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Poly(bromophenol blue)/CoSn(OH)6 cubic particles modified pencil graphite electrode for electrochemical determination of diphenhydramine
(Springer Nature, 2026) Karakaya, Serkan; Bakırdere, Sezgin; Şaylan, Meltem; Dilgin, Yusuf
In this study, a poly(bromophenol blue) (poly(BPB))-coated CoSn(OH)6 cubic particles -modified pencil graphite electrode (poly(BPB)@CoSn(OH)6/PGE) was developed, and its electrochemical activity towards diphenhydramine (DPHN) oxidation was systematically investigated. Cyclic voltammetric studies revealed that the oxidation of DPHN at the modified electrode is governed by a diffusion-controlled process, indicating strong interaction between DPHN molecules and the poly(BPB) film. The incorporation of the CoSn(OH)6 cubic structure enhances electron transfer kinetics by increasing the density of electroactive sites and facilitating charge transport across the electrode interface. This cooperative interaction between the conductive polymer and metal hydroxide structure results in a significant amplification of the oxidation response. Under optimized conditions, the proposed electrode exhibited a linear response in the concentration range of 1.0-500.0 µM with a detection limit (LOD) of 0.30 µM. Although the analytical performance is comparable to previously reported systems, the present work provides deeper insight into the role of polymer-metal hydroxide interfaces in governing electrochemical sensing behavior. The sensor also demonstrated acceptable selectivity and applicability in pharmaceutical, biological, and environmental samples. These findings highlight the importance of interfacial design in improving electrochemical performance and offer a useful framework for developing advanced hybrid sensing platforms.
Fluorescence HPLC analysis of teriflunomide in human plasma following derivatization with 4-chloro-7-nitrobenzofurazan: Method development and application to a prototype pharmacokinetic evaluation
(MDPI Publishing, 2026) Çayci, Meltem; Ceylan, Burhan; Önal, Cem
Background/Objectives: Teriflunomide is an active metabolite of leflunomide and acts as a selective and reversible inhibitor of dihydroorotate dehydrogenase, a key enzyme in de novo pyrimidine biosynthesis. It exhibits immunomodulatory activity by reducing the proliferation of activated T and B lymphocytes and is widely used in the treatment of rheumatoid arthritis and relapsing multiple sclerosis. This study aimed to develop a rapid, accurate, and simple high-performance liquid chromatography (HPLC) method with fluorometric detection for quantifying teriflunomide in human plasma. Methods: Plasma samples were prepared by liquid–liquid extraction followed by pre-column derivatization with NBD-Cl. Teriflunomide was derivatized with 4-chloro-7-nitrobenzofurazan (NBD-Cl) and separated using a reversed-phase C18 column (5 µm, 4.6 × 150 mm) at 30 ◦C with isocratic elution. The mobile phase consisted of acetonitrile and 0.1% orthophosphoric acid (80:20, v/v) at a flow rate of 1.1 mL/min. Fluorescence detection was performed at λex = 465 nm and λem = 535nm. ThemethodmeetsEuropean Medicines Agency (EMA) guide lines for bioanalytical validation and was successfully applied to pharmacokinetic studies, including AUC0–t, AUC0–∞, Cmax, Tmax, and t½. Results: Teriflunomide showed a retention time of 2.55 ± 0.01 min. The method exhibited linearity in the range of 0.01–30 ng/mL (r2 = 0.9998), with a limit of detection and quantification of 0.003 and 0.01 ng/mL, respec tively. The relative standard deviation was 3.27%. Conclusions: This work introduces a novel, cost-effective, and highly sensitive HPLC with fluorescence detection (HPLC-FL) method for the determination of teriflunomide in human plasma, providing an efficient alternative to LC-MS/MS for routine pharmacokinetic and bioequivalence studies.
