Yazar "Ayyildiz, H. Filiz" seçeneğine göre listele

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    Application of multivariate chemometric techniques for simultaneous determination of five parameters of cottonseed oil by single bounce attenuated total reflectance Fourier transform infrared spectroscopy
    (ELSEVIER, 2014) Talpur, M. Younis; Kara, Huseyin; Sherazi, S. T. H.; Ayyildiz, H. Filiz; Topkafa, Mustafa; Arslan, Fatma Nur; Naz, Saba
    Single bounce attenuated total reflectance (SB-ATR) Fourier transform infrared (FTIR) spectroscopy in conjunction with chemometrics was used for accurate determination of free fatty acid (FFA), peroxide value (PV), iodine value (IV), conjugated diene (CD) and conjugated triene (CT) of cottonseed oil (CSO) during potato chips frying. Partial least square (PLS), stepwise multiple linear regression (SMLR), principal component regression (PCR) and simple Beer's law (SBL) were applied to develop the calibrations for simultaneous evaluation of five stated parameters of cottonseed oil (CSO) during frying of French frozen potato chips at 170 degrees C. Good regression coefficients (R-2) were achieved for FFA, PV, IV, CD and CT with value of > 0.992 by PLS, SMLR, PCR, and SBL. Root mean square error of prediction (RMSEP) was found to be less than 1.95% for all determinations. Result of the study indicated that SB-ATR FTIR in combination with multivariate chemometrics could be used for accurate and simultaneous determination of different parameters during the frying process without using any toxic organic solvent. (C) 2014 Elsevier B.V. All rights reserved.
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    A Highly Efficient Automated Flow Injection Method for Rapid Determination of Free Fatty Acid Content in Corn Oils
    (SPRINGER, 2014) Ayyildiz, H. Filiz; Kara, Huseyin
    In the present study, a new flow injection (FI) methodology for determination of free fatty acid (FFA) content in corn oil samples is proposed. The proposed method is based on monitoring the absorbance changes at 580 nm, lambda (max), as a result of neutralization of FFA in oil samples by KOH in the reagent. The analyses were performed with a single-line FI manifold system created by modification of high performance liquid chromatography. The main parameters, such as sample and reagent volumes, reaction coil, reagent concentration and temperature were all optimized. With the newly developed sampling strategy, the oil sample and reagent at micro level were directly injected together without any pre-treatment. The proposed flow injection analysis method was validated statistically and it was found to be linear (between 0.09 and 1.50 FFA %), accurate (recovery 87.19-122.22 %), and precise (relative standard deviation < 1 % for both intra-day and inter-day precision). The limit of detection and limit of quantification were found to be 7.41 x 10(-3) and 2.24 x 10(-2) oleic acid %, respectively. The results were also compared with those obtained by the American Oil Chemists Society (Ca-5a-40) method using statistical t and F tests, and a significant difference was not observed between the methods at the 95 % confidence level. These results strongly suggest that this method is suitable for automated routine analysis of FFA in edible oils due to its simplicity, reliability, speed, and economy of solvents and sample.
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    Investigating sorption characteristics of copper ions onto insolubilized humic acid by using a continuously monitored solid phase extraction technique
    (ELSEVIER SCIENCE BV, 2007) Gezici, Orhan; Kara, Huseyin; Yanik, Sema; Ayyildiz, H. Filiz; Kucukkolbasi, Semahat
    The sorption characteristics of Cu(II) in an insolubilized humic acid (IHA) mediated column system were investigated at various experimental conditions using a solid phase extraction (SPE) technique. Sodium form of the IHA (INaA) was used as solid phase and sorption behaviors were evaluated by using common adsorption isotherms as well as Scatchard plot analysis. Regeneration, loading, washing and stripping steps of SPE were carried out consecutively, and their progresses were monitored through breakthrough curves obtained from a continuous flow-through cell adapted UV-vis spectrophotometer. So, the breakthrough curves were used to visualize distribution of Cu(II) concentration between mobile phase and solid phase, and amount of the Cu(II) sorbed by INaA was obtained from AAS analysis of effluents collected during the stripping steps of particular run. Thus, from the obtained results, the sorption characteristics and usability of IHA as a solid phase for SPE of metal ions was evaluated in detail. (c) 2007 Elsevier B.V. All rights reserved.
