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GÖREN, AHMET CEYHAN

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AHMET CEYHAN
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    HPLC and LC-MS/MS methods for determination of sodium benzoate and potassium sorbate in food and beverages: Performances of local accredited laboratories via proficiency tests in Turkey
    (2015-05-15T00:00:00Z) Goren, AHMET CEYHAN; BILSEL, Gokhan; SIMSEK, Adnan; BILSEL, Mine; AKCADAG, Fatma; TOPAL, Keyser; OZGEN, Hasan; GÖREN, AHMET CEYHAN
    High Performance Liquid Chromatography LC-UV and LC-MS/MS methods were developed and validated for quantitative analyses of sodium benzoate and potassium sorbate in foods and beverages. HPLC-UV and LC-MS/MS methods were compared for quantitative analyses of sodium benzoate and potassium sorbate in a representative ketchup sample. Optimisation of the methods enabled the chromatographic separation of the analytes in less than 4 min. A correlation coefficient of 0.999 was achieved over the measured calibration range for both compounds and methods (HPLC and LC-MS/MS). The uncertainty values of sodium benzoate and potassium sorbate were found as 0.199 and 0.150 mg/L by HPLC and 0.072 and 0.044 mg/L by LC-MS/MS, respectively.
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    Isolation of active constituents from cherry laurel (Laurocerasus officinalis Roem.) leaves through bioassay-guided procedures
    (2012-01-31T00:00:00Z) Akkol, Esra Kupeli; Kirmizibekmez, Hasan; Kucukboyaci, Nurgun; Goren, AHMET CEYHAN; Yesilada, Erdem; GÖREN, AHMET CEYHAN
    Ethnopharmacological relevance: The fresh leaves of Laurocerasus officinalis Roem. (Rosaceae) are externally used against pain and feverish symptoms in Turkish folk medicine.
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    Fatty Acid Methyl Ester Composition of Some Turkish Apiaceae Seed Oils: New Sources for Petroselinic Acid
    (2016-11-01T00:00:00Z) Kucukboyaci, Nurgun; Ayaz, Fatma; Adiguzel, Nezaket; Bani, Baris; Goren, AHMET CEYHAN; GÖREN, AHMET CEYHAN
    The seed oils of twenty-six species of Apiaceae belonging to the genera Bunium, Cnidium, Ferula, Ferulago, Heracleum, Hippomarathrztm, Malabaila, Myrrhoides, Olymposciadium, Pimpinella, Prangos, Szovitsia, Trigonasciadium, Trinia and Zosima, collected in Turkey, were investigated for their oil content, and amount of petroselinic acid (PA), as well as for the composition of their fatty acid methyl esters (FAMEs) by GC-MS. Seed oil content ranged from 7.1% in Szovitsia callicarpa to 29.3% in Ferula haussknechtii. The results showed that the seed oils of the studied species contained high amounts of PA (1.2-72.2%), followed by significant amounts of linoleic (LA, 13.8-50.8%) and oleic (OA, 4.2-61.6%) acids. PA was found in all the analyzed species, except for Olymposciadium caespitosum, which belongs to a monotypic endemic genus of the family. According to data from our study, PA was found to be predominantly in the seed oils of Hippomarathrum cristatum (72.2%), Trinia glauca (64.9%) and Bunium microcarpum (59.7%) and, therefore these species might be considered as new sources of PA, and represent a potential oleochemical raw material. This is the first extensive study of the composition of Turkish Apiaceae species. The high amounts of PA may also have chemotaxonomic significance.