Integrating green chemistry principles into the fabrication of MIP electrochemical sensors for heavy metal monitoring
(Taylor & Francis, 2026) Dorreh, Setareh; Kaya, Beril Sena; Aydemir, Zeynep; Al Faysal, Abdullah; Gölcü, Ayşegül
Heavy metal contamination remains a critical global environmental issue due to the persistence, bioaccumulation, and toxicity of metal ions such as Pb2+, Cd2+, Hg2+, and As³+. Although conventional analytical techniques provide high sensitivity and accuracy, they often rely on energy-intensive instrumentation, hazardous reagents, and generate considerable chemical waste, raising concerns regarding their environmental sustainability. In this context, molecularly imprinted polymer (MIP)-based electrochemical sensors have emerged as promising alternatives, offering high selectivity, operational simplicity, and compatibility with miniaturized and in situ analysis. This review critically examines the integration of Green Analytical Chemistry (GAC) principles into the design and fabrication of MIP-based electrochemical sensors for heavy metal monitoring. Particular attention is given to material selection, polymerization strategies, template removal approaches, and electrode modification techniques, with emphasis on their environmental implications. The applicability of quantitative greenness assessment tools, including the Analytical Eco-Scale, GAPI, AGREE, and AGREEMIP, is discussed in the context of sensor development workflows, highlighting both their strengths and current limitations in addressing fabrication stages, nanomaterial synthesis, and end-of-life considerations. By identifying methodological bottlenecks, particularly solvent-intensive template removal and limited reusability, this review outlines practical directions for advancing more sustainable sensor platforms. Overall, the work provides a critical framework for aligning analytical performance with environmental responsibility in next-generation MIP-based electrochemical sensing systems.
Ultra-fast liquid chromatographic determination of atomoxetine, duloxetine, paroxetine, fluoxetine and sertraline in tap water, urine, and pharmaceutical formulations using 7,7,8,8-tetracyanoquinodimethane as a derivatization reagent
(Editura Acad Romane, 2026) Önal, Cem; Ceylan, Burhan; Önal, Armağan
The widespread consumption of pharmaceuticals, including both human and veterinary drugs, has resulted in the accumulation of these substances in aquatic ecosystems, presenting significant ecological threats. Psychoactive drugs, particularly antidepressants, raise particular concern due to their direct effects on brain chemistry. The growing contamination of global water systems, especially in urban environments, underscores the increasing presence of these substances in nature. A novel analytical method using UFLC-UV was developed and validated for the quantification of Atomoxetine (ATM), Duloxetine (DLX), Paroxetine (PRX), Fluoxetine (FLX) and Sertraline (SRT) in tap water, urine, and pharmaceutical samples. This technique relies on creating a purple chromogen through a displacement reaction with TCNQ in acetonitrile, with heating at 80 °C for 20 minutes. The processed sample was then injected into a C18 column. Separation was performed using acetonitrile–water (85:15) as mobile phase at 1.0 mL/min flow rate. Detection was carried out at 567 nm. The method showed linearity in the range of 10–100 ng/mL for all compounds. The validated procedure was successfully implemented to identify these antidepressants in tap water, urine, and pharmaceutical formulations. Recovery values were found between 95.41 to 100.85%. The LOD values ranged from 1.02 to 1.98 ng/mL in all of the sample matrices.
A novel HPLC technique for the determination of casticin in pharmaceutical preparations and human plasma
(Marmara University Press, 2026) Egeli Yılmaz, Derya; Tırıs, Gizem; Kepekçi Tekkeli, Şerife Evrim
This study introduces a combined HPLC and UV detection technique for the quantification of casticin in capsule and human plasma samples. The chromatographic separation was carried out utilizing a C18 column (150 mm × 4.6 mm × 5 μm) at a temperature of 25 ºC. Isocratic elution with a mobile phase comprising 60:40 v/v (methanol-0.05% formic acid) was employed. Flow rate was adjusted 1 mL/min. The analyte was determined at a wavelength of 258 nm, with a retention time of 14.7±0.01 min. The developed method underwent validation according to ICH criteria, covering specificity, linearity, precision, accuracy, detection and quantitation limits, as well as robustness. The linear range was determined to be 10-60 ng/mL for both capsule and spiked plasma specimens. The suggested technique was performed to the analysis of casticin in spiked human plasma and pharmaceutical preparations, yielding a recovery of 106.04% and demonstrating precision through intra-day and inter-day experiments with the highest relative standard deviation (RSD %) value of 4.94. Consequently, the technique was performed to the quantifying of human plasma specimens from in a patient taking medication containing casticin.
