Yazar "Temel, Nuket Kartal" seçeneğine göre listele
Listeleniyor 1 - 9 / 9
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe A new ion-pair ultrasound assisted-cloud point extraction approach for determination of trace V(V) and V(IV) in edible vegetal oils and vinegar by spectrophotometry(Elsevier, 2019) Temel, Nuket Kartal; Kus, Berna; Gurkan, RamazanA new ion-pair ultrasound-assisted-cloud point extraction (UA-CPE) procedure for the preconcentration and determination of V(V) and V(IV) in edible vegetal oils and vinegar by spectrophotometry at 530 nm was developed. The method is based on selective and sensitive anionic chelation of V(V) and V(IV) with EDTA, and then a stable ion-pair formation of the formed chelate complexes with cationic phenazine dye, Safranin T, at pH 4.0 and/or pH 5.0 respectively, which can be easily extracted into the micellar phase of Triton X-114 with the help of ultrasound energy. The variables affecting ion-pair formation and extraction efficiency were evaluated and optimized. Under the optimized conditions, there was a linear relationship in range of 1-40 mu g/L for V(IV) at pH 5.0 with higher calibration sensitivity while it obtained a rectilinear behavior in the range of 2-180 mu g/L for V(V) at pH 4.0. The limits of detection and quantification for V(IV) were 0.26 and 0.85 mu g/L with a sensitivity enhancement of 83.6 from preconcentration of 35-mL sample, respectively where these values are 0.53 and 1.77 mu g/L, respectively, for V(V). The recovery rate and precision for five replicate measurements of 5, 25 and 100 mu g/L V(V) and V(IV) were in range of 98-101%, 3.1-4.2% and 3.2-4.5%, respectively. The accuracy was statistically verified by analysis of a certified oil sample with both the developed method and independent comparison method, and the method was successfully applied to the analysis of total V contents of edible vegetal oils and vinegar samples after preconcentration.Öğe Application of Ultrasound-Assisted Cloud-Point Extraction and Spectrophotometry for Preconcentration and Determination of Trace Amounts of Copper(II) in Beverages(Pleiades Publishing Inc, 2019) Temel, Nuket Kartal; Gurkan, RamazanA new method for preconcentration of trace Cu(II) in beverages before determination by spectrophotometry is presented. The method is based on the ternary complex formation of Cu(II) with Safranin T in presence of pyrogallol at pH 5.5 followed by its extraction into the micellar phase of Triton X-114. The ternary complex was monitored by spectrophotometry at 532 nm. Variables affecting extraction efficiency were evaluated and optimized. Under the optimal conditions, the detection limit was 0.6 mu g/L in the range of 2-300 mu g/L with sensitivity enhancement of 55 after preconcentration from 15 mL of the sample, and precision was in the range of 2.5-3.9%. The accuracy was verified by the analysis of two certified samples and recovery studies of the spiked samples. The intra- and inter-day precision varied in the ranges of 3.7-4.6 and 3.9-5.2%, respectively. The method was successfully applied to determination of trace Cu(II) in beverages.Öğe Comparison of the effect of various carbon-based nanomaterials for the removal of Cu2+ ions from aqueous solutions(Springer Int Publ Ag, 2024) Temel, Nuket Kartal; Sertakan, Kadriye SibelWater pollution caused by heavy metals is one of the most important issues threatening the environment. The study, presented here was focused on the removal of heavy metal Cu2+ ions from aqueous solution by using pristine multi-walled carbon nanotubes (p-MWCNT), acid treated MWCNTs (a-MWCNTs) and unzipped MWCNTs (u-MWCNTs). The size dependency of MWCNTs on the adsorption of Cu2+ ions was evaluated. Moreover, pH, adsorbent dosage, initial metal ion concentration and temperature effects on the adsorption process were explored. The maximum adsorption efficiency was found to be 98.5% for u-MWCNTs that is fabricated from the layered MWCNTs having an outer diameter of 50-80 nm and an inner diameter of 10-20 nm at 0.5 g L-1 adsorbent mass. The absorption kinetic data fitted best to the pseudo-second-order model. The thermodynamic assessments indicated that the adsorption was endothermic and randomness process. [GRAPHICS]Öğe Katalitik Kinetik Spektrofotometri ile Çevresel Örneklerde Eser Miktarlardaki Toplam Fe'nin Fe(II) Olarak Belirlenmesi(2017) Temel, Nuket Kartal; Gürkan, RamazanYöntem, Coomassie Brillant Blue 2R'nin bromat ile oksidasyonuna, aktivatör olarak 1,10-fenantrolin varlığında demir (II) iyonlarının seçici katalitik etkisine dayanır. Katalitik tepkime yaklaşık 3 dakikalık sabitlenmiş-zaman yaklaşımı ile 520 nm'de spektrofotometrik olarak izlenmiştir. Uygulama koşullarının optimizasyonu araştırılmıştır. Elde edilen optimalkoşullar: 1.5 mL Coomassie Brillant Blue 2R (1.0 × 10-4 mol L- 1), 0.6 mL bromat (0.01 mol L-1), 1.5 mL 1,10-fenantrolin (1.0 × 10-3 mol L-1), 25 oC tepkime sıcaklığı and pH 2.0 de, 520 nm'de 3 dakikalık tepkime zamanıdır. Önerilen yöntem, 0.0141 mg L-1 ve 0.047 mg L-1 lik seçme ve nicelleştirme sınırı ile 0.05-5 mg L-1 aralığında demir (II)'nin tayinine izin verir. 