) Erdoğan, Ayşegül; Demirel, Zeliha; Conk Dalay, Meltem; Eroğlu, Ahmet EminProduction of fucoxanthin by diatoms has become an alternative research area due to their low cost, convenience and diversity. The fucoxanthin content of Cylindrotheca closterium and its enhancement by altering the cultivation conditions via oxidative stress were investigated in this study. For this purpose, the extraction parameters were optimized and the highest fucoxanthin concentration (6.58 mg g-1) was achieved within 15.0 minutes at 40 °C. Then, this yield reached to 10.15 mg g-1 in the presence of NaOCl and Fe2+. It is worth noting that, this is the first time that the effect of oxidative stress on fucoxanthin production in diatom has been studied according to our knowledge. Therefore, the results of this study and the discussion about the mechanisms can be a reference for the enrichment of fucoxanthin from other diatoms.Article Citation - WoS: 19Citation - Scopus: 21Kinetic and Thermodynamic Investigations of Strontium Ions Retention by Natural Kaolinite and Clinoptilolite Minerals(Walter De Gruyter Gmbh, 2005) Akar, Dilek; Shahwan, Talal; Eroğlu, Ahmet EminThe current study was devoted to the determination of various thermodynamic and kinetic parameters resulting from the fixation of Sr2+ by natural samples of kaolinite and clinoptilolite minerals. The sorption process followed pseudo second order kinetics, with faster sorption on kaolinite compared to clinoptilolite, where the uptake is affected by intraparticle diffusion. Freundlich and Dubinin-Radushkevich isotherm models described the data more adequately than Langmuir model, and clinoptilolite showed a higher strontium sorption capacity than kaolinite. Thermodynamically, the activation energy of Sr2+ sorption by kaolinite and clinoptilolite were respectively, -8.5 and -18.4 kJ/mol. The sorption process on both minerals was spontaneous and endothermic at all the studied concentrations, with ΔH° being 11.3 and 9.8 kJ/mol, for sorption on kaolinite and clinoptilolite, respectively. The findings of this study were compared with those of an earlier study on the uptake of Cs+ by the same minerals.Article Citation - WoS: 14Citation - Scopus: 15Chitosan-Immobilized Pumice for the Removal of As(v) From Waters(Springer Verlag, 2014) Turan, Dilek; Kocahakimoğlu, Cemre; Boyacı, Ezel; Sofuoğlu, Sait Cemil; Eroğlu, Ahmet EminA novel sorbent, chitosan-immobilized pumice, has been prepared for the sorption of As(V) from waters prior to its determination by hydride generation atomic absorption spectrometry. The success of the immobilization has been checked with such characterization techniques as scanning electron microscopy, thermal gravimetric analysis, and elemental analysis. Points of zero charge of the sorbents were determined with potentiometric mass titration. Batch-type equilibration studies have shown that the novel sorbent can be employed at a wide pH range resulting in quantitative sorption (>90 %) at pH 3.0-7.0 and greater than 70 % sorption at pH >8.0. These results demonstrate the advantage of immobilizing chitosan onto pumice, because, under the same conditions, pumice displays <20 % sorption toward As(V), whereas chitosan gives approximately 90%sorption only at pH 3.0. The validity of the method was verified through the analysis of ultrapure, bottled drinking, and tap water samples spiked with arsenate; the respective sorption percentages of 93.2 (±0.7), 89.0 (±1.0), and 80.9 (±1.3) were obtained by batch-type equilibration. Arsenic sorption was also examined in the presence of common interfering ions resulting in competing effects of PO3- 4 and NO- 3on As(V) adsorption.Article Citation - WoS: 16Citation - Scopus: 17Electrospun Amino-Functionalized Pdms as a Novel Spme Sorbent for the Speciation of Inorganic and Organometallic Arsenic Species†(Royal Society of Chemistry, 2013) Boyacı, Ezel; Horzum, Nesrin; Çağır, Ali; Demir, Mustafa Muammer; Eroğlu, Ahmet EminSol–gel based amine-functionalized SPME fibers (PDMS-weak anion exchanger) were prepared and used for direct mode extraction of dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), and arsenate (As(V)) from aqueous solutions followed by HPLC-ICPMS determination. Two different methods of coating were employed: (i) electrospinning and (ii) dip coating. Electrospinning was used for the first time for preparation of sol–gel based SPME fibers and was found to be superior in terms of extracted amount of arsenicals, coating homogeneity, accessibility of amine groups on the surface, and preparation time for a single fiber. Various parameters such as solution pH, extraction time, agitation speed, extraction temperature, and ionic strength were studied. Optimum extraction conditions were determined as pH of 5.0, extraction time of 30 min, agitation speed of 700 rpm, and extraction temperature of 20 C. Extraction ability of the novel coating decreased by the addition of NaCl as a consequence of the competition between anionic arsenic species and chloride ions for active sites of the weak anion exchanger. This novel sol–gel coating prepared by electrospinning was found to be promising for SPME applications. Vibrational spectroscopy revealed the alignment of PDMS chains by elongational force under electrospinning process. The chain alignment accordingly orients the pendant amino functional groups perpendicular to the fiber surface, which may develop the free active functional groups available to the medium and lead to the enhancement of the extraction performance. Moreover, the proposed coating strategy through electrospinning might be able to break new ground for various applications in analytical chemistry as well as other disciplines.Article Citation - WoS: 119Citation - Scopus: 151Batch Removal of Aqueous Cu2+ Ions Using Nanoparticles of Zero-Valent Iron: a Study of the Capacity and Mechanism of Uptake(American Chemical Society, 2008) Karabelli, Duygu; Üzüm, Çağrı; Shahwan, Talal; Eroğlu, Ahmet Emin; Scott, Tom B.; Hallam, Keith R.; Lieberwirth, IngoIn this study, nZVI prepared by borohydride reduction was applied for the removal of Cu2+ ions under a variety of experimental conditions. The uptake experiments investigated the effects of initial concentration, contact time, pH, and repetitive loading on the extent of retardation of Cu2+ ions. Within the applied conditions, the sorbent demonstrated fast uptake kinetics and outstanding fixation abilities up to an initial Cu2+ concentration of 200.0 mg/L. Partitioning of Cu2+ ions between liquid and solid phases demonstrated an isotherm of L-type. Within the studied conditions, the capacity of uptake was found to be 250 mg of Cu2+ per g of nZVI. According to X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) results, Cu2+ ions were sorbed primarily via a redox mechanism that resulted in the formation of Cu2O and Cu0. The contact of iron nanoparticles with aqueous media caused extensive formation of iron oxide. However, the material did not completely lose its removal capacity and was repeatedly applied at low concentrations for further uptake trials.