Green MIP-based electrochemical sensing platform for environmental ivermectin analysis
(American Chemical Society, 2026) Aydemir, Zeynep; Kaya, Beril Sena; Dorreh, Setareh; Al Faysal, Abdullah; Erdoğan, Taner; Gölcü, Ayşegül
Ivermectin (IVM), a macrocyclic lactone derived from Streptomyces avermitilis, is widely recognized as a “wonder drug” for its broad-spectrum efficacy against internal and external parasites in human and veterinary medicine. Owing to its potent pharmacological activity, precise quantification of IVM is essential for therapeutic monitoring and dose optimization. In this study, we report the design of a novel electrochemical sensor based on molecularly imprinted polymer (MIP) technology, specifically tailored for the selective detection of IVM. The sensor was fabricated via an electropolymerization strategy employing methacrylic acid (MAA) as the functional monomer and aniline as the comonomer in phosphate-buffered saline (PBS, pH 7.0). To the best of our knowledge, this represents the first electropolymerization-based MIP sensor developed for IVM determination. The resulting MAA-IVM@MIP/GCE sensor was thoroughly characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Electrochemical detection was achieved through an indirect redox probe approach with 5.0 mM [Fe(CN)6] 3−/4−, providing a wide linear range (1 × 10−12 −1 × 10−11 M) and remarkably low limits of detection (LOD: 2.91 × 10−13 M) and quantification (LOQ: 9.71 × 10−13 M). The sensor demonstrated high sensitivity, reproducibility, and selectivity, clearly distinguishing IVM from structurally related compounds. It maintained strong analytical performance in pharmaceutical formulations, biological matrices, and environmental samples such as tap water and soil, showing minimal matrix interference. These results confirm the platform’s robustness and applicability. Density functional theory (DFT) calculations were performed to evaluate template−monomer interactions and determine the optimal template:monomer ratio for the MIP-based sensor. The results revealed that the 1:1 complex exhibited the most favorable binding characteristics, consistent with the experimental findings. In addition, the sensor fabrication strategy was designed in accordance with green analytical chemistry principles. The electropolymerization process was performed in aqueous phosphate-buffered saline under mild conditions without the use of excessive cross-linkers or hazardous reagents. The approach minimizes organic solvent consumption, reduces energy requirements, and enables sensor reusability, thereby contributing to a sustainable and environmentally responsible analytical platform. Overall, this cost-effective, scalable, and environmentally conscious electrochemical sensor provides a practical tool for reliable IVM monitoring and has strong potential for clinical diagnostics, pharmacokinetics, and pharmaceutical quality control.
A green electrochemical sensor based on molecular imprinting for etoposide detection in environmental matrices
(Elsevier, 2026) Al Faysal, Abdullah; Kaya, Beril Sena; Dorreh, Setareh; Erdoğan, Taner; Gölcü, Ayşegül
A semisynthetic form of podophyllotoxin, etoposide (ETO), is frequently used to manage multiple types of cancer, including lung, testicular, bladder, prostate, and gastric malignancies. Having been utilized in clinical settings for over twenty years, it is one of the most frequently prescribed anticancer agents globally. The primary cytotoxic mechanism of ETO involves the inhibition of topoisomerase II. In the present work, an innovative electrochemical detection platform utilizing MIP was successfully established to enable both highly selective and exceptionally sensitive determination of ETO in pharmaceutical injection forms and environmental specimens. An ETO-specific MIP sensor was fabricated through a photopolymerization process and immobilized onto a GCE, where AMPS served as the active monomer, and EGDMA functioned as the cross-linking agent. This study marks the first instance of a MIP-based electrochemical sensor designed explicitly for ETO identification. The AMPS ETO@MIP/GCE sensor was subjected to electrochemical and morphological assessments through FTIR, SEM, CV, and EIS. An indirect measurement approach was employed using a 5.0 mM potassium ferricyanide/ferro cyanide system to ascertain the analytical detection range from 1.0 to 10.0 pM. The sensor demonstrated excellent sensitivity, reproducibility, and selectivity, enabling effective discrimination of ETO from structurally similar compounds while retaining reliable performance in complex matrices such as soil and tap water. Results from validation experiments in pharmaceutical matrices indicated superior recovery, supporting the sensor's practical effectiveness and stability. To further investigate the experimental results and better understand the nature of template–monomer interactions, a series of DFT calculations was performed. Binding energies were evaluated for ETO–AMPS complexes across varying template-to-monomer ratios.