0.2 ve 3 mg L demir (II)'nin beş tekrarlı analizi için elde edilen bağıl standart sapma değerleri sırasıyla %3.8 ve %2.3 tür. Yöntem, pH 4.0 ve 40 oC'de sülfit ile demir (III)'ün demir (II)'ye ön indirgenmesi sonrası demir eksikliği tedavisinde kullanılan farmasötik örnekler (ferrosolanol ve maltoz gibi) ve göl, nehir ve kuyu suyu gibi bazı çevresel yüzey sularında toplam demir tayininde uygulanmış, olası örnek matriks etkisi için yaş asitle çözme sonrası standart eklemeye dayanan analizle %98.7-102.7 aralığında değişen kantitatif gerikazanımlar elde edilmiştirÖğe New catalyst systems for the degradation of chlorophenols(ELSEVIER SCIENCE BV, 2011) Temel, Nuket Kartal; Sokmen, MunevverThe aim of this study is to investigate new catalyst systems for the oxidative degradation of chlorophenol (CP) derivatives that have been classified as first-degree toxic pollutants. Oxidative degradation and degradation products of chlorinated phenols, namely 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol, are discussed in detail. Homogenous catalyst systems Fenton [Fe(II)/H(2)O(2)) and Fenton-like [Cu(II)/H(2)O(2) and V (IV)/H(2)O(2)] methods were employed at higher CP concentrations (1 x 10(-2) mol/L). Heterogeneous catalyst systems titanium dioxide [TiO(2)/UV) and silver loaded titanium dioxide [Ag-TiO(2)/UV] processes were also investigated at lower concentrations. Chemical oxygen demand (COD), which is defined as oxygen equivalent of organic matter before and after degradation system was determined. The removal of each CP was determined by GC/MS analysis after derivatization. CPs are generally resistant to degradation and in some cases oxidation byproducts are produced rather than the destruction of molecular structure. High degradation and removal efficiencies for each CP derivative have already been obtained by the Fenton system and this was supported by both GC/MS and COD results. However the Ag-TiO(2)/UV photocatalytic system achieved the most effective degradation of all CPs studied in this work. In addition, the results indicate that the silver loaded catalyst system achieves the best degradation efficiencies in a short exposure period. (C) 2011 Elsevier B.V. All rights reserved.Öğe Photocatalytic TiO2-catalyzed degradation of bromophenol blue-mediated Mo(VI)-peroxo complexes inthe presence of SDS(DESALINATION PUBL, 2016) Temel, Nuket Kartal; Gurkan, Ramazan; Ayan, FiratIn the present study, the photocatalytic TiO2-catalyzed degradation of bromophenol blue (BPB)-mediated Mo(VI)-peroxo complexes in the presence of sodium dodecyl sulfate (SDS) under UV irradiation was investigated. The analytical variables, such as pH, TiO2 catalyst dosage, initial concentration of the dye, concentrations of H2O2, Mo(VI), and SDS influencing the photocatalytic degradation of BPB, were studied in detail. The obtained optimum conditions were as follows: pH 5.0, 0.5mL of 11.0mol L-1 H2O2, 200gL(-1) Mo, 0.02mmol L-1 SDS, 5mg L-1 dye, 1.0g L-1 TiO2. Under the optimized conditions, the percent removals have been 85.4 and 75.3% for TiO2-UV-H2O2-Mo(VI) system with and without SDS, while they are 65.2 and 59.4% for TiO2-UV system with and without H2O2. As a result, it has been observed that the maximum removal rate is obtained for TiO2-UV-H2O2-Mo(VI) in presence of SDS at premicellar concentration with a value of 85.4%. The removal rate of the dye was spectrophotometrically monitored at 590nm during the analysis.Öğe Removal of Bromophenol Blue from Aqueous Solution Using Bentonite, Zeolite and Graphene Oxide(2024) Temel, Nuket Kartal; Erdem, İbrahim GökçeIn this study, an anionic dyestuff bromophenol blue (BrPB) from the aqueous solution was removed by adsorption in the presence of bentonite (B), zeolite (Z) and graphene oxide (GO). The effects of pH, adsorbent amount, initial concentration of BrPB, temperature and time on adsorption were investigated. After the adsorption process, ultraviolet-visible region spectrophotometer (UV-VIS) was used to measure the amount of dyestuff remaining in the solution which is not adsorbed. It’s found that; the optimum values obtained for the adsorption process; the