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Öğe Adsorption and on-line preconcentration of Cu(II), Cd(II) and Pb(II) ions from aqueous solution using procion red MX-3B immobilized poly(EGDMA-HEMA) microbeads(Parlar Scientific Publications (P S P), 2008) Buyuktuncel, Ebru; Satiroglu, Nuray; Denizli, Adil; Bektas, SemaThe adsorption and preconcentration studies of Cu(II), Pb(II) and Cd(II) were investigated on Procion Red MX-3B attached poly(ethylene glycol dimethacrylate-hydroxyethyl methacrylate) [poly(EGDMA-HEMA)] microbeads. The effects of various experimental parameters were investigated using a batch and column technique. The adsorption data followed Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms, but the Langmuir model is better to represent the adsorption process. Procion Red MX-3B- poly(EGDMA-HEMA) microbeads were used as packing material for the minicolumn in an on-line preconcentration system for Cu(II), Pb(II) and Cd(II) determination. Metal ions were sorbed in the minicolumn, from which it could be eluted directly to the nebulizer-burner system of the flame atomic absorption spectrometer (FAAS). Elution of all metal ions from minicolumn can be made with 0.2 mol L-1 HNO3. For a preconcentration time of 2 min, the preconcentration factors were 51, 55 and 48, and the detection limits 1.25, 0.5 and 10 mu g L-1, for Cu(II), Cd(II) and Pb(II), respectively. When using 10 min preconcentration time for Pb(II), the preconcentration factor and detection limit were found to be 273 and 1.1 mu g L-1, respectively. The influence of diverse ions on the microbeads performance was also investioated. The accuracy of the method was tested by analyzing certified reference water (SPS-SW2- Surface Water and LGC 6010 - Hard Drinking Water) and spiked tap water samples. These results proved that the procedure can be applied satisfactorily for lead, copper and cadmium determination in water samples.Öğe Catechin-Molecularly Imprinted Cryogel for Determination of Catechin in Red Wines by HPLC-DAD-Fluorescence Detector(Akademiai Kiado Zrt, 2018) Buyuktuncel, Ebru; Porgali, Esra; Ozkara, SerpilA new molecularly imprinted polymer (MIP) was prepared by using catechin (C) as the template molecule. The polymer was characterized by swelling tests, scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), and Fourier transform infrared (FTIR) spectroscopy. The MIP with high recovery was selected as a solid-phase extraction (SPE) sorbent in this work. The standard solutions were directly applied onto the SPE cartridges following loading, washing, and elution procedures. A solution of the collected fractions was analyzed by high-performance liquid chromatography-diode-array detection (DAD) and fluorescence detector. The optimization of the method and validation was achieved on a C18 column (5 mu m, 250 x 4.6 mm) with methanol-water (35:65, v/v) mixture adjusted pH 2.5 as the mobile phase at a flow rate of 1 mL min(-1) at room temperature. The selectivity coefficient (k) of imprinted p(HEMA-MAH) cryogel was 5.1-fold that of non-imprinted cryogel. It showed good selectivity and affinity for C molecule. A comparison was made between the results obtained with the MIP cartridges and a traditional C18 reversed-phase cartridge. It was observed that 2.3 times higher recovery of C can be obtained on catechin-MIP cryogel. The results of the presented work showed that the prepared MIP can be used as SPE sorbent for extracting of C from red wines.Öğe Comparison of stereochemical structures of cholesterol from different sources by HPLC(Marmara Univ, Fac Pharmacy, 2012) Satilmis, Basri; Guldur, Tayfun; Karakurt, Arzu; Buyuktuncel, Ebru; Ertan, MevlutIt is known that only one stereoisomeric form, nat-cholesterol, naturally occurs. Nat-cholesterol and its enantiomer, ent-cholesterol, sometimes show enantiospecific interactions with biological molecules. If cholesterol is naturally found only one form, then the question of why does cholesterol show an enantiomeric selectivity? arises. For this purpose, stereoisomer analysis of cholesterol obtained from porcine liver and wool wax were carried out with three different high performance liquid chromatography (HPLC) systems including reversed-phase, reversed-phase with different cyclodextrins as a mobile phase modifier, and chiral. Results from HPLC analysis of both cholesterol samples by permethylated gamma-cyclodextrin and amylose tris-(3,5-dimethylphenylcarbamate) chiral columns showed that there was no stereoisomer of cholesterol present. However reversed-phase HPLC analysis of cholesterol samples from porcine liver carried out with various cyclodextrins as mobile phase modifiers presented a peak which was not observed in the analysis of cholesterol samples from wool wax. On the other hand, different storage conditions of cholesterol samples and addition of cyclodextrins as mobile phase modifiers produced almost identical alterations in chromatograms of fresh samples by reversed-phase HPLC. This could be attributed to catalytic properties of cyclodextrins. Cyclodextrins may not be suitable as a mobile phase modifier in the stereoisomer analysis of cholesterol with high performance liquid chromatography.