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Öğe A New Ultrasonic Assisted Cloud Point Extraction and Preconcentration Procedure for the Spectrophotometric Oxalate Determination in Beverages(2017) Gürkan, Ramazan; Altunay, NailAnew ultrasonic-assisted cloud point extraction procedure (UA-CPE) was developed for preconcentration of oxalate in beverages prior to determination via spectrophotometry. At optimal conditions, the calibration curve was highly linear in a working range of 0.4–170 µg L? 1. The limits of detection and quantification were 0.12 and 0.40 µg L? 1. the precision as the percentage relative standard deviation, RSD% (n: 5; 10, 15, 30 µg L? 1) was lower than 3.5%. The method was successfully applied to the determination of soluble and total oxalate in beverage samples using two different acidic extraction approaches under ultrasonic power. Finally, the method was validated by comparing the results obtained with those of the reference method.Öğe A novel indicator reaction for the catalytic determination of V(V) at ppb levels by the kinetic spectrophotometric method(Atlantis Livros Ltda., 2009) Ulusoy, Halil Ibrahim; Gürkan, RamazanA novel sensitive and relatively selective kinetic method is presented for the determination of V(V), based on its catalytic effect on the oxidation reaction of Ponceau Xylydine by potassium bromate in presence of 5-sulfosalicylic acid (SSA) as activator. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of Ponceau Xylydine at 640 nm between 0.5 to 7 min (the fixed time method) in H 3PO4 medium at 25°C. The effect of various parameters such as concentrations of H3PO4, SSA, bromate and Ponceau Xylydine, temperature and ionic strength on the rate of net reaction were studied. The method is free from most interferences, especially from large amounts of V(IV). The decrease in absorbance is proportional to the concentration of V(V) over the entire concentration range tested (1-15 ng mL-1) with a detection limit of 0.46 ng mL-1 (according to statistical 3Sblank/k criterion) and a coefficient of variation (CV) of 1.8% (for ten replicate measurement at 95% confidence level). The proposed method suffers few interferences such as Cr(VI) and Hg(II) ions. The method was successfully applied to the determination of V(V) in tap water, drinking water, bottled mineral water samples and a certified standard reference material such as SRM-1640 with satisfactory results. The vanadium contents of water samples were also determined by FAAS for a comparison. The recovery of spiked vanadium(V) was found to be quantitative and the reproducibility was satisfactory. It was observed that the results of the SRM 1640 were in good agreement with the certified value.Öğe Bazı metal komplekslerinin TLC/IR birleşik sistemi ile tuz kaması yöntemi kullanılarak ayrılması ve tanısı(Cumhuriyet Üniversitesi, 1996) Gürkan, Ramazan; ,ÖZET Yüksek Lisans Tezi Bazı Metal Komplekslerinin TLC/IR-Birleşik Sistemi ile Tuz Kaması Yöntemi Kullanılarak Ayrılması ve Tanısı Ramazan GÜRKAN Cumhuriyet Üniversitesi Fen Bilimleri Enstitüsü Kimya Anabilim Dalı Danışman:Yrd.Doç.Dr. Şahin SAVAŞÇI Karışımları ayırmakta etkin bir analitik sistem olan TLC ile saf bileşenlerin kesin tanısını yapmakta ideal bir yöntem olan IR-spektroskopisiyle bazı metal komplekslerinin nitel ayrılma ve tanınma olanaklarının araştırılması amaçlanmıştır. Sodyum-Dietilditiyokarbamat, 1,5-Difeniltiyokarbazon ( Dithizon ) ve 8- Hidroksi kinolin ligandlan kullanılarak belli bir pH ya da pH aralığında bazı