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GÖREN, AHMET CEYHAN

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Author: Goren, AHMET CEYHAN × Author: BILSEL, Mine ×

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Now showing 1 - 7 of 7
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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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    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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    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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    Validation of a GC-IDMS method for the metrologically traceable quantification of selected FAMEs in biodiesel
    (2015-10-01T00:00:00Z) MORALES, Valle; Goren, AHMET CEYHAN; HELD, Andrea; BILSEL, Mine; GUNDUZ, Simay; YILMAZ, Hasibe; GÖREN, AHMET CEYHAN
    Current methods for the analysis of fatty acid methyl esters (FAMEs) in rapeseed oil-based biodiesel refer to operationally defined measurands, which is a practical solution for routine analysis. In this paper, a new method for the SI-traceable quantification of selected FAMEs in biodiesel and its validation are described. This method has the potential to be a reference method for applications requiring structurally defined measurands and traceability to the SI as it allows direct comparisons to well-characterised calibrants through the use of isotopically labelled analogues of the analytes as well as establishing a full uncertainty budget. The method is based on gas chromatography-isotope dilution mass spectrometry. Its performance is demonstrated through its implementation and validation in two independent laboratories and is shown to provide reliable and traceable results for selected FAMEs in biodiesel test samples.
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    Polyphenol contents and antioxidant activity of lyophilized aqueous extract of propolis from Erzurum, Turkey
    (2010-08-01T00:00:00Z) GÜLÇİN, İlhami; Bursal, Ercan; Sehitoglu, M. Hilal; BILSEL, Mine; Goren, AHMET CEYHAN; GÖREN, AHMET CEYHAN
    Propolis, an extremely complex resinous material, exhibits valuable pharmacological and biological properties attributed to the presence of polyphenols. In this study, we determined the antioxidant properties of lyophilized aqueous extract of propolis (LAEP) from Erzurum province of Turkey and correlated the values with total levels of polyphenolic compounds. In order to estimate the capacity of LAEP to act as antioxidants, we studied its 1,1-diphenyl-2-picryl-hydrazyl radicals (DPPH center dot), 2,2--azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) radicals (ABTS(center dot+)), N,N-dimethyl-p-phenylenediamine radicals (DMPD center dot+), superoxide anion radicals (O-2(center dot-)) and hydrogen peroxide (H2O2) scavenging activity, total antioxidant activity, ferric ions (Fe3+) and cupric ions (Cu2+) reducing ability, ferrous ions (Fe2+) chelating activity. LAEP inhibited 93.2% lipid peroxidation of a linoleic acid emulsion at 30 mu g/mL concentration. On the other hand, BHA, BHT, alpha-tocopherol and trolox displayed 83.3%, 82.1%, 68.1% and 81.3% inhibition of peroxidation at the same concentration, respectively. Quantitative amounts of caffeic acid, ferulic acid, syringic acid, ellagic acid, quercetin, alpha-tocopherol, pyrogallol, p-hydroxybenzoic acid, vanillin, p-coumaric acid, gallic acid and ascorbic acid were detected by high performance liquid chromatography and tandem mass spectrometry (LC-MS/MS). This study will bring an innovation for further studies with regard to the antioxidant properties of LAEP. (C) 2010 Elsevier Ltd. All rights reserved.
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    C-13/C-12 pattern of honey from Turkey and determination of adulteration in commercially available honey samples using EA-IRMS
    (2012-02-15T00:00:00Z) SIMSEK, Adnan; BILSEL, Mine; Goren, AHMET CEYHAN; GÖREN, AHMET CEYHAN
    Honey adulteration particularly by adding cheap sugars such as High Fructose Corn Syrup (HFCS) and cane sugar syrup into natural honey is widespread. This study reports (C-13/C-12,parts per thousand) patterns of 31 authentic honey samples obtained from different sources and regions of Turkey as well as 43 commercial honey samples to determine the adulteration using mass spectrometer coupled to elemental analyzer (EA-IRMS). The analyses indicated that the ranges of (C-13/C-12, parts per thousand) values of honey and protein fractions of Turkish honey are from -23.30 to -27.58 parts per thousand and -24.13 to -26.76 parts per thousand, respectively. These values for commercial honey samples were determined to range from -11.28 to -25.54 parts per thousand and -19.35 to -25.61 parts per thousand, respectively. The numbers of adulterated commercial honey samples were found to be 10, which corresponds to 23% of the total number of the samples. Diastase activity, HMF content, electrical conductivity and moisture content of honey samples were also determined. Method validation and uncertainty budget calculations were also reported. (C) 2011 Elsevier Ltd. All rights reserved.
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    Lessons learned from inter-laboratory studies of carbon isotope analysis of honey
    (2019-01-01) DUNN, Philip J. H.; HILL, Sarah; COWEN, Simon; GOENAGA-INFANTE, Heidi; SARGENT, Mike; Goren, AHMET CEYHAN; BILSEL, Mine; SIMSEK, Adnan; OGRINC, Nives; POTOCNIK, Doris; ARMISHAW, Paul; HAI, LU; KONOPELKO, Leonid; CHUBCHENKO, Yan; CHESSON, Lesley A.; VAN DER PEIJL, Gerard; BLAGA, Cornelia; POSEY, Robert; CAMIN, Federica; CHERNYSHEV, Anatoly; CHOWDHURY, Sadia A.; GÖREN, AHMET CEYHAN
    Forensic application of carbon isotope ratio measurements of honey and honey protein to investigate the degree of adulteration with high fructose corn syrup or other C-4 plant sugars is well established. These measurements must use methods that exhibit suitable performance criteria, particularly with regard to measurement uncertainty and traceability - low levels of adulteration can only be detected by methods that result in suitably small measurement uncertainties such that differences of 1960 or less can be reliably detected. Inter-laboratory exercises are invaluable to assess the state-of-the art of measurement capabilities of laboratories necessary to achieve such performance criteria. National and designated metrology institutes from a number of countries recently participated in an inter-laboratory assessment (CCQM-K140) of stable carbon isotope ratio determination of bulk honey. The same sample material was distributed to a number of forensic isotope analysis laboratories that could not participate directly in the metrological comparison. The results from these studies have demonstrated that the majority of participants provided isotope delta values with acceptable performance metrics; that all participants ensured traceability of their results; and that where measurement uncertainties were reported; these were fit-for-purpose. A number of the forensic laboratories only reported precision rather than full estimates of measurement uncertainty and this was the major cause of the few instances of questionable performance metrics. Reporting of standard deviations in place of measurement uncertainties is common practice outside metrology institutes and the implications for interpretations of small differences in isotopic compositions are discussed. The results have also highlighted a number of considerations that are useful for organisers of similar inter-laboratory studies in the future.