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Öğe A novel core-shell-based chromatographic method supported by ratio derivative spectrophotometry for the simultaneous determination of perindopril, indapamide, and amlodipine ternary mixtures(TUBİTAK, 2018) Karadurmuş, Leyla; Gümüştaş, Mehmet; Kurbanoğlu, Sevinç; Uslu, Bengi; Özkan, Sibel AyşılIn this work, ratio spectra of the frst derivative spectrophotometric and liquid chromatographic methods have been described for the frst time for the simultaneous determination of perindopril (PER), indapamide (IND), and amlodipine (AML) in dosage forms. For chromatographic separations several mobile phase compositions were tested for efcient separation with the use of a new column technology related to superfcially porous particles. Optimum chromatographic separation was achieved using a Kinetex C18 column (150 × 4.6 mm I.D. 5 ?m) at a flow rate of 1.5 mL min-1. The separation was carried out at 30 ° C and the diode array detector was adjusted to 215 nm. As a comparison, a spectrophotometric method depending on the frst derivative of the ratio spectra was developed. The frst derivative of the ratio amplitudes at 227.2 nm for PER, 269.4 nm for AML, 292.0 nm for IND were selected. The proposed methods were successfully applied for the simultaneous assay of the drug combination in pharmaceutical dosage forms and the methods were compared to each other in terms of Student t and F tests for the comparison of their accuracy and precision parameters. © 2018 TUBITAK. All rights reserved.Öğe A sensitive and selective RP-LC method for the simultaneous determination of the antihypertensive drugs, enalapril, lercanidipine, nitrendipine and their validation(2013) Kurbanoğlu, Sevinç; Gümüştaş, Mehmet; Uslu, Bengi; Özkan, Sibel AyşılA RP-LC method is presented, which is sensitive and selective for the simultaneous determination of enalapril-lercanidipine and enalapril-nitrendipine binary mixtures in their pharmaceutical dosage forms. The analyte peaks were detected using the LC method with the mobile phase ratio of methanol: water (70:30 v/v, pH 3.0) and a 1.0 mL min-1 flow rate. The detection wavelength was selected at 210 nm using photo diode array detector and column temperature was optimized to 30 C. Linearity was obtained at different concentration ranges for all working pharmaceutically active compounds between 0.5 and 25 ?g mL-1. The proposed methods were extensively validated according to USP 27 requirements and ICH guidelines. The methods were applied to the analysis of pharmaceutical dosage forms containing binary mixtures of enalapril-lercanidipine and enalapril-nitrendipine. Moreover, the proposed methods were applied for the degradation studies of the selected compounds. Degradation studies were conducted using stress conditions such as UV light, acidic and alkaline hydrolysis, oxidation and heat in oven, to evaluate the ability of the separation of the response of standard compounds from their degradation products. © 2013 Springer-Verlag Berlin Heidelberg.Öğe Development and validation of a stability-indicating RP-LC method for the determination of anticancer drug epirubicin in pharmaceuticals(Taylor and Francis Inc., 2014) Kurbanoğlu, Sevinç; Bozal Palabıyık, Burçin; Gümüştaş, Mehmet; Şanlı, Senem; Uslu, Bengi; Özkan, Sibel AyşılIn the present paper, sensitive, rapid, and different analytical methodology was developed for the determination of anticancer drug epirubicin (EPR). The mixture of epirubicin and moxifloxacin as internal standard was separated on a reversed phase Waters Spherisorb ODS1 column (250mm × 4.6mm × 5mm) using acetonitrile/water (30:70 v/v) mixture containing 15 mM phosphoric acid as mobile phase at 0.6 mL min-1 flow rate and 30 C. Also degradation studies were conducted as stress conditions of UV light, acidic hydrolysis, alkaline hydrolysis, oxidation, and heat in oven (100°C), to evaluate the ability of the proposed method for the separation of EPR from its degradation products. The validated method suggests routine analysis of EPR in differently equipped laboratories. © 2014 Copyright Taylor & Francis Group, LLC.