Determination of guaifenesin in spiked human breast milk: HPLC-UV method development, validation, and uncertainty evaluation
(Taras Shevchenko National University of Kyiv, 2025) Ceylan, Burhan; Önal, Cem; Önal, Armağan
A simple, sensitive, and reliable isocratic reversed-phase high-performance liquid chromatography (HPLC UV) method was developed, validated, and applied for the quantitative determination of guaifenesin in spiked human breast milk. Chromatographic separation was achieved on a C18 column (150 x 4.6 mm, 5 µm) using a mobile phase composed of methanol and water (50:50, v/v), where the aqueous phase was acidified with orthophosphoric acid (pH=3.2). The flow rate was 0.8 mL min-1, and detection was performed at 230 nm. The method exhibited excellent linearity over the concentration range of 5.0-30.0 ng mL-1 with a correlation coefficient of r2=0.9999. Liquid-liquid extraction (LLE) was used for sample preparation and resulted in a mean relative recovery of 98.82% with an absolute recovery of 99.52%, while effectively minimizing matrix interferences associated with breast milk. Method validation was performed in accordance with European Medicines Agency (EMA) bioanalytical guidelines, including assessments of selectivity, accuracy, precision, sensitivity, robustness, and stability. The method demonstrated strong reproducibility, did not require an internal standard, and provided a short analysis time suitable for routine application. This study presents the first simple, cost-effective, and sensitive HPLC-UV method for the determination of guaifenesin in human breast milk, offering a valuable analytical tool for evaluating drug safety during lactation.
CuSn(OH)6 nanoparticles as a novel adsorbent for the preconcentration of cadmium ions in onion extract
(Springer Nature Link, 2026) Şaylan, Meltem; Gürsoy, Selim; Polat Korkunç, Ümmügülsüm; Zaman, Buse Tuğba; Bakırdere, Sezgin
The present study aims to develop a new preconcentration strategy for the determination of non-essential cadmium ions in red onion samples. Determination of the extracted cadmium ions was carried out using flame atomic absorption spectrom etry for efficient and sensitive detection. The synthe sis of CuSn(OH)6 nanoparticles was accomplished via a single-step one-pot coprecipitation method under ambient conditions to obtain nanoparticles below 100 nm in size, which are particularly effec tive for preconcentration procedures. The morphol ogy and structure of the nanoparticles were confirmed with different characterization techniques. Under the optimized conditions, the calibration curve of the presented method showed good linearity between 2.5 and 50 μg/L, with a detection limit of 0.84 μg/L. The accuracy of this method was confirmed by obtaining recoveries of spiked red onion extracts. This method offers a sensitive, efficient, and eco-friendly method for the separation/detection of trace cadmium ions in aqueous plant-derived matrixes, especially red onion extracts.
