Profile Picture


Organizational Units

Job Title

First Name


Last Name



Email Address

Birth Date

Search Results

Now showing 1 - 10 of 14
  • Publication
    Simultaneous determination of hydrochlorothiazide, amlodipine, and telmisartan with spectrophotometric and HPLC green chemistry applications.
    (2022-06-03T00:00:00Z) Tiris, GİZEM; Mehmandoust, Mohammad; Lotfy, Hayam M; Erk, Nevin; Joo, Sang-Woo; Dragoi, Elena-Niculina; Vasseghian, Yasser; TIRIS, GİZEM
  • Publication
    Determination of active ingredients in antihypertensive drugs using a novel green HPLC method approach
    (2022-09-01T00:00:00Z) TIRIS, GİZEM; Mehmandoust, Amirhossein; Karimi, Fatemeh; ERK, NEVİN; TIRIS, GİZEM
    © 2022 Elsevier LtdA novel, sensitive, fast, and pratic RP-HPLC methods were presented for the quantitative amounts of Telmisartan (TEL) and Olmesartan (OLM) in the presence of Amlodipin (AML) in a binary mixture of pharmaceutical preparation. Waters Spherisorb ODS-2 C18 column was used for separation. These methods were valid over linearity ranges of 2.5–30 μμg/mlL, 2–85 μμg/mlL, and 2–35 μμg/mlL for OLM, TEL, and AML, respectively. The mobile phase system consisted of acetonitrile:methanol: phosphate buffer at pH 3.0 (65:5:30 v/v/v), and the flow rate was 1,5 mlL/min for OLM and AML. The mobile system-s other mixture (TEL and AML) was acetonitrile:methanol: phosphate buffer at pH 2.5 (65:5:30 v/v/v), and the flow rate was 1,5 mlL/min. These procedures were successfully applied to bulk, laboratory synthetic mixture, and medicinal dosage forms to use active ingredients quantitatively. The studied methods were validated according to ICH guidelines. In the developed HPLC method, the limit of detection values was found to be 0.020 μμg/mlL for TEL, 0.025 μμg/mlL for OML, and 0.070 μμg/mlL for AML. The correlation coefficients for the HPLC method were found to be 0.9938 for TEL, 0.9996 for OML, and 0.9982 for AML. The calibration range is between 2.5 and -30, 5–35, and 2–85 μμg/mlL for OLM, AML, and TEL, respectively. The proposed HPLC method is a convenient, effective, sensitive, green, and time-saving method for the rapid determination of TEL and OLM in the presence of AML.
  • Publication
    Novel approaches for determination of antiretroviral reverse transcriptase inhibitor agent in commercial dosage forms by using spectrofluorimetric, first derivative spectrophotometric, and HPLC methods
    (2020-09-01T00:00:00Z) Tiris, Gizem; Ciloglu, Emine; ERK, NEVİN; TIRIS, GİZEM
    Background: Rapid, simple, and sensitive spectrofluorimetric, first derivative spectrophotometric, and high-performance liquid chromatographic (HPLC) methods have been developed and validated for determination of tenofovir in pharmaceutical preparations. Spectrofluorimetric method is based on measuring the native fluorescence intensity of tenofovir at 375.0 nm after excitation at 275.0 nm. Calibration graphics were plotted and were found linear over 4.72-15.75 mu g/mL concentration range (r(2)= 0.9994). The second method developed was the first derivative spectrophotometric method for the analysis of tenofovir performed by measuring the amplitude at 251.7 and 272.6 nm. Linearity was observed in the concentration range 10.0-28.0 mu g/mL (r(2)= 0.9998). On the other hand, HPLC with a diode array detector (DAD). Ritonavir was used as internal standard (IS). HPLC analysis was carried out on a C(18)column (Wakosil-II 5 C-18 AR, 4.6 x 250 mm) using a mobile phase consisting of acetonitrile: 0.5% formic acid (99.5:0.5; v/v) at a flow rate of 1.0 mL/min. Injection volume was 5.0 mu L. DAD signals at 260.0 nm were used. HPLC method was found to be linear over the concentration range of 10.0-100.0 mu g/mL (r(2)= 0.9990).
  • Publication
    A novel stability-indicating method for determination of a new antidepressant effect of vortioxetine in a pharmaceutical formulation by using RP-HPLC
    (2020-12-01T00:00:00Z) TIRIS, GİZEM; Alver, Cansu; ERK, NEVİN; TIRIS, GİZEM
    Background: A novel rapid, accurate, and stability-indicating reversed-phase high performance liquid chromatographic (RP-HPLC) and first derivative spectrophotometric determination were explained for the assay of vortioxetine (VRT) in bulk and pharmaceutical formulations. For RP-HPLC method, optimal separation and determination of VRT were achieved with a Waters Symmetry C-18, (100 x 4.6 mm, 3.5 mu m) analytical column using a mobile phase consisting of methanol:0.05 M potassium dihydrogen phosphate (pH:3.0 +/- 0.05) (30:70, v/v) in isocratic mode with flow rate of 1.3 mL min(-1). Injection volume was 20 mu L. The maximum absorption wavelength of VRT is 225.0 nm; hence, 225.0 nm was studied as the detection wavelength and column at 50 degrees C temperature. The caffeine was used as the internal standard (IS). On the other hand, the first derivative spectrophotometric method for the analysis of vortioxetine was performed by measuring the amplitude at 251.7 and 272.6 nm.
  • Publication
    A sensitive voltammetric sensor for specific recognition of vitamin C in human plasma based on MAPbl(3) perovskite nanorods
    (2022-01-01T00:00:00Z) TIRIS, GİZEM; Khoshnavaz, Yasamin; Oven, Elif Naz; Mehmandoust, Mohammad; ERK, NEVİN; TIRIS, GİZEM
    A novel and sensitive electrode was suggested for the rapid determination of ascorbic acid (AA) using a glassy carbon electrode (GCE) modified with synthesized MAPbl(3) and L-cys (L-cys/MAPbl(3)/GCE). Determination of ascorbic acid as an important component of the human diet due to help in decreasing blood pressure and improving endothelial function is crucial. The synthesized MAPbl(3) was characterized by different methods, including transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The fabricated electrode exhibited superior electrical conductivity and fast electron transfer kinetics. The results illustrated that the developed electrode had an outstanding electrocatalytic activity towards the oxidation of AA in 0.1 M Britton-Robinson buffer(B-R) as a supporting electrolyte. The modified electrode demonstrated a linear range in differential pulse voltammetry of 0.02-11.4 mu M with a low detection limit of 8.0 nM for ascorbic acid. It can be stated that the proposed sensor can be successfully applied to the determination of ascorbic acid in human plasma samples.
  • Publication
    Trade-off efficacy and data processing strategy in the power of spectral resolution of co-formulated antihypertensive pharmaceuticals
    (2021-02-01T00:00:00Z) Rostom, Yasmin; Lotfy, Hayam M.; Ozturk, Meltem; Tiris, Gizem; ERK, NEVİN; Saleh, Sarah S.; TIRIS, GİZEM