Öğe Effect of Catalytically Active Zinc Oxide-Carbon Nanotube Composite on Sensitive Assay of Desloratadine Metabolite(Wiley-V C H Verlag Gmbh, 2020) Ozturk, Kubra; Bakirhan, Nurgul K.; Ozkan, Sibel A.; Uslu, BengiDesloratadine is one of the most effective second-generation antihistamines and the electrochemical behavior of the active agent of desloratadine was investigated with a new nanosensor designed with the addition of zinc oxide and multiwalled carbon nanotube (ZnO : MWCNT) mixture on glassy carbon (GCE). By investigating and using cyclic, differential pulse and square wave voltammetry techniques with ZnO : MWCNT/GCE, it is planned to obtain information about quantification and mechanism of desloratadine. The efficiency of experimental parameters such as pH, scan rate, accumulation potential and time on the anodic response of desloratadine were studied. Differential pulse voltammetry was selected as assay method and under developed method and optimized conditions, the current showed linear dependence with concentration in the range between 2x10(-8) and 8x10(-6) M in pH 5.5 acetate buffer. The achieved limits of detection (LOD) and quantification (LOQ) are 0.769 nM and 2.56 nM respectively. Applicability of the methods was demonstrated by their implementation in pharmaceutical dosage forms of desloratadine and the accuracy, precision, selectivity, sensitivity, intra-day and day-to-day reproducibility of the methods were clearly explored. Finally, this sensor was successfully applied on real sample as a selective, simple, reproducible, repeatable an electrochemical sensor.Öğe Effect of Polymer-Based Nanoparticles on the Assay of Antimicrobial Drug Delivery Systems(Elsevier Science Bv, 2017) Gumustas, Mehmet; Sengel-Turk, Ceyda T.; Gumustas, Aysen; Ozkan, Sibel A.; Uslu, Bengi[Abstract Not Available]Öğe Electroanalytical characteristics of antipsychotic drug ziprasidone and its determination in pharmaceuticals and serum samples on solid electrodes(Elsevier B.V., 2010) Kul, Dilek; Gümüştaş, Mehmet; Uslu, Bengi; Özkan, Sibel AyşılZiprasidone is a psychotropic agent used for the treatment of schizophrenia. Its oxidation was investigated electrochemically at boron-doped diamond and glassy carbon electrodes using cyclic, differential pulse, and square wave voltammetry. The dependence of the peak current and peak potentials on pH, concentration, nature of the buffer, and scan rate were examined. The process was diffusion and adsorption controlled for boron-doped diamond and glassy carbon electrodes, respectively. The possible mechanism of oxidation was discussed with some model compounds that have indole and piperazine oxidations. A linear response was obtained between 8 × 10-7 and 8 × 10-5 M for the first peak in acetate buffer (pH 5.5) and between 2 × 10-6 and 2 × 10-4 M for the second peak in 0.1 M H2SO4 with boron-doped diamond electrode for differential pulse and square wave voltammetric techniques. The reproducibility and accuracy of the proposed methods were found between 0.31 and 1.20, 99.27 and 100.22, respectively. The recovery studies were also achieved to check selectivity and accuracy of the methods. The proposed methods were applied for the determination of ziprasidone from pharmaceutical dosage forms and human serum samples without any time-consuming extraction, separation, evaporation or adsorption steps prior to drug assay except precipitation of the proteins using acetonitrile. The results were statistically compared with those obtained through an established LC-UV technique, no significant differences were been found between the voltammetric and LC methods. © 2010 Elsevier B.V. All rights reserved.Öğe Electroanalytical characterization of levodropropizine and its voltammetric determination in pharmaceuticals(2013) Ağın, Fatma; Karadaş Bakırhan, Nurgül; Uslu, Bengi; Özkan, Sibel AyşılLevodropropizine is a cough suppressant and easily oxidizable at the carbon-base electrodes. The electrooxidative behavior and determination of levodropropizine on glassy carbon and boron-doped diamond electrodes were investigated using cyclic, linear sweep, differential pulse, and square wave voltammetric methods. The dependence of the peak current and peak potentials on pH, concentration, nature of the buffer, and scan rate were examined. In this study, also simple and fully validated reverse phase-liquid chromatography (RP-LC) method for the assay of levodropropizine in syrup dosage form has been developed using X-Select RP-18 column (250x4.60 mm ID x ?5) at 25 °C with the mobile phase (containing 15 mM o-phosphoric acid) of acetonitrile:water (30:70, v/v) adjusted to pH 8.0. The proposed methods allow a number of cost and time saving benefits. Levodropropizine was also exposed to thermal, photolytic, oxidative stress, acid and base hydrolysis conditions, and the stressed samples were detected by the proposed LC method. The proposed methods were successfully applied for the determination of levodropropizine from pharmaceutical dosage forms. © 2013 Bentham Science Publishers.Öğe Electrochemical approach for the sensitive determination of anticancer drug epirubicin in pharmaceuticals in the presence of anionic surfactant(Editions de l'Academie Republique Populaire, 2013) Bozal Palabıyık, Burçin; Kurbanoğlu, Sevinç; Gümüştaş, Mehmet; Uslu, Bengi; Özkan, Sibel AyşılIn this research, sensitive, rapid, different electrochemical methods were developed for the determination of anticancer drug epirubicin. The aim of the study was to fully validated determination of epirubicin in pharmaceuticals, by means of electroanalytical methods. The detailed electrooxidative behavior of epirubicin was investigated using cyclic, differential pulse and square wave voltammetry at boron-doped diamond electrode. The possible oxidation mechanism was discussed. Surfactant effect was also examined using 1×10-3 M sodium dodecyl sulphate. The oxidation process was found nearly irreversible over the pH range studied and exhibited diffusion controlled electrode process. All experimental parameters have been optimized and the following studies were realized under the optimum conditions. The sensor used in this research is suitable for the analysis of the trace amounts of epirubicin in pharmaceuticals. The proposed methods were applied to commercial preparations and average percentage recovery was in good agreement between each other (differential pulse and square wave voltammetry).Öğe Electrochemical Approach on Mechanism of an Oral Progestin in Aqueous Media and its Fully Validated Detection via a Carbon-Metal Based Composite Sensor(Wiley-VCH Verlag, 2018) Karadaş Bakırhan, Nurgül; Baymak Çelik, Melek Şirin; Çelik, Hayati; Uslu, Bengi; Özkan, Sibel AyşılDienogest is a synthetic oral progestogen with unique pharmacological properties that is used orally in the treatment of endometrosis. The first time, the detailed electrochemical mechanism of dienogest is investigated in different aqueous mediums. Different progestins were used to understand completely oxidation mechanism. The electrochemical oxidation of dienogest was investigated systematically by cyclic voltammetry, differential pulse voltammetry, and square wave voltammetry. A simple adsorptive stripping square wave voltammetry method has been developed for the fully validated direct determination of dienogest in Visanne Tablets for the first time. Nano based sensor was fabricated with reduced graphene oxide, gold and carboxylic acid functionalized multi-walled carbon nanotube materials, and were used on glassy carbon electrode that performed sensitive and validated analysis of dienogest by adsorptive stripping square wave voltammetry. Validation parameters were investigated in detail. The results yielded good precision, accuracy and reproducibility. Calibration range was found as 2.00×10?7 M to 6.00×10?6 M, with LOD and LOQ values as 1.88×10?8 M and 6.27×10?8 M, respectively. In the future, the developed sensor can be applied in different media such as environment, soil and water for the detection of some progestins or hormones by researchers. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, WeinheimÖğe Erratum to: UPLC versus HPLC on drug analysis: advantageous, applications and their validation parameters(2013) Gümüştaş, Mehmet; Kurbanoğlu, Sevinç; Uslu, Bengi; Özkan, Sibel AyşılThe authors would like to call the reader’s attention to the fact that unfortunately there were several references faultily assigned in Table 1.