Application of liquid-liquid microextraction techniques for trace level determination of organic/inorganic analytes in biological, medical, environmental and forensic samples
(Elsevier, 2025) Chormey, Dotse Selali; Bodur, Sezin Erarpat; Öztürk Er, Elif; Zaman, Buse Tuğba; Bodur, Süleyman; Şaylan, Meltem; Dalgıç Bozyiğit, Gamze; Serbest, Hakan; Bakırdere, Sezgin
The drawbacks of the conventional liquid-liquid extraction method have been greatly alleviated with the advent of liquid-liquid microextraction methods, which are being actively utilized as effective sample preparation tools for biological, medical, environmental and forensic samples. The complex nature of these sample matrices tend to hinder the accuracy and precision of analytical measurements, and have the potential to cause false positive and false negative results. With sample preparation remaining an integral part of accurate determination of organic and inorganic analytes in complex samples, liquid-liquid microextraction as an efficient sample preparation approach facilitates the acquisition of analytes in final forms that are suitable for modern and classical analytical instruments. The use of very low solvent volumes in liquid-liquid microextraction methods leads to very high enrichment factors, and the availability of different extractants paves way for selective analyte extractions. Recent calls for greener approaches of analysis have been met with the introduction of several green solvents that boost the greenness of liquid-liquid microextraction methods and equally maintain the superiority of the methods. © 2024 Elsevier Inc. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
Nio nanoflower based sorbent extraction for a novel HPLC–UV method for the determination of solifenacin in human plasma and its application to a prototype pharmacokinetic study
(Springer Nature Link, 2025) Ceylan, Burhan; Önal, Cem; Kurnaz Yetim, Nurdan; Hasanoğlu Özkan, Elvan; Önal, Armağan
Solifenacin is an active pharmaceutical product used in overactive therapy. The main goal of this work was to develop a high-performance liquid chromatographic (HPLC) method with ultraviolet detection for measuring the amount of quanti fied solifenacin in human plasma samples that is rapid, straightforward, and accurate. Prior to chromatographic analysis, a nanomaterial-based sorbent extraction technique utilizing NiO nanoflowers was employed for plasma sample preparation. In this method, NiO nanoflowers were employed, and the adsorption process underwent optimization. Chromatographic separation was carried out using a reversed-phase C18 analytical column (5 µm×4.6 mm×150 mm) with a mobile phase composed of water (0.2% triethylamine) and acetonitrile (30:70 v/v), and the pH was adjusted to 3.5 with ortho-phosphoric acid. The flow rate was set at 1.0 mL/min, and the investigation was performed using UV at 220 nm. The retention time of solifenacin is 3.10±0.01 min. The linear behaviour of the proposed approach was examined in the 0.01–30 ng/mL range (r 2=0.9995). The proposed method is in alignment with the criteria established by the European Medical Agency (EMA) about the accuracy, precision, repeatability, specificity, robustness and detection and quantification. Limit of detection and limit of quantification are determined to be 0.003 and 0.01 ng/mL, whereas relative standard deviation was determined to be less than 2.75% for intra-run and inter-run measurements. The plasma concentration–time profile and pharmacokinetic parameters such as AUC0–t , AUC0–∞, Cmax, tmax, and t1/2, were calculated according to the assays. The proposed method is feasible to investigate the bioequivalence, bioavailability, and routine analysis of the drug in plasma.
NiO-SnO2 nanocomposite as an adsorbent for the preconcentration of manganese ions in chamomile tea extract
(Elsevier, 2026) Şaylan, Meltem; Gürsoy, Selim; Zaman, Buse Tuğba; Bakırdere, Sezgin
Matricaria chamomilla L., referred to as chamomile, is a well-known medicinal plant that is widely distributed throughout the world. In this study, a novel NiO-SnO2 nanocomposite- assisted preconcentration method was established for efficient extraction and separation of manganese ions from chamomile tea extract. This pre concentration method was coupled with flame atomic absorption spectroscopy (FAAS). NiO-SnO2 nano composites were synthesized using simple one-pot co-precipitation procedure and calcined at 650 ◦C to obtain nanoparticles with sizes below 100 nm. X-ray diffraction (XRD) analysis indicated that the crystallite size of NiO SnO2 nanocomposites was estimated to be 46.03 nm using the Monshi–Scherrer equation. The LOD (limit of detection) and linear working range were determined as 3.6 μg/L and 10–100 μg/L, respectively. The proposed method was successfully validated, and recoveries ranged from 87.2 %–117.0 %. NiO-SnO2 nanocomposites represent a promising low-cost adsorbent for the preconcentration and subsequent determination of other heavy metal ions in diverse herbal extracts.