metal katyonlarının kompleksleri hazırlanmıştır. Bu metal komplekslerinin hazır ve laboratuarda hazırlanan TLC tabakaları üzerinde optimum ayrılma koşulları ve Rf değerlerinin tekrarlanabilirliği araştırılmıştır. Adsorban olarak silika jel kökenli dört farklı Silika jel ( Silika jel-60H, 6OHF254, 6OPF254 ve 6OGF254. ) ve çözücü sistemi olarak polariteleri farklı çözücü ve çözücü sistemleri kullanılmıştır. Nötral metal komplekslerinin bağıl olarak adsorpsiyona dayanan TLC ile ayrılmalarında, diklormetan, benzen.toluen ve ksilen gibi orta şiddette polariteye sahip çözücü ya da çözücü sistemleri yürütücü olarak kullanılmıştır. Metal komplekslerinin Rf değerleri ; Aynı çözücü yada çözücü sistemiyle farklı adsorbanla kaplanmış TLC tabakaları üzerinde yürütülerek, aynı adsorbanla kaplanmış TLC tabakaları üzerinde farklı çözücü veya çözücü sistemiyle yürütülerek, aynı adsorbanla kaplanmış TLC tabakaları üzerinde çözücü sisteminin bileşimini değiştirerek yürütmeyle, aynı adsorbanla kaplanmış TLC tabakaları üzerinde aynı çözücü veya çözücü sistemiyle tek boyutlu çoklu yürütme yapılarak belirlenmiştir.Tek boyutlu çoklu yürütme, tabakanın aynı mobil fazla aynı yönde ve aynı göç uzaklığında tekrarlanır biçimde yürütüldüğü bir yürütme tekniğidir.Bu teknik, kromatogram üzerinde beneklerin daha düşük Rf aralığında ( ^ 0.5 ) ayrılmasına imkan sağlar. Tabaka, mobil fazı buharlaştırmak için yürütmeler arasında yürütme tankından çıkartılır.Herbir yürütme sonunda bu işlem tekrarlanır. Bu işlemle bir dizi kromatografik ölçümün tekrarlanırlığı istatistiksel olarak belirlenir. Aynı adsorban ve aynı çözücü veya çözücü sistemiyle N=5 veya 6 ölçüm serisi için tek boyutlu çoklu kromatogram yürütmelerinden elde edilen alıkonma faktörleri, Rf için standart sapmalar ve bağıl standart sapmalar belirlenmiştir. Standart sapma boyutunda aynı ve birbirine yakın Rf değerleri veren metal komplekslerinin kesin tanısı için,, komplekslerin Tuz Kaması ucunda zenginleştirilerek IR-spektrumlan alınmıştır. Bu spektrumlardan herbir kompleks türün kendine özgü ayırdedici soğurma bandıyla ayrılabileceği görülmüştür. Herbir kompleks için spesifik olan bu ayırdedici soğurma bandlarının olası nicel çalışmalarda referans spektral bandlar olarak alınabileceği öngörülmüştür. Ayrılmayan kompleks türler için IR-spektrofotometresinin TLC dedektörü olarak kullanılmasıyla daha etkin ve başarılı bir nitel analiz yapılabileceği sonucuna varılmıştır. ANAHTAR KELİMELER: TLC, Tuz Kaması, Karekterizasyon, Dedeksiyon, TLC/IRÖğe Determination of trace amounts of selenium in natural spring waters and tea samples by catalytic kinetic spectrophotometry(Atlantis Livros Ltda., 2019) Gürkan, Ramazan; Gürkan, Nevalnur ZeynepIn this work, a new kinetic method is described for the determination of trace Se(IV) in natural spring waters and commercial tea samples. The method is based on the activation of Se(IV) onto the indicator reaction in acidic medium. The reaction was monitored using a fixed time approach of 20 min at 680 nm. The variables affecting the reaction rate were evaluated and optimized. The method allows the determination of Se(IV) in the range of 0.0125-1.0 mg L-1 with a detection limit of 3.6 µg L-1. The precision was in range of 0.63-3.15% (as RSD %) with a higher recovery than 98.6%. The method has been found to be selective against matrix effect. The method was applied to the speciation analysis of inorganic Se species present in the selected samples. The method was statistically validated by analysis of two certified samples and comparing the obtained results to those of HG-AAS analysis. Also, the total Se levels of the samples were determined by using both methods after conversion of Se(VI) into Se(IV) in ultrasonic bath in acidic medium for 30 min at 85-90 °C. The results were in good agreement with those of HG-AAS. The Se(VI) level of the samples was calculated from the difference between amounts of total Se and Se(IV). © 2019 Atlantis Livros Ltda.. All rights reserved.