Öğe Fully validated simultaneous determination of bisoprolol fumarate and hydrochlorothiazide in their dosage forms using different voltammetric, chromatographic, and spectrophotometric analytical methods(2013) Bozal Palabıyık, Burçin; Gümüştaş, Mehmet; Doğan Topal, Burcu; Uslu, Bengi; Özkan, Sibel AyşılVoltammetric, chromatographic, and spectrophotometric methods were developed for the simultaneous determination of bisoprolol fumarate (BIS) and hydrochlorothiazide (HCZ). Differential pulse and square wave voltammetry techniques were used to analyze BIS and HCZ simultaneously by measuring at about 1400 and 1100 mV, respectively. RP-HPLC was the second method for simultaneous analysis of the compounds. The mixture of BIS, HCZ, and moxifloxacin as an internal standard was separated on an RP Zorbax Eclipse XDB-C18 column (150 × 4.6 mm, id, 5 ?m particle size) using acetonitrile-15 mM phosphate (25 + 75, v/v) mobile phase at a 1.0 mL/min flow rate. The third method was based on first derivative of the ratio-spectra method obtained from the measurements of the amplitudes at 246 and 257 nm for BIS and HCZ, respectively. All the proposed methods were effectively applied for the simultaneous determination of BIS and HCZ in tablet dosage forms without any time-consuming extraction, sample preparation, or derivatization procedures.Öğe Functionalized carbon nanotubes - With silver nanoparticles to fabricate a sensor for the determination of zolmitriptan in its dosage forms and biological samples(2013) Karadaş Bakırhan, Nurgül; Bozal Palabıyık, Burçin; Uslu, Bengi; Özkan, Sibel AyşılA simple, sensitive and reproducible silver nanoparticle/multi walled carbon nanotubes modified glassy carbon electrode was developed as a sensor for the voltammetric determination of zolmitriptan with good accuracy and precision. The electrochemical behavior of zolmitriptan was investigated in detail using the proposed modified glassy carbon electrode. The results showed that the modified electrode significantly enhanced the oxidation peak current of zolmitriptan. Experimental conditions, such as pH, scan rate, accumulation time and potential, amount of silver nanoparticle and functionalized multi walled carbon nanotubes on the glassy carbon electrode were optimized for zolmitriptan assay. Under optimum conditions, the voltammetric determination of zolmitriptan was performed between the linear range of 1.00 × 10-8 and 8.00 × 10-7 M with a detection limit of 1.47 × 10-9 M. The developed method was successfully applied to the determination of the drug in tablets and human urine samples with good recoveries. The detection limit was found as 2.08 × 10-9 M for zolmitriptan in urine samples with a linear range of 1.00 × 10-8 to 1.00 × 10-7 M. No electroactive interferences from the tablet excipients and endogenous substances from biological material were found. The possible electrooxidation pathway and the number of transferred electrons were investigated in detail. Also, controlled potential coulometric experiments were carried out. © 2013 Elsevier B.V.Öğe Investigation of voltammetric behavior and electroanalytical determination of anticancer epirubicin via glassy carbon electrode using differential pulse and square wave voltammetry techniques(Editions de l'Academie Republique Populaire, 2015) Kurbanoğlu, Sevinç; Bozal Palabıyık, Burçin; Gümüştaş, Mehmet; Uslu, Bengi; Özkan, Sibel AyşılThe electrochemical oxidation of epirubicin was investigated using cyclic, differential pulse and square wave voltammetry at glassy carbon electrode. The aim of the study was to determine epirubicin levels in pharmaceuticals via electrochemical methods. The oxidation process was quasi-reversible over the pH range studied and exhibited diffusion controlled electrode process. All experimental parameters have been optimized under the optimum conditions. The oxidation peak current was linearly proportional to the concentration of epirubicin in the range of 2×10-7-3.6×10-5 M with a detection limit of 4.1×10-8 M and 4.9×10-8 M by differential pulse and square wave voltammetry, respectively. These unique properties make the sensor suitable for the analysis of the trace amounts of epirubicin in pharmaceutical preparations. The proposed methods were applied to commercial preparations. Differential pulse and square wave voltammetry techniques were compared with t-test and F-test.