Computational insights into iron coordination disruption in the human transferrin–neisseria meningitidis bacterial protein complex
(MDPI Publishing, 2025) Dervişoğlu Özdemir, Celile; Duran, Gizem Nur; Fındık, Volkan; Özbil, Mehmet; Sağ Erdem, Safiye
Among many metal ions in biological systems, iron plays a fundamental role. Transferrins are iron-binding glycoproteins responsible for transporting Fe3+ in vertebrate blood. Neisse ria meningitidis, a Gram-negative pathogen causing meningitis, relies on iron for survival and acquires it from human transferrin (hTf) using two surface proteins, TbpA and TbpB. These proteins interact with hTf to form a ternary TbpA–TbpB–hTf complex, enabling iron capture from the host. The absence of an experimental crystal structure for this complex has hindered computational studies, a detailed understanding of Fe3+ dissociation, and designing efficient therapeutics. This study presents the first computational model of the ternary complex, its validation, and molecular dynamics simulations. Structural analyses revealed key electrostatic interactions regulating Fe3+ coordination and essential contact regions between proteins. The role of Lys359 from TbpA was investigated via QM/MM calculations by evaluating Fe3+ binding energies of isolated hTf, the ternary complex, and Lys359Ala, Lys359Arg, Lys359Asp mutant models. Results revealed that the proton trans fer from Lys359 leads to disruption of Tyr517–Fe3+ coordination, facilitating iron transfer to the bacterial system. Natural bond orbital analysis confirmed this mechanism. The findings provide new molecular insight into N. meningitidis iron acquisition and identify Lys359 as a potential target for covalent inhibitor design, guiding the development of novel therapeutics against meningococcal infection.
LC-MS/MS methods for the determination of paclitaxel in biological fluids: A review
(Gece Kitaplığı, 2025) Şenol, Mahmut Raşit; Sağlık Aslan, Serap
Oncology stands out as a dynamic field of science, driven by contin uous development and innovative research leading to advances in treat ment methods. In this context, paclitaxel is a chemotherapy drug that is effectively used in the treatment of a wide variety of cancer types. The drug’s areas of application include breast, ovarian, bladder, lung, prostate, melanoma, oesophageal cancers, Kaposi’s sarcoma, and various other solid tumours. This review details paclitaxel’s therapeutic indications, its mechanism of action at the cellular level, its role in suppressing tumour cell proliferation, as well as dosage adjustments, infusion protocols, routes of administration, and possible contraindications; it also emphasises the clinical importance of monitoring patients undergoing treatment. Pacli taxel, initially known as “taxol” when it was first discovered, is a natural diterpenoid compound derived from the Pacific yew tree (Taxus brevifo lia). The drug’s discovery was the result of natural product screening pro grammes conducted by the National Cancer Institute (NCI) in the United States in the late 1960s and early 1970s. During this process, research ers examined various plant extracts in an effort to identify compounds with anticancer potential, and paclitaxel’s pronounced cytotoxic effects attracted attention. In particular, its capacity to halt the cell cycle and induce apoptosis by inhibiting microtubule depolymerisation has made paclitaxel a priority agent in anticancer research (1).