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    Potential reference measurement procedures for PBDE in surface water at levels required by the EU Water Frame Directive
    (2016-05-15T00:00:00Z) SWART, Claudia; GANTOIS, Fanny; PETROV, Panayot; ENTWISLE, John; GOENAGA-INFANTE, Heidi; NOUSIAINEN, Marjaana; BILSEL, Mine; BINICI, Burcu; GONZALEZ-GAGO, Adriana; PROEFROCK, Daniel; Goren, AHMET CEYHAN; GÖREN, AHMET CEYHAN
    Polybrominated diphenylethers (PBDE), used as flame retardants, are named as priority substances in the Directive 2000/60/EC of the European parliament and of the council establishing a framework for Community action in the field of water policy. An annual average environmental quality standard (EQS) for inland surface waters of 0.0005 mu g/L (0.0002 mu g/L for other surface waters) for PBDE congeners involved in the technical penta-PBDE mixtures containing PBDE with five bromine atoms has been established. The directives focus especially on the congeners PBDE 28, 47, 99, 100, 153 and 154 contained in the penta-PBDE mixture. Up to now, no reference measurement procedures have been established reaching the limits of quantification (LOQs) and the associated uncertainties as defined in the directives with results traceable to the SI. Within a recent European project on metrology, different approaches for the traceable quantification of PBDE, based on liquid/liquid or solid phase extraction followed by the detection with gas chromatography coupled to either inductively coupled plasma mass spectrometry or triple quadrupole mass spectrometry, were investigated and the related LOQs and expanded uncertainties of the results were compared. A complete uncertainty budget for each method was estimated according to the Guide to the Expression of Uncertainty in Measurement (GUM). All presented analytical procedures can serve as reference measurement procedures regarding the LOQs and their associated expanded uncertainties for monitoring the six priority PBDEs named above. LOQs as low as 0.026 ng/kg with an associated expanded uncertainty of 0.002 ng/kg could be achieved (C) 2016 The Authors. Published by Elsevier B.V.
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    Sambulin A and B, non-glycosidic iridoids from Sambucus ebulus, exert significant in vitro anti-inflammatory activity in LPS-induced RAW 264.7 macrophages via inhibition of MAPKs-s phosphorylation
    (2017-07-12T00:00:00Z) Balkan, Irem Atay; Akulke, Ayca Zeynep Ilter; Bagatur, Yesim; Telci, Dilek; Goren, AHMET CEYHAN; Kirmizibekmez, Hasan; Yesilada, Erdem; GÖREN, AHMET CEYHAN
    Ethnopharmacological relevance: The leaves of Sambucus ebulus L. (Adoxaceae) are widely used in Turkish folk medicine particularly against inflammatory disorders. The fresh leaves after wilted over fire or the poultices prepared are directly applied externally to heal burns, edema, eczema, urticarial and abscess. Two iridoids were recently isolated (sambulin A, sambulin B) from the leaves of S. ebulus.
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    Analysis of Combustion Stability and Its Relation to Performance Characteristics in a Compression Ignition Engine Fueled with Diesel-biodiesel Blends
    (2011-01-01T00:00:00Z) CEVİZ, Münacettin; Koncuk, F.; Kucuk, O.; Goren, AHMET CEYHAN; Yuksel, F.; GÖREN, AHMET CEYHAN
    This article investigates the effects of using diesel-biodiesel blends on compression ignition engine performance characteristics. Combustion stability observed from in-cylinder pressure related parameters, biodiesel composition, and the fuel properties of the blends are used to analyze the variations of the characteristics. Making biodiesel from hazelnut oil is done by esterification and then experiments are conducted with the neat diesel and diesel-biodiesel blends in a four stroke naturally aspirated direct injection diesel engine. Volumetric blending ratios of biodiesel with no. 1 diesel were set at 0, 20, 40, 60, 80, and 100. It has been found that, in general, the hazel nut oil-based biodiesels behave comparably to the diesel fuel in terms of engine performance characteristics. There is no significant brake torque and power reduction, and there is a slight increase in brake specific fuel consumption when the engine is operated with diesel-biodiesel blends. The engine effective efficiency shows improvements as compared to that of the diesel fuel operating under similar conditions, especially at low blending ratios of biodiesel. The engine performance characteristics and exhaust emissions improve remarkably at B20 operations and identifying the mechanism for biodiesel blending effects is attempted.
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    Determination of sulfonamides in milk by ID-LC-MS/MS
    (2018-01-01T00:00:00Z) Unsal, Isin Aydin; Tasan, Murat; GOKCEN, Taner; Goren, AHMET CEYHAN; GÖREN, AHMET CEYHAN
    In this study, an ID-LC-MS method was developed and validated for the determination of 14 sulfonamides in milk samples. Recovery results were found to be in the range of 91%-114% for milk samples. The relative measurement uncertainty was between 7.5%-12.7%. Validated method was performed on milk samples obtained from market and street vendors. The amount of sulfonamides in the analyzed samples was found to be below the legal limits (Sulfamethazine: 6.46 +/- 0.76 ng/g and sulfisoxazole: 7.3 +/- 0.71 ng/g).