Öğe Nanosized Drug Carriers for Oral Delivery of Anticancer Compounds and the Importance of the Chromatographic Techniques(Elsevier, 2017) Şengel Türk, Ceyda Tuba; Gümüştaş, Mehmet; Uslu, Bengi; Özkan, Sibel AyşılCancer is the primary leading cause of mortality in the world. The key of a successful cancer treatment depends on many important parameters, such as the application route, anticancer compound, and dosage form. Among the administration routes, oral application is the most widely used application method. However, oral administration of many molecules as conventional dosage forms is limited due to a major problem-low bioavailability. Nanoscale drug delivery systems can ensure oral administration and improve the oral bioavailability of the drugs. Determination of the chemotherapeutically active molecules from the developed nanoscale systems has an important role in the effectiveness of the nanoparticles. Chromatographic techniques, especially liquid chromatography, are very suitable and accurate ways to determine the content of a pharmaceutical ingredient and its stability in both in vitro and in vivo systems. This chapter describes the importance of lipid- and polymer-based nanoscale drug delivery technologies of the anticancer molecules and summarizes the effect and type of the nanostructures, characterization parameters, analysis parameters, such as column types and mobile phase compositions, and validation parameters. © 2017 Elsevier Inc. All rights reserved.Öğe Polarographic investigation of dienogest(Electrochemical Society Inc., 2018) Baymak Çelik, Melek Şirin; Çelik, Hayati; Karadaş Bakırhan, Nurgül; Uslu, Bengi; Özkan, Sibel AyşılDienogest (DGN), is an orally administered synthetic progestin that has shown to have selective progesterone receptor (PR) agonistic activity and oral progestational potency on endometrium. In this paper, the investigation of electrochemical reduction of Dienogest on dropping mercury electrode (DME) is achieved and resulted in a reduction scheme that involves a two electron reduction of 3-keto-delta-4-group in the A-ring of the molecule. This observation is supported by comparison of the compound with model compounds of testosterone and norethisterone. In this study, electrochemical determination of the compound and its validation is also studied by differential pulse polarograhy (DPP). The results yielded good precision, accuracy and reproducibility. Calibration range was found as 2.00 × 10-6M to 1.00 × 10-4M, with LOD and LOQ values as 0.58 × 10-6M and 1.90 × 10-6M, respectively. © 2018 The Electrochemical Society.Öğe Simple and sensitive adsorptive stripping voltammetric assay of granisetron from its dosage form by platinum nanoparticles modified electrodes(Elsevier B.V., 2017) Doulache, Merzak; Karadaş Bakırhan, Nurgül; Uslu, Bengi; Saidat, Boubakeur; Trari, Mohamed; Özkan, Sibel AyşılBase to the interfacial adsorptive nature of granisetron (GRN) on platinum particles modified glassy carbon electrode (PtPs/GCE). A sensitive analytical method for trace analysis of GRN based on the adsorptive stripping technique has been developed. The application of a square wave mode for the stripping of adsorbed GRN has proved to be much more sensitive compared to differential pulse scan. A study of the variation in the peak current with solution variables such as pH, concentration of granisetron, possible interference, and instrumental variables, such as accumulation time and accumulation potential, has resulted in the optimization of the oxidation signal for analytical purposes. Under the optimized conditions, the square wave peak current showed two linear ranges of GRN concentration: 0.01–0.5 ?M and 0.5–25 ?M with correlation coefficients of 0.997 and 0.998, respectively. Nanomolar detection limit was obtained as 1.95 nM for the first linear range. Possible interferences by substances usually present in the pharmaceutical formulations were also evaluated. The proposed electrochemical procedure was successfully applied for the determination of GRN in pharmaceutical injection samples (SETRON® 3 mg/3 mL) with average recovery of 100.30%. © 2017 Elsevier B.V.