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Öğe Amalgamation performances of gold-coated quartz wool, alumina, silica, sand and carbon fiber for the determination of inorganic mercury in waters by cold vapor atomic absorption spectrometry(Maik Nauka/Interperiodica/Springer, 2017) Simsek, Arzu Erdem; Yayayuruk, Asli Erdem; Shahwan, Talal; Eroglu, Ahmet E.Different gold-coated sorbents for amalgamation were applied for the determination of inorganic mercury in waters using a home-made cold vapor generation unit coupled to atomic absorption spectrometry. Among the gold-coated materials investigated (quartz wool, alumina, silica, sand and carbon fiber) quartz wool was found to give the most efficient results in terms of sorption and release. Analytical performance of the system without and with amalgamation was investigated and it was found that when amalgamation was applied, the linearity and slope of the calibration plots were independent on the sample volume for 1.0, 5.0 and 10.0 mL. Method validation was realized through the analysis of a sample of spring water spiked with 1.0 mu g/L inorganic mercury and the spike recoveries were found to be 95 +/- 1, 91 +/- 3, and 99 +/- 5% for 1.0, 5.0, and 10.0 mL, respectively. The results demonstrated that the methodology can be applied to these types of samples directly or after amalgamation, depending on the mercury concentration.Öğe Carotenoid Profile in Prochlorococcus sp and Enrichment of Lutein Using Different Nitrogen Sources(Springer, 2016) Erdogan, Aysegul; Demirel, Zeliha; Eroglu, Ahmet E.; Dalay, Meltem ConkVarious carotenoids of the cyanobacterium Prochlorococcus sp. are identified using chromatographic/spectroscopic techniques and quantified using HPLC-DAD. In the present study, beta-apo-8'-carotenal was used as internal standard. Identification of carotenoids was carried out by comparing the retention time, absorption spectra, and mass spectra of unknown peaks with reference standards. All-trans-lutein was found to be the major carotenoid in this cyanobacterium, and, therefore, algal productivity and the potential for lutein accumulation were analyzed as a function of different nitrogen sources such as nitrate, nitrite, ammonia, and urea for cultivation. Among them, urea clearly led to the best lutein accumulation. According to the experimental evidence, lutein increased from 2.54 to 3.34 mg g(-1) in the cyanobacteria when urea was used as the nitrogen source.Öğe Fucoxanthin Content of Cylindrotheca Closterium and Its Oxidative Stress Mediated Enhancement(Central Fisheries Research Inst, 2016) Erdogan, Aysegul; Demirel, Zeliha; Dalay, Meltem Conk; Eroglu, Ahmet E.Production 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 degrees 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.Öğe Preparation and characterization of sodium dodecyl sulfate doped polypyrrole solid phase micro extraction fiber and its application to endocrine disruptor pesticide analysis(Elsevier, 2013) Korba, Korcan; Pelit, Levent; Pelit, Fusun Okcu; Ozdokur, K. Volkan; Ertas, Hasan; Eroglu, Ahmet E.; Ertas, F. 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 degrees C and 45 min, 200 degrees C, 600 rpm and 10 g L-1, respectively. Limit of detection was estimated in the range of 0.073-1.659 ng mL(-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. (C) 2013 Elsevier B.V. All rights reserved.Öğe Trypsin-Immobilized Silica: A Novel Adsorbent for V(IV) and V(V) Removal from Water(Water Environment Federation, 2018) Yayayuruk, Asli Erdem; Shahwan, Talal; Sanli-Mohamed, Gulsah; Eroglu, Ahmet E.In 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.Öğe Use of amberlite XAD-7HP for the separation of Mn(II) and Mn(VII) in waters(Maik Nauka/Interperiodica/Springer, 2017) Yayayuruk, Asli Erdem; Eroglu, Ahmet E.A simple method is proposed for the determination and speciation of Mn(II) and Mn(VII) in waters utilizing a macroporous resin, Amberlite XAD-7HP. The batch method was employed and flame atomic absorption spectrometry was used in all determinations. Amberlite XAD-7HP resin was shown to retain Mn(VII) between pH 4 and 12. If the solution contains only one of the species, either Mn(II) or Mn(VII), the resin behaves selectively depending on the pH of the solution. The elution from the sorbent was realized using K2C2O4 in HNO3. The efficiency of the method was checked via spike recovery experiments. The proposed method was successfully applied to industrial wastewater samples and quantitative recoveries (>= 96.0%) confirmed the accuracy of the method.