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    A Novel Approach for Determination of Free Fatty Acids in Vegetable Oils by a Flow Injection System with Manual Injection
    (WILEY, 2011) Ayyildiz, H. Filiz; Kara, Huseyin; Sherazi, S. T. H.
    A non-aqueous flow injection method for determining free fatty acid (FFA) content in corn and sunflower oil samples was developed. A single-line manifold system was built by modification of an HPLC for flow injection analysis (FIA). Without pre-treatment, oil samples were injected into a n-propanol solution containing KOH and phenolphthalein (PHP). The main parameters, such as flow rate of carrier phase, length, geometry, inner diameters of the coils and reagent concentration were all optimized. The proposed FIA method was validated for precision, accuracy, linear region, limit of detection (LOD) and limit of quantification (LOQ). The intra- and inter-day measurements of the precision of the method were found to be within the limits of acceptance criteria (RSD < 1%), and were rugged when the method was performed by a different analyst. The linear concentration range was calculated as 0.09-1.50 and 0.07-1.40 FFA% for corn and sunflower oils, correspondingly. The LOD and LOQ were found to be 7.53 x 10(-4)-2.28 x 10(-3) oleic acid % and 7.11 x 10(-4)-2.23 x 10(-3) oleic acid % for corn and sunflower oils, respectively. The results were compared with those obtained by the AOCS (Ca-5a-40) method using statistical t and F tests, and a significant difference was not observed between the methods at a 95% confidence level. The proposed method is suitable for quality control of routine applications due to its simplicity, high sample throughput, and economy of solvents and sample, offering considerable promise as a low cost analytical system that needs minimum human intervention over long periods of time.
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    Removal and Preconcentration of Cobalt Ions from Aqueous Media Using ImHA Packed Column by On-Line SPE System
    (SPRINGER INTERNATIONAL PUBLISHING AG, 2012) Ayyildiz, H. Filiz; Topkafa, Mustafa; Arslan, FatmaNur; Durmaz, Fatih; Kucukkolbasi, Semahat; Tarhan, Ismail; Kara, Huseyin
    This work assesses the use of immobilized humic acid (ImHA) onto aminopropyl silica (APS) as a sorbent for the removal and preconcentration of trace amounts of cobalt ions by on-line solid phase extraction (SPE) technique in the column system prepared in our laboratory. Different parameters, such as the effect of the pH, concentration, and flow rate, were studied and throughput was observed by a UV detector. All SPE steps were monitored by breakthrough curves used to visualize distribution of cobalt concentration between mobile and solid phase. The solutions collected from stripping steps were analyzed in atomic absorption spectrometer (AAS) and the amount of sorbed ions was calculated. Sorption characteristics were evaluated by using common adsorption isotherms and Scatchard plot analysis. From the obtained results, it was seen that sorption mechanism of cobalt ions were fitted to Langmuir model on a large scale and thought to be localized. Mean free energy (E = 40.82 kJ mol(-1)) calculated from D-R isotherm showed that chemical interactions are more effective than physical interactions. This investigation reveals a new, simple, environmentally friendly, and cost-effective method for removal and preconcentration of cobalt ions from aqueous solutions by a new aminopropyl silica-immobilized humic acid material.