    Versatile, extraction-free univariate spectrophotometric methods have been modified to get effective spectral resolution of mixtures in accordance with their feature challenges. The proposed methods have been applied and validated for analyzing some antihypertensive medicines in their co-formulated medicinal products. Two mixtures have been used: the first one [Mix I (OLM/ADB)] is composed of Olmesartan medoxomil (OLM) and Amlodipine besylate (ADB) with partly-overlapped spectra while the second [Mix II (TEL/HCT)] is made up Telmisartan (TEL) and Hydrochlorothiazide (HCT) with total-overlapped spectra. Induced dual wavelength, absorbance correction and ratio subtraction coupled with constant multiplication methods were applied to Mix I (OLM/ADB), while dual wavelength, advanced absorbance subtraction and constant center coupled with spectrum subtraction methods were applied to Mix II (TEL/HCT). Calibration graphs were established with good correlation coefficients. The methods exhibit significant advantages as simplicity, sensitivity, minimal data manipulation besides optimum robustness. Selectivity was inspected using lab-mixtures with diverse ratios. Accuracy, precision and repeatability were found to be within the acceptable limits. The proposed methods are good enough to be used for co-assay of analytes in combined forms without any interfering from excipients. Moreover, all results were estimated in accordance with ICH criteria and successfully compared with those of the reported methods applying t-test and F-test at 95% confidence level. Generally, these methods can be used efficiently for routine quality control testing. (C) 2020 Elsevier B.V. All rights reserved.
  • Publication
    A New HPLC Method with UV Detection for the Determination of Carnosol in Human Plasma and Application to a Pharmacokinetic Study
    This article aims to present a simple and sensitive, HPLC-UV method, which was developed to determine carnosol in human plasma samples. Chromatographic separation was achieved with C18 column (150 mm x 4.6 mm x 5 mu m), at 25 degrees C with gradient elution of the mobile phase consisting of methanol-water (2% o-phosphoric acid) at flow rate 1.2 mL/min. The analyte was detected at 230 nm by UV detector. The retention time of carnosol is 3.40 +/- 0.01 min. This currently developed method was validated according to ICH criteria by evaluating the specificity, linearity, precision, accuracy and robustness. The method was determined to be linear in a concentration range of 1-20 ng/mL with the correlation coefficient of 0.9942. The proposed method was applied successfully to the analysis of carnosol in spiked human plasma with good recovery as 96.4% and the precision of the method was determined by intra day and interday assays with the highest RSD % values 5.71. The method successfully applied to a pharmacokinetic study with determination of C-max, t(max), t(1/2) and AUC, by administration of carnosol to a healthy volunteer.
  • Publication
    Analytical tools for greenness assessment of chromatographic approaches: Application to pharmaceutical combinations of Indapamide, Perindopril and Amlodipine
    (2020-12-01T00:00:00Z) Saleh, Sarah S.; Lotfy, Hayam M.; Tiris, GİZEM; Erk, Nevin; Rostom, Yasmin; TIRIS, GİZEM
    The green profile of the proposed method was assessed and compared with reported classical methods via four tools of greenness which are: Eco-Scale, National Environmental Methods Index (NEMI), Assessment of Green Profile (AGP) and Green Analytical Procedure Index (GAPI). A simple, precise and rapid (RP-HPLC) has been developed for the quantification of Indapamide (IND), perindopril (PER) arginine and amlodipine besylate (ADB) in binary and ternary mixtures. A greener alternate RP-HPLC method was presented for the determination of pharmaceutical combinations composed of the cited medications using an eco-friendly eluent and quick run time with the least waste yield. Chromatographic separation was achieved using Waters Spherisorb ODS-2 C18 column (150 x 4.6 mm, i.d., 5 mu m) and eluent formed of acetonitrile : phosphate buffer (20 mM, pH = 3): methanol in the ratio of (65: 30: 5, by volume) at flow rate 1.0 mL/min with DAD-detection at 220 nm. This procedure was valid over linearity ranges of 0.5-20 mu g/mL, 2.5-40 mu g/mL and 2-40 mu g/mL for IND, PER and AML, respectively. The presented chromatographic method was completely validated regarding ICH guidelines and were statistically compared with those of the reported methods applying t-test and F-test at 95% confidence. The proposed method was found to be greener in terms of usage of hazardous chemicals and solvents, energy consumption, and waste production.
  • Publication
    Ultra fast liquid chromatographic analysis of nonsteroidal anti-inflammatory drugs with fluorimetric detection in tap water, urine, and pharmaceutical samples
    (2022-06-01T00:00:00Z) Onal, Cem; TIRIS, GİZEM; Tekkeli, Evrim Kepekci; Onal, Armagan; TIRIS, GİZEM; TEKKELİ, ŞERİFE EVRİM
    A novel analytical method based on ultra-fast liquid chromatography using fluorimetric detector was developed and validated for determination of non-steroidal anti-inflammatory drugs (NSAIDs) (ibuprofen (IBP), etodolac (ETD), dexketoprofen (DKP), sodium diclofenac (SDCF), and naproxen (NPX) in tap water, urine and pharmaceutical samples. Precolumn derivatisation of targeted NSAIDs was carried out with 4-bromomethyl-7-methoxy coumarin (BrMmC) using dibenzo-18-crown-6-ether as reaction catalyst leading to the formation of a fluorescent compound. The obtained fluorescent compound of NSAIDs were measured at excitation wavelength as 325 nm, and emission wavelength of 395 nm. Optimum analytical conditions were carefully studied and improved. C18 column, with the dimensions of 4.0 x 100 mm and 3 mu m particle size, was used. Gradient elution with methanol: water 40:60; v/v (eluent A) and acetonitrile 100% (eluent B) were used as mobile phase and flow rate of 0.4 mL/min. The linearity range of the analytes were between 0.01-10.0 mu g mL(-1). Recovery values obtained from pharmaceutical preparations were found as 100.04%, 99.99%, 100.09%, 99.98% and 100.47% for IBP, ETO, DKP, SDCF, NPX, respectively. LOD values were found to vary between 0.00009 mu g mL(-1) and 0.00048 mu g mL(-1) in tap water, urine and pharmaceutical samples. The optimised technique was successfully applied for the determination of NSAIDs in tap water, urine, and pharmaceutical specimen. The specified NSAIDs were not found in real tap water samples.
  • Publication