Öğe Simultaneous determination of amlodipine besylate and rosuvastatin calcium in binary mixtures by voltammetric and chromatographic techniques(Institute for Ionics, 2016) Karadaş Bakırhan, Nurgül; Gümüştaş, Mehmet; Uslu, Bengi; Özkan, Sibel AyşılVoltammetric and liquid chromatographic (LC) methods have been developed for the simultaneous determination of amlodipine besylate (AML) and rosuvastatin calcium (ROS) for the first time. Detailed electrochemical behavior and simultaneous voltammetric determination of AML and ROS were investigated in detail using glassy carbon electrode (GCE). High-performance liquid chromatography (HPLC) and ultra-performance liquid chromatography (UPLC) were also developed for the comparison. Voltammetric method exhibited linear dynamic responses for the simultaneous assay of AML and ROS in the concentration range between 0.006 and 2.85 ?g/mL and between 0.01 and 5.00 ?g/mL, with detection limits of 0.001 and 0.003 ?g/mL, respectively. On the other hand, LC methods presented a wider linearity range than that of the SWV method between 0.5 and 100 ?g/mL with the detection limits of 0.011 and 0.027 ?g/mL for AML and 0.034 and 0.042 ?g/mL for ROS by UPLC and HPLC techniques, respectively.Öğe The Role and the Place of High-Performance Liquid Chromatography for the Determination of Fermented Dairy Products(Academic Press Ltd-Elsevier Science Ltd, 2017) Gumustas, Mehmet; Uslu, Bengi; Ozkan, Sibel A.[Abstract Not Available]Öğe UPLC versus HPLC on drug analysis: Advantageous, applications and their validation parameters(2013) Gümüştaş, Mehmet; Kurbanoğlu, Sevinç; Uslu, Bengi; Özkan, Sibel AyşılLiquid chromatography (LC) is a separation technique used in many different areas to aid the identification and quantification of substances in various matrices. LC techniques with various detection modes have been widely used for the sensitive and selective determination of trace amounts of pharmaceutical active compounds in biological samples and their dosage forms. A completely new system design with advanced technology has been developed, called ultra high performance liquid chromatography, which has evolved from high performance liquid chromatography. The application of LC methods to drug analysis introduces a powerful tool for therapeutic drug monitoring as well as for clinical research. The advantages of short turnaround time, method reliability, method sensitivity, and drug specificity justify the use of LC techniques for various groups of the drug active compounds. This review describes some of the principles of ultra high performance liquid chromatography and high performance liquid chromatography, validation of these methods, system suitability tests for the methods, and application of methods to pharmaceutical analysis in the last 3 years. © 2013 Springer-Verlag Berlin Heidelberg.Öğe Voltammetric Analysis of Thiram with Bimetallic Nanosensor and Investigation of Adsorption Mechanism by DFT-D3 Method(ELECTROCHEMICAL SOC INC, 2023) Çelik, Murat; Kanbeş Dindar, Çiğdem; Karayel, Arzu; Bozal Palabıyık, Burçin; Uslu, BengiIn this study, to detect thiram electrochemically, a simple nanosensor based on a glassy carbon electrode (GCE) modified with green-synthesized Ag and Au nanoparticles was designed. AuNPs@AgNPs/GCE nanosensor gave considerably greater signal for 5 ppm thiram in pH 3.0 phosphate buffer solution using adsorptive stripping differential pulse voltammetry compared to bare GCE. Under ideal conditions, the nanosensor produced a linear concentration calibration curve extending from 0.2 to 1.4 ppm for thiram, with limits of detection and quantification of 0.033 ppm and 0.100 ppm, respectively. The developed electrochemical bimetallic nanosensor demonstrated high sensitivity and stability, showing that it is a novel and promising platform for thiram determination. Furthermore, the nanosensor was used to assess thiram in human serum and recovery was obtained as 103.6%. DFT-D3 results showed that covalent modification of GCE with AuNPs/AgNPs occurs with the electron transfer between the electrode surface and thiram by bonding sulfur atoms of thiram to AgNPs and AuNPs. Both experimental and theoretical analyses showed that the modification with Ag and Au, GCE appeared to be a key property to improve the electronic activity at the surface and increase the charge transfer that facilitates the adsorption of the selected guest.