Öğe Eco-friendly trace analysis of silver in beer/wine samples using a new co-polymeric nanocomposite based-ultrasound assisted-cloud point extraction combined with spectrophotometry(ELSEVIER, 5 şubat 2021) Zengin, Hacı Bayram; Gürkan, RamazanIn this study, a new magnetic nanocomposite based on the tris(2-hydroxymethyl)aminomethane-modified poly (styrene-co-N-maleimide) copolymer and Fe3O4 nanoparticles were prepared as a new micellar interface for preconcentration of trace levels of silver from aqueous solutions by ultrasound assisted-cloud point extraction (UACPE). The structure of the nanocomposite was characterized by using some instrumental tools in detail. The method is selectively based on charge transfer among silver and reagents at pH 5.0, and detection by microvolume UV–vis spectrophotometry at 346 nm. The main variables affecting extraction efficiency were evaluated and optimized in detail. Under the optimized conditions, the method shows good linear relationships in ranges of 2.5..... 125 μg L.... 1 and 4.... 160 μg L.... 1 by two calibration curves (established in solvent and beer/wine matrices) with a better determination coefficient (r2) than 0.992. The limits of detection, repeatability/intermediate precision (as RSDs%, 5, 25 and 100 μg L-1, n: 5) and recovery percentages were 0.85/1.21 μg L-1, 3.5–7.1% and 91.5–98.5%, respectively. From pre-concentration of 25-mL sample solution, a pre-concentration factor was found to be 62.5 with sensitivity enhancement of 23.2-fold in calibration. A matrix effect was not observed for the triplicate measurements of 100 μg L... 1 Ag+ in the presence of various interfering species. The method accuracy was validated with the outcome of validation that was carried out. The method after two sample preparation procedures was successfully applied to reliable determination of total Ag in beer and wine samples. The total Ag levels were in range of 2.5–4.2 and 2.7–5.5 μg L.... 1 in beer and wine samples, respectively.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 A magnetic nanocomposite based on amine?functionalized pH?sensitive functional poly(styrene?co?maleic anhydride) copolymer for selective extraction, pre?concentration and determination of sub?trace Ag+ and Cu2+ ions from edible vegetable oils by a combination of spectrophotometry and ultrasound?assisted cloud point extraction(Springer, 04.04.2022) Zengin, Hacıbayram; Gürkan, RamazanIn this study, a new magnetic nanocomposite based on amine-functionalized pH-sensitive poly(styrene-co-maleic anhydride) copolymer derived from the tris(2-hydroxymethyl)aminomethane and Fe3O4 nanoparticles was designed, characterized and used in selective extraction and pre-concentration of sub-trace Ag+/ Cu2+ ions from aqueous solutions by ultrasoundassisted cloud point extraction. The method is based on the formation of charge transfer complexes among Ag+/ Cu2+ ions and weak basic amidic copolymer matrix at pH 4.0/5.0, respectively, in the presence of pH-sensitive anionic surfactant, and their detection by spectrophotometry at 346 