Development and validation of an HPLC method for quantification of solifenacin in spiked human breast milk
(Korean Society of Analytical Sciences, 2025) Ceylan, Burhan; Çayci, Meltem; Önal, Cem; Önal, Armağan
An efficient and reliable reversed phase high performance liquid chromatography (HPLC) method was established and validated for the quantitative analysis of solifenacin succinate in fortified human breast milk samples. Chromatographic separation was carried out on a C18 column (150 × 4.6 mm, 5 μm particle size) and a isocratic mobile phase composed of acetonitrile and phosphate buffer (pH 3.5) in a 65:35 (v/v) ratio. The flow rate was at 1.1 mL/min, and detection was performed at 225 nm using a ultraviolet (UV) detector. The method exhibited excellent linearity in the range of 1.0 to 40.0 ng/mL (r² = 0.9999). The validation process was performed in accordance with European Medicines Agency (EMA) bioanalytical guidelines, and included selectivity, accuracy, precision, sensitivity, recovery, robustness, and stability assessments. The liquid-liquid extraction (LLE) procedure used for sample pretreatment provided satisfactory recovery (mean: 99.32 %) and minimized matrix interferences from breast milk. The method showed high reproducibility, did not require an internal standar, and offered a rapid analysis time of approximately 3.4 minutes. This study offers a simple, cost-effective, and sensitive HPLC-UV method for monitoring solifenacin levels in breast milk matrices, providing a valuable tool for evaluating drug safety during lactation.
Development of an HPLC method for the determination of fampridine (dalfampridine) in human plasma by fluorimetric derivatization and application to a prototype pharmacokinetic study
(Editions de l'Academie Republique Populaire, 2025) Ceylan, Burhan; Önal, Cem; Önal, Armağan
Fampridine (dalfampridine) is used to improve walking in people who have multiple sclerosis. In this study, a new, fast and sensitive HPLC method with fluorometric detection was developed for the determination of fampridine in human plasma and applied to a pharmacokinetic study. Fampridine was precolumn derivatized with 7-chloro-4-nitrobenzofurazan (NBD-Cl) and the fluorescent derivative was separated on a C18 (150 × 4.6 mm × 2.6 μm) analytical column at 30 ºC using a mobile phase composed of acetonitrile – 0.1% o-phosphoric acid in water (80:20, v/v) by isocratic elution with flow rate of 1.0 mL min–1 . The method was based on the measurement of the derivative using fluorescence detection (λex= 310 nm, λem = 365 nm). The retention time of fampridine is 4.10 ± 0.02 min. This currently developed method was validated according to EMA criteria by evaluating the specificity, linearity, precision, accuracy and robustness. The method was determined to be linear in a concentration range of 0.01–20 ng mL–1 with the correlation coefficient of 0.9996. LOD and LOQ were found to be 0.003 and 0.01 ng mL–1 , respectively. Intraday and interday RSD values were less than 2.45%. The plasma concentration-time profile and pharmacokinetic parameters such as AUC0–t, AUC0–∞, Cmax, tmax, t1/2, were calculated according to the assays. The presented method can certainly be used for bioequivalence and bioavailability investigations and routine analysis of the drug in plasma.
Fluorimetric derivatization-based HPLC-FL method for the prototype pharmacokinetic analysis of selexipag in human plasma
(Taras Shevchenko National University, 2025) Ceylan, Burhan; Çayci, Meltem; Önal, Cem; Önal, Armağan
A simple and cost-effective HPLC-FL method has been developed for measuring selexipag in human plasma, showcasing its suitability for pharmacokinetic research. Selexipag was precolumn derivatized with 7-chloro-4-nitrobenzofurazan (NBD-Cl) and the fluorescent derivative was separated on a C18 (150 mm × 4.6 mm × 2.6 μm) analytical column at 30 ºC using a mobile phase composed of acetonitrile – 0.1% o-phosphoric acid in water (70:30, v/v) by isocratic elution with flow rate of 1.0 mL min-1. The method was based on measuring the derivative using fluorescence detection (λex = 380 nm, λem = 420 nm). The retention time of selexipag is 6.40 ± 0.01 min. This currently developed method was validated according to EMA criteria by evaluating the specificity, linearity, precision, accuracy, and robustness. The method was determined to be linear in a concentration range of 0.01-20 ng mL-1 with a correlation coefficient of 0.9998. LOD and LOQ were found to be 0.003 and 0.01 ng mL-1, respectively. Intraday and interday RSD values were less than 1.75%. The plasma concentration-time profile and pharmacokinetic parameters such as AUC0–t, AUC0–∞, Cmax, tmax, t1/2, were calculated according to the assays. The presented method can be effectively used for bioequivalence and bioavailability investigations, as well as for routine analysis of the drug in plasma.