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    Role of Different Bleaching Earths for Sunflower Oil in a Pilot Plant Bleaching System
    (DE GRUYTER OPEN LTD, 2013) Topkafa, Mustafa; Ayyildiz, H. Filiz; Arslan, Fatma Nur; Kucukkolbasi, Semahat; Durmaz, Fatih; Sen, Seyit; Kara, Huseyin
    The purpose of present study is to investigate the efficiency of different kinds of Turkish commercial bleaching earth materials for changes in different colour pigment concentrations in neutralized sunflower oils. The bleaching experiments were performed in a pilot system under at stable vacuum (50 mmHg) and temperature (100 degrees C) for 30 min. By examining the changes in chlorophyll, beta-carotene and red colour, bleaching process parameters such as type and dosage of the bleaching material were optimised. The sorption characteristics of colour pigments were evaluated using common adsorption isotherms and Scatchard plot analysis. Ads-3 acid-activated earth material at 1% (w/w) per samples was found to be the most appropriate sorbent and the amount of sorbed pigments was calculated as 1.01x10(-4)mmol/g ads. for chlorophyll, 1.15x10(-3)mmol/g ads. for carotene and 1.70 red on Lovibond colour scale. The procedure indicated that this system can be easily adapted to the actual oil refining systems.
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    SIMULTANEOUS AND ACCURATE DETERMINATION OF WATER- AND FAT-SOLUBLE VITAMINS IN MULTIVITAMIN TABLETS BY USING AN RP-HPLC METHOD
    (SOC BRASILEIRA QUIMICA, 2013) Kucukkolbasi, Semahat; Bilber, Onur; Ayyildiz, H. Filiz; Kara, Huseyin
    In the present study, a reversed-phase high-performance liquid chromatographic (RP-HPLC) procedure was developed and validated for the simultaneous determination of seven water-soluble vitamins (thiamine, riboflavin, niacin, cyanocobalamin, ascorbic acid, folic acid, and p-aminobenzoic acid) and four fat-soluble vitamins (retinol acetate, cholecalciferol, alpha-tocopherol, and phytonadione) in multivitamin tablets. The linearity of the method was excellent (R-2 > 0.999) over the concentration range of 10-500 ng mL(-1). The statistical evaluation of the method was carried out by performing the intra-and inter-day precision. The accuracy of the method was tested by measuring the average recovery; values ranged between 87.4% and 98.5% and were acceptable quantitative results that corresponded with the label claims.
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    Use of aminoprophyl silica-immobilized humic acid for Cu(II) ions removal from aqueous solution by using a continuously monitored solid phase extraction technique in a column arrangement
    (ELSEVIER SCIENCE BV, 2008) Kara, Huseyin; Ayyildiz, H. Filiz; Topkafa, Mustafa
    Humic acid (HA) which originated from Leonardite was purified and immobilized onto aminoprophyl silica (APS). Afterwards, the remaining amino groups on the silica are successfully end-capped using acetic anhydride in DMF media and this material was used for Cu(II) ions removal from aqueous solution by using continuously solid phase extraction (SPE) technique in a column arrangement. The sorption characteristics of Cu(II)-immobilized humic acid (ImHA) system were investigated at various experimental conditions, and output was observed by a UV detector. All solid phase extraction (SPE) steps were monitored through breakthrough curves used to visualize distribution of Cu(II) concentration between mobile phase and solid phase. In addition to this, the solutions collected from stripping steps were analyzed in atomic absorption spectrophotometry (AAS) and the amount of adsorbed Cu(II) ions was calculated. It was found that there was a high correlation (R-2 = 1) between the peak area and AAS data of stripping steps. Sorption characteristics were evaluated by using Freundlich, Langmuir, and Dubinin-Radushkevich (D-R) adsorption isotherms, as well as by Scatchard plot analysis. Thus, the sorption characteristics and usability of ImHA as a solid phase for SPE of Cu(II) ions was evaluated in detail. From the obtained results, it was seen that sorption mechanism of Cu(II) fits to Langmuir model on a large scale, sorption was thought to be localized. From D-R isotherm mean free energy of sorption (E) was calculated (17.68 kJ mol(-1)), and it was deduced that chemical interactions were more effective than physical interactions for Cu(II). This investigation provides a new, environmentally friendly and cost-effective possibility to remove Cu(II) ions from aqueous solution by using the new APS-ImHA material. (c) 2007 Elsevier B.V. All rights reserved.