optimum pH value 5 for B and Z, 4 for GO; 0.03 g amount of adsorbent and 60 minutes for the equilibrium time. The compatibility of Langmiur and Freundlich isotherm models was found as Z> GO> B and GO> B> Z respectively. In terms of kinetics aspect, it was observed that all adsorbents were comply with pseudo-second order reaction kinetics. To be positive of ?G° value for B and Z is of physical nature of adsorption, to be negative of ?G° value for GO requires to be chemical nature of adsorption. When the obtained ?H° values were examined, it was observed that the reaction was endothermic for B and Z and exothermic for GO. The negative value of ?S° for B and Z adsorbent species indicates that the randomness between solid and liquid decreases, whereas the positive ?S° value for GO indicates that the randomness between solid and liquid increases. The highest adsorption capacity value obtained after the measurements made under optimum conditions is 589 mg g-1 for GO and 15.7 and 19.8 mg g-1 for B and Z, respectively.Öğe Ultrasound assisted-cloud point extraction coupled with spectrophotometry for determination of low levels of formaldehyde from milk-based products(Academic Press Inc Elsevier Science, 2024) Temel, Nuket KartalIn this study, a preconcentration method is proposed for the separation, extraction and spectrophotometric determination of free formaldehyde (FA) from milk-based products. The method is based on ion-pair formation between phenoxazine 3-one, resazurin, and hydroxymethanesulfonate (HMS), which is selectively formed by the reaction of FA with sulfite at pH 5.0, followed by its extraction into the micellar phase of Triton X-114. Resazurin was adopted as ion-pairing reagent for detection of low levels of FA at 610 nm. The variables affecting the extraction efficiency were evaluated and optimized. A linear relationship was obtained in the range of 2-120 mu g L-1 with a detection limit of 0.501 mu g L-1. Under optimum conditions such as pH 5.0, 8 mu mol L-1 Resazurin, 0.4 mg L-1 sulfide, 0.03% (v/v) of Triton X-114, after applying ultrasonic assisted-cloud point extraction (UA-CPE), spectrophotometric determination was made at 610 nm to measure the concentration of FA found in trace amounts in milk-based products such as liquid, semi-solid and solid-milk products including whole milk, semiskimmed milk, cacao milk, banana flavored milk, strawberry flavored milk, goat milk, yogurt, fruit flavored yogurt, white cheese. The precision was in the range 2.5-4.8% (n: 5, for 5, 25 and 100 mu g L-1). After preconcentration of a 15 mL sample, a sensitivity enhancement factor of 55.6 was obtained. To represent the sample matrix, the validation was checked by intra-day/inter-day accuracy and precision analysis of a spiked quality control sample and its recoveries at three concentration levels. Finally, the method was successfully applied to the determination of free FA in samples, and recoveries in the range 90.8-97.4% with RSD lower than 5.7% after spiking were obtained.Öğe Using Safranin T as a Charge Transfer-Sensitive Ion-Pairing Reagent in Ultrasound-Assisted Cloud Point Extraction: Determination of Bisphenol A in Selected Beverages(Aoac Int, 2018) Temel, Nuket Kartal; Gurkan, RamazanIn this study, a new ultrasonic-assisted cloud point extraction method coupled with spectrophotometry was developed to extract from and determine bisphenol A (BPA) in a sample matrix. The method is based on charge transfer-sensitive ion-pairing complex formation between BPA and Safranin T in the presence of nitrate in a micellar interface at pH 5.0. The variables affecting extraction efficiency were optimized. A good linear relationship with a significant sensitivity difference was obtained in the ranges of 2-40 and 2-120 mu g/L with LODs of 0.54 and 0.38 mu g/L after preconcentration with two different extractants, respectively. From a preconcentration of a 15 mL sample, a preconcentration factor of 60 was obtained. Due to the lack of a certified material compatible with the sample matrix, the method was validated by conducting intraday and interday accuracy and precision studies based on two spiked QC samples (with a recovery rate greater than 94% and an RSD ranging from 3.8 to 5.9%). Moreover, the beverage samples were analyzed by the standard addition method to control for possible matrix effects. BPA was detected in the range of 1.8-7.2 mu g/L in beverages with Triton X-114, whereas the levels changed to a range of 1.8-7.3 mu g/L with Triton X-45. In such a way not to create a threat, these levels were considerably lower than the specific migration limit set by the European Union.