nm. The variables affecting extraction efficiency were optimized in detail. Under the optimized conditions, the good linear relationships were obtained in ranges of 0.8–110/1.0–120 μg L− 1 for Ag+ and 1–125/2.0–140 μg L− 1 for Cu2+ by two calibration curves with a better determination coefficient than 0.992. The limits of detection, repeatability/intermediate precision (as RSDs%, 5, 25 and 100 μg L− 1, n: 5) and the percent recoveries were 0.25/0.41 μg L− 1, 3.0–7.1% and 90.4–98.5%, respectively. From pre-concentration of 25 mL sample solution, a pre-concentration factor was found to be of 62.5 with sensitivity enhancements of 35.2- and 28.3-fold in calibration for each ion. A matrix effect was not observed (n: 3, for 50 μg L− 1 of each ion). The accuracy was validated by analysis of the two certified samples. The standard addition method after two sample pre-treatment procedures was successfully applied to determination of total Ag/Cu contents of edible vegetable oils, and the quantitative recoveries were obtained in the ranges of 87–94% with lower RSD than 6.8% after spiking with 10 μg L− 1.Öğe A New Enrichment Method for Quantification of 5-Hydroxymethylfurfural by Indirect Flame Atomic Absorption Spectrometry in Honey and Jam Samples(OXFORD UNIV PRESS INCJOURNALS DEPT, 2001 EVANS RD, CARY, NC 27513, 2021) Gürkan, RamazanBackground: Because of increasing amounts of 5-hydroxymethylfurfural (5-HMF) in processed foods and the complexity of the matrix, monitoring of trace 5-HMF requires accurate and reliable methods. Hence, an efficient sample pretreatment procedure is necessary for extraction and preconcentration of 5-HMF from the matrix. Objective: In this study, a new and efficient sample preparation method utilizing ultrasound-assisted-cloud point extraction (UA-CPE), indirectly followed by flame atomic absorption spectrometry (FAAS), was introduced for the monitoring of trace amounts of 5-HMF in honey and jam samples. Method: With this method, hydroxylamine was used as a derivatizing agent in the presence of Mn(II) and an anionic surfactant, SDS for extraction of 5-HMF at pH 9.0. For dispersing reagents in sample solution, low amounts of mixed surfactant, triton X-45 and SDS were mixed and fast-injected into the extraction media. A cloudy solution formed, and after reaction of 5-HMF with reagents, the cloudy solution was centrifuged. The extracted 5-HMF in the surfactant-rich phase was dissolved in acidic acetone and indirectly analyzed by FAAS. Results: The method showed a detection limit of 1.27 lg/L in linear working range of 4–240 lg/L, good precision (2.3–6.5%), and recovery rates (93.5–97%) after preconcentration of 70-fold. Conclusions: Within this study, an accurate and reliable method for the indirect quantification of 5-HMF in selected samples was successfully developed with a sensitivity improvement factor of 30.6. Highlights: The figures of merit for the developed indirect method were appropriate. The applicability of the method for the analysis of 5-HMF in processed foods was excellent.