Öğe Determination of phenolic composition and antioxidant capacity of native red wines by high performance liquid chromatography and spectrophotometric methods(Elsevier Science Bv, 2012) Porgali, Esra; Buyuktuncel, EbruA reversed-phase high performance chromatographic method for simultaneous determination of 14 phenolic compounds in native red wines was developed in this study. The identified compounds contained gallic acid, (+)-catechin, 3,4-dihydroxybenzoic acid, chlorogenic acid, (-)-epicatechin, 4-hydroxybenzoic acid, syringic acid, caffeic acid, p-coumaric acid, rutin, resveratrol, myricetin, quercetin and kaempferol. The method includes liquid-liquid extraction of acidic pH with ethylacetate. The analysis used a Zorbax Eclipse XDB-C18 column (5 pm, 4.6 mm x 250 mm). The chromatographic separation of these compounds performed in a single run by using the mobile phase gradient elution of methanol water mixture (% 0.2 formic acid) at room temperature, with flow rate at 1 mL/min. Detection was carried out by UV-vis and fluorescence detector. Each analysis required an equilibration period of 10 min and a run time of 14 min for completion. The optimized chromatographic method was carefully validated for precision and accuracy. Our findings indicated that the developed HPLC method was precise, accurate, specific and sensitive for simultaneous determination of phenolic compounds. Consequently, the described method was applied to the analysis of six wines from Malatya and Elazig. Gallic acid was dominant phenolic acid in red wines. (+)-catechin, (-)-epicatechin and p-coumaric acid were the next most abundant phenolics. The highest level of trans-resveratrol among the red wines was found Buzbagi (Bogazkere-Okuzgozu). The red wines were analyzed for total polyphenol content (TP) by Folin-Ciocalteu (FC) method, using gallic acid as standard. Antioxidant activities (M) of the red wines were measured using the DPPH (2,2-diphenyl-1-picrylhydrazyl) assay. There was a very high correlation between AA and TP in all of the wines tested. (C) 2011 Elsevier Ltd. All rights reserved.Öğe Determination of Regional Intestinal Permeability of Diclofenac and Metoprolol Using a Newly-Developed and Validated High Performance Liquid Chromatographic Method(Pharmacotherapy Group, 2015) Kaynak, Mustafa Sinan; Buyuktuncel, Ebru; Caglar, Hatice; Sahin, SelmaPurpose: To develop a simple and rapid reversed-phase high performance liquid chromatographic (HPLC) method with UV detection for the simultaneous determination of diclofenac, metoprolol tartrate, phenol red and propyl paraben in intestinal segments. Methods: The mobile phase consisted of 55% methanol, 45% of 12.5 mM potassium dihydrogen phosphate (KH2PO4) aqueous solution, adjusted to pH 7.0 using 0.2 N sodium hydroxide (NaOH) solution, and to which 0.3% (v/v) triethylamine was added. Analysis was run at a flow rate of 1.0 mL/min with a 12 min total run time at ambient temperature. The developed method was successfully applied to determination of the analytes in samples obtained from in situ single pass intestinal perfusion (SPIP) studies. Results: The calibration curves were linear for all compounds (r > 0.999) with a limit of detection (LOD) of 0.005, 0.1, 0.075 mu g/mL, and limit of quantification of 0.1, 0.3, 0.2 mu g/mL for metoprolol tartrate, phenol red and diclofenac respectively. The coefficient of variation for intra-day and inter-day precision was < 5% and accuracy was between 98 and 102%. Based on SPIP and HPLC studies, the estimated mean permeability in jejunum, ileum and colon was 0.319 +/- 0.184, 0.639 +/- 0.241 and 0.84 3 +/- 0.517 x 10(-4) cm/sec, respectively, for metoprolol tartrate while the corresponding permeability values were 1.585 +/- 0.729, 1.154 +/- 0.433 and 1.775 +/- 1.576 x 10(-4) cm/sec for diclofenac. Conclusion: The findings indicate that diclofenac is a highly permeable compound and its absorption occurs throughout the intestinal tract. Furthermore, the developed method is suitable for the analysis of diclofenac and metoprolol in intestinal regions.