    A reusable and sensitive electrochemical sensor for determination of idarubicin in environmental and biological samples based on NiFe2O4 nanospheres anchored N-doped graphene quantum dots composite; an electrochemical and molecular docking investigation

    (2022-09-01T00:00:00Z) Mehmandoust, Mohammad; Pourhakkak, Pouran; TIRIS, GİZEM; Karimi-Maleh, Hassan; ERK, NEVİN; TIRIS, GİZEM
    An ultrasensitive and selective voltammetric sensor with ultra-trace level detection limit is introduced for idarubicin (IDA) determination in real samples. The as-synthesized nanocomposite was characterized by several techniques, including Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Raman spectroscopy, Energy-dispersive X-ray spectroscopy (EDX), and Field emission scanning electron microscopy (FESEM). The electrocatalytic performance of the developed electrode was observed by cyclic voltammetry (CV), differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS), and chronoamperometry. The limit of detection (LOD) of the developed sensor for idarubicin is 1.0 nM, and the response is found to be in the dynamic concentration range of 0.01-1.9 mu mol/L in a Britton-Robinson buffer (B-R, pH = 6.0). Moreover, the fabricated electrode illustrated high selectivity with good repeatability and reproducibility for diagnosing idarubicin as an anthracycline antileukemic drug. Furthermore, to evaluate the validity of the recommended method, three real samples, including human plasma, urine, and water samples, were analyzed with satisfactory recovery and compared with high-performance liquid chromatography (HPLC). The minor groove-binding mode of interaction was also supported by docking simulation studies, emphasizing that IDA can bind to ds-DNA preferably and confirmed experimental results. The reduced assay time and the possibility of measuring a single sample with another anticancer drug without any interference are significant advantages compared to the HPLC. The developed and validated sensor could be a valuable point-of-care diagnostic tool for IDA quantification in patients.