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    Towards tributyltin quantification in natural water at the Environmental Quality Standard level required by the Water Framework Directive
    (2016-11-01T00:00:00Z) ALASONATI, Enrica; Fettig, Ina; RICHTER, Janine; PHILIPP, Rosemarie; MILACIC, Radmila; SCANCAR, Janez; ZULIANI, Tea; TUNC, Murat; BILSEL, Mine; Goren, AHMET CEYHAN; FISICARO, Paola; GÖREN, AHMET CEYHAN
    The European Union (EU) has included tributyltin (TBT) and its compounds in the list of priority water pollutants. Quality standards demanded by the EU Water Framework Directive (WFD) require determination of TBT at so low concentration level that chemical analysis is still difficult and further research is needed to improve the sensitivity, the accuracy and the precision of existing methodologies. Within the frame of a joint research project -Traceable measurements for monitoring critical pollutants under the European Water Framework Directive- in the European Metrology Research Programme (EMRP), four metrological and designated institutes have developed a primary method to quantify TBT in natural water using liquid-liquid extraction (LLE) and species-specific isotope dilution mass spectrometry (SSIDMS). The procedure has been validated at the Environmental Quality Standard (EQS) level (0.2 ng L-1 as cation) and at the WFD-required limit of quantification (LOQ) (0.06 ng L-1 as cation). The LOQ of the methodology was 0.06 ng L-1 and the average measurement uncertainty at the LOQ was 36%, which agreed with WFD requirements. The analytical difficulties of the method, namely the presence of TBT in blanks and the sources of measurement uncertainties, as well as the interlaboratory comparison results are discussed in detail. (C) 2016 Elsevier B.V. All rights reserved.
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    Secondary metabolites from Sambueus ebulus
    (2015-01-01T00:00:00Z) Atay, Irem; Kirmizibekmez, Hasan; Goren, AHMET CEYHAN; Yesilada, Erdem; GÖREN, AHMET CEYHAN
    A new nonglycosidic iridoid, sambulin B (1), was isolated from the methanol extract of Sambucus ebulus L. leaves along with a recently reported new nonglycosidic iridoid, 10-O-acetylpatrinoside aglycone (sambulin A) (2); 2 flavonoids, isorhamnetin-3-O-beta-D-glucopyranoside (3) and isorhamnetin-3-O-rutinoside (4); and a mixture of 2 flavonoids (5), quercetin-3-O-beta-D-glucopyranoside and quercetin-3-O-beta-D-galactopyranoside. Their structures were elucidated by 1-D and 2-D nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry (MS) experiments.
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    Facile synthesis of -green- gold nanocrystals using cynarin in an aqueous solution
    (2014-11-01T00:00:00Z) Katircioglu, Zeynep; Sakalak, Huseyin; Ulasan, Mehmet; Goren, AHMET CEYHAN; Yavuz, Mustafa Selman; GÖREN, AHMET CEYHAN
    Herein we describe a water-based protocol that generates Au nanoparticles (AuNPs) by mixing aqueous solutions of HAuCl4 and cynarin (a natural product extract from artichoke leaf). Based on the observations from H-1 NMR spectrum of AuNPs, a polyol oxidation mechanism by metal ions which eventually results in AuNPs formation, is proposed. Basically, the aromatic alcohol groups (1,2-benzenediol) of cynarin are oxidized to alpha-hydroxy ketone intermediate product, and then further oxidized to the vicinal diketone final product while the Au3+ ions are reduced to its atomic form (Au-0) which leads the generation of Au nanoparticles. This new protocol has also been employed to prepare multiply twinned Pd nanoparticles and Ag cubical aggregates. Due to exclusion of organic solvent, surfactant, or stabilizer for all these synthesis, this protocol may provide a simple, versatile, and environmentally benign route to fabricate noble-metal nanoparticles having various compositions and morphologies. (C) 2014 Elsevier B.V. All rights reserved.