Development of a sensitive spectrophotometric method for determination of the charge-transfer complex of aripiprazole in pharmaceutical formulations: Spectrometric characteristics and analytical applications
(Taras Shevchenko National University, 2024) Dinçel, Demet; Bahadori, Fatemeh; Kepekçi Tekkeli, Şerife Evrim; Önal, Armağan
This study presents a simple, rapid, and accurate spectrophotometric method for the determination of Aripiprazole (ARP) in tablets. The determination procedure is based on the reaction of ARP with 7,7,8,8-tet racyanoquinodimethane (TCNQ), producing a colored product that was quantitated spectrophotometrically at 392 nm. Various variables affecting the reaction were optimized. The method exhibited a good linearity range with a correlation coefficient of 0.9994, observed as 0.25–3 μg/mL. The developed method was validated according to the International Council for Harmonisation (ICH) guidelines, assessing specificity, linearity, accuracy, precision, robustness, limit of detection (LOD), and limit of quantitation (LOQ). The formation of the CT-complex and the interaction sites were confirmed by elemental analysis, DSC, IR, and 1H NMR spectroscopy. The method was successfully applied to the determination of ARP in pharmaceutical preparation.
Quantification of agnuside in human plasma with a novel high-performance liquid chromatographic method and pharmacokinetic study
(Oxford University Press, 2025) Egeli, Derya; Tiris, Gizem; Kepekçi Tekkeli, Şerife Evrim
This study presents a combination of High Performance Liquid Chromatography (HPLC) and ultraviolet (UV) detection that provides the quantification of agnuside in human plasma specimens. Reverse-phase chromatographic separation was carried out with C18 column (150 mm × 4.6 mm × 5 μm), at 25°C with isocratic elution of the mobile phase containing methanol: 0.1% formic acid (35:65 v/v) at 0.6 mL/min flow rate. Experiments were carried out at a wavelength of 258 nm. The retention time of the analyte is 9.70 ± 0.01 min. The developed technique was validated based on the International Conference on Harmonization guideline. The correlation coefficient of the technique was 0.9915, and the calibration range was 5–125 μg/mL. The recovery value of the proposed method was found to be 101.4%, and the precision of the method was calculated as 6.35 with the highest RSD% value. A pharmacokinetic study was performed by administering agnuside to a healthy volunteer.
Preconcentration of bismuth using nickel hydroxide nanoflower from water samples and determination by FAAS
(Springer, 2025) Yıldız, Barış; Durukan, İlknur; Şaylan, Meltem; Zaman, Buse Tuğba; Bakırdere, Sezgin
In this study, a preconcentration strategy based on Ni(OH)2 nanofowers (NFs) was developed for the extraction/separation of bismuth ions from environmental water samples before the determination by fame atomic absorption spectrometry (FAAS). The homogeneous coprecipitation method was employed for the synthesis of the fower-shaped Ni(OH)2 and used as an adsorbent for the preconcentration of bismuth. The extraction variables were determined by a univariate optimization strategy to obtain maximum extraction performance. The optimal parameters of the method were as follows: 15 min mechanical shaking at 120 rpm, pH 6.0 bufer solution (1.0 mL), 20 mg of sorbent, and 250 µL of 6.0 M nitric acid for the elution. Under the optimized instrumental and extraction conditions, LOD (limit of detection), LOQ (limit of quantitation), and linear dynamic range were determined as 2.8 µg/L, 9.4 µg/L, and 0.010–0.30 mg/L, respectively. The enhancement factor of the sorbent-based method was calculated as 139.1-folds by comparing the slopes of calibration plots obtained from FAAS and the preconcentration method. To assess the feasibility and reliability of the developed method, tap water and spring water samples were analyzed under optimized conditions. The satisfactory %recoveries were obtained close to 100% using the direct comparison method. The obtained results show that the presented method is a promising candidate for efcient extraction and trace determination of bismuth in several sample mediums.

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