Öğe pH-controlled charge transfer sensitive 2-aminobenzimidazole modified poly(styrene-co-maleic anhydride) copolymer for selective extraction, pre-concentration and determination of trace Hg2+ and CH3Hg+ in vinegar by combination of ultrasound assisted-cloud point extraction with UV–VIS spectrophotometry(Elsevier, 8 July 2022) Zengin, Hacıbayram; Gürkan, RamazanIn this study, a separation/pre-concentration procedure, ultrasound assisted-cloud point extraction with modified 2-aminobenzimidazole (2-ABzI), was developed for the extraction of trace Hg2+ and CH3Hg+ and from vinegar samples- modified copolymer coupled with Hg-binding chelator, 2-ABzI. The imidic copolymer was characterized, and used for detection of the enriched Hg species by spectrophotometer at 332 nm. The method is based on their pH-induced charge transfer sensitive complexation with copolymer matrix via 2-AmBzI moiety at pH 6.0 and 4.5, and their extraction into the mixed micellar phase of the mixed non-ionic/ionic surfactants as extractant/sensitivity enhancer. The variables influencing the extraction efficiency were optimized. From preconcentration of 25-mL sample, with a changing calibration sensitivity and pre-concentration factor of 62.5, a good rectilinear relationship between absorbance and concentrations of Hg species in ranges of 1–15, 15–150 μg L... 1 was obtained. The detection limits are 0.30 and 0.31 μg L... 1, respectively. Its precision/accuracy were in range of 3.1–7.6 % and 90.5–96 % after spiking (n: 5, for measurements of 5, 25 and 100 μg L in same day and three consecutive days). The matrix effect was also studied (n: 3, 100 μg L... 1). The method is simple, costeffective, fast, accurate, safe, highly stable and selective, which has successfully been applied to the speciation of mercury in vinegar.Öğe Photocatalytic Decolourization of Bromophenol Blue in Aqueous Solution with Cu(II)-Peroxo Complexes in Presence of SDS(Taylor and Francis Ltd., 2016) Kartal Temel, Nuket; Gürkan, RamazanIn the current work, the photocatalytic decolourization of Bromophenol blue (BrPB) with Cu(II)-peroxo complexes in presence of sodium dodecyl sulfate (SDS) under UV light was investigated. The analytical parameters such as pH, titanium dioxide (TiO2) catalyst dosage, initial concentration of the dye, amounts of H2O2, Cu(II) and SDS affecting the photocatalytic decolourization of BrPB were studied. The obtained optimal values were as follows: pH 6.0, 55 mmol L-1 H2O2, 60 ?g L-1 Cu(II), 0.02 mmol L-1 SDS, 5 mg L-1 dye, 1.0 g L-1 TiO The percent removals have been obtained as 81.6% and 76.3% for TiO2 -UV-H2O2-Cu(II) system with and without SDS while they are 74.3% and 66.2% for TiO2-UV system with and without H2O2 under the optimized conditions. Consequently, it has been observed that the maximum removal rate is obtained for TiO2 -UV-H2O2-Cu(II) in presence of SDS at premicellar region with a value of 81.6%. The removal rate of the dye was monitored by measuring the absorbance at 592 nm, using UV-visible spectrophotometer. © 2016 Har Krishan Bhalla & Sons.Öğe Selective extraction and enrichment of 5-hydroymethylfurfural from honey, molasses, jam and vinegar samples prior to sensitive determination by micro-volume UV-vis spectrophotometry(CADEMIC PRESS INC ELSEVIER SCIENCE525 B ST, STE 1900, SAN DIEGO, CA 92101-4495, 2021) Dağdeviren Baş, Semahat; Gürkan, RamazanIn this study, a new method was developed for the extraction/enrichment of 5-hydroxymethylfurfural (5-HMF) from sample matrix prior to analysis. The method is based on the selective formation of the imine adduct and ionpair between 5-HMF and phenosafranine (weak base, PSF+) in the presence of sodium dodecyl sulfate (SDS) at pH 5.5 by the base induced disproportionation. Then, the complexes were enriched into the micellar phase of Triton X-114, diluted with ethanol, and detected at 532 nm by micro-volume UV–vis spectrophotometry. The variables affecting extraction efficiency were optimized. In optimal conditions, the calibration curves were over the range of 2... 