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Öğe Determination of seven synthetic colourants in pharmaceutics, foods, and beverages by a validated HPLC-PDA method: A risk assessment study(Academic Press Inc., 2024) Tamer, Fatma Selen; Oymak, Tülay; Dural, EmrahA simple, rapid, sensitive and reliable high-performance liquid chromatography method based-on ultraviolet determination was developed and validated for the simultaneous determination of the tartrazine-TR, sunset yellow-SY, ponceau-4R P4R, allura red-AR, patent blue-PBV, brilliant blue-BB, erythrosine B-EB. The limit of detections were found as ?0.083 µg/mL, determination coefficiencies were found as ?0.999 in the range of 0.5 – 20 µg/mL for all colourants. Precision was ?6.75 (RSD) and accuracy was between (-6.52) and 6.80 (RE%). This developed analytical method was successfully used to quantitatively detect the presence of these synthetic colourants in confectionery (n = 13), beverages (n = 12) and pharmaceutical products (n = 13) and a risk assessment was made based on the lowest exposure scenario. The risk index values determined in confectionery range between 0.10 and 5.78 (1.46 ± 1.52, mean ± SD), in beverages range between 0.001 and 2.79 (0.034 ± 0.082The risk index of five of the monitored confectionery samples (38.50 %) was determined to be above one in terms of the relevant food dyes. © 2024 Elsevier Inc.Öğe Determination of Sulfadiazine in Natural Waters by Pine Needle Biochar – Derivatized Magnetic Nanocomposite Based Solid-Phase Extraction (SPE) with High-Performance Liquid Chromatography (HPLC)(06.04.2022) Avcı, Remziye Nur; Oymak, Tülay; Bağda, EsraA magnetic solid-phase extraction (MSPE) method was developed forthe facile and sensitive determination of sulfadiazine prior to high-performance liquid chromatography (HPLC) analysis. The magneticsorbent was prepared by the chemical co-precipitation of Fe3O4magnetic nanocomposites modified with biochar. Characterization ofthe synthesized Fe3O4@BC-PN (Fe3O4loaded pine leaves derived bio-char) was performed by scanning electron microscopy–energy dis-persive x-ray spectrometry (SEM-EDS), X-ray diffraction (XRD),vibrating sample magnetometry (VSM), and Brunauer–Emmett–Teller (BET) surface analysis. The saturation magnetization value was17.95 emu/g by vibrating sample magnetometry. The Fe3O4@BC-PNparticle sizes were determined to be 11.8 nm using the Debye-Scherrer relationship. The pH, mass of adsorbent, type, and volumeof eluent were optimized. The limits of detection and quantificationof the developed MSPE HPLC method were 10.7lg/L and 35.5lg/L,respectively. The intra-day and inter-day repeatabilities were below4.2% and 7.7%, respectively. The developed method was employedto determine trace levels of sulfadiazine in spiked water samplÖğe Development of quantum dot-phthalocyanine integrated G-quadruplex /double-stranded DNA biosensor(Academic Press Inc., 2022) Topcu, Ayşe; Bağda, Esra; Oymak, Tülay; Durmuş, MahmutIn the present study, the phthalocyanine (Pc) integrated mercaptopropionic acid capped quantum dot (mpa@QD) biosensor has been developed for the quantitative determination of G-quadruplex and double-stranded DNA. The working principle of the developed biosensor platform is based on the quenching of the emission signal of the mpa@QD in the presence of Pc (closed position) and the recovery of the fluorescence signal in the presence of DNA (open position). The parameters affecting biosensor performance, such as Pc type and concentration, were optimized. Since the developed biosensor aimed to determine G-quadruplex and double-stranded DNA in biological samples, the effect of common ions (such as Na+, Mg2+) and serum albumin found in many biological matrices on the biosensor performance were examined. The effect of common ions on biosensor signal was negligible, except Zn2+. The analytical properties of the biosensor, such as linear range, calibration sensitivity, relative standard deviation %, the limit of detection, and quantification, were determined. The limit of detection and quantification values were found 0.055 ?M and 0.18 ?M for AS1411, 0.061 ?M and 0.20 ?M for Tel21, 0.038 ?M and 0.13 ?M for Tel45 and 0.091 ?M and 0.30 ?M for ctDNA. Several different synthetic samples were prepared. The spiked synthetic samples such as mammalian cell medium were used to evaluate the analytical performance of Pc-mpa@QD. All synthetic samples were prepared with polyethylene glycol, which resembles biological samples' crowded environment. © 2022 Elsevier Inc.