Öğe Development of a HPLC Method for the Determination of Cyclosporine A From Chitosan Nanoparticles(Colegio Farmaceuticos Provincia De Buenos Aires, 2012) Buyuktuncel, Ebru; Yucel, Cigdem; Kaynak, M. Sinan; Aktas, YesimA reversed-phase high performance liquid chromatographic method was developed for the determination of cyclosporine A from chitosan nanoparticles. Ibuprofen was used as internal standard. The separation was achieved on a Phenomenex C18 column (150 x 4.6mm, 5 mu m) using 60: 20: 20, acetonitril: methanol: water mixture at pH 4 as mobile phase under isocratic conditions. The system was operated at 80 degrees C and the flow rate of mobile phase was adjusted to 1 mL/min. The detection wavelength was set at 205 nm. The calibration curve was linear from 2 to 150 mu g/mL with correlation coefficient values from 0.9994 to 0.9997. The lower limit of quantification 2 mu g/mL and limit of detection was 0.5 mu g/mL. Recovery was 99-101 % and the intra-and inter-day coefficients of variation were 0.94-2.32 and 2.52-3.45 %, respectively depending on the concentration. The method was found to be specific, accurate, precise and sensitive for the determination of cyclosporine A from chitosan based drug delivery systems.Öğe HPLC METHOD DEVELOPMENT AND VALIDATION: SIMULTANEOUS DETERMINATION OF DICLOFENAC, METOPROLOL AND PHENOL RED IN BIOLOGICAL MATRIX FOR INTESTINAL PERFUSION STUDIES(Elsevier Science Bv, 2009) Caglar, Hatice; Kaynak, Mustafa Sinan; Sahin, Selma; Buyuktuncel, Ebru[Abstract Not Available]Öğe Main spectrophotometric methods for the determination of total phenolic content and antioxidant capacity(Marmara Univ, Fac Pharmacy, 2013) Buyuktuncel, EbruThis article gives the information regarding mainly spectrophotometric methods that used to measure antioxidant activity. Ideally, the antioxidant activity should be tested using both in vitro and in vivo techniques but due to the high cost of in vivo testing, many products are evaluated by in vitro testing. On the basis of chemical reactions mechanism, major antioxidant capacity assays can be divided into two categories: hydrogen atom transfer (HAT) reaction based assay and single electron transfer (SET) reaction based assay. HAT-based assays include Oxygen Radical Absorbance Capacity (ORAC), Total Radical Trapping Antioxidant Paramater (TRAP) and Crocin Bleaching Assays. SET-based assays include the total phenols assay by Folin-Ciocalteu reagent (FCR), Trolox (6-hydroxy2,5,7,8- tetramethylchroman-2-carboxylic acid) equivalence antioxidant capacity (TEAC), ferric ion reducing antioxidant power (FRAP), 2,2-diphenyl-1-picrylhydrazyl radical scavenging capacity (DPPH) assay and total antioxidant potential assay using a Cu(II) complex as an oxidant (CUPRAC).Öğe Microchip Electrophoresis and Bioanalytical Applications(Bentham Science Publ Ltd, 2019) Buyuktuncel, EbruMicroanalytical systems have aroused great interest because they can analyze extremely small sample volumes, improve the rate and throughput of chemical and biochemical analysis in a way that reduces costs. Microchip Electrophoresis (ME) represents an effective separation technique to perform quick analytical separations of complex samples. It offers high resolution and significant peak capacity. ME is used in many areas, including biology, chemistry, engineering, and medicine. It is established the same working principles as Capillary Electrophoresis (CE). It is possible to perform electrophoresis in a more direct and convenient way in a microchip. Since the electric field is the driving force of the electrodes, there is no need for high pressure as in chromatography. The amount of the voltage that is applied in some electrophoresis modes, e.g. Micelle Electrokinetic Chromatography (MEKC) and Capillary Zone Electrophoresis (CZE), mainly determines separation efficiency. Therefore, it is possible to apply a higher electric field along a considerably shorter separation channel, hence it is possible to carry out ME much quicker.Öğe Simultaneous Determination of Theobromine, Paraxanthine, Theophylline, and Caffeine in Urine by Reversed-Phase High-Performance Liquid Chromatography with Diode Array UV Detection(Taylor & Francis Inc, 2010) Buyuktuncel, EbruA reversed-phase high performance liquid chromatographic method was improved for the simultaneous determination of theobromine, paraxanthine, theophylline, and caffeine in urine. The method includes a liquid-liquid extraction at alkaline pH with ethylacetate. The 7-(2,3-dihidroxypropyl) theophylline was used as an internal standard (ISTD). The separation was achieved on a C18 column using 14:86 methanol:buffer (25mM KH2PO4 adjusted to pH 4 with ortho-phosphoric acid) solution as mobile phase under isocratic conditions at a flow rate 1mLmin-1. An ultraviolet absorption at 274nm was monitored. In these conditions, the LOD was 0.03gmL-1 for theobromine, 0.02gmL-1 for paraxanthine, 0.04gmL-1 for theophylline, and 0.08gmL-1 for caffeine. The method has been applied to urine samples.