100 and 2... 200 μg L... 1 with the detection limits of 0.53 and 0.75 μg L.. 1 using 0.2 and 3.0 mL of 1.0 × 10-3 mol L... 1 SDS. From enrichment of 15-mL sample, an enrichment factor of 37.5-fold was obtained. The accuracy/ precision studies after spiking were performed, and observed to be in range of 97.3–102.3 % and 2.5... 3.8% (10, 25 and 75 μg L.... 1, n: 5). After validation, the method was applied to the analysis of the selected foods. From the results, it was observed that 5-HMF levels were in the range of 1.05–18.10 mg kg... 1 with a RSD% of 3.0–4.2 % and recovery of 95.5–98.0 % by sample extraction with sonication while they ranged from 1.15–18.05 mg kg ..1 with a RSD% of 3.0–4.2 % and recovery of 95–99 % without sonication. Finally, it was observed that the results obtained were in agreements with those of the modified White method, statistically validating the method.Öğe Selenyumun katalizlediği (indikatör-redoks) tepkimelere dayalı olarak eser derişimde selenyumun kinetik-spektrofotometrik yöntemle belirlenmesi(Cumhuriyet Üniversitesi, 2002) Gürkan, Ramazan; Akçay, MehmetÖZET DOKTORA TEZİ SELENYUMUN KATALİZLEDİĞİ (İNDİKATÖR-REDOKS) TEPKİMELERE DAYALI OLARAK ESER DERİŞİMDE SELENYUMUN KİNETİK-SPEKTROFOTOMETRİK YÖNTEMLE BELİRLENMESİ Ramazan GÜRKAN Cumhuriyet Üniversitesi Fen Bilimleri Enstitüsü Kimya Anabilim Dalı Danışman: Prof. Dr. Mehmet AKÇAY Eser miktarlarda selenyumun belirlenmesi için basit ve duyarlı bir katalitik spektrofotometrik yöntem geliştirilmiştir. Yöntem, Maxilon Blue-SG'nin sodyum sülfür ile indirgenmesine selenyumun (Se(TV) olarak) katalitik etkisine dayanır. İndikatör tepkime, 30±0.1°C'Iık sabit sıcaklık ve Xnax=654 nm'de sabitlenmiş-zaman yöntemiyle absorbans değişimini ölçmek suretiyle spektrofotometrik olarak izlenmiştir. Selenyum, 0.205 ng Se(IV)/mL'lik bir gözlenebilme sınırıyla (3Sb) 0.002-0.2 ug Se(TV)/mL derişim aralığında nicel olarak belirlenmiştir. Tepkime hızım etkileyen değişkenler araştırılmış ve maksimum duyarlık veren optimum koşullar belirlenmiştir. Optimum koşullar altında katalizlenmiş ve katalizlenmemiş tepkimeler için hız sabitleri ve aktiflerime enerjileri belirlenmiştir. Ayrıca hız-belirleyici basamakta indikatör tepkimeye katılan türlerin yükleri çarpımı ve tepkime mekanizmasının aydınlatılması için birincil kinetik tuz etkisi araştırılmıştır. Geliştirilen yöntem, küçük laboratuarlarda kullanım için uygun, kolay, kesin, duyarlı ve seçicidir. 0.004, 0.016, 0.040 ve 0.160 ug Se(TV)/mL'lik standart selenyum derişimleri için yöntemin bağıl standart sapmaları (N=12) sırasıyla %2.27; %1.55; %1.51 ve %0.32'dir. Farklı anyon ve katyonların katalitik tepkimeye girişim etkilen incelenmiştir. Bir çok metal katyonunun sülfür iyonuna ilgisinden dolayı, girişimci katyonik türlerin uzaklaştırılması için Amberlite IR-120 plus gibi kuvvetli katyon değiştirici reçine ve elüent olarak da su kullanılmıştır. Katalitik tepkimenin seçiciliği katyon değiştirici reçine kullanılarak büyük oranda arttırılmıştır. Geliştirilen kinetik-katalitik yöntem, zenginleştirme olmaksızın Antioksidant-S, Selsun (kepeklenmeyi önleyici şampuan) ve analitik saflıkta sodyum metabisülfit ve ^S^**** +&*n kaplıca suyu örnekleri gibi gerçek örneklerdeki selenyumun belirlenmesine uygulanmıştır. Bu yöntemle, uygun standart eklemeler için kabul edilebilir geri kazanımlar elde edilmiştir. Anahtar Kelimeler: Selenyum, kinetik-katalitik yöntem, sabitlenmiş-zaman yöntemi, spektrofotometri, kaplıca suyu, sağlık-bakım ürünü.