Öğe Development of quantum dot-phthalocyanine integrated G-quadruplex/double-stranded DNA biosensor(1 October 2022) Topcu, Ayşe; Bağda, Esra; Oymak, Tülay; Durmuş, Mahmutn the present study, the phthalocyanine (Pc) integrated mercaptopropionic acid capped quantum dot (mpa@QD) biosensor has been developed for the quantitative determination of G-quadruplex and double-stranded DNA. The working principle of the developed biosensor platform is based on the quenching of the emission signal of the mpa@QD in the presence of Pc (closed position) and the recovery of the fluorescence signal in the presence of DNA (open position). The parameters affecting biosensor performance, such as Pc type and concentration, were optimized. Since the developed biosensor aimed to determine G-quadruplex and double-stranded DNA in biological samples, the effect of common ions (such as Na+, Mg2+) and serum albumin found in many biological matrices on the biosensor performance were examined. The effect of common ions on biosensor signal was negligible, except Zn2+. The analytical properties of the biosensor, such as linear range, calibration sensitivity, relative standard deviation %, the limit of detection, and quantification, were determined. The limit of detection and quantification values were found 0.055 μM and 0.18 μM for AS1411, 0.061 μM and 0.20 μM for Tel21, 0.038 μM and 0.13 μM for Tel45 and 0.091 μM and 0.30 μM for ctDNA. Several different synthetic samples were prepared. The spiked synthetic samples such as mammalian cell medium were used to evaluate the analytical performance of Pc-mpa@QD. All synthetic samples were prepared with polyethylene glycol, which resembles biological samples' crowded environment.Öğe Removal of a toxic basic dye-malachite green from aqueous solution by Onopordum turcicum Danin as natural biosorbent(2018) Eruygur, Nuraniye; Oymak, TülayBiosorption of malachite green (MG) was studies using natural origin adsorbent Onopordum turcicum Danin.Batch adsorption studies were carried out to evaluate the potentiality of O. turcicum for the removal of malachite greendye from wastewater, on different parameters such as pH, adsorbent dose, contact time and initial MG concentration.The effective pH was 8.0 for adsorption of MG by the biomass. The equilibrium isotherm was analyzed with theLangmuir and Freundlich models of adsorption. The biosorption data of MG on Onopordum turcicum Danin was fittedwith Langmuir model with a maximum adsorption capacity was 1110.1 mg/g. The acquired results show that O.turcicum was effective in removal of MG dye from aqueous solution.Öğe Sütteki Sülfonamidlerin Tayini için Yeni bir Yüksek Performanslı Sıvı Kromatografisi Yönteminin Geliştirilmesi ve Valide Edilmesi(2024) Oymak, TülayBu çalışmada sülfonamidler (SAs) grubunda bulunan sülfadiazin (SDZ), sülfamerazin (SMR) ve sülfometaksazol’ün (SMX) süt numunelerinde analizi için hızlı, hassas ve basit bir yüksek performanslı sıvı kromatografi (HPLC) yöntemi geliştirilmiş ve valide edilmiştir. SDZ, SMR ve SMX’in sütten ekstraksiyonunda protein çöktürme yöntemi kullanılmıştır. Protein çöktürme yönteminde çöktürücü reaktif türü ve miktarı optimize edilmiştir. Çalışma matriks etkisinin analizlere olan etkisinin gözlemlenmesi amacıyla tüm validasyon parametreleri süt numuneleri kullanılarak çalışılmıştır. Yöntemin validasyonunda ICH klavuzu uyarınca doğrusallık, sağlamlık, doğruluk ve kesinlik testleri gerçekleştirilmiştir. Süt numunelerinde sülfonamidlerin tayini için geliştirilen yöntemin gözlenebilme sınırları (LOD) SDZ, SMR ve SMX için sırasıyla 0.11, 0.10 ve 0.14 µg/mLve tayin sınırları (LOQ) 0.34, 0.30 ve 0.43 µg/mL’dir. SAs’lerin sütteki ortalama geri kazanımları ≥ %93.0±4.4’tür. Yöntemin gün içi ve günler arası tekrarlanabilirliğini % bağıl standart sapma cinsinden sırasıyla ≤ %6.0 ve ≤% 5.4’dir. Geliştirilen yöntem doğru ve güvenilir olup gıda kontrol ve toksikolojik analiz laboratuvarlarında süt numunelerinin içeriğindeki SAs'lerin rutin analizi için kullanılabilir.Öğe The synthesis and characterization of iron nanoparticles with lemon peel and its use in magnetic solid phase extraction for trace levels of lead (II)(Springer, 03/03/2022) Çakmak, Emre; Oymak, TülayIn this study, a new magnetic solid phase extraction method (MSPE) was developed for the enrichment and separation of trace amount Pb(II) on the magnetic nanoparticles synthesized using lemon peel ( Fe3O4-LP). The determination of Pb(II) in the samples was performed with inductively coupled plasma mass spectrometry. The Fe3O4- LP was characterized by scanning electron microscopy, X-ray powder diffractometry, Brunauer–Emmett–Teller surface area analysis, and vibration sample magnetometry. The effect of different parameters such as pH, adsorption and elution time, concentration of eluent and volume and matrix effect on the recovery of Pb(II) was investigated for the MSPE. Considering preconcentration factor, the detection limit value of the proposed method was calculated to be 39 ng/L for Pb (II). The accuracy of the developed method was tested with analysis of the BCR 185 R Bovine Liver and 2976a Mussel Tissue certified reference materials. The results